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Sample records for ferrimagnetic double perovskites

  1. Large magnetization and frustration switching of magnetoresistance in the double-perovskite ferrimagnet Mn2FeReO6.

    Science.gov (United States)

    Arévalo-López, Angel M; McNally, Graham M; Attfield, J Paul

    2015-10-05

    Ferrimagnetic A2 BB'O6 double perovskites, such as Sr2 FeMoO6 , are important spin-polarized conductors. Introducing transition metals at the A-sites offers new possibilities to increase magnetization and tune magnetoresistance. Herein we report a ferrimagnetic double perovskite, Mn2 FeReO6 , synthesized at high pressure which has a high Curie temperature of 520 K and magnetizations of up to 5.0 μB which greatly exceed those for other double perovskite ferrimagnets. A novel switching transition is discovered at 75 K where magnetoresistance changes from conventional negative tunneling behavior to large positive values, up to 265 % at 7 T and 20 K. Neutron diffraction shows that the switch is driven by magnetic frustration from antiferromagnetic Mn(2+) spin ordering which cants Fe(3+) and Re(5+) spins and reduces spin-polarization. Ferrimagnetic double perovskites based on A-site Mn(2+) thus offer new opportunities to enhance magnetization and control magnetoresistance in spintronic materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Canted ferrimagnetism and giant coercivity in the nonstoichiometric double perovskite L a2N i1.19O s0.81O6

    Science.gov (United States)

    Feng, Hai L.; Reehuis, Manfred; Adler, Peter; Hu, Zhiwei; Nicklas, Michael; Hoser, Andreas; Weng, Shih-Chang; Felser, Claudia; Jansen, Martin

    2018-05-01

    The nonstoichiometric double perovskite oxide L a2N i1.19O s0.81O6 was synthesized by solid-state reaction and its crystal and magnetic structures were investigated by powder x-ray and neutron diffraction. L a2N i1.19O s0.81O6 crystallizes in the monoclinic double perovskite structure (general formula A2B B'O6 ) with space group P 21/n , where the B site is fully occupied by Ni and the B ' site by 19% Ni and 81% Os atoms. Using x-ray absorption spectroscopy an O s4.5 + oxidation state was established, suggesting the presence of about 50% paramagnetic O s5 + (5 d3 , S =3 /2 ) and 50% nonmagnetic O s4 + (5 d4 , Jeff=0 ) ions at the B ' sites. Magnetization and neutron diffraction measurements on L a2N i1.19O s0.81O6 provide evidence for a ferrimagnetic transition at 125 K. The analysis of the neutron data suggests a canted ferrimagnetic spin structure with collinear N i2 + -spin chains extending along the c axis but a noncollinear spin alignment within the a b plane. The magnetization curve of L a2N i1.19O s0.81O6 features a hysteresis with a very high coercive field, HC=41 kOe , at T =5 K , which is explained in terms of large magnetocrystalline anisotropy due to the presence of Os ions together with atomic disorder. Our results are encouraging to search for rare-earth-free hard magnets in the class of double perovskite oxides.

  3. Magnetoresistance stories of double perovskites

    Indian Academy of Sciences (India)

    grain surfaces have also been proposed to act as tunnel barriers in Sr2FeMoO6. ... these double perovskites, a gradual decrease in the low-field MR and saturation ... simultaneously, and therefore serious material engineering was needed.

  4. Magnetoresistance stories of double perovskites

    Indian Academy of Sciences (India)

    2015-05-28

    May 28, 2015 ... Tunnelling magnetoresistance (TMR) in polycrystalline double perovskites has been an important research topic for more than a decade now, where the nature of the insulating tunnel barrier is the core issue of debate. Other than the nonmagnetic grain boundaries as conventional tunnel barriers, intragrain ...

  5. Effective field study of ising model on a double perovskite structure

    Energy Technology Data Exchange (ETDEWEB)

    Ngantso, G. Dimitri; El Amraoui, Y. [LMPHE, (URAC 12), Faculté des Sciences, Université Mohammed V, Rabat (Morocco); Benyoussef, A. [LMPHE, (URAC 12), Faculté des Sciences, Université Mohammed V, Rabat (Morocco); Center of Materials and Nanomaterials, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); El Kenz, A., E-mail: elkenz@fsr.ac.ma [LMPHE, (URAC 12), Faculté des Sciences, Université Mohammed V, Rabat (Morocco)

    2017-02-01

    By using the effective field theory (EFT), the mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model adapted to a double perovskite structure has been studied. The EFT calculations have been carried out from Ising Hamiltonian by taking into account first and second nearest-neighbors interactions and the crystal and external magnetic fields. Both first- and second-order phase transitions have been found in phase diagrams of interest. Depending on crystal-field values, the thermodynamic behavior of total magnetization indicated the compensation phenomenon existence. The hysteresis behaviors are studied by investigating the reduced magnetic field dependence of total magnetization and a series of hysteresis loops are shown for different reduced temperatures around the critical one. - Highlights: • Magnetic properties of double perovskite Structure have been studied. • Compensation temperature has been observed below the critical temperature. • Hysteresis behaviors have been studied.

  6. Effective field study of ising model on a double perovskite structure

    International Nuclear Information System (INIS)

    Ngantso, G. Dimitri; El Amraoui, Y.; Benyoussef, A.; El Kenz, A.

    2017-01-01

    By using the effective field theory (EFT), the mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model adapted to a double perovskite structure has been studied. The EFT calculations have been carried out from Ising Hamiltonian by taking into account first and second nearest-neighbors interactions and the crystal and external magnetic fields. Both first- and second-order phase transitions have been found in phase diagrams of interest. Depending on crystal-field values, the thermodynamic behavior of total magnetization indicated the compensation phenomenon existence. The hysteresis behaviors are studied by investigating the reduced magnetic field dependence of total magnetization and a series of hysteresis loops are shown for different reduced temperatures around the critical one. - Highlights: • Magnetic properties of double perovskite Structure have been studied. • Compensation temperature has been observed below the critical temperature. • Hysteresis behaviors have been studied.

  7. Double perovskites with strong spin-orbit coupling

    Science.gov (United States)

    Cook, Ashley M.

    We first present theoretical analysis of powder inelastic neutron scattering experiments in Ba2FeReO6 performed by our experimental collaborators. Ba2FeReO6, a member of the double perovskite family of materials, exhibits half-metallic behavior and high Curie temperatures Tc, making it of interest for spintronics applications. To interpret the experimental data, we develop a local moment model, which incorporates the interaction of Fe spins with spin-orbital locked magnetic moments on Re, and show that it captures the experimental observations. We then develop a tight-binding model of the double perovskite Ba 2FeReO6, a room temperature ferrimagnet with correlated and spin-orbit coupled Re t2g electrons moving in the background of Fe moments stabilized by Hund's coupling. We show that for such 3d/5d double perovskites, strong correlations on the 5d-element (Re) are essential in driving a half-metallic ground state. Incorporating both strong spin-orbit coupling and the Hubbard repulsion on Re leads to a band structure consistent with ab initio calculations. The uncovered interplay of strong correlations and spin-orbit coupling lends partial support to our previous work, which used a local moment description to capture the spin wave dispersion found in neutron scattering measurements. We then adapt this tight-binding model to study {111}-grown bilayers of half-metallic double perovskites such as Sr2FeMoO6. The combination of spin-orbit coupling, inter-orbital hybridization and symmetry-allowed trigonal distortion leads to a rich phase diagram with tunable ferromagnetic order, topological C= +/-1, +/-2 Chern bands, and a C = +/-2 quantum anomalous Hall insulator regime. We have also performed theoretical analysis of inelastic neutron scattering (INS) experiments to investigate the magnetic excitations in the weakly distorted face-centered-cubic (fcc) iridate double perovskites La2ZnIrO 6 and La2MgIrO6. Models with dominant Kitaev exchange seem to most naturally

  8. Fragility of ferromagnetic double exchange interactions and pressure tuning of magnetism in 3 d -5 d double perovskite Sr2FeOsO6

    Science.gov (United States)

    Veiga, L. S. I.; Fabbris, G.; van Veenendaal, M.; Souza-Neto, N. M.; Feng, H. L.; Yamaura, K.; Haskel, D.

    2015-06-01

    The ability to tune exchange (magnetic) interactions between 3 d transition metals in perovskite structures has proven to be a powerful route to discovery of novel properties. Here we demonstrate that the introduction of 3 d -5 d exchange pathways in double perovskites enables additional tunability, a result of the large spatial extent of 5 d wave functions. Using x-ray probes of magnetism and structure at high pressure, we show that compression of Sr2FeOsO6 drives an unexpected continuous change in the sign of Fe-Os exchange interactions and a transition from antiferromagnetic to ferrimagnetic order. We analyze the relevant electron-electron interactions, shedding light into fundamental differences with the more thoroughly studied 3 d -3 d systems.

  9. Structures and Phase Transitions in Ordered Double Perovskites

    International Nuclear Information System (INIS)

    Kennedy, Brendan; Zhou, Qingdi; Cheah, Melina

    2005-01-01

    Full text: The basic perovskite structure is ubiquitous in the study of metal oxides, yet very few oxides actually adopt the archetypal cubic structure. The perovskite structure is based on corner sharing octahedra and in most cases cooperative rotations of successive octahedra lower the symmetry of the perovskite structure. Solid State Chemists have been fascinated by these distortions for many years, not only for their intrinsic interest but also to understand how these distortions control the electronic and magnetic properties of perovskite oxides. In this presentation we will describe the use of high-resolution powder diffraction methods to unravel the temperature and composition dependence of the structures in two series of double perovskites, Sr 1-x A x NiWO 6 (A = Ba, Ca) where there is essentially complete ordering of Ni and W cations and in Sr 1-x Ca x CrNbO 6 where there is extensive disorder of the Cr and Nb cations. (authors)

  10. Magnetoresistance and magnetic properties of the double perovskites

    International Nuclear Information System (INIS)

    Philipp, J.B.; Majewski, P.; Resinger, D.; Gepraegs, S; Opel, M.; Reb, A.; Alff, L.; Gross, R.

    2004-01-01

    The magnetic double perovskite materials of composition A 2 BB'O 6 with A an alkaline earth ion and B and B' a magnetic and non-magnetic transition metal or lanthanide ions, respectively, have attracted considerable attention due to their interesting magnetic properties ranging from antiferromagnetism to geometrically frustrated spin systems and ferromagnetism. With respect to application in spin electronics, the ferromagnetic double perovskites with BB' = CrW, CrRe, FeMo or FeRe and A = Ca, Ba, Sr are highly interesting due to their in most cases high Curie temperatures well above room temperature and their half-magnetic behaviour. Here, we summarize the structural, magnetotransport, magnetic and optical properties of the ferromagnetic double perovskites and discuss the underlying physics. In particular, we discuss the impact of the steric effects resulting in a distorted perovskite structure, doping effects obtained by a partial replacing of the divalent alkaline earth ions on the A site by a trivalent lanthanide as well as B/B' cationic disorder on the Curie temperature T C , the saturation magnetization and the magnetotransport properties. Our results support the presence of a kinetic energy driven mechanism in the ferromagnetic double perovskites, where ferromagnetism is stabilised by a hybridization of states of the non-magnetic B'- site positioned in between the high spin B-sites. (author)

  11. On the possibility of excitonic magnetism in Ir double perovskites

    Czech Academy of Sciences Publication Activity Database

    Pajskr, K.; Novák, Pavel; Pokorný, Vladislav; Kolorenč, Jindřich; Arita, R.; Kuneš, Jan

    2016-01-01

    Roč. 93, č. 3 (2016), 1-6, č. článku 035129. ISSN 1098-0121 R&D Projects: GA ČR GA13-25251S Institutional support: RVO:68378271 Keywords : spin-orbit coupling * double perovskite * excitonic magnetism Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  12. Lieb-Mattis ferrimagnetic superstructure and superparamagnetism in Fe-based double perovskite multiferroics

    Czech Academy of Sciences Publication Activity Database

    Kuzian, R. O.; Laguta, Valentyn; Richter, J.

    2014-01-01

    Roč. 90, č. 13 (2014), "134415-1"-"134415-13" ISSN 1098-0121 R&D Projects: GA ČR GA13-11473S Institutional support: RVO:68378271 Keywords : multiferroics * superantiferromagnetism * DFT calculations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  13. Magnetic transition in double perovskite systems

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, O., E-mail: navarro@servidor.unam.m [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-360, 04510 Mexico DF (Mexico); Aguilar, B. [Laboratorio Interinstitucional de Magnetismo Natural, Instituto de Geofisica, Sede Michoacan, Universidad Nacional Autonoma de Mexico, Morelia (Mexico); Avignon, M. [Institut Neel, CNRS and Universite Joseph Fourier, BP 166, 38042 Grenoble Cedex 9 (France)

    2010-05-15

    The search for materials having complete spin polarization and high Curie temperature have received a lot of attention in view of spintronics applications, especially the ferromagnetic (F) Sr{sub 2}FeMoO{sub 6}, because of its fairly high Curie temperature (T{sub C}= 450 K), half-metallic character, large magnetoresistance and potential applications. On the other hand, Sr{sub 2}FeWO{sub 6} is insulating and antiferromagnetic (AF) with T{sub N}=37K. With a double exchange type model it has been shown that F-AF transition can be driven by super-exchange interactions with increasing Fe-M (M=Mo, W) charge transfer energy. So, the charge transfer energy is expected to be larger in FeW than in FeMo compounds. Using a tight-binding model with the renormalized perturbation expansion technique, we determine the density of states for the AF phase and the electronic energy difference for the F- and AF-phases as a function of the Fe-M charge transfer energy. The F-AF transition in the ordered system Sr{sub 2}FeMo{sub x}W{sub 1-x}O{sub 6} occurs for xapprox0.3, in good agreement with the experimental value. We also studied the effect of the diagonal disorder in the variation of the number of conduction electrons on Fe and M sites. Finally, the behavior of the Curie temperature as a function of the Mo/W concentration is determined.

  14. Magnetic transitions in double perovskite Sr2FeRe1-xSbxO6 (0≤x≤0.9)

    International Nuclear Information System (INIS)

    Jung, Alexandra; Ksenofontov, Vadim; Reiman, Sergey; Therese, Helen Annal; Felser, Claudia; Tremel, Wolfgang; Kolb, Ute

    2006-01-01

    The double perovskites Sr 2 FeMO 6 (M=Re,Mo) belong to the important class of half-metallic magnetic materials. In this study we explore the effect of replacing the electronic 5d buffer element Re with variable valency by the main group element Sb with fixed valency. X-ray diffraction reveals Sr 2 FeRe 1-x Sb x O 6 (0 2 FeReO 6 changes to antiferromagnetic upon Sb substitution as was determined by magnetic susceptibility measurements. Samples up to a doping level of 0.3 are ferrimagnetic, while Sb contents higher than 0.6 result in an overall antiferromagnetic behavior. 57 Fe and 121 Sb Moessbauer spectroscopy specifies the valence state of Sb to be +5 within the whole range of substitution whereas the Fe valence state changes from +2.7 for the parent compound to +2.9 for Sr 2 FeRe 0.1 Sb 0.9 O 6 . Accordingly, Fe adopts the role of an electronic buffer element from Re upon heavy Sb doping. Additionally, 57 Fe Moessbauer results show a coexistence of ferri- and antiferromagnetic clusters within the same perovskite-type crystal structure in the Sb substitution range 0.3 2 FeReO 6 and Sr 2 FeRe 0.9 Sb 0.1 O 6 are ''purely'' ferrimagnetic and Sr 2 FeRe 0.1 Sb 0.9 O 6 contains antiferromagnetically ordered Fe sites only. Consequently, a replacement of the Re atoms by a nonmagnetic main group element such as Sb blocks the superexchange pathways -Fe-O-Re(Sb)-O-Fe- along the crystallographic axis of the perovskite unit cell and destroys the itinerant magnetism of the parent compound

  15. In- and Ga-based inorganic double perovskites with direct bandgaps for photovoltaic applications.

    Science.gov (United States)

    Dai, Jun; Ma, Liang; Ju, Minggang; Huang, Jinsong; Zeng, Xiao Cheng

    2017-08-16

    Double perovskites in the form of A 2 B'B''X 6 (A = Cs, B' = Ag, B'' = Bi) have been reported as potential alternatives to lead-containing organometal trihalide perovskites. However, all double perovskites synthesized to date exhibit indirect bandgaps >1.95 eV, which are undesirable for photovoltaic and optoelectronic applications. Herein, we report a comprehensive computer-aided screening of In- and Ga-based double perovskites for potential photovoltaic applications. To this end, several preconditions are implemented for the screening of optimal candidates, which include structural stability, electronic bandgaps, and optical absorption. Importantly, four In- and Ga-based double perovskites are identified to possess direct bandgaps within the desirable range of 0.9-1.6 eV for photovoltaic applications. Dominant optical absorption of the four double perovskites is found to be in the UV range. The structural and thermal stability of the four double perovskites are examined using both the empirical Goldschmidt ratio and convex-hull calculations. Only Cs 2 AgInBr 6 is predicted to be thermodynamically stable.

  16. Investigation of Iron-based double perovskite oxides on the magnetic phase stability, mechanical, electronic and optical properties via first-principles calculation

    Energy Technology Data Exchange (ETDEWEB)

    Rached, H., E-mail: habib_rached@yahoo.fr [Laboratoire des Matériaux Magnétiques, Faculté des Sciences Exactes, Université Djillali Liabès de Sidi Bel-Abbès, Sidi Bel-Abbès, 22000 (Algeria); Département de Physique, Faculté des Sciences Exactes et Informatique, Université Hassiba BenBouali de Chlef, Chlef, 02000 (Algeria); Bendaoudia, S. [Laboratoire des Matériaux Magnétiques, Faculté des Sciences Exactes, Université Djillali Liabès de Sidi Bel-Abbès, Sidi Bel-Abbès, 22000 (Algeria); Rached, D., E-mail: rachdj@yahoo.fr [Laboratoire des Matériaux Magnétiques, Faculté des Sciences Exactes, Université Djillali Liabès de Sidi Bel-Abbès, Sidi Bel-Abbès, 22000 (Algeria)

    2017-06-01

    The main goal of the present work is to obtain report on the magnetic phase stability, mechanical, electronic and optical properties of double perovskite oxides Pb{sub 2}FeMO{sub 6} (M = Mo, Re and W) by employing the ab-initio plane-wave method, based on the density functional theory (DFT). The exchange-correlation (XC) energy of electrons was treated using the Perdew–Burke–Ernzerhof parametrization. The ground-state electronic properties for different magnetic configurations were calculated. The formation enthalpies has been evaluated in order to determinate the stability of our compounds. The independent elastic constants and the related mechanical properties are investigated. The electronic structure calculation reveal the half-metallic ferrimagnets (FiM-HM) for all investigated compounds. The optical constants as the dielectric function, refractive index, optical reflectivity and absorption coefficient were calculated and discussed in detail. Therefore, our compounds are identified as potential candidates for spintronic applications and high performance electronic devices. - Highlights: • Based on the DFT calculation, the Pb{sub 2}FeMO{sub 6} (M = Mo, Re and W) compounds have been investigated. • The ground-state properties are predicted. • The mechanical properties reveals that these compounds are stable against any elastic deformations. • The electronic structures reveals the half-metallic ferrimagnets (FiM-HM) for all investigated compounds.

  17. Optimized effective potential model for the double perovskites Sr2-xYxVMoO6 and Sr2-xYxVTcO6

    International Nuclear Information System (INIS)

    Solovyev, I V

    2011-01-01

    In an attempt to explore half-metallic properties of the double perovskites Sr 2-x Y x VMoO 6 and Sr 2-x Y x VTcO 6 , we construct an effective low-energy model, which describes the behavior of the t 2g states of these compounds. All parameters of such a model are derived rigorously on the basis of first-principles electronic structure calculations. In order to solve this model, we employ the optimized effective potential method and treat the correlation interactions in the random phase approximation. Although correlation interactions considerably reduce the intraatomic exchange splitting in comparison with the Hartree-Fock approach, this splitting still substantially exceeds the typical values obtained in the local-spin-density approximation (LSDA), which alters many predictions based on the LSDA. Our main results are summarized as follows. (i) All ferromagnetic states are expected to be half-metallic. However, their energies are generally higher than those of the ferrimagnetic ordering between V and Mo/Tc sites (except Sr 2 VMoO 6 ). (ii) All ferrimagnetic states are metallic (except fully insulating Y 2 VTcO 6 ) and no half-metallic antiferromagnetism has been found. (iii) Moreover, many of the ferrimagnetic structures appear to be unstable with respect to the spin-spiral alignment. Thus, the true magnetic ground state of these systems is expected to be more complex. In addition, we discuss several methodological issues related to nonuniqueness of the effective potential for the half-metallic and magnetic insulating states.

  18. Optimized effective potential model for the double perovskites Sr2 - xYxVMoO6 and Sr2 - xYxVTcO6

    Science.gov (United States)

    Solovyev, I. V.

    2011-08-01

    In an attempt to explore half-metallic properties of the double perovskites Sr2 - xYxVMoO6 and Sr2 - xYxVTcO6, we construct an effective low-energy model, which describes the behavior of the t2g states of these compounds. All parameters of such a model are derived rigorously on the basis of first-principles electronic structure calculations. In order to solve this model, we employ the optimized effective potential method and treat the correlation interactions in the random phase approximation. Although correlation interactions considerably reduce the intraatomic exchange splitting in comparison with the Hartree-Fock approach, this splitting still substantially exceeds the typical values obtained in the local-spin-density approximation (LSDA), which alters many predictions based on the LSDA. Our main results are summarized as follows. (i) All ferromagnetic states are expected to be half-metallic. However, their energies are generally higher than those of the ferrimagnetic ordering between V and Mo/Tc sites (except Sr2VMoO6). (ii) All ferrimagnetic states are metallic (except fully insulating Y2VTcO6) and no half-metallic antiferromagnetism has been found. (iii) Moreover, many of the ferrimagnetic structures appear to be unstable with respect to the spin-spiral alignment. Thus, the true magnetic ground state of these systems is expected to be more complex. In addition, we discuss several methodological issues related to nonuniqueness of the effective potential for the half-metallic and magnetic insulating states.

  19. Multiferroic Double Perovskites ScFe1-xCrxO3 (1 /6 ≤x ≤5 /6 ) for Highly Efficient Photovoltaics and Spintronics

    Science.gov (United States)

    Cai, Tian-Yi; Liu, Shi-Chen; Ju, Sheng; Liu, Cheng-You; Guo, Guang-Yu

    2017-09-01

    Ferroelectric oxides are attractive materials for constructing efficient solar cells. Nevertheless, a wide band gap of nearly 3.0 eV in these ferroelectric oxides would result in poor overall sunlight absorption and, hence, low energy conversion efficiency. Here, by systematic first-principles density-functional calculations, we demonstrate that double-perovskite semiconductors ScFe1-xCrxO3 (1 /6 ≤x ≤5 /6 ) with a narrow band gap of approximately 1.8 eV would simultaneously exhibit large ferroelectric polarization (100 μ C /cm2 ) and ferrimagnetic magnetization (170 emu/cm3 ). Within a Schottky-based model for a typical sandwich solar-cell structure, a power-conversion efficiency of 9.0% can be reached by neglecting all other sources of photovoltaicity in ferroelectric materials. This value is larger than the largest value of 8.1% observed in ferroelectric oxides. Furthermore, these double perovskites are found to be single-spin semiconductors, and the obtained photocurrent is fully spin polarized over almost the entire Sun spectrum. These fascinating advantages would make ScFex Cr1 -xO3 (1 /6 ≤x ≤5 /6 ) semiconductors promising candidates for highly efficient solar cells and spin photovoltaic devices.

  20. Bandgap Engineering of Double Perovskites for One- and Two-photon Water Splitting

    DEFF Research Database (Denmark)

    Castelli, Ivano Eligio; Thygesen, Kristian Sommer; Jacobsen, Karsten Wedel

    2013-01-01

    Computational screening is becoming increasingly useful in the search for new materials. We are interested in the design of new semiconductors to be used for light harvesting in a photoelectrochemical cell. In the present paper, we study the double perovskite structures obtained by combining 46...... stable cubic perovskites which was found to have a finite bandgap in a previous screening-study. The four-metal double perovskite space is too large to be investigated completely. For this reason we propose a method for combining different metals to obtain a desired bandgap. We derive some bandgap design...... rules on how to combine two cubic perovskites to generate a new combination with a larger or smaller bandgap compared with the constituent structures. Those rules are based on the type of orbitals involved in the conduction bands and on the size of the two cubic bandgaps. We also see that a change...

  1. Half-metallic antiferromagnetism in double perovskite BiPbCrCuO6

    International Nuclear Information System (INIS)

    Weng, Ke-Chuan; Wang, Y. K.

    2015-01-01

    The electronic structure and magnetic properties of BiPbCrCuO 6 double perovskite are investigated based on first-principles density functional calculations with generalized gradient approximation (GGA) and GGA incorporated with Coulomb correlation interaction U (GGA + U). The results suggest the half-metallic (HM) and antiferromagnetic (AFM) properties of BiPbCrCuO 6 double perovskite. The HM-AFM property of the double perovskite is caused by the double-exchange mechanism between neighboring Cr 5+ (t 2g 1 ↓) and Cu 2+ (t 2g 3 ↑t 2g 3 ↓e g 2 ↑e g ↓) via the intermediate O 2− (2s 2 2p 6 ) ion

  2. Double Charged Surface Layers in Lead Halide Perovskite Crystals

    KAUST Repository

    Sarmah, Smritakshi P.

    2017-02-01

    Understanding defect chemistry, particularly ion migration, and its significant effect on the surface’s optical and electronic properties is one of the major challenges impeding the development of hybrid perovskite-based devices. Here, using both experimental and theoretical approaches, we demonstrated that the surface layers of the perovskite crystals may acquire a high concentration of positively charged vacancies with the complementary negatively charged halide ions pushed to the surface. This charge separation near the surface generates an electric field that can induce an increase of optical band gap in the surface layers relative to the bulk. We found that the charge separation, electric field, and the amplitude of shift in the bandgap strongly depend on the halides and organic moieties of perovskite crystals. Our findings reveal the peculiarity of surface effects that are currently limiting the applications of perovskite crystals and more importantly explain their origins, thus enabling viable surface passivation strategies to remediate them.

  3. Nano sized La2Co2O6 double perovskite synthesized by sol gel method

    Science.gov (United States)

    Solanki, Neha; Lodhi, Pavitra Devi; Choudhary, K. K.; Kaurav, Netram

    2018-05-01

    We report here the synthesis of double perovskite La2Co2O6 (LCO) compound by a sol gel route method. The double perovskite structure of LCO system was confirmed via X-ray diffraction (XRD) analysis. Further, the lattice parameter, unit cell volume and bond length were refined by means of rietveld analysis using the full proof software. Debye Scherer formula was used to determine the particle size. The compound crystallized in triclinic structure with space group P-1 in ambient condition. We also obtained Raman modes from XRD spectra of poly-crystalline LCO sample. These results were interpreted for the observation of phonon excitations in this compound.

  4. Parity-Forbidden Transitions and Their Impact on the Optical Absorption Properties of Lead-Free Metal Halide Perovskites and Double Perovskites.

    Science.gov (United States)

    Meng, Weiwei; Wang, Xiaoming; Xiao, Zewen; Wang, Jianbo; Mitzi, David B; Yan, Yanfa

    2017-07-06

    Using density functional theory calculations, we analyze the optical absorption properties of lead (Pb)-free metal halide perovskites (AB 2+ X 3 ) and double perovskites (A 2 B + B 3+ X 6 ) (A = Cs or monovalent organic ion, B 2+ = non-Pb divalent metal, B + = monovalent metal, B 3+ = trivalent metal, X = halogen). We show that if B 2+ is not Sn or Ge, Pb-free metal halide perovskites exhibit poor optical absorptions because of their indirect band gap nature. Among the nine possible types of Pb-free metal halide double perovskites, six have direct band gaps. Of these six types, four show inversion symmetry-induced parity-forbidden or weak transitions between band edges, making them not ideal for thin-film solar cell applications. Only one type of Pb-free double perovskite shows optical absorption and electronic properties suitable for solar cell applications, namely, those with B + = In, Tl and B 3+ = Sb, Bi. Our results provide important insights for designing new metal halide perovskites and double perovskites for optoelectronic applications.

  5. Development of organic-inorganic double hole-transporting material for high performance perovskite solar cells

    Science.gov (United States)

    Jo, Jea Woong; Seo, Myung-Seok; Jung, Jae Woong; Park, Joon-Suh; Sohn, Byeong-Hyeok; Ko, Min Jae; Son, Hae Jung

    2018-02-01

    The control of the optoelectronic properties of the interlayers of perovskite solar cells (PSCs) is crucial for achieving high photovoltaic performances. Of the solution-processable interlayer candidates, NiOx is considered one of the best inorganic hole-transporting layer (HTL) materials. However, the power conversion efficiencies (PCEs) of NiOx-based PSCs are limited by the unfavorable contact between perovskite layers and NiOx HTLs, the high density of surface trap sites, and the inefficient charge extraction from perovskite photoactive layers to anodes. Here, we introduce a new organic-inorganic double HTL consisting of a Cu:NiOx thin film passivated by a conjugated polyelectrolyte (PhNa-1T) film. This double HTL has a significantly lower pinhole density and forms better contact with perovskite films, which results in enhanced charge extraction. As a result, the PCEs of PSCs fabricated with the double HTL are impressively improved up to 17.0%, which is more than 25% higher than that of the corresponding PSC with a Cu:NiOx HTL. Moreover, PSCs with the double HTLs exhibit similar stabilities under ambient conditions to devices using inorganic Cu:NiOx. Therefore, this organic-inorganic double HTL is a promising interlayer material for high performance PSCs with high air stability.

  6. Double-layered ZnO nanostructures for efficient perovskite solar cells

    KAUST Repository

    Mahmood, Khalid; S. Swain, Bhabani; Amassian, Aram

    2014-01-01

    To date, a single layer of TiO2 or ZnO has been the most successful implementations of any electron transport layer (ETL) in solution-processed perovskite solar cells. In a quest to improve the ETL, we explore a new nanostructured double-layer ZnO film for mesoscopic perovskite-based thin film photovoltaics. This approach yields a maximum power conversion efficiency of 10.35%, which we attribute to the morphology of oxide layer and to faster electron transport. The successful implementation of the low-temperature hydrothermally processed double-layer ZnO film as ETL in perovskite solar cells highlights the opportunities to further improve the efficiencies by focusing on the ETL in this rapidly developing field. This journal is

  7. Dielectric relaxation in double perovskite oxide, Ho2CdTiO6

    Indian Academy of Sciences (India)

    Double perovskite oxide with general formula, A2B B O6 unit structure .... oclinic phase at room temperature with cell parameters a = 9·3858, b .... by the empirical relation ε∗ = ε∞ + ... portional to the resistance of that process, while the peak.

  8. Structural, electronic and magnetic properties of the series of double perovskites (Ca,Sr){sub 2−x}La{sub x}FeIrO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Bufaiçal, L., E-mail: lbufaical@ufg.br [Instituto de Física, Universidade Federal de Goiás, 74001-970 Goiânia, GO (Brazil); Adriano, C. [Instituto de Física “Gleb Wataghin”, UNICAMP, 13083-859 Campinas, SP (Brazil); Lora-Serrano, R. [Instituto de Física, Universidade Federal de Uberlândia, 38400-902 Uberlândia, MG (Brazil); Duque, J.G.S. [Núcleo de Física, Universidade Federal de Sergipe, Campus Itabaiana, 49500-000 Itabaiana, SE (Brazil); Mendonça-Ferreira, L. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-170 Santo André, SP (Brazil); Rojas-Ayala, C.; Baggio-Saitovitch, E.; Bittar, E.M. [Centro Brasileiro de Pesquisas Físicas, 22290-180 Rio de Janeiro, RJ (Brazil); Pagliuso, P.G. [Instituto de Física “Gleb Wataghin”, UNICAMP, 13083-859 Campinas, SP (Brazil)

    2014-04-01

    Polycrystalline samples of the series of double perovskites Sr{sub 2−x}La{sub x}FeIrO{sub 6} were synthesized. Their structural, electronic and magnetic properties were investigated by X-ray powder diffraction, Mössbauer spectroscopy, magnetic susceptibility, heat capacity and electrical resistivity experiments. The compounds crystallize in a monoclinic structure and were fitted in space group P2{sub 1}/n, with a significant degree of Fe/Ir cationic disorder. As in Ca{sub 2−x}La{sub x}FeIrO{sub 6} the Sr-based system seems to evolve from an antiferromagnetic ground state for the end members (x=0.0 and x=2.0) to a ferrimagnetic order in the intermediate regions (x∼1). Since Mössbauer spectra indicate that Fe valence remains 3+ with doping, this tendency of change in the nature of the microscopic interaction could be attributed to Ir valence changes, induced by La{sup 3+} electrical doping. Upon comparing both Ca and Sr series, Sr{sub 2−x}La{sub x}FeIrO{sub 6} is more structurally homogenous and presents higher magnetization and transition temperatures. Magnetic susceptibility measurements at high temperatures on Sr{sub 1.2}La{sub 0.8}FeIrO{sub 6} indicate a very high ferrimagnetic Curie temperature T{sub C}∼700K. For the Sr{sub 2}FeIrO{sub 6} compound, electrical resistivity experiments under applied pressure suggest that this material might be a Mott insulator. - Graphical abstract: The Weiss constant as a function of La doping for the (Ca,Sr){sub 2−x}La{sub x}FeIrO{sub 6} series, indicating changes in Fe–Ir magnetic coupling on both families. - Highlights: • The double perovskite series (Ca,Sr){sub 2−x}La{sub x}FeIrO{sub 6} were synthesized. • Changes in the Fe-Ir magnetic coupling due to La doping on both series. • Evidence of high T{sub C} on Sr{sub 1.2}La{sub 0.8}FeIrO{sub 6}. • Indication of Mott insulator behavior on Sr{sub 2}FeIrO{sub 6}.

  9. Study of disorder effects in La substituted Ca2FeMoO6 ferrimagnet using magnetic and transport measurements

    International Nuclear Information System (INIS)

    Muthuselvam, I. Panneer; Poddar, Asok; Bhowmik, R.N.

    2009-01-01

    We have substituted non-magnetic La in ferrimagnetic Ca 2-x La x FeMoO 6 double perovskite. The cell volume showed expansion with the increase of La substitution in monoclinic crystal structure and space group P2 I /n. Analysis of XRD spectrum indicated the increase of disorder in lattice structure. Surface structure of the material is modified from adhesive type for x = 0 sample to brittle type in La doped samples, suggesting the increase of grain boundary contributions. DC magnetization and ac susceptibility measurements showed reduction of magnetic moment, enhancement of T C , and cluster spin-glass phase in the ferromagnetic matrix. These experimental results confirmed the enhancement of magnetic disorder in La doped samples. The reduction of metallic nature in the compound provided additional support of enhanced disorder upon La doping in double perovskite structure.

  10. NMR and XAS Study of Fe-Mo Double Perovskites

    International Nuclear Information System (INIS)

    Zajac, D.A.; Kapusta, C.; Borowiec, M.; Sikora, M.; Marquina, C.; Blasco, J.; Ibarra, M.R.

    2005-01-01

    The results of NMR and XAS measurements of the A 2 FeMoO 6 double perovskites (DP) (A 2 =Sr 2 , SrBa, Ba 2 , Ca 2 ) at the Fe and Mo K edges are reported and the information on the individual site electronic and magnetic properties is analysed. The compounds studied belong to the family of materials exhibiting a high field '' colossal '' magnetoresistance as well as a low field '' giant '' magnetoresistance. Magnetoresistive properties of the compounds arise from their half-metallicity, i.e. only one spin direction being populated in the conduction band, which consists of overlapping spin down 3d Fe, 2p O and 4d Mo electron bands. Within the model, a spin-down electron undergoes a fast hopping through unoccupied oxygen 2p orbitals between Fe 3+ (3d 5 - spin up) and Mo 6+ (4d 0 ) ionic cores. This mechanism implicates an anti-parallel coupling of the Fe and Mo spins and leads to non-integer magnetic moments and a metallic character below TC. The interaction, in analogy with the '' double exchange '' (DE) in manganites, is called '' double exchange-like '' interaction. The superexchange interaction (SE) is also expected to be present, resulting also in an anti-parallel coupling of 3d Fe 3+ and 4d Mo 5+ spins through occupied oxygen 2p orbitals. The insulating character of SE is connected with an increase of the tilt angle of the Fe-O-Mo bond, which is related to a change of the structural tolerance factor f and results in structural distortions. The molybdenum NMR measurements revealed the existence of a non-integer magnetic moment at Mo and Fe, which can be attributed to the DE-like interaction. However, experiments using Moessbauer spectroscopy have shown the existence of two Fe ionisation states - with integer (SE) and non integer (DE) magnetic moments. The 95 Mo and 97 Mo NMR measurements on A 2 FeMoO 6 (A 2 =Sr 2 , SrBa, Ba 2 , Ca 2 ) presented in this work show different values of the Mo hyperfine field and the corresponding magnetic moment. This is attributed

  11. On the bonding nature of electron states for the Fe-Mo double perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Carvajal, E.; Cruz-Irisson, M. [ESIME-Culhuacán, Instituto Politécnico Nacional, Av. Santa Ana 1000, C.P. 04430, México, D.F. (Mexico); Oviedo-Roa, R. [Programa de Investigación en Ingeniería Molecular, Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas Norte 152, C.P. 07730, México, D.F. (Mexico); Navarro, O. [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, A.P. 70-360, 04510, México, D.F. (Mexico)

    2014-05-15

    The electronic transport as well as the effect of an external magnetic field has been investigated on manganese-based materials, spinels and perovskites. Potential applications of double perovskites go from magnetic sensors to electrodes in solid-oxide fuel cells; besides the practical interests, it is known that small changes in composition modify radically the physical properties of double perovskites. We have studied the Sr{sub 2}FeMoO{sub 6} double perovskite compound (SFMO) using first-principles density functional theory. The calculations were done within the generalized gradient approximation (GGA) scheme with the Perdew-Burke-Ernzerhof (PBE) functional. We have made a detailed analysis of each electronic state and the charge density maps around the Fermi level. For the electronic properties of SFMO it was used a primitive cell, for which we found the characteristic half-metallic behavior density of states composed by e{sub g} and t{sub 2g} electrons from Fe and Mo atoms. Those peaks were tagged as bonding or antibonding around the Fermi level at both, valence and conduction bands.

  12. Role of rare-earth ionic radii on the spin-phonon coupling in multiferroic ordered double perovskites

    Czech Academy of Sciences Publication Activity Database

    Macedo Filho, R.B.; Barbosa, D.A.B.; Reichlová, Helena; Martí, Xavier; de Menezes, A.S.; Ayala, A.P.; Paschoal, C.W.A.

    2015-01-01

    Roč. 7, č. 2 (2015), 075201 ISSN 2053-1591 Institutional support: RVO:68378271 Keywords : double perovskites * spin-phonon coupling * multiferroics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.968, year: 2015

  13. First Principles Study of Electronic and Magnetic Structures in Double Perovskites

    Science.gov (United States)

    Ball, Molly

    At present, electronic devices are reaching their storage and processing limit causing a major push to find materials that can be used in the next generation of devices. Double perovskites with A2BB'O 6 stoichiometry form one of the leading classes of materials currently being studied as a potential candidate because of their extremely wide range and tunability of functional properties, along with economic and highly scalable synthesis routes. Having a thorough understanding of their electronic and magnetic structure and their dependence on composition and local structure is the basis for targeted development of novel and optimized double perovskites. While the body of knowledge and rules within the field of materials chemistry has enabled many previous discoveries, recent developments within density functional theory (DFT) allow by now a rather realistic description of the electronic and magnetic properties of materials and especially identification of their origin from geometry and orbital structure. This thesis details computational work based on DFT within several collaborative studies to better understand the electronic and magnetic properties of double perovskites and related materials that show promise for future use in multifunctional devices. First, we will begin with a general introduction to the double perovskite structure, their properties, and the computational methods used to study them. In the next section, we will look at the case of the antiferromagnetic, insulating double perovskite Sr2CoOsO6, where measurements showed that the transition metal ions in the two sublattices undergo magnetic ordering independently of each other, indicating weak magnetic short-range coupling and a dominance of longer-range interactions, which has previously not been observed. Here, we performed DFT calculations to extract the exchange strengths between the ions and explain this unique dominance of the long-range interactions. Then, we will look at studies done on thin

  14. Transport and dielectric properties of double perovskite Pr2CoFeO6

    Science.gov (United States)

    Pal, Arkadeb; Singh, A.; Gangwar, V. K.; Chatterjee, Sandip

    2018-04-01

    The transport and dielectric measurements have been investigated for the polycrystalline double perovskite Pr2CoFeO6. In the temperature dependent resistivity measurement, we have observed semiconducting nature of the sample with activation energy 0.246 eV. In dielectric measurement as a function of temperature, a giant value of dielectric constant is observed at room temperature, the frequency dependence suggests a relaxor type dielectric relaxation.

  15. Ferromagnetic coupling strength and electron-doping effects in double perovskites

    International Nuclear Information System (INIS)

    Fontcuberta, J.; Rubi, D.; Frontera, C.; Garcia-Munoz, J.L.; Wojcik, M.; Jedryka, E.; Nadolski, S.; Izquierdo, M.; Avila, J.; Asensio, M.C.

    2005-01-01

    We review experiments and results on ferromagnetic and metallic A 2 FeMoO 6 double perovskites that made it possible to obtain a detailed understanding of the nature of the ferromagnetic coupling and paved the way for further enhancement of the Curie temperature. We show that appropriate chemical substitutions, combined with detailed structural, magnetotransport and spectroscopic data allow us to map quite a complete picture of the properties of these oxides

  16. Structural phase transitions in the ordered double perovskite Sr2MnTeO6

    International Nuclear Information System (INIS)

    Ortega-San Martin, L; Chapman, J P; Hernandez-Bocanegra, E; Insausti, M; Arriortua, M I; Rojo, T

    2004-01-01

    The crystal structure of the ordered double perovskite Sr 2 MnTeO 6 has been refined at ambient temperature from high resolution neutron and x-ray powder diffraction data in the monoclinic space group P 12 1 /n 1 with a 5.7009(1) A, b = 5.6770(1) A, c = 8.0334(1) A and β = 90.085(1) deg. This represents a combination of in-phase (+) and out-of-phase (-) rotations of virtually undistorted MnO 6 and TeO 6 octahedra in the (-+) sense about the axes of the ideal cubic perovskite. High temperature x-ray powder diffraction shows three structural phase transitions at approximately 250, 550 and 675 deg. C, each corresponding to the disappearance of rotations about one of these axes. The first transition was analysed by differential scanning calorimetry and showed a thermal hysteresis with an enthalpy of 0.55 J g -1 . We propose the (P12 1 /n1 → I12/m1 → I4/m → Fm3barm) sequence of structural transitions which has not been previously reported for a double perovskite oxide

  17. High-Pressure Band-Gap Engineering in Lead-Free Cs 2 AgBiBr 6 Double Perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Li, Qian [Department of Chemistry, Southern University of Science and Technology, SUSTech, Shenzhen Guangdong 518055 P.R. China; College of Chemistry, Nankai University, Tianjin 300071 P.R. China; Wang, Yonggang [High Pressure Synergetic Consortium, HPSynC, Geophysical Laboratory, Carnegie Institution of Washington, Argonne IL 60439 USA; Pan, Weicheng [Wuhan National Laboratory for Optoelectronics, WNLO and School of Optical and Electronic Information, Huazhong University of Science and Technology, HUST, Wuhan 430074 P.R. China; Yang, Wenge [High Pressure Synergetic Consortium, HPSynC, Geophysical Laboratory, Carnegie Institution of Washington, Argonne IL 60439 USA; Zou, Bo [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 P.R. China; Tang, Jiang [Wuhan National Laboratory for Optoelectronics, WNLO and School of Optical and Electronic Information, Huazhong University of Science and Technology, HUST, Wuhan 430074 P.R. China; Quan, Zewei [Department of Chemistry, Southern University of Science and Technology, SUSTech, Shenzhen Guangdong 518055 P.R. China

    2017-11-15

    Novel inorganic lead-free double perovskites with improved stability are regarded as alternatives to state-of-art hybrid lead halide perovskites in photovoltaic devices. The recently discovered Cs2AgBiBr6 double perovskite exhibits attractive optical and electronic features, making it promising for various optoelectronic applications. However, its practical performance is hampered by the large band gap. In this work, remarkable band gap narrowing of Cs2AgBiBr6 is, for the first time, achieved on inorganic photovoltaic double perovskites through high pressure treatments. Moreover, the narrowed band gap is partially retainable after releasing pressure, promoting its optoelectronic applications. This work not only provides novel insights into the structure–property relationship in lead-free double perovskites, but also offers new strategies for further development of advanced perovskite devices.

  18. High-pressure band-gap engineering in lead-free Cs{sub 2}AgBiBr{sub 6} double perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Li, Qian [Department of Chemistry, Southern University of Science and Technology, SUSTech, Shenzhen, Guangdong (China); College of Chemistry, Nankai University, Tianjin (China); Wang, Yonggang; Yang, Wenge [High Pressure Synergetic Consortium, HPSynC, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, IL (United States); Pan, Weicheng; Tang, Jiang [Wuhan National Laboratory for Optoelectronics, WNLO and School of Optical and Electronic Information, Huazhong University of Science and Technology, HUST, Wuhan (China); Zou, Bo [State Key Laboratory of Superhard Materials, Jilin University, Changchun (China); Quan, Zewei [Department of Chemistry, Southern University of Science and Technology, SUSTech, Shenzhen, Guangdong (China)

    2017-12-11

    Novel inorganic lead-free double perovskites with improved stability are regarded as alternatives to state-of-art hybrid lead halide perovskites in photovoltaic devices. The recently discovered Cs{sub 2}AgBiBr{sub 6} double perovskite exhibits attractive optical and electronic features, making it promising for various optoelectronic applications. However, its practical performance is hampered by the large band gap. In this work, remarkable band gap narrowing of Cs{sub 2}AgBiBr{sub 6} is, for the first time, achieved on inorganic photovoltaic double perovskites through high pressure treatments. Moreover, the narrowed band gap is partially retainable after releasing pressure, promoting its optoelectronic applications. This work not only provides novel insights into the structure-property relationship in lead-free double perovskites, but also offers new strategies for further development of advanced perovskite devices. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Double perovskites overtaking the single perovskites: A set of new solar harvesting materials with much higher stability and efficiency

    Science.gov (United States)

    Kangsabanik, Jiban; Sugathan, Vipinraj; Yadav, Anuradha; Yella, Aswani; Alam, Aftab

    2018-05-01

    Solar energy plays an important role in substituting the ever declining source of fossil fuel energy. Finding novel materials for solar cell applications is an integral part of photovoltaic research. Hybrid lead halide perovskites are one of, if not the most, well sought material in the photovoltaic research community. Its unique intrinsic properties, flexible synthesis techniques, and device fabrication architecture made the community highly buoyant over the past few years. Yet, there are two fundamental issues that still remain a concern, i.e., the stability in external environment and the toxicity due to Pb. This led to a search for alternative materials. More recently, double perovskite [A2B B'X6 (X =Cl, Br, I)] materials have emerged as a promising choice. Few experimental synthesis and high throughput computational studies have been carried out to check for promising candidates of this class. The main outcome from these studies, however, can essentially be summarized into two categories: (i) either they have an indirect band gap or (ii) a direct but large optical band gap, which is not suitable for solar devices. Here we propose a large set of stable double perovskite materials, Cs2B B 'X6 (X =Cl, Br, I), which show indirect to direct band gap transition via small Pb+2 doping at both B and B'sites. This is done by careful band (orbital) engineering using first-principles calculations. This kind of doping has helped to change the topology of the band structure, triggering an indirect to direct transition that is optically allowed. It also reduces the band gap significantly, bringing it well into the visible region. We also simulated the optical absorption spectra of these systems and found a comparable/higher absorption coefficient and solar efficiency with respect to the state of the art photovoltaic absorber material CH3NH3PbI3 . A number of materials Cs2(B0.75Pb0.25) (B0.75'Pb0.25) X6 (for various combinations of B ,B ', and X ) are found to be promising

  20. Tungsten and molybdenum double perovskites as pinning centers in melt-textured Y123

    Energy Technology Data Exchange (ETDEWEB)

    Sawh, Ravi-Persad; Weinstein, Roy; Parks, Drew; Gandini, Alberto; Ren, Yanru; Rusakova, Irene

    2003-01-01

    Y123+30 mol% Y211 powders were doped with tungsten and platinum, and textured. Microstructure studies show the presence of profuse spherical deposits, 200-300 nm in diameter. These deposits were identified as (W{sub 0.5}Pt{sub 0.5})YBa{sub 2}O{sub 6}, a double perovskite. The size of the W-rich deposits is independent of the W doping level. There is no substitution of W into the Y123 matrix. For Pt doping >0.5 wt.%, trapped field is observed to increase monotonically up to 40% for W doping of up to 0.48 wt.%. We conservatively estimate that this corresponds to a 60% increase in J{sub c} at constant field. Thus (W{sub 0.5}Pt{sub 0.5})YBa{sub 2}O{sub 6} double perovskites deposits act as pinning centers. Similar studies of molybdenum doping indicate deposits 200-300 nm, of (Mo{sub 0.5}Pt{sub 0.5})YBa{sub 2}O{sub 6}, also a double perovskite. The (W{sub 0.5}Pt{sub 0.5})YBa{sub 2}O{sub 6} and (Mo{sub 0.5}Pt{sub 0.5})YBa{sub 2}O{sub 6} deposits are remarkably similar to the (U{sub 0.6}Pt{sub 0.4})YBa{sub 2}O{sub 6} deposits found earlier in U-doped Y123. Therefore, W and Mo are suitable non-radioactive substitutes for U.

  1. Intrinsic Defect Physics in Indium-based Lead-free Halide Double Perovskites.

    Science.gov (United States)

    Xu, Jian; Liu, Jian-Bo; Liu, Bai-Xin; Huang, Bing

    2017-09-21

    Lead-free halide double perovskites (HDPs) are expected to be promising photovoltaic (PV) materials beyond organic-inorganic halide perovskite, which is hindered by its structural instability and toxicity. The defect- and stability-related properties of HDPs are critical for the use of HDPs as important PV absorbers, yet their reliability is still unclear. Taking Cs 2 AgInBr 6 as a representative, we have systemically investigated the defect properties of HDPs by theoretical calculations. First, we have determined the stable chemical potential regions to grow stoichiometric Cs 2 AgInBr 6 without structural decomposition. Second, we reveal that Ag-rich and Br-poor are the ideal chemical potential conditions to grow n-type Cs 2 AgInBr 6 with shallow defect levels. Third, we find the conductivity of Cs 2 AgInBr 6 can change from good n-type, to poorer n-type, to intrinsic semiconducting depending on the growth conditions. Our studies provided important guidance for experiments to fabricate Pb-free perovskite-based solar cell devices with superior PV performances.

  2. Large intragrain magnetoresistance above room temperature in the double perovskite Ba2FeMoO6

    International Nuclear Information System (INIS)

    Maignan, A.; Raveau, B.; Martin, C.; Hervieu, M.

    1999-01-01

    Large intragrain magnetoresistance (MR) in the ordered double perovskite, Ba 2 FeMo 6 , is shown for the first time. The latter appears near T c (340 K), i.e., above room temperature. This effect originates from a double-exchange-like mechanism, based on antiferromagnetic coupling of localized high spin 3d 5 Fe 3+ , and itinerant 4d 1 Mo 5+ species. Besides this bulk MR, low field tunneling MR at lower temperatures (T 2 FeMoO 6 . Such a coexistence of both effects, intragrain and intergrain magnetoresistance, might extend to all members of this double perovskite family, suggesting the possibility of optimizing the MR for working at room temperature in a low magnetic field, by tuning the T c of solid solutions of such perovskites

  3. Correlation between magnetic properties and nuclear magnetic resonance observations in Sr2FeMoO6 double perovskite

    International Nuclear Information System (INIS)

    Colis, S.; Pourroy, G.; Panissod, P.; Meny, C.; Dinia, A.

    2004-01-01

    We present the influence of the sintering temperature on the magnetic properties of Sr 2 FeMoO 6 double perovskite, on the basis of magnetization and nuclear magnetic resonance (NMR) measurements. Interestingly, the saturation magnetization originating mainly from the Fe moments is correlated with the amount of Mo magnetic moments observed by NMR measurements. We show that there is an optimum temperature of 1000 deg. C for which the reaction leading to the double perovskite becomes more advanced and/or the number of antisite defects is minimum

  4. Chemical Origin of the Stability Difference between Copper(I)- and Silver(I)-Based Halide Double Perovskites.

    Science.gov (United States)

    Xiao, Zewen; Du, Ke-Zhao; Meng, Weiwei; Mitzi, David B; Yan, Yanfa

    2017-09-25

    Recently, Cu I - and Ag I -based halide double perovskites have been proposed as promising candidates for overcoming the toxicity and instability issues inherent within the emerging Pb-based halide perovskite absorbers. However, up to date, only Ag I -based halide double perovskites have been experimentally synthesized; there are no reports on successful synthesis of Cu I -based analogues. Here we show that, owing to the much higher energy level for the Cu 3d 10 orbitals than for the Ag 4d 10 orbitals, Cu I atoms energetically favor 4-fold coordination, forming [CuX 4 ] tetrahedra (X=halogen), but not 6-fold coordination as required for [CuX 6 ] octahedra. In contrast, Ag I atoms can have both 6- and 4-fold coordinations. Our density functional theory calculations reveal that the synthesis of Cu I halide double perovskites may instead lead to non-perovskites containing [CuX 4 ] tetrahedra, as confirmed by our material synthesis efforts. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Crystal structures of the double perovskites Ba2Sr1-x Ca x WO6

    International Nuclear Information System (INIS)

    Fu, W.T.; Akerboom, S.; IJdo, D.J.W.

    2007-01-01

    Structures of the double perovskites Ba 2 Sr 1- x Ca x WO 6 have been studied by the profile analysis of X-ray diffraction data. The end members, Ba 2 SrWO 6 and Ba 2 CaWO 6 , have the space group I2/m (tilt system a 0 b - b - ) and Fm3-barm (tilt system a 0 a 0 a 0 ), respectively. By increasing the Ca concentration, the monoclinic structure transforms to the cubic one via the rhombohedral R3-bar phase (tilt system a - a - a - ) instead of the tetragonal I4/m phase (tilt system a 0 a 0 c - ). This observation supports the idea that the rhombohedral structure is favoured by increasing the covalency of the octahedral cations in Ba 2 MM'O 6 -type double perovskites, and disagrees with a recent proposal that the formation of the π-bonding, e.g., d 0 -ion, determines the tetragonal symmetry in preference to the rhombohedral one. - Graphical abstract: Enlarged sections showing the evolution of the basic (222) and (400) reflections in Ba 2 Sr 1- x Ca x WO 6 . Tick marks below are the positions of Bragg's reflections calculated using the space groups I2/m (x=0), R3-bar (x=0.25, 0.5 and 0.75) and Fm3-barm (x=1), respectively

  6. Magnetoelastic coupling in Sr2(Fe1-xCrx)ReO6 double perovskites

    International Nuclear Information System (INIS)

    Serrate, D; Teresa, J M De; Algarabel, P A; Marquina, C; Blasco, J; Ibarra, M R; Galibert, J

    2007-01-01

    We have investigated magnetoelastic coupling in Sr 2 (Fe 1-x Cr x )ReO 6 polycrystalline double perovskites. The end compound, Sr 2 CrReO 6 , shows a high ferromagnetic transition temperature of 635 K and is thought to exhibit a nearly half-metallic conduction band. We probed the unexpected high orbital moment borne by the Re atom by means of volume and anisotropic magnetostriction measurements in magnetic fields up to 12 T. Our magnetostriction results can be explained by the existence of a large spin-orbit coupling which, in combination with crystal-field effects, produces a single-ion type magnetostrictive response. The Re orbital moment triggers a greatly enhanced magnetocrystalline anisotropy compared to other ferromagnetic double perovskites. From our magnetostriction data, the temperature dependence of the coercive field as a function of Cr-doping is obtained. We discovered that the coercive field increases as Fe is replaced with Cr, which is linked to a strong enhancement of the magnetic anisotropy. This suggests a close relationship between the Fe[Cr]-O-Re coupling and the magnetic anisotropy. We also analysed the impact of the Re orbital moment on the spin-dependent transport across Sr 2 CrReO 6 grain boundaries. The present work opens up the possible use of these compounds for magnetostrictive applications in a wide temperature and magnetic field range

  7. Comparative Study of Electronic Structure and Magnetic Properties of Osmate Double Perovskites: Ca2FeOsO6 versus Ca2Co(Ni)OsO6

    Science.gov (United States)

    Samanta, Kartik; Saha-Dasgupta, Tanusri

    2018-04-01

    Employing density functional theory, we study the trend in the electronic and magnetic properties of 3d-5d double perovskites, upon varying the 3d element for a fixed choice of 5d element, namely Ca2BOsO6 (B = Fe/Co/Ni). While all three compounds are reported to be ferrimagnets, the magnetic transition temperature of Ca2FeOsO6 is reported to be 2-2.4 times larger than that of Ca2CoOsO6 or Ca2NiOsO6. Our first-principles study provides microscopic insight into this trend. This trend is found to be caused by the downward shift in the position of d level energies of the B site element with respect to that of the Os t2g level upon moving across the 3d series from Fe to Co and Ni. This in turn changes the nominal valence of the Os ion from 5+ in Ca2FeOsO6 to 6+ in Ca2CoOsO6 and Ca2NiOsO6, resulting in differing superexchange paths between Ca2FeOsO6 and Ca2Co(Ni)OsO6, and additionally enabling the hybridization-mechanism-driven magnetism in Ca2FeOsO6. These together significantly enhance the magnetic transition temperature in Ca2FeOsO6 compared with that in Ca2Co(Ni)OsO6.

  8. Experiments on ferrimagnetism

    International Nuclear Information System (INIS)

    Kraftmakher, Yaakov

    2013-01-01

    Ferrimagnetism undoubtedly deserves a proper place in the undergraduate laboratory on electricity and magnetism. Four student experiments on ferrimagnetism are considered: (i) the hysteresis loops and permeability of a ‘soft’ ferrite; (ii) the differential permeability versus a dc bias; (iii) the frequency dependence of the complex permeability and (iv) the electromagnetic interference suppression by ferrite chokes and beads. Two ferrite cores taken off a low-frequency choke and a power cord are used. The measurements are simple and straightforward and show the important properties of ferrites and their applications. The values of the permeability of the ferrite core determined in experiments (i)–(iii) are in reasonable agreement. The frequency dependence of the complex permeability of the ferrites is similar to that given by the manufacturers. The capability of absorbing electromagnetic waves in a definite frequency range shown in experiment (iv) demonstrates one of the principles of Stealth technology. The equipment necessary for the experiments can be found in many student laboratories. (paper)

  9. Magnetic and structural behavior of Sr2ZrMnO6 double perovskite

    International Nuclear Information System (INIS)

    Llamosa, D.P.; Landinez Tellez, D.A.; Roa-Rojas, J.

    2009-01-01

    We report synthesis and characterization of new Sr 2 ZrMnO 6 manganite-like material. Samples were produced by the solid state reaction method with sinterization temperatures up to 1400 deg. C. X-ray diffraction experiments reveal that structure belongs to the perovskite system, space group Fm3-barm(no. 225). Lattice parameter a=7.86A was obtained by means of Rietveld-type refinement, through the GSAS code. Magnetic properties were studied by using an MPMS Quantum Design SQUID. From measurements of magnetization as a function of temperature, we determine the occurrence of a paramagnetic-antiferromagnetic transition with Neel temperature 50 K. Curie-Weiss fitting permitted to obtain the magnetic characteristic parameters. At temperature regimes below the Neel temperature, strong evidences of frustration and an irreversibility temperature between zero field cooling (ZFC) and field cooling (FC) measurements were observed. Curves of magnetization as a function of applied field were performed at T=4K. Results show a hysteretic feature for Sr 2 ZrMnO 6 magnetic material. This response is attributed to formation of magnetic clusters as a consequence of cationic (magnetic and no magnetic) disorder along the double perovskite structure.

  10. Mesoscopic Oxide Double Layer as Electron Specific Contact for Highly Efficient and UV Stable Perovskite Photovoltaics.

    Science.gov (United States)

    Tavakoli, Mohammad Mahdi; Giordano, Fabrizio; Zakeeruddin, Shaik Mohammed; Grätzel, Michael

    2018-04-11

    The solar to electric power conversion efficiency (PCE) of perovskite solar cells (PSCs) has recently reached 22.7%, exceeding that of competing thin film photovoltaics and the market leader polycrystalline silicon. Further augmentation of the PCE toward the Shockley-Queisser limit of 33.5% warrants suppression of radiationless carrier recombination by judicious engineering of the interface between the light harvesting perovskite and the charge carrier extraction layers. Here, we introduce a mesoscopic oxide double layer as electron selective contact consisting of a scaffold of TiO 2 nanoparticles covered by a thin film of SnO 2 , either in amorphous (a-SnO 2 ), crystalline (c-SnO 2 ), or nanocrystalline (quantum dot) form (SnO 2 -NC). We find that the band gap of a-SnO 2 is larger than that of the crystalline (tetragonal) polymorph leading to a corresponding lift in its conduction band edge energy which aligns it perfectly with the conduction band edge of both the triple cation perovskite and the TiO 2 scaffold. This enables very fast electron extraction from the light perovskite, suppressing the notorious hysteresis in the current-voltage ( J-V) curves and retarding nonradiative charge carrier recombination. As a result, we gain a remarkable 170 mV in open circuit photovoltage ( V oc ) by replacing the crystalline SnO 2 by an amorphous phase. Because of the quantum size effect, the band gap of our SnO 2 -NC particles is larger than that of bulk SnO 2 causing their conduction band edge to shift also to a higher energy thereby increasing the V oc . However, for SnO 2 -NC there remains a barrier for electron injection into the TiO 2 scaffold decreasing the fill factor of the device and lowering the PCE. Introducing the a-SnO 2 coated mp-TiO 2 scaffold as electron extraction layer not only increases the V oc and PEC of the solar cells but also render them resistant to UV light which forebodes well for outdoor deployment of these new PSC architectures.

  11. High-pressure crystal growth and electromagnetic properties of 5d double-perovskite Ca3OsO6

    Science.gov (United States)

    Feng, Hai Luke; Shi, Youguo; Guo, Yanfeng; Li, Jun; Sato, Akira; Sun, Ying; Wang, Xia; Yu, Shan; Sathish, Clastin I.; Yamaura, Kazunari

    2013-05-01

    Single crystals of the osmium-containing compound Ca3OsO6 have been successfully grown under high-pressure conditions, for the first time. The crystal structure of Ca3OsO6 were characterized as an ordered double-perovskite structure of space group P21/n with the Ca and Os atoms being fully ordered at the perovskite B-site. The electromagnetic analysis shows that the crystal exhibits a semiconductor-like behavior below 300 K and undergoes an antiferromagnetic transition at 50 K.

  12. Thermal stability of Dion-Jacobson mixed-metal-niobate double-layered perovskites

    International Nuclear Information System (INIS)

    Hermann, Andrew T.; Wiley, John B.

    2009-01-01

    The thermal stability and decomposition pathways of six Dion-Jacobson-related double-layered perovskites, ALaNb 2 O 7 (A = H, Li, Na, Ag) and (ACl)LaNb 2 O 7 (A = Fe, Cu), are investigated. These compounds are made by low temperature ( 2 O 7 . All the compounds are low temperature phases with some of them exhibiting decomposition exotherms consistent with metastability. Decomposition temperatures and reactions pathways vary with the identity of A with most decompositions resulting in the formation of a niobate (containing A) and LaNbO 4 . Results from differential scanning calorimetry and high temperature X-ray powder diffraction studies are presented and structural parameters pertinent to compound stability discussed

  13. Ab-initio study of double perovskite Ba2YSbO6

    Science.gov (United States)

    Mondal, Golak; Jha, D.; Himanshu, A. K.; Lahiri, J.; Singh, B. K.; Kumar, Uday; Ray, Rajyavardhan

    2018-04-01

    The density functional theory with generalized gradient approximation has been used to investigate the electronic structure of double perovskite oxide Ba2YSbO6 (BYS) synthesized in polycrystalline form by solid state reaction. Structural characterization of the compound was done through X-ray diffraction (XRD) followed by Riedvelt analysis of the XRD pattern. The crystal structure is cubic, space group being Fm-3m (No. 225) with the lattice parameter, a = 8.424 Å. Optical band-gap of this system has been calculated using UV-Vis Spectroscopy and Kubelka-Munk (KM) function, having the value 4.56eV. A detailed study of the electronic properties has also been carried out using the Full-Potential Linear Augmented Plane Wave (FPLAPW) as implemented in WIEN2k. BYS is found to be a large band-gap insulator with potential technological applications, such as dielectric resonators and filters in microwave applications.

  14. Electronic Structure of the Double Perovskite Ba2Er(Nb,Sb)O6

    International Nuclear Information System (INIS)

    Rebaza, A V Gil; Toro, C E Deluque; Téllez, D A Landínez; Roa-Rojas, J

    2014-01-01

    In this work, we present a detailed study of the structural and the electronic structure of the double perovskite Ba 2 Er(Nb,Sb)O 6 . All calculations were performed with the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) based on the Density Functional Theory (DFT). From the minimization of energy as a function of volume using the Murnaghan's state equation has been obtained the equilibrium lattice parameter and the bulk modulus of these compounds. The study of the electronic structure was based in the analysis of the electronic density of states (DOS), and the density of charge, showing that these compounds have a total magnetic moment of 3.0 μ B per formula unit due to Er atoms

  15. Magnetocaloric effect in Sr2CrIrO6 double perovskite: Monte Carlo simulation

    Science.gov (United States)

    El Rhazouani, O.; Slassi, A.; Ziat, Y.; Benyoussef, A.

    2017-05-01

    Monte Carlo simulation (MCS) combined with the Metropolis algorithm has been performed to study the magnetocaloric effect (MCE) in the promising double perovskite (DP) Sr2CrIrO6 that has not so far been synthetized. This paper presents the global magneto-thermodynamic behavior of Sr2CrIrO6 compound in term of MCE and discusses the behavior in comparison to other DPs. Thermal dependence of the magnetization has been investigated for different values of reduced external magnetic field. Thermal magnetic entropy and its change have been obtained. The adiabatic temperature change and the relative cooling power have been established. Through the obtained results, Sr2CrIrO6 DP could have some potential applications for magnetic refrigeration over a wide temperature range above room temperature and at large magnetic fields.

  16. Synthesis, surface structure and optical properties of double perovskite Sr{sub 2}NiMoO{sub 6} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Lei; Wan, Yingpeng [State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123 (China); Xie, Hongde, E-mail: xiehongde@suda.edu.cn [State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123 (China); Huang, Yanlin; Yang, Li [State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123 (China); Qin, Lin [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan, 608-737 (Korea, Republic of); Seo, Hyo Jin, E-mail: hjseo@pknu.ac.kr [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan, 608-737 (Korea, Republic of)

    2016-12-15

    Highlights: • Double perovskite Sr{sub 2}NiMoO{sub 6} nanoparticles were prepared via sol-gel route. • The nanoparticles have efficient optical absorption in visible light. • The band structure and energy positions were determined. • The perovskite has efficient photocatalytic on RhB photodegradation. • Multivalent Mo and Ni-ions on the surfaces were investigated. - Abstract: Double perovskite Sr{sub 2}NiMoO{sub 6} nanoparticles were synthesized via the chemical sol-gel route. The phase formation was investigated through X-ray polycrystalline diffraction (XRD) and Rietveld refinements. The perovskite crystallized in worm-like nano-grains with the diameter of 20–50 nm. The optical properties were measured by the optical absorption spectra. The nanoparticles present an indirect allowed transition with a narrow band gap of 2.1 eV. Sr{sub 2}NiMoO{sub 6} nanoparticles have obvious photocatalytic ability on the degradation of Rhodamine B (RhB) solutions under the irradiation of visible light. The transport behaviors of the excitons were investigated from the photoluminescence spectra and the corresponding decay lifetimes. Sr{sub 2}NiMoO{sub 6} nanoparticles present several advantages for photocatalysis such as the appropriate band energy positions, the quenched luminescence, and the coexistence of multivalent ions in the lattices.

  17. Fe-Mo double perovskite: From small clusters to bulk material

    Energy Technology Data Exchange (ETDEWEB)

    Carvajal, E., E-mail: ecarvajalq@ipn.mx [Instituto Politecnico Nacional, ESIME-Culhuacan, Av. Santa Ana 1000, C.P. 04430 Mexico, D.F. (Mexico); Oviedo-Roa, R. [Programa de Investigacion en Ingenieria Molecular, Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas Norte 152, 07730 Mexico, D.F. (Mexico); Cruz-Irisson, M. [Instituto Politecnico Nacional, ESIME-Culhuacan, Av. Santa Ana 1000, C.P. 04430 Mexico, D.F. (Mexico); Navarro, O. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, A.P. 70-360, 04510 Mexico, D.F. (Mexico)

    2012-09-20

    To understand the differences in behaviour between up- and down-spin electrons observed in the half-metallic Sr{sub 2}FeMoO{sub 6} double perovskite, the density of states (DOS) was studied for the (FeO{sub 6}){sup -4} and (MoO{sub 6}){sup -6} octahedral clusters using first-principles density functional theory within the generalised gradient approximation (GGA) scheme and the Perdew-Burke-Ernzerhof (PBE) functional. Our results reveal that half-metallic character is present, even starting from an isolated (FeO{sub 6}){sup -4} cluster, and is a consequence of spin decoupling of antibonding hybridisations between iron t{sub 2g} states and oxygen p states (t{sub 2g}{sup a} states), i.e., t{sub 2g}{sup a} states lie below the Highest Occupied Molecular Orbital (HOMO) in the up-spin channel, whereas they lie above the HOMO level in the down-spin channel. The spin-induced shifting between up-spin and down-spin DOS situates the HOMO in such a way that the molecular orbitals oxygen p states (p bands) are fully spin-paired by octet electrons. Thus, the down-spin channel has metallic character because the HOMO lies just at the p bands, and the up-spin channel is semiconducting because the HOMO falls within the energy gap between the t{sub 2g}{sup a} and e{sub g}{sup a} bands. Finally, the (MoO{sub 6}){sup -6} octahedron does not inhibit the perovskite half-metallic character since this cluster has a zero total spin.

  18. O3 perovskite ceramic

    Indian Academy of Sciences (India)

    The prepared sample remains as double phases with the perovskite struc- ture. The structure ... Ferroelectric oxides with perovskite structure are the subject of many investigations. ... in optical devices and heterojunction solar cells. 1765 ...

  19. Interactions among magnetic moments in the double perovskites Sr{sub 2}Fe{sub 1+x}Mo{sub 1−x}O{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Pilo, J. [Escuela Superior de Ingeniería Mecánica y Eléctrica-Culhuacán, Instituto Politécnico Nacional Av. Santa Ana 1000, México, D. F., C. P. 04430, México (Mexico); Carvajal, E., E-mail: ecarvajalq@ipn.mx [Escuela Superior de Ingeniería Mecánica y Eléctrica-Culhuacán, Instituto Politécnico Nacional Av. Santa Ana 1000, México, D. F., C. P. 04430, México (Mexico); Oviedo-Roa, R. [Programa de Investigación en Ingeniería Molecular, Instituto Mexicano del Petróleo Eje Central Lázaro Cárdenas Norte 152, México, D. F., C. P. 07730, México (Mexico); Cruz-Irisson, M. [Escuela Superior de Ingeniería Mecánica y Eléctrica-Culhuacán, Instituto Politécnico Nacional Av. Santa Ana 1000, México, D. F., C. P. 04430, México (Mexico); Navarro, O. [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México A.P. 70-360, México, D. F., C. P. 04510, México (Mexico)

    2014-12-15

    It is well known that every double perovskite shows a characteristic magnetic behavior, as a consequence of the interactions among the magnetic moments associated with the atoms in their cells; at the same time, the electric and magnetic properties of the bulk double perovskite Sr{sub 2}FeMoO{sub 6} are well characterized. In this work we studied the iron rich compounds Sr{sub 2}Fe{sub 1+x}Mo{sub 1−x}O{sub 6}, using a supercell to model such concentrations that made Fe richer perovskites by ±66.6% and ±200%. Starting from the stoichiometric double perovskite, and modifying the Fe/Mo ratio in the compound, the study of these materials were based on the calculation of the magnetic moment at each atom, as well as the partial density of states.

  20. Interactions among magnetic moments in the double perovskites Sr2Fe1+xMo1−xO6

    International Nuclear Information System (INIS)

    Pilo, J.; Carvajal, E.; Oviedo-Roa, R.; Cruz-Irisson, M.; Navarro, O.

    2014-01-01

    It is well known that every double perovskite shows a characteristic magnetic behavior, as a consequence of the interactions among the magnetic moments associated with the atoms in their cells; at the same time, the electric and magnetic properties of the bulk double perovskite Sr 2 FeMoO 6 are well characterized. In this work we studied the iron rich compounds Sr 2 Fe 1+x Mo 1−x O 6 , using a supercell to model such concentrations that made Fe richer perovskites by ±66.6% and ±200%. Starting from the stoichiometric double perovskite, and modifying the Fe/Mo ratio in the compound, the study of these materials were based on the calculation of the magnetic moment at each atom, as well as the partial density of states

  1. Colloidal Nanocrystals of Lead-Free Double-Perovskite (Elpasolite) Semiconductors: Synthesis and Anion Exchange To Access New Materials.

    Science.gov (United States)

    Creutz, Sidney E; Crites, Evan N; De Siena, Michael C; Gamelin, Daniel R

    2018-02-14

    Concerns about the toxicity and instability of lead-halide perovskites have driven a recent surge in research toward alternative lead-free perovskite materials, including lead-free double perovskites with the elpasolite structure and visible bandgaps. Synthetic approaches to this class of materials remain limited, however, and no examples of heterometallic elpasolites as nanomaterials have been reported. Here, we report the synthesis and characterization of colloidal nanocrystals of Cs 2 AgBiX 6 (X = Cl, Br) elpasolites using a hot-injection approach. We further show that postsynthetic modification through anion exchange and cation extraction can be used to convert these nanocrystals to new materials including Cs 2 AgBiI 6 , which was previously unknown experimentally. Nanocrystals of Cs 2 AgBiI 6 , synthesized via a novel anion-exchange protocol using trimethylsilyl iodide, have strong absorption throughout the visible region, confirming theoretical predictions that this material could be a promising photovoltaic absorber. The synthetic methodologies presented here are expected to be broadly generalizable. This work demonstrates that nanocrystal ion-exchange reactivity can be used to discover and develop new lead-free halide perovskite materials that may be difficult or impossible to access through direct synthesis.

  2. Crystal structural, magnetic and electrical transport properties of CeKFeMoO6 double perovskite

    International Nuclear Information System (INIS)

    Huo Guoyan; Ren Minghui; Wang Xiaoqing; Zhang Hongrui; Shi Pengfei

    2010-01-01

    The crystal structural, magnetic and electrical transport properties of double perovskite CeKFeMoO 6 have been investigated. The crystal structure of the compound is assigned to the monoclinic system with space group P2 1 /n and its lattice parameters are a=0.55345(3) nm, b=0.56068(2) nm, c=0.78390(1) nm, β=89.874(2). The divergence between zero-field-cooling and field-cooling M-T curves demonstrates the anisotropic behavior. The Curie temperature measured from C p -T curve is about 340 K. Isothermal magnetization curve shows that the saturation and spontaneous magnetization are 1.90 and 1.43 μ B /f.u. at 300 K, respectively. The electrical behavior of the sample shows a semiconductor. The electrical transport behavior can be described by variable range hopping model. Large magnetoresistance, -0.88 and -0.18, can be observed under low magnetic field, 0.5 T, at low and room temperature, respectively.

  3. Computer predictions on Rh-based double perovskites with unusual electronic and magnetic properties

    Science.gov (United States)

    Halder, Anita; Nafday, Dhani; Sanyal, Prabuddha; Saha-Dasgupta, Tanusri

    2018-03-01

    In search for new magnetic materials, we make computer prediction of structural, electronic and magnetic properties of yet-to-be synthesized Rh-based double perovskite compounds, Sr(Ca)2BRhO6 (B=Cr, Mn, Fe). We use combination of evolutionary algorithm, density functional theory, and statistical-mechanical tool for this purpose. We find that the unusual valence of Rh5+ may be stabilized in these compounds through formation of oxygen ligand hole. Interestingly, while the Cr-Rh and Mn-Rh compounds are predicted to be ferromagnetic half-metals, the Fe-Rh compounds are found to be rare examples of antiferromagnetic and metallic transition-metal oxide with three-dimensional electronic structure. The computed magnetic transition temperatures of the predicted compounds, obtained from finite temperature Monte Carlo study of the first principles-derived model Hamiltonian, are found to be reasonably high. The prediction of favorable growth condition of the compounds, reported in our study, obtained through extensive thermodynamic analysis should be useful for future synthesize of this interesting class of materials with intriguing properties.

  4. Neutron Powder Diffraction Studies of Ca2-xSrxCoWO6 Double Perovskites

    International Nuclear Information System (INIS)

    Zhou, Qingdi; Kennedy, Brendan; Elcombe, Margaret

    2005-01-01

    Full text: A series of double perovskite compounds of A 2-x Sr x CoWO 6 (A = Ca, Ba) were synthesized and the room- and variable-temperature structural phase transitions have been studied by synchrotron and neutron powder diffraction techniques. These studies demonstrated that the symmetry increases as the average size of the A-site cation increases. These transitions are associated with the gradual reduction and ultimately removal of the octahedral tiles of the BO 6 octahedra. Temperature dependent structural studies have been undertaken for selected samples. The transition to cubic is continuous in the three Ca doped samples studied as a function of temperature, Ca 2-x Sr x CoWO 6 x = 1.8, 1.7, 1.6, however in each case analysis of the spontaneous strain shows the transition to be tricritical rather than second order in nature. Where observed the temperature induced P2 1 /n to I4/m transition is first order as required by symmetry. (authors)>>>>

  5. Giant magnetostriction in Ca2FeReO6 double perovskite

    International Nuclear Information System (INIS)

    Serrate, D.; De Teresa, J.M.; Algarabel, P.A.; Marquina, C.; Morellon, L.; Blasco, J.; Ibarra, M.R.

    2005-01-01

    We report magnetostriction measurements in polycrystalline Ca 2 FeReO 6 magnetic double perovskite up to 20T and in the temperature range 4.2-250K. This compound shows a high Curie temperature (T C =523K) and a structural transition at low temperatures (T S =110K). By combining magnetostriction measurements parallel and perpendicular to the magnetic field, we evaluate the anisotropic (λ t ) and volume magnetostriction (ω). The λ t at room temperature is large and reaches below T S the giant value of ∼0.1% at 15T. Below T S , the ω is also found to be large: ∼0.05% at 15T at 5K. These results are interpreted within a scenario where the Re orbital state plays a crucial role in the ground state. The observed effect could open a new way to observe giant magnetostriction effects in transition-metal-based magnetic oxides through suitable tuning of the orbital effects in the transition metals

  6. Large magnetoresistance in (AA')2FeReO6 double perovskites

    International Nuclear Information System (INIS)

    Teresa, J.M. de; Serrate, D.; Blasco, J.; Ibarra, M.R.; Morellon, L.

    2005-01-01

    We review the main structural, magnetic and magnetotransport properties of the intriguing (AA') 2 FeReO 6 magnetic double perovskites. As the average cation size decreases, the crystallographic structure at room temperature evolves from cubic [(AA') 2 =Ba 2 , Ba 1.5 Sr 0.5 , BaSr, Ba 0.5 Sr 1.5 ] to tetragonal [(AA') 2 =Sr 2 ] and monoclinic [(AA') 2 =Ca 0.5 Sr 1.5 , CaSr, Ca 1.5 Sr 0.5 , Ca 2 ]. The Curie temperature increases anomalously from ∼303K for Ba 2 to ∼522K for Ca 2 in sharp contrast with the observed behaviour in the isostructural compounds (AA') 2 FeMoO 6 . Other anomalous features in the (AA') 2 FeReO 6 series are: the large magnetic anisotropy, the large magnetoelastic coupling and the semiconducting behaviour of the monoclinic compounds. The monoclinic compounds undergo a structural/magnetic transition at T S below 125K. Three different magnetoresistance mechanisms have been identified: the intergrain negative magnetoresistance effect, which is present across the whole series of compounds, and in the case of the monoclinic compounds below T S a negative magnetoresistance effect associated to the melting of the low-temperature phase and a positive magnetoresistance effect only present in (AA') 2 =Ca 2 below T∼50K

  7. Magnetic entropy change and critical exponents in double perovskite Y2NiMnO6

    Science.gov (United States)

    Sharma, G.; Tripathi, T. S.; Saha, J.; Patnaik, S.

    2014-11-01

    We report the magnetic entropy change (ΔSM) and the critical exponents in the double perovskite manganite Y2NiMnO6 with a ferromagnetic to paramagnetic transition TC~85 K. For a magnetic field change ΔH=80 kOe, a maximum magnetic entropy change ΔSM=-6.57 J/kg K is recorded around TC. The critical exponents β=0.363±0.05 and γ=1.331±0.09 obtained from power law fitting to spontaneous magnetization MS(T) and the inverse initial susceptibility χ0-1(T) satisfy well to values derived for a 3D-Heisenberg ferromagnet. The critical exponent δ=4.761±0.129 is determined from the isothermal magnetization at TC. The scaling exponents corresponding to second order phase transition are consistent with the exponents from Kouvel-Fisher analysis and satisfy Widom's scaling relation δ=1+(γ/β). Additionally, they also satisfy the single scaling equation M(H,ɛ)=ɛβf±(H/ɛ) according to which the magnetization-field-temperature data around TC should collapse into two curves for temperatures below and above TC.

  8. Optical absorption analysis of quaternary molybdate- and tungstate-ordered double perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Tablero, C., E-mail: ctablero@etsit.upm.es

    2015-08-05

    Highlights: • These compounds present a high optical absorption. • The absorption coefficients using different DFT + U alternatives have been compared. • The absorption coefficients have been split into different contributions. • The maximum efficiency is near the maximum efficiency for multiple-gap solar cells. - Abstract: Quaternary-ordered double perovskite A{sub 2}MM′O{sub 6} (M = Mo,W) semiconductors are a group of materials with a variety of photocatalytic and optoelectronic applications. An analysis focused on the optoelectronic properties is carried out using first-principles density-functional theory with several U orbital-dependent one-electron potentials applied to different orbital subspaces. The structural non-equivalence of the atoms resulting from the symmetry has been taken in account. In order to analyze optical absorption in these materials deeply, the absorption coefficients have been split into inter- and intra-non-equivalent species contributions. The results indicate that the effect of the A and M′ atoms on the optical properties are minimal whereas the largest contribution comes from the non-equivalent O atoms to M transitions.

  9. High-pressure crystal growth and electromagnetic properties of 5d double-perovskite Ca3OsO6

    International Nuclear Information System (INIS)

    Feng, Hai Luke; Shi, Youguo; Guo, Yanfeng; Li, Jun; Sato, Akira; Sun, Ying; Wang, Xia; Yu, Shan; Sathish, Clastin I.; Yamaura, Kazunari

    2013-01-01

    Single crystals of the osmium-containing compound Ca 3 OsO 6 have been successfully grown under high-pressure conditions, for the first time. The crystal structure of Ca 3 OsO 6 were characterized as an ordered double-perovskite structure of space group P2 1 /n with the Ca and Os atoms being fully ordered at the perovskite B-site. The electromagnetic analysis shows that the crystal exhibits a semiconductor-like behavior below 300 K and undergoes an antiferromagnetic transition at 50 K. - Graphical Abstract: Schematic image of crystal structure of Ca 3 OsO 6 as determined by X-ray diffraction, where the gray and black octahedrons are occupied by Ca and Os, respectively. Top inset reveals an optic image of a typical Ca 3 OsO 6 single crystal. Highlights: ► Single crystals of Ca 3 OsO 6 have been successfully grown under high-pressure. ► Ca 3 OsO 6 crystalizes into an ordered double-perovskite structure. ► The Ca 3 OsO 6 undergoes an antiferromagnetic transition at 50 K

  10. High-pressure crystal growth and electromagnetic properties of 5d double-perovskite Ca₃OsO₆

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Hai Luke, E-mail: FENG.Hai@nims.go.jp [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Graduate School of Chemical Science and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Shi, Youguo [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Institute of Physics, Chinese Academy of Science, Beijing 100190 (China); Guo, Yanfeng; Li, Jun [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Sato, Akira [Materials Analysis Station, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Sun, Ying [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Wang, Xia; Yu, Shan [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Sathish, Clastin I. [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Graduate School of Chemical Science and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Yamaura, Kazunari, E-mail: YAMAURA.Kazunari@nims.go.jp [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Graduate School of Chemical Science and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan)

    2013-05-01

    Single crystals of the osmium-containing compound Ca₃OsO₆ have been successfully grown under high-pressure conditions, for the first time. The crystal structure of Ca₃OsO₆ atoms being fully ordered at the perovskite B-site. The electromagnetic analysis shows that the crystal exhibits a semiconductor-like behavior below 300 K and undergoes an antiferromagnetic transition at 50 K. - Graphical Abstract: Schematic image of crystal structure of Ca₃OsO₆ as determined by X-ray diffraction, where the gray and black octahedrons are occupied by Ca and Os, respectively. Top inset reveals an optic image of a typical Ca₃OsO₆ single crystal. Highlights: • Single crystals of Ca₃OsO₆ have been successfully grown under high-pressure. • Ca₃OsO₆ crystalizes into an ordered double-perovskite structure. • The Ca₃OsO₆ undergoes an antiferromagnetic transition at 50 K.

  11. Half-metallic and insulating natures in Ru-based ordered double perovskite oxides Ba_2X"I"I"IRu"VO_6 (X = V, Cr) induced by 3d-t_2_g"n orbital filling

    International Nuclear Information System (INIS)

    Saad, H.-E.M. Musa; Althoyaib, S.S.

    2017-01-01

    In this paper, we present results of a comprehensive systemic study of the crystal, electronic and magnetic structures on two members of Ru-based ordered double perovskite oxides Ba_2XRuO_6 (X = V, Cr). For the corporate compound, the analysis of density of states (DOS) results suggests that the 3d-t_2_g orbital filling plays a major role in governing the conduction mechanism in these systems. The DOS and magnetic results show that Ba_2XRuO_6 exhibits half-metallic (HM) nature as X = V, where the electronic structure of Ba_2V"I"I"IRu"VO_6 with 3d-t_2_g"2 behaves like that of HM ferrimagnetic (FI), switches to compensate FI insulating behavior as X = Cr, with an extra electron filled 3d-t_2_g"3 in Ba_2Cr"I"I"IRu"VO_6. We find, on consideration of electron correlation (LSDA+U) and spin-orbital coupling (SOC) effects that the electronic structure of Ba_2XRuO_6 takes a HM nature, whereas it is completely transformed to insulating nature once an extra electron filled the 3d-t_2_g orbitals in X = Cr case. Such tuning is accompanied by spin-state hopping of one electron from half-filled spin-state in Ru"V (t_2_g"3 e_g"0) to two and three occupied spin-state in V"I"I"I (t_2_g"2 e_g"0) and Cr"I"I"I (t_2_g"3 e_g"0), respectively. The charge distribution results show that this extra electron occupies chiefly the spin-down of conduction orbitals and plays a major role in determining the electronic and magnetic structures of Ba_2XRuO_6 system. - Highlights: • Half-metallic and insulating natures are observed in Ba_2XRuO_6 (X = V, Cr). • 3d-t_2_g"n orbitals filling plays a major role in governing the conduction mechanism. • LSDA+U method under density functional theory (DFT) is considered. • HM ferrimagnetic (FI) (X = V) switch to compensate FI insulating (X = Cr).

  12. Synthesis and thermal stability studies of a series of metastable Dion–Jacobson double-layered neodymium-niobate perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Josepha, Elisha A.; Farooq, Sara; Mitchell, Cinnamon M.; Wiley, John B., E-mail: jwiley@uno.edu

    2014-08-15

    The Dion–Jacobson double-layered perovskite, RbNdNb{sub 2}O{sub 7}, is used as a precursor to synthesize the series ANdNb{sub 2}O{sub 7} (A=H, Li, Na, K, NH{sub 4}, Ag), and (MCl)NdNb{sub 2}O{sub 7} (M=Mn, Fe, Cu) through ion-exchange reactions ≤400 °C. Thermal stability studies indicated that most of these compounds are metastable. A combination of X-ray powder diffraction and differential thermal analysis were used to determine various low temperature decomposition pathways; these pathways were very dependent on the interlayer species. Overall the ANdNb{sub 2}O{sub 7} series was found to be less stable than the corresponding lanthanides, ALaNb{sub 2}O{sub 7}. - Graphical abstract: A new series of topochemically-prepared metastable neodymium-containing layered perovskites are studied. - Highlights: • A series of new layered neodymium containing perovskites were synthesized by ion exchange. • Products were studied by variable temperature X-ray diffraction and thermal analysis. • Most of the series are metastable showing exothermic transitions on decomposition. • The Nd compounds are less stable due to the smaller size of the Nd relative to La.

  13. Bandgap Engineering of Lead-Free Double Perovskite Cs2 AgBiBr6 through Trivalent Metal Alloying.

    Science.gov (United States)

    Du, Ke-Zhao; Meng, Weiwei; Wang, Xiaoming; Yan, Yanfa; Mitzi, David B

    2017-07-03

    The double perovskite family, A 2 M I M III X 6 , is a promising route to overcome the lead toxicity issue confronting the current photovoltaic (PV) standout, CH 3 NH 3 PbI 3 . Given the generally large indirect band gap within most known double perovskites, band-gap engineering provides an important approach for targeting outstanding PV performance within this family. Using Cs 2 AgBiBr 6 as host, band-gap engineering through alloying of In III /Sb III has been demonstrated in the current work. Cs 2 Ag(Bi 1-x M x )Br 6 (M=In, Sb) accommodates up to 75 % In III with increased band gap, and up to 37.5 % Sb III with reduced band gap; that is, enabling ca. 0.41 eV band gap modulation through introduction of the two metals, with smallest value of 1.86 eV for Cs 2 Ag(Bi 0.625 Sb 0.375 )Br 6 . Band structure calculations indicate that opposite band gap shift directions associated with Sb/In substitution arise from different atomic configurations for these atoms. Associated photoluminescence and environmental stability of the three-metal systems are also assessed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Bandgap engineering of lead-free double perovskite Cs_2AgBiBr_6 through trivalent metal alloying

    International Nuclear Information System (INIS)

    Du, Ke-zhao; Mitzi, David B.; Meng, Weiwei; Wang, Xiaoming; Yan, Yanfa

    2017-01-01

    The double perovskite family, A_2M"IM"I"I"IX_6, is a promising route to overcome the lead toxicity issue confronting the current photovoltaic (PV) standout, CH_3NH_3PbI_3. Given the generally large indirect band gap within most known double perovskites, band-gap engineering provides an important approach for targeting outstanding PV performance within this family. Using Cs_2AgBiBr_6 as host, band-gap engineering through alloying of In"I"I"I/Sb"I"I"I has been demonstrated in the current work. Cs_2Ag(Bi_1_-_xM_x)Br_6 (M=In, Sb) accommodates up to 75 % In"I"I"I with increased band gap, and up to 37.5 % Sb"I"I"I with reduced band gap; that is, enabling ca. 0.41 eV band gap modulation through introduction of the two metals, with smallest value of 1.86 eV for Cs_2Ag(Bi_0_._6_2_5Sb_0_._3_7_5)Br_6. Band structure calculations indicate that opposite band gap shift directions associated with Sb/In substitution arise from different atomic configurations for these atoms. Associated photoluminescence and environmental stability of the three-metal systems are also assessed. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Glassy dielectric response in Tb2NiMnO6 double perovskite with similarities to a Griffiths phase

    Science.gov (United States)

    Nhalil, Hariharan; Nair, Harikrishnan S.; Bhat, H. L.; Elizabeth, Suja

    2013-12-01

    Results of frequency-dependent and temperature-dependent dielectric measurements performed on the double-perovskite Tb2NiMnO6 are presented. The real (\\epsilon_1 (f,T)) and imaginary (\\epsilon_2 (f,T)) parts of dielectric permittivity show three plateaus suggesting dielectric relaxation originating from the bulk, grain boundaries and the sample-electrode interfaces, respectively. The \\epsilon_1 (f,T) and \\epsilon_2 (f,T) are successfully simulated by a RC circuit model. The complex plane of impedance, Z'\\text{-}Z'' , is simulated using a series network with a resistor R and a constant phase element. Through the analysis of \\epsilon (f,T) using the modified Debye model, two different relaxation time regimes separated by a characteristic temperature, T^* , are identified. The temperature variation of R and C corresponding to the bulk and the parameter α from modified Debye fit lend support to this hypothesis. Interestingly, the T^* compares with the Griffiths temperature for this compound observed in magnetic measurements. Though these results cannot be interpreted as magnetoelectric coupling, the relationship between lattice and magnetism is markedly clear. We assume that the observed features have their origin in the polar nanoregions which originate from the inherent cationic defect structure of double perovskites.

  16. Thermal conductivity of ferrimagnet GdBaMn2O5.0 single crystals

    Directory of Open Access Journals (Sweden)

    J. C. Wu

    2017-05-01

    Full Text Available GdBaMn2O5.0 is a double-perovskite ferrimagnet consisting of pyramidal manganese layers. In this work, we study the in-plane and the c-axis thermal conductivities of GdBaMn2O5.0 single crystals at low temperatures down to 0.3 K and in high magnetic fields up to 14 T. The κc(T curve shows a broad hump below the Néel temperature (TN = 144 K, which indicates the magnon heat transport along the c axis. Whereas, the κa(T shows a kink at TN, caused by a magnon-phonon scattering effect. This anisotropic behavior is caused by the anisotropy of spin interactions along different directions. At very low temperatures, magnetic-field-induced changes of κa and κc, which is likely due to phonon scattering by free Gd3+ spins, is rather weak. This indicates that the spin coupling between Gd3+ and Mn2+/Mn3+ is rather strong at low temperatures.

  17. Intrinsic Instability of Cs2In(I)M(III)X6 (M = Bi, Sb; X = Halogen) Double Perovskites: A Combined Density Functional Theory and Experimental Study.

    Science.gov (United States)

    Xiao, Zewen; Du, Ke-Zhao; Meng, Weiwei; Wang, Jianbo; Mitzi, David B; Yan, Yanfa

    2017-05-03

    Recently, there has been substantial interest in developing double-B-cation halide perovskites, which hold the potential to overcome the toxicity and instability issues inherent within emerging lead halide-based solar absorber materials. Among all double perovskites investigated, In(I)-based Cs 2 InBiCl 6 and Cs 2 InSbCl 6 have been proposed as promising thin-film photovoltaic absorber candidates, with computational examination predicting suitable materials properties, including direct bandgap and small effective masses for both electrons and holes. In this study, we report the intrinsic instability of Cs 2 In(I)M(III)X 6 (M = Bi, Sb; X = halogen) double perovskites by a combination of density functional theory and experimental study. Our results suggest that the In(I)-based double perovskites are unstable against oxidation into In(III)-based compounds. Further, the results show the need to consider reduction-oxidation (redox) chemistry when predicting stability of new prospective electronic materials, especially when less common oxidation states are involved.

  18. Impact of A cation size of double perovskite A2AlTaO6 (A = Ca, Sr, Ba) on dielectric and catalytic properties

    International Nuclear Information System (INIS)

    Gorodea, I.; Goanta, M.; Toma, M.

    2015-01-01

    Highlights: • Synthesis by solid state reaction of the double perovskite A 2 AlTaO 6 , where A = Ca, Sr and Ba. • The role of different A-site cations on their synthesis and structures was investigated. • The influence of the divalent A-site cations on the dielectric properties was evaluated by resistivity measurements. • Catalytic properties were evaluated in water splitting process, under gamma-rays irradiation emitted by a 60 Co source, for the first time. - Abstract: Double perovskite-type oxide A 2 AlTaO 6 materials, where A = Ca, Sr and Ba, were prepared using conventional solid state reaction. The role of different A-site cations on their synthesis, structures, dielectric and catalytic properties was investigated. Double perovskite oxide structures were evaluated using X-ray diffraction (XRD). As the average cation size decreases, the crystallographic structure at room temperature evolves from cubic to monoclinic. The influence of the nature of the divalent A-site cations on the dielectric properties was evaluated by resistivity measurements in the frequency range of 10–10 6 Hz. It can be found that relative permittivity and dielectric loss regularly changed with A cation size. Catalytic properties of the obtained compounds were evaluated in water splitting process, under gamma-rays irradiation emitted by a 60 Co source for the first time. From experimental data it was noticed that the double perovskite Ca 2 AlTaO 6 had a higher catalytic effect

  19. First-principles study of electronic and optical properties of lead-free double perovskites Cs2NaBX6 (B = Sb, Bi; X = Cl, Br, I)

    Science.gov (United States)

    Zhao, Shuai; Yamamoto, Kumiko; Iikubo, Satoshi; Hayase, Shuzi; Ma, Tingli

    2018-06-01

    Organolead halide perovskite is regarded as the most promising light-harvesting material for next-generation solar cells; however, the intrinsic instability and toxicity of lead are still of great concern. Bismuth is ecofriendly and has electronic properties similar to those of lead, which has gradually attracted interest for optoelectronic applications. However, the valence state of bismuth is different from that of lead, eliminating the possibility of replacing lead by bismuth in organolead halide perovskites. To address this matter, one feasible strategy is to construct B-site double perovskites by the combination of Bi3+ and B+ in 1:1 ratio. In this work, lead-free halide double perovskites of the form Cs2NaBX6 (B = Sb, Bi; X = Cl, Br, I) were investigated by first-principles calculations. The electronic properties, optical absorption coefficients, and thermodynamic stability of these compounds were investigated to ascertain their potential application in solar energy conversion. The results provide theoretical support for the exploration of lead-free perovskite materials in potential optoelectronic applications.

  20. Synthesis, crystal structure, and properties of the ordered double perovskite Sr_2CoOsO_6

    International Nuclear Information System (INIS)

    Kumar Paul, Avijit; Reehuis, Manfred; Felser, Claudia; Abdala, Paula M.; Jansen, Martin

    2013-01-01

    Sr_2CoOsO_6, a new osmium based ordered semiconductor double perovskite was prepared by solid state synthesis from the respective binary oxides. Room temperature PXRD analysis shows the compound to be tetragonal [I4/m; a = 5.5503(1) Aa and c = 7.9320(1) Aa], whereas low temperature synchrotron data refinement has revealed a second monoclinic polymorph [I2/m; a = 5.4969(2) Aa, b = 5.4979(2) Aa, c = 8.0090(1) Aa and γ = 90.527(1) ] with a fully ordered rocksalt arrangement of cobalt and osmium atoms over the perovskite B-sites. Heat capacity and magnetic measurements indicate that Sr_2CoOsO_6 shows antiferromagnetic ordering below T_N = 108 K followed by a second magnetic transition at T_2 = 65 K. It was shown that the change from the tetragonal to the monoclinic phase occurs at T_N. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Crystallographic and electronic structure of the Ca2TiMnO6 double perovskite

    International Nuclear Information System (INIS)

    López, J.P. Garzón; Cardona, R.; Santos, A. Sarmiento; Téllez, D.A. Landínez; Roa-Rojas, J.

    2014-01-01

    In this work, we report synthesis and crystalline structure study of the Ca 2 TiMnO 6 complex perovskite, by X-ray diffraction experiments and through the application of the Rietveld refinement using the GSAS code. Results revealed the crystallization of the system in a tetragonal perovskite with the characteristic structure given by I4/m (#87) space group and lattice parameters a=5.339(4) Å and c=7.736(6) Å. Ab initio calculations of density of states (DOS) and electronic structure were carried out for this perovskite-like system, by the Density Functional Theory (DFT) and using the Full-potential Linearized Augmented Plane Waves (FP-LAPW) method. The exchange-correlation potential was treated using the Generalized Gradient Approximation (GGA). All calculations were carried-out using spin polarization. For the up spin orientation the compound has a semiconducting behavior and for down spin polarization it behaves like a conductor. The calculated effective magnetic moment in cell was 4.02 μ B , which is close to the expected value calculated from Hund's rules

  2. Structural phase transition and magnetic properties of double perovskites Ba2CaMO6 (M=W, Re, Os)

    International Nuclear Information System (INIS)

    Yamamura, Kazuhiro; Wakeshima, Makoto; Hinatsu, Yukio

    2006-01-01

    Structures and magnetic properties for double perovskites Ba 2 CaMO 6 (M=W, Re, Os) were investigated. Both Ba 2 CaReO 6 and Ba 2 CaWO 6 show structural phase transitions at low temperatures. For Ba 2 CaReO 6 , the second order transition from cubic Fm3-bar m to tetragonal I4/m has been observed near 120K. For Ba 2 CaWO 6 , the space group of the crystal structure is I4/m at 295K and the transition to monoclinic I2/m has been observed between 220K. Magnetic susceptibility measurements show that Ba 2 CaReO 6 (S=1/2) and Ba 2 CaOsO 6 (S=1) transform to an antiferromagnetic state below 15.4 and 51K, respectively. Anomalies corresponding to their structural phase transition and magnetic transition have been also observed through specific heat measurements

  3. Synthesis and thermal stability studies of a series of metastable Dion-Jacobson double-layered neodymium-niobate perovskites

    Science.gov (United States)

    Josepha, Elisha A.; Farooq, Sara; Mitchell, Cinnamon M.; Wiley, John B.

    2014-08-01

    The Dion-Jacobson double-layered perovskite, RbNdNb2O7, is used as a precursor to synthesize the series ANdNb2O7 (A=H, Li, Na, K, NH4, Ag), and (MCl)NdNb2O7 (M=Mn, Fe, Cu) through ion-exchange reactions ≤400 °C. Thermal stability studies indicated that most of these compounds are metastable. A combination of X-ray powder diffraction and differential thermal analysis were used to determine various low temperature decomposition pathways; these pathways were very dependent on the interlayer species. Overall the ANdNb2O7 series was found to be less stable than the corresponding lanthanides, ALaNb2O7.

  4. Electron and hole doping effects in Sr{sub 2}FeMoO{sub 6} double perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, D. E-mail: diana.sanchez@icmm.csic.es; Alonso, J.A.; Garcia-Hernandez, M.; Martinez-Lope, M.J.; Casais, M.T.; Martinez, J.L.; Fernandez-Diaz, M.T

    2004-05-01

    Electron and hole doping effects in the ferromagnetic and structural properties of the double perovskite Sr{sub 2}FeMoO{sub 6} are studied along the series Sr{sub 2-x}La{sub x}FeMoO{sub 6} (0{<=}x{<=}1) and Sr{sub 2-x}FeMoO{sub 6} (0{<=}x{<=}0.4) from neutron powder diffraction and magnetization data. Sr-deficient samples (hole doped) show moderate changes in the structure and both T{sub c} and M{sub s} rapidly decrease with x. On the contrary, a change from tetragonal to monoclinic symmetry and a non monotonic behaviour in T{sub c} is found in the La-substituted series (electron doped)

  5. Structural and dielectric characteristics of double perovskite La2(NiFe)1/2MnO6

    Science.gov (United States)

    Nasir, Mohd.; Kandasami, Asokan; Sen, Somaditya

    2018-05-01

    Recently, La2NiMnO6 has drawn significant interest because large magnetic field induced changes in dielectric properties makes this compound a promising material for potential spintronic device applications. In the present study, the structural and dielectric characteristics of sol-gel prepared La2(Ni1/2Fe1/2)MnO6 double perovskite ceramics were evaluated. La2(Ni1/2Fe1/2)MnO6 was crystallized in the monoclinic P21/n structure with ordered Ni2+/Fe2+ and Mn4+ cations. A giant dielectric constant with relaxor-like behavior was observed, which was attributed to the dipolar effects arising from hopping between Ni2+/Fe2+ and Mn4+ ions.

  6. Processing and characterization of Sr{sub 2−x}VMoO{sub 6−δ} double perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Weisentein, A.J., E-mail: a.weisenstein@gmail.com [Department of Mechanical and Industrial Engineering, Montana State University, Bozeman, MT 59717-3800 (United States); Childs, N., E-mail: nick.childs@msu.montana.edu [Department of Physics, Montana State University, Bozeman, MT 59717-3804 (United States); Amendola, R., E-mail: roberta.amendola@coe.montana.edu [Department of Chemical and Biological Engineering, Montana State University, Bozeman, MT 59717-3920 (United States); Driscoll, D., E-mail: davidrobertdriscoll@gmail.com [Department of Mechanical and Industrial Engineering, Montana State University, Bozeman, MT 59717-3800 (United States); Sofie, S.W., E-mail: ssofie@me.montana.edu [Department of Mechanical and Industrial Engineering, Montana State University, Bozeman, MT 59717-3800 (United States); Gannon, P., E-mail: pgannon@coe.montana.edu [Department of Chemical and Biological Engineering, Montana State University, Bozeman, MT 59717-3920 (United States); Smith, R., E-mail: smith@physics.montana.edu [Department of Physics, Montana State University, Bozeman, MT 59717-3804 (United States)

    2013-05-15

    In this study, the analysis and characterization of the processing and sintering of Sr{sub 2−x}VMoO{sub 6−δ} perovskites, where x = 0.0, 0.1 and 0.2, was investigated with application potential in high temperature fuel cell electrodes and electro-catalysts. Sr{sub 2−x}VMoO{sub 6−δ} substrates were sintered in a reducing (5%H{sub 2} 95%N{sub 2}) atmosphere at 1100 °C, 1200 °C, and 1300 °C. The X-ray diffraction patterns indicate that the double perovskite is the primary phase for Sr{sub 2−x}VMoO{sub 6−δ} pellets sintered at 1200 °C and 1300 °C for 20 h; however, these pellets show a secondary phase of SrMoO{sub 4−δ}. X-ray photoelectron spectroscopy revealed a deficiency of vanadium on the pellet surfaces, in which samples yielded surface vanadium concentrations of less than 5%. The vanadium inhomogeneity can be explained by the formation of the SrMoO{sub 4−δ} scheelite phase (ABO{sub 4}) due to oxygen exposure on the surface of the pellets, which indicates inward vanadium migration to the bulk, and was exhibited in redox cycling. Sr{sub 2−x}VMoO{sub 6−δ} pellets sintered at 1300 °C showed the lowest resistivity at both SOFC operating temperature (800 °C) and room temperature. The resistivity tests also show a semiconductor to metallic transition for all double perovskites, from heating up to 800 °C to cooling down to room temperature in a reducing atmosphere, related to the reduction of Mo{sup 6+} to Mo{sup 4+}. - Highlights: ► Primary Sr{sub 2−x}VMoO{sub 6−δ} phase only shown to form in excess of 1300 °C in reducing. ► Surface formation of secondary phase SrMoO{sub 4−δ} (Mo{sup 6+}) observed at RT in air. ► Surface vanadium deficiency induced by inward atomic diffusion. ► Semiconductor to metallic transition is related to the reduction of Mo{sup 6+} to Mo{sup 4+}.

  7. Processing and characterization of Sr2−xVMoO6−δ double perovskites

    International Nuclear Information System (INIS)

    Weisentein, A.J.; Childs, N.; Amendola, R.; Driscoll, D.; Sofie, S.W.; Gannon, P.; Smith, R.

    2013-01-01

    In this study, the analysis and characterization of the processing and sintering of Sr 2−x VMoO 6−δ perovskites, where x = 0.0, 0.1 and 0.2, was investigated with application potential in high temperature fuel cell electrodes and electro-catalysts. Sr 2−x VMoO 6−δ substrates were sintered in a reducing (5%H 2 95%N 2 ) atmosphere at 1100 °C, 1200 °C, and 1300 °C. The X-ray diffraction patterns indicate that the double perovskite is the primary phase for Sr 2−x VMoO 6−δ pellets sintered at 1200 °C and 1300 °C for 20 h; however, these pellets show a secondary phase of SrMoO 4−δ . X-ray photoelectron spectroscopy revealed a deficiency of vanadium on the pellet surfaces, in which samples yielded surface vanadium concentrations of less than 5%. The vanadium inhomogeneity can be explained by the formation of the SrMoO 4−δ scheelite phase (ABO 4 ) due to oxygen exposure on the surface of the pellets, which indicates inward vanadium migration to the bulk, and was exhibited in redox cycling. Sr 2−x VMoO 6−δ pellets sintered at 1300 °C showed the lowest resistivity at both SOFC operating temperature (800 °C) and room temperature. The resistivity tests also show a semiconductor to metallic transition for all double perovskites, from heating up to 800 °C to cooling down to room temperature in a reducing atmosphere, related to the reduction of Mo 6+ to Mo 4+ . - Highlights: ► Primary Sr 2−x VMoO 6−δ phase only shown to form in excess of 1300 °C in reducing. ► Surface formation of secondary phase SrMoO 4−δ (Mo 6+ ) observed at RT in air. ► Surface vanadium deficiency induced by inward atomic diffusion. ► Semiconductor to metallic transition is related to the reduction of Mo 6+ to Mo 4+

  8. Effect of Codoping Cl Anion and 5-AVA Cation on Performance of Large-Area Perovskite Solar Cells with Double-Mesoporous Layers

    Directory of Open Access Journals (Sweden)

    Yaxian Pei

    2016-01-01

    Full Text Available For the perovskite solar cells (PSCs, the performance of the PSCs has become the focus of the research by improving the quality of the perovskite absorption layer. So far, the performance of the large-area PSCs is lower than that of small-area PSCs. In the paper, the experiments were designed to improve the photovoltaic performance of the large-area PSCs by improved processing technique. Here we investigated the optoelectronic properties of the prototypical CH3NH3PbI3 (MAPbI3 further modulated by introducing other extrinsic ions (specifically codoped Cl− and 5-AVA+. Moreover, we used inorganic electron extraction layer to achieve very rapid photogenerated carrier extraction eliminating local structural defects over large areas. Ultimately, we fabricated a best-performing perovskite solar cell based on codoping Cl anion and 5-AVA cation which uses a double layer of mesoporous TiO2 and ZrO2 as a scaffold infiltrated with perovskite and does not require a hole-conducting layer. The experiment results indicated that an average efficiency of double-mesoporous layer-based devices with codoping Cl anion and 5-AVA cation was obtained with exceeding 50% enhancement, compared to that of pure single-mesoporous layer-based device.

  9. The role of nonmagnetic d{sup 0} vs. d{sup 10}B-type cations on the magnetic exchange interactions in osmium double perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Hai L., E-mail: Hai.Feng@cpfs.mpg.de [Max Planck Institute for Chemical Physics of Solids, Dresden 01187 (Germany); Yamaura, Kazunari [Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Tjeng, Liu Hao [Max Planck Institute for Chemical Physics of Solids, Dresden 01187 (Germany); Jansen, Martin, E-mail: M.Jansen@fkf.mpg.de [Max Planck Institute for Chemical Physics of Solids, Dresden 01187 (Germany); Max Planck Institute for Solid State Research, Stuttgart 70569 (Germany)

    2016-11-15

    Polycrystalline samples of double perovskites Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) were synthesized by solid state reactions. They adopt the cubic double perovskite structures (space group, Fm-3m) with ordered B and Os arrangements. Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) show antiferromagnetic transitions at 93 K, 69 K, and 28 K, respectively. The Weiss-temperatures are −590 K for Ba{sub 2}ScOsO{sub 6}, −571 K for Ba{sub 2}YOsO{sub 6}, and −155 K for Ba{sub 2}InOsO{sub 6}. Sc{sup 3+} and Y{sup 3+} have the open-shell d{sup 0} electronic configuration, while In{sup 3+} has the closed-shell d{sup 10}. This indicates that a d{sup 0} B-type cation induces stronger overall magnetic exchange interactions in comparison to a d{sup 10}. Comparison of Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) to their Sr and Ca analogues shows that the structural distortions weaken the overall magnetic exchange interactions. - Graphical abstract: Magnetic properties of osmium double perovskites Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) were studied. Comparison of Ba{sub 2}BOsO{sub 6}indicates that a d{sup 0} B-type cation induces stronger overall magnetic exchange interactions in comparison to a d{sup 10}. - Highlights: • Magnetic properties of double perovskites Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) were studied. • A d{sup 0}B-type cation induces stronger magnetic interactions than a d{sup 10}. • Structural distortions weaken the overall Os{sup 5+}-Os{sup 5+} magnetic interactions.

  10. Double perovskite cathodes for proton-conducting ceramic fuel cells: are they triple mixed ionic electronic conductors?

    Science.gov (United States)

    Téllez Lozano, Helena; Druce, John; Cooper, Samuel J; Kilner, John A

    2017-01-01

    18 O and 2 H diffusion has been investigated at a temperature of 300 °C in the double perovskite material PrBaCo 2 O 5+ δ (PBCO) in flowing air containing 200 mbar of 2 H 2 16 O. Secondary ion mass spectrometry (SIMS) depth profiling of exchanged ceramics has shown PBCO still retains significant oxygen diffusivity (~1.3 × 10 -11 cm 2 s -1 ) at this temperature and that the presence of water ( 2 H 2 16 O), gives rise to an enhancement of the surface exchange rate over that in pure oxygen by a factor of ~3. The 2 H distribution, as inferred from the 2 H 2 16 O - SIMS signal, shows an apparent depth profile which could be interpreted as 2 H diffusion. However, examination of the 3-D distribution of the signal shows it to be nonhomogeneous and probably related to the presence of hydrated layers in the interior walls of pores and is not due to proton diffusion. This suggests that PBCO acts mainly as an oxygen ion mixed conductor when used in PCFC devices, although the presence of a small amount of protonic conductivity cannot be discounted in these materials.

  11. Iron valence in double-perovskite (Ba,Sr,Ca)2FeMoO6: isovalent substitution effect

    International Nuclear Information System (INIS)

    Yasukawa, Y.; Linden, J.; Chan, T.S.; Liu, R.S.; Yamauchi, H.; Karppinen, M.

    2004-01-01

    In the Fe-Mo based B-site ordered double-perovskite, A 2 FeMoO 6.0 , with iron in the mixed-valence II/III state, the valence value of Fe is not precisely fixed at 2.5 but may be fine-tuned by means of applying chemical pressure at the A-cation site. This is shown through a systematic 57 Fe Moessbauer spectroscopy study using a series of A 2 FeMoO 6.0 [A=(Ba,Sr) or (Sr,Ca)] samples with high degree of Fe/Mo order, the same stoichiometric oxygen content and also almost the same grain size. The isomer shift values and other hyperfine parameters obtained from the Moessbauer spectra confirm that Fe remains in the mixed-valence state within the whole range of A constituents. However, upon increasing the average cation size at the A site the precise valence of Fe is found to decrease such that within the A=(Ba,Sr) regime the valence of Fe is closer to II, while within the A=(Sr,Ca) regime it is closer to the actual mixed-valence II/III state. As the valence of Fe approaches II, the difference in charges between Fe and Mo increases, and parallel with this the degree of Fe/Mo order increases. Additionally, for the less-ordered samples an increased tendency of clustering of the antisite Fe atoms is deduced from the Moessbauer data

  12. Electronic structure, magnetic, mechanical and thermo-physical behavior of double perovskite Ba2MgOsO6

    Science.gov (United States)

    Dar, Sajad Ahmad; Srivastava, Vipul; Sakalle, Umesh Kumar; Parey, Vanshree

    2018-02-01

    The electronic structure, the magnetic, elasto-mechanical and thermodynamic belongings of cubic double oxide perovskites Ba2MgOsO6 have been successfully investigated within the full potential linearized augmented plane wave method (FP-LAPW), based upon the density functional theory (DFT). The structural examination reveals ferromagnetic stability and the spin polarized electronic band structure and density of states display half-metallic nature of the compound. The calculated magnetic moment was found to have an integer value of 2μ_B. From the knowledge of obtained elastic constants mechanical properties like Young's modulus ( E), shear modulus ( G), Poisson ratio (ν) and the anisotropic factor have been predicted. The calculated B/ G and Cauchy pressure ( C_{12}-C_{44}) both portray the ductile nature of the compound. For a complete understanding of the thermo-physical behavior of vital parameters like heat capacity, thermal expansion, Grüneisen parameter and Debye temperature were predicted using quasi harmonic Debye approximation.

  13. Enhancement of thermoelectric power factor of Sr2CoMoO6 double perovskite by annealing in reducing atmosphere

    Science.gov (United States)

    Tanwar, Khagesh; Saxena, Mandvi; Maiti, Tanmoy

    2017-10-01

    In general, n-type thermoelectric materials are rather difficult to design. This study particularly pivoted on designing potential environmentally benign oxides based n-type thermoelectric material. We synthesized Sr2CoMoO6 (SCMO) polycrystalline ceramics via the solid-state synthesis route. XRD, SEM, and thermoelectric measurements were carried out for phase constitution, microstructure analysis, and to determine its potential for thermoelectric applications. As-sintered SCMO sample showed an insulator like behavior till 640 °C after which it exhibited an n-type non-degenerate semiconductor behavior followed by a p-n type conduction switching. To stabilize a high temperature n-type behavior, annealing of SCMO in reducing atmosphere (H2) at 1000 °C was carried out. After annealing, the SCMO demonstrated an n-type semiconductor behavior throughout the temperature range of measurement. The electrical conductivity (σ) and the power factor (S2σ) were found to be increased manifold in the annealed SCMO double perovskite.

  14. Double perovskite cathodes for proton-conducting ceramic fuel cells: are they triple mixed ionic electronic conductors?

    Science.gov (United States)

    Téllez Lozano, Helena; Druce, John; Cooper, Samuel J.; Kilner, John A.

    2017-12-01

    18O and 2H diffusion has been investigated at a temperature of 300 °C in the double perovskite material PrBaCo2O5+δ (PBCO) in flowing air containing 200 mbar of 2H216O. Secondary ion mass spectrometry (SIMS) depth profiling of exchanged ceramics has shown PBCO still retains significant oxygen diffusivity ( 1.3 × 10-11 cm2s-1) at this temperature and that the presence of water (2H216O), gives rise to an enhancement of the surface exchange rate over that in pure oxygen by a factor of 3. The 2H distribution, as inferred from the 2H216O- SIMS signal, shows an apparent depth profile which could be interpreted as 2H diffusion. However, examination of the 3-D distribution of the signal shows it to be nonhomogeneous and probably related to the presence of hydrated layers in the interior walls of pores and is not due to proton diffusion. This suggests that PBCO acts mainly as an oxygen ion mixed conductor when used in PCFC devices, although the presence of a small amount of protonic conductivity cannot be discounted in these materials.

  15. Layered Halide Double Perovskites Cs3+nM(II)nSb2X9+3n (M = Sn, Ge) for Photovoltaic Applications.

    Science.gov (United States)

    Tang, Gang; Xiao, Zewen; Hosono, Hideo; Kamiya, Toshio; Fang, Daining; Hong, Jiawang

    2018-01-04

    Over the past few years, the development of lead-free and stable perovskite absorbers with excellent performance has attracted extensive attention. Much effort has been devoted to screening and synthesizing this type of solar cell absorbers. Here, we present a general design strategy for designing the layered halide double perovskites Cs 3+n M(II) n Sb 2 X 9+3n (M = Sn, Ge) with desired photovoltaic-relevant properties by inserting [MX 6 ] octahedral layers, based on the principles of increased electronic dimensionality. Compared to Cs 3 Sb 2 I 9 , more suitable band gaps, smaller carrier effective masses, larger dielectric constants, lower exciton binding energies, and higher optical absorption can be achieved by inserting variable [SnI 6 ] or [GeI 6 ] octahedral layers into the [Sb 2 I 9 ] bilayers. Moreover, our results show that adjusting the thickness of inserted octahedral layers is an effective approach to tune the band gaps and carrier effective masses in a large range. Our work provides useful guidance for designing the promising layered antimony halide double perovskite absorbers for photovoltaic applications.

  16. Magnetic interactions in rhenium-containing rare earth double perovskites Sr{sub 2}LnReO{sub 6} (Ln=rare earths)

    Energy Technology Data Exchange (ETDEWEB)

    Nishiyama, Atsuhide; Doi, Yoshihiro; Hinatsu, Yukio, E-mail: hinatsu@sci.hokudai.ac.jp

    2017-04-15

    The perovskite-type compounds containing both rare earth and rhenium Sr{sub 2}LnReO{sub 6} (Ln=Y, Tb-Lu) have been prepared. Powder X-ray diffraction measurements and Rietveld analysis show that Ln{sup 3+} and Re{sup 5+} ions are structurally ordered at the B site of the perovskite SrBO{sub 3}. Magnetic anomalies are found in their magnetic susceptibility and specific heat measurements at 2.6–20 K for Ln=Y, Tb, Dy, Yb, Lu compounds. They are due to magnetic interactions between Re{sup 5+} ions. The results of the magnetic hysteresis and remnant magnetization measurements for Sr{sub 2}YReO{sub 6} and Sr{sub 2}LuReO{sub 6} indicate that the antiferromagnetic interactions between Re{sup 5+} ions below transition temperatures have a weak ferromagnetic component. The analysis of the magnetic specific heat data for Sr{sub 2}YbReO{sub 6} shows that both the Yb{sup 3+} and Re{sup 5+} ions magnetically order at 20 K. For the case of Sr{sub 2}DyReO{sub 6}, magnetic ordering of the Re{sup 5+} moments occurs at 93 K, and with decreasing temperature, the moments of Dy{sup 3+} ferromagnetically order at 5 K from the measurements of magnetic susceptibility and specific heat. - Graphical abstract: Crystal structure of double perovskite Sr{sub 2}LnReO{sub 6}. Red and black lines show cubic and monoclinic unit cells, respectively. - Highlights: • Double perovskites Sr{sub 2}LnReO{sub 6} (Ln=rare earths) were prepared. • They show an antiferromagnetic transition at 2.6–20 K. • In Sr{sub 2}DyReO{sub 6}, Dy and Re moments magnetically order at 5 and 93 K, respectively.

  17. STRUCTURAL, MAGNETIC, MULTIFERROIC, AND ELECTRONIC PROPERTIES OF SR2 TIMNO6 DOUBLE PEROVSKITE

    Directory of Open Access Journals (Sweden)

    DAVID LANDÍNEZ-TÉLLEZ

    2012-01-01

    Full Text Available En este trabajo reportamos el análisis estructural, ordenamiento magnético, carácter ferroeléctrico y estructura electrónica de la perovskite compleja Sr2TiMnO6. Las muestras fueron producidas mediante reacción de estado sólido. El análisis cristalográfico fue realizado a través de refinamiento Rietveld de los patrones experimentales de rayos x. Los resultados muestran que este material cristaliza en una perovskita tetragonal correspondiente al grupo espacial I4/mmm. Hemos obtenido un acuerdo del 99% entre las propiedades estructurales predichas por la teoría del funcional de la densidad y el ordenamiento estructural determinado mediante refinamiento Rietveld. A través de medidas de susceptibilidad en función de la temperatura encontramos ordenamiento magnético para una temperatura crítica de 44.8 K. Por medio del ajuste con la teoría molecular de ferrimagnetismo establecimos que el ordenamiento magnético se relaciona con una transición paramagnético-ferrimagnético, la cual se corrobora por el comportamiento del inverso de la susceptibilidad en función de la temperatura. La constante de Curie permitió determinar un momento magnético efectivo de 3.5 mB. Medidas de magnetización en función del campo aplicado a T = 40 K, muestra un comportamiento histerético. La curva de polarización en función del campo eléctrico evidencia una característica ferroeléctrica. Experimentalmente se demuestra que el material se comporta como un multiferróico. Cálculos Ab initio de la densidad de estados fueron realizados por medio de la teoría de funcional densidad y del método ondas planas aumentadas linealizadas para orientaciones de espín arriba y abajo. Los cálculos de intercambio y potencial de correlación fueron incluidos a través de la aproximación de densidad local LDA+U. Los resultados de la densidad de estados muestran la característica aislante de este material con un momento magnético efectivo de 3.3mB.

  18. Magnetostructural coupling behavior at the ferromagnetic transition in double-perovskite S r2FeMo O6

    Science.gov (United States)

    Yang, Dexin; Harrison, Richard J.; Schiemer, Jason A.; Lampronti, Giulio I.; Liu, Xueyin; Zhang, Fenghua; Ding, Hao; Liu, Yan'gai; Carpenter, Michael A.

    2016-01-01

    The ordered double-perovskite S r2FeMo O6 (SFMO) possesses remarkable room-temperature low-field colossal magnetoresistivity and transport properties which are related, at least in part, to combined structural and magnetic instabilities that are responsible for a cubic-tetragonal phase transition near 420 K. A formal strain analysis combined with measurements of elastic properties from resonant ultrasound spectroscopy reveal a system with weak biquadratic coupling between two order parameters belonging to Γ4+ and m Γ4+ of parent space group F m 3 ¯m . The observed softening of the shear modulus by ˜50% is due to the classical effects of strain/order parameter coupling at an improper ferroelastic (Γ4+) transition which is second order in character, while the ferromagnetic order parameter (m Γ4+ ) couples only with volume strain. The influence of a third order parameter, for ordering of Fe and Mo on crystallographic B sites, is to change the strength of coupling between the Γ4+ order parameter and the tetragonal shear strain due to the influence of changes in local strain heterogeneity at a unit cell scale. High anelastic loss below the transition point reveals the presence of mobile ferroelastic twin walls which become pinned by oxygen vacancies in a temperature interval near 340 K. The twin walls must be both ferroelastic and ferromagnetic, but due to the weak coupling between the magnetic and structural order parameters it should be possible to pull them apart with a weak magnetic field. These insights into the role of strain coupling and relaxational effects in a system with only weak coupling between three order parameters allow rationalization and prediction of how static and dynamic properties of the material might be tuned in thin film form by choice of strain contrast with a substrate.

  19. Half-metallic and insulating natures in Ru-based ordered double perovskite oxides Ba{sub 2}X{sup III}Ru{sup V}O{sub 6} (X = V, Cr) induced by 3d-t{sub 2g}{sup n} orbital filling

    Energy Technology Data Exchange (ETDEWEB)

    Saad, H.-E.M. Musa, E-mail: musa.1964@gmail.com; Althoyaib, S.S.

    2017-04-01

    In this paper, we present results of a comprehensive systemic study of the crystal, electronic and magnetic structures on two members of Ru-based ordered double perovskite oxides Ba{sub 2}XRuO{sub 6} (X = V, Cr). For the corporate compound, the analysis of density of states (DOS) results suggests that the 3d-t{sub 2g} orbital filling plays a major role in governing the conduction mechanism in these systems. The DOS and magnetic results show that Ba{sub 2}XRuO{sub 6} exhibits half-metallic (HM) nature as X = V, where the electronic structure of Ba{sub 2}V{sup III}Ru{sup V}O{sub 6} with 3d-t{sub 2g}{sup 2} behaves like that of HM ferrimagnetic (FI), switches to compensate FI insulating behavior as X = Cr, with an extra electron filled 3d-t{sub 2g}{sup 3} in Ba{sub 2}Cr{sup III}Ru{sup V}O{sub 6}. We find, on consideration of electron correlation (LSDA+U) and spin-orbital coupling (SOC) effects that the electronic structure of Ba{sub 2}XRuO{sub 6} takes a HM nature, whereas it is completely transformed to insulating nature once an extra electron filled the 3d-t{sub 2g} orbitals in X = Cr case. Such tuning is accompanied by spin-state hopping of one electron from half-filled spin-state in Ru{sup V} (t{sub 2g}{sup 3} e{sub g}{sup 0}) to two and three occupied spin-state in V{sup III} (t{sub 2g}{sup 2} e{sub g}{sup 0}) and Cr{sup III} (t{sub 2g}{sup 3} e{sub g}{sup 0}), respectively. The charge distribution results show that this extra electron occupies chiefly the spin-down of conduction orbitals and plays a major role in determining the electronic and magnetic structures of Ba{sub 2}XRuO{sub 6} system. - Highlights: • Half-metallic and insulating natures are observed in Ba{sub 2}XRuO{sub 6} (X = V, Cr). • 3d-t{sub 2g}{sup n} orbitals filling plays a major role in governing the conduction mechanism. • LSDA+U method under density functional theory (DFT) is considered. • HM ferrimagnetic (FI) (X = V) switch to compensate FI insulating (X = Cr).

  20. Ferromagnetism and half metallicity induced by oxygen vacancies in the double perovskite BaSrNiWO{sub 6}: DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Aharbil, Y. [Laboratoire de Chimie Physique des Matériaux LCPM, Faculté des Sciences Ben M' Sik, Casablanca (Morocco); Labrim, H. [Unité Science de la Matière/DERS/Centre National de l’Energie, des Sciences et des Techniques Nucléaires (CNESTEN), Rabat (Morocco); Benmokhtar, S.; Haddouch, M. Ait [Laboratoire de Chimie Physique des Matériaux LCPM, Faculté des Sciences Ben M' Sik, Casablanca (Morocco); Bahmad, L., E-mail: bahmad@fsr.ac.ma [Mohammed V University in Rabat, Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E. URAC-12, B.P. 1014, Rabat (Morocco); Belhaj, A. [LIRST, Département de Physique, Faculté Poly-disciplinaire, Université Sultan Moulay Slimane, Béni Mellal (Morocco); Ez-Zahraouy, H.; Benyoussef, A. [Mohammed V University in Rabat, Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E. URAC-12, B.P. 1014, Rabat (Morocco)

    2016-11-01

    Using the spin polarized density functional theory (DFT) and exploring the Plane-Wave Self-Consistent Field (PWscf) code implemented in Quantum-ESPRESSO package, we investigate the effect of the Oxygen vacancies (V{sub O}) and the Oxygen interstitial (O{sub i}) on the double perovskite BaSrNiWO{sub 6}. This deals with the magnetic ordering and the electronic structure in such a pure sample exhibiting the insulating anti-ferromagnetic (AFM) state. This study shows that the presence of oxygen deficient defects converts the insulating to half metal with ferromagnetic or anti-ferromagnetic states. The magnetic ordering in BaSrNiWO{sub 6−δ} depends on the position of the Oxygen vacancy in the unit cell. However, it has been shown that the Oxygen interstitial preserves the anti-ferromagnetic propriety. We have computed the formation energies of different positions of the Oxygen vacancy (V{sub O}) and the Oxygen interstitial (O{sub i}) in the BaSrNiWO{sub 6} compound. We showed that the formation of V{sub O} is easier and vice versa for the O{sub i} formation. The obtained results reveal(V{sub O}) and the Oxygen interstitial (O{sub i}) that the anti-ferromagnetic can be converted to ferromagnetic in the double perovskite BaSrNiWO{sub 6} induced by Oxygen vacancies V{sub O}. - Highlights: • We have studied the ferromagnetism and Half Metallicity in Double Perovskite BaSrNiWO{sub 6}. • We have applied the Ab-inito calculations using the DFT approach. • We showed the effects induced by Oxygen Vacancies and Oxygen interstitial. • We found that the magnetic ordering in BaSrNiWO{sub 6−δ} depends on the position of the Oxygen vacancy in the unit cell.

  1. Colossal change in thermopower with temperature-driven p-n-type conduction switching in La x Sr2-x TiFeO6 double perovskites

    Science.gov (United States)

    Roy, Pinku; Maiti, Tanmoy

    2018-02-01

    Double perovskite materials have been studied in detail by many researchers, as their magnetic and electronic properties can be controlled by the substitution of alkaline earth metals or lanthanides in the A site and transition metals in the B site. Here we report the temperature-driven, p-n-type conduction switching assisted, large change in thermopower in La3+-doped Sr2TiFeO6-based double perovskites. Stoichiometric compositions of La x Sr2-x TiFeO6 (LSTF) with 0  ⩽  x  ⩽  0.25 were synthesized by the solid-state reaction method. Rietveld refinement of room-temperature XRD data confirmed a single-phase solid solution with cubic crystal structure and Pm\\bar{3}m space group. From temperature-dependent electrical conductivity and Seebeck coefficient (S) studies it is evident that all the compositions underwent an intermediate semiconductor-to-metal transition before the semiconductor phase reappeared at higher temperature. In the process of semiconductor-metal-semiconductor transition, LSTF compositions demonstrated temperature-driven p-n-type conduction switching behavior. The electronic restructuring which occurs due to the intermediate metallic phase between semiconductor phases leads to the colossal change in S for LSTF oxides. The maximum drop in thermopower (ΔS ~ 2516 µV K-1) was observed for LSTF with x  =  0.1 composition. Owing to their enormous change in thermopower of the order of millivolts per kelvin, integrated with p-n-type resistance switching, these double perovskites can be used for various high-temperature multifunctional device applications such as diodes, sensors, switches, thermistors, thyristors, thermal runaway monitors etc. Furthermore, the conduction mechanisms of these oxides were explained by the small polaron hopping model.

  2. A -Site Ordered Double Perovskite CaMnTi 2 O 6 as a Multifunctional Piezoelectric and Ferroelectric–Photovoltaic Material

    Energy Technology Data Exchange (ETDEWEB)

    Gou, Gaoyang [Frontier Institute; Charles, Nenian [Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States; Shi, Jing [MOE Key Laboratory; Rondinelli, James M. [Department; Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States

    2017-09-11

    The double perovskite CaMnTi2O6, is a rare A site ordered perovskite oxide that exhibits a sizable ferroelectric polarization and relatively high Curie temperature. Using first-principles calculations combined with detailed symmetry analyses, we identify the origin of the ferroelectricity in CaMnTi2O6. We further explore the material properties of CaMnTi2O6, including its ferroelectric polarization, dielectric and piezoelectric responses, magnetic order, electronic structure, and optical absorption coefficient. It is found that CaMnTi2O6 exhibits room-temperature-stable ferroelectricity and moderate piezoelectric responses. Moreover, CaMnTi2O6 is predicted to have a semiconducting energy band gap similar to that of BiFeO3, and its band gap can further be tuned-via distortions of the planar Mn-O bond lengths. CaMnTi2O6 exemplifies a new class of single-phase semiconducting ferroelectric perovskites for potential applications in ferroelectric photovoltaic solar cells.

  3. Ultrafast atomic layer-by-layer oxygen vacancy-exchange diffusion in double-perovskite LnBaCo2O5.5+δ thin films.

    Science.gov (United States)

    Bao, Shanyong; Ma, Chunrui; Chen, Garry; Xu, Xing; Enriquez, Erik; Chen, Chonglin; Zhang, Yamei; Bettis, Jerry L; Whangbo, Myung-Hwan; Dong, Chuang; Zhang, Qingyu

    2014-04-22

    Surface exchange and oxygen vacancy diffusion dynamics were studied in double-perovskites LnBaCo2O5.5+δ (LnBCO) single-crystalline thin films (Ln = Er, Pr; -0.5 atoms in the LnBCO thin films is taking the layer by layer oxygen-vacancy-exchange mechanism. The first principles density functional theory calculations indicate that hydrogen atoms are present in LnBCO as bound to oxygen forming O-H bonds. This unprecedented oscillation phenomenon provides the first direct experimental evidence of the layer by layer oxygen vacancy exchange diffusion mechanism.

  4. Structure, magnetism and electronic properties in 3d-5d based double perovskite ({Sr_{1-x}} Y x )2FeIrO6

    Science.gov (United States)

    Kharkwal, K. C.; Pramanik, A. K.

    2017-12-01

    The 3d-5d based double perovskites are of current interest as they provide model systems to study the interplay between electronic correlation (U) and spin-orbit coupling (SOC). Here, we report detailed structural, magnetic and transport properties of doped double perovskite material (Sr1-x Y x )2FeIrO6 with x ≤slant 0.2 . With substitution of Y, the system retains its original crystal structure but structural parameters change with x in nonmonotonic fashion. The magnetization data for Sr2FeIrO6 show antiferromagnetic type magnetic transition around 45 K however, a close inspection of the data indicates a weak magnetic phase transition around 120 K. No change of structural symmetry has been observed down to low temperature, although the lattice parameters show sudden changes around the magnetic transitions. Sr2FeIrO6 shows an insulating behavior over the whole temperature range, which nevertheless does not change with Y substitution. The nature of charge conduction is found to follow thermally activated Mott’s variable range hopping and power law behavior for parent and doped samples, respectively. Interestingly, evolution of structural, magnetic and transport behavior in (Sr1-x Y x )2FeIrO6 is observed to reverse with x > 0.1 , which is believed to arise due to a change in the transition metal ionic state.

  5. First principles study of the structural and electronic properties of double perovskite Ba{sub 2}YTaO{sub 6} in cubic and tetragonal phases

    Energy Technology Data Exchange (ETDEWEB)

    Deluque Toro, C.E., E-mail: deluquetoro@gmail.com [Grupo de Nuevos Materiales, Universidad Popular del Cesar, Valledupar (Colombia); Rodríguez M, Jairo Arbey [Grupo de Estudios de Materiales—GEMA, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Landínez Téllez, D.A. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Moreno Salazar, N.O. [Departamento de Física, Universidade Federal de Sergipe (Brazil); Roa-Rojas, J. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia)

    2014-12-15

    The Ba{sub 2}YTaO{sub 6} double perovskite presents a transition from cubic (Fm−3m) to tetragonal structure (I4/m) at high temperature. In this work, we present a detailed study of the structural and electronic properties of the double perovskite Ba{sub 2}YTaO{sub 6} in space group Fm−3m and I4/m. Calculations were made with the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient (GGA) and Local Density (LDA) approximations. From the minimization of energy as a function of volume and the fitting of the Murnaghan equation some structural characteristics were determined as, for example, total energy, lattice parameter (a=8.50 Å in cubic phase and a=5.985 Å and c=8.576 Å in tetragonal), bulk modulus (135.6 GPa in cubic phase and 134.1 GPa in tetragonal phase) and its derivative. The study of the electronic characteristics was performed from the analysis of the electronic density of states (DOS). We find a non-metallic behavior for this with a direct band gap of approximately 3.5 eV and we found that the Ba{sub 2}YTaO{sub 6} (I4/m) phase is the most stable one. {sup ©} 2013 Elsevier Science. All rights reserved.

  6. First principles study of the structural and electronic properties of double perovskite Ba2YTaO6 in cubic and tetragonal phases

    International Nuclear Information System (INIS)

    Deluque Toro, C.E.; Rodríguez M, Jairo Arbey; Landínez Téllez, D.A.; Moreno Salazar, N.O.; Roa-Rojas, J.

    2014-01-01

    The Ba 2 YTaO 6 double perovskite presents a transition from cubic (Fm−3m) to tetragonal structure (I4/m) at high temperature. In this work, we present a detailed study of the structural and electronic properties of the double perovskite Ba 2 YTaO 6 in space group Fm−3m and I4/m. Calculations were made with the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient (GGA) and Local Density (LDA) approximations. From the minimization of energy as a function of volume and the fitting of the Murnaghan equation some structural characteristics were determined as, for example, total energy, lattice parameter (a=8.50 Å in cubic phase and a=5.985 Å and c=8.576 Å in tetragonal), bulk modulus (135.6 GPa in cubic phase and 134.1 GPa in tetragonal phase) and its derivative. The study of the electronic characteristics was performed from the analysis of the electronic density of states (DOS). We find a non-metallic behavior for this with a direct band gap of approximately 3.5 eV and we found that the Ba 2 YTaO 6 (I4/m) phase is the most stable one. © 2013 Elsevier Science. All rights reserved

  7. Photovoltaic performance and stability of fullerene/cerium oxide double electron transport layer superior to single one in p-i-n perovskite solar cells

    Science.gov (United States)

    Xing, Zhou; Li, Shu-Hui; Wu, Bao-Shan; Wang, Xin; Wang, Lu-Yao; Wang, Tan; Liu, Hao-Ran; Zhang, Mei-Lin; Yun, Da-Qin; Deng, Lin-Long; Xie, Su-Yuan; Huang, Rong-Bin; Zheng, Lan-Sun

    2018-06-01

    Interface engineering that involves in the metal cathodes and the electron transport layers (ETLs) facilitates the simultaneous improvement of device performances and stability in perovskite solar cells (PSCs). Herein, low-temperature solution-processed cerium oxide (CeOx) films are prepared by a facile sol-gel method and employed as the interface layers between [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) and an Ag back contact to form PC61BM/CeOx double ETLs. The introduction of CeOx enables electron extraction to the Ag electrode and protects the underlying perovskite layer and thus improves the device performance and stability of the p-i-n PSCs. The p-i-n PSCs with double PC61BM/CeOx ETLs demonstrate a maximum power conversion efficiency (PCE) of 17.35%, which is superior to those of the devices with either PC61BM or CeOx single ETLs. Moreover, PC61BM/CeOx devices exhibit excellent stability in light soaking, which is mainly due to the chemically stable CeOx interlayer. The results indicate that CeOx is a promising interface modification layer for stable high-efficiency PSCs.

  8. Enhanced thermoelectric figure-of-merit in environmentally benign BaxSr2-xTiCoO6 double perovskites

    Science.gov (United States)

    Saxena, Mandvi; Roy, Pinku; Acharya, Megha; Bose, Imon; Tanwar, Khagesh; Maiti, Tanmoy

    2016-12-01

    Environmental friendly, non-toxic double perovskite BaxSr2-xTiCoO6 compositions with 0 ≤ x ≤ 0.2 were synthesized using solid-state reaction route for high temperature thermoelectric (TE) applications. XRD and SEM studies confirmed the presence of single-phase solid solution with highly dense microstructure for all the oxide compositions. Temperature dependent electrical conductivity measurement showed semiconductor to metal (M-S) transition in these double perovskites. Incorporation of barium in Sr2TiCoO6 pushed M-S transition to higher temperature making it a potential candidate for high temperature TE applications. Conductivity behaviors of these oxides were explained by small polaron model. Furthermore, these oxides exhibit a glass like behavior resulting in low thermal conductivity. Low temperature dielectric measurement revealed relaxor ferroelectric behavior in these oxides below room temperature. Transition of these relaxors into a glassy state beyond Burns temperature (TD) was found responsible for having low thermal conductivity in these oxides. Maximum dimensionless TE figure-of-merit ZT = 0.29 at 1223 K was achieved for BaxSr2-xTiCoO6 composition with x = 0.2.

  9. Structure, magnetism and electronic properties in 3d-5d based double perovskite (Sr1-xYx)2FeIrO6.

    Science.gov (United States)

    Kharkwal, Kishor Chandra; Pramanik, Ashim Kumar

    2017-10-17

    The 3$d$-5$d$ based double perovskites are of current interest as they provide model system to study the interplay between electronic correlation ($U$) and spin-orbit coupling (SOC). Here we report detailed structural, magnetic and transport properties of doped double perovskite material (Sr$_{1-x}$Y$_x$)$_2$FeIrO$_6$ with $x$ $\\leq$ 0.2. With substitution of Y, system retains its original crystal structure but structural parameters modify with $x$ in nonmonotonic fashion. The magnetization data for Sr$_2$FeIrO$_6$ show antiferromagnetic type magnetic transition around 45 K, however, a close inspection in data indicates a weak magnetic phase transition around 120 K. No change of structural symmetry has been observed down to low temperature, although the lattice parameters show sudden changes around the magnetic transitions. Sr$_2$FeIrO$_6$ shows an insulating behavior over the whole temperature range which yet does not change with Y substitution. Nature of charge conduction is found to follow thermally activated Mott's variable range hopping and power law behavior for parent and doped samples, respectively. Interestingly, evolution of structural, magnetic and transport behavior in (Sr$_{1-x}$Y$_x$)$_2$FeIrO$_6$ is observed to reverse with $x$ $>$ 0.1 which is believed to arise due to change in transition metal ionic state. © 2017 IOP Publishing Ltd.

  10. Magnetic entropy change and critical exponents in double perovskite Y{sub 2}NiMnO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, G. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India); Tripathi, T.S. [Inter-University Accelerator Centre, New Delhi-110067 (India); Saha, J. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India); Patnaik, S., E-mail: spatnaik@mail.jnu.ac.in [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India)

    2014-11-15

    We report the magnetic entropy change (ΔS{sub M}) and the critical exponents in the double perovskite manganite Y{sub 2}NiMnO{sub 6} with a ferromagnetic to paramagnetic transition T{sub C}∼85K. For a magnetic field change ΔH=80kOe, a maximum magnetic entropy change ΔS{sub M}=−6.57J/kgK is recorded around T{sub C}. The critical exponents β=0.363±0.05 and γ=1.331±0.09 obtained from power law fitting to spontaneous magnetization M{sub S}(T) and the inverse initial susceptibility χ{sub 0}{sup −1}(T) satisfy well to values derived for a 3D-Heisenberg ferromagnet. The critical exponent δ=4.761±0.129 is determined from the isothermal magnetization at T{sub C}. The scaling exponents corresponding to second order phase transition are consistent with the exponents from Kouvel–Fisher analysis and satisfy Widom's scaling relation δ=1+(γ/β). Additionally, they also satisfy the single scaling equation M(H,ϵ)=ϵ{sup β}f±(H/ϵ{sup β+γ}) according to which the magnetization-field-temperature data around T{sub C} should collapse into two curves for temperatures below and above T{sub C}. - Highlights: • The magneto-caloric (MC) effect and the critical exponent analysis in Y{sub 2}NiMnO{sub 6} are studied. • Methods such as Kouvel–Fisher, Widom's and Mean-Field scaling are used. • The magnetic ground state in Y{sub 2}NiMnO{sub 6} is based on isotropic 3D Heisenberg model. • The large MC effect can be utilized towards magnetic refrigeration around 77 K. • The nearest neighbor interaction in Y{sub 2}NiMnO{sub 6} rules out ferroelectricity.

  11. Coexistence of room temperature ferroelectricity and ferrimagnetism in multiferroic BiFeO3-Bi0.5Na0.5TiO3 solid solution

    International Nuclear Information System (INIS)

    Tian, Z.M.; Wang, C.H.; Yuan, S.L.; Wu, M.S.; Ma, Z.Z.; Duan, H.N.; Chen, L.

    2011-01-01

    Highlights: → In this study, the coexistence of ferroelectrics and ferrimagnetism have been observed at room temperature for the (1 - x)BiFeO 3 -xBi 0.5 Na 0.5 TiO 3 (x = 0.37) solid solutions. → X-ray diffraction and Raman spectroscopy measurements show a single-phase perovskite structure with no impurities identified. → A magnetic transition from paramagnetic (PM) to ferrimagnetic (Ferri) ordering is observed for the solution with Curie temperature T C ∼ 330 K. - Abstract: The structure, ferroelectric and magnetic properties of (1 - x)BiFeO 3 -xBi 0.5 Na 0.5 TiO 3 (x = 0.37) solid solution fabricated by a sol-gel method have been investigated. X-ray diffraction and Raman spectroscopy measurements show a single-phase perovskite structure with no impurities identified. Compared with pure BiFeO 3 , the coexistence of ferroelectricity and ferrimagnetism have been observed at room temperature for the solution with remnant polarization P r = 1.41 μC/cm 2 and remnant magnetization M r = 0.054 emu/g. Importantly, a magnetic transition from ferrimagnetic (FM) ordering to paramagnetic (PM) state is observed, with Curie temperature T C ∼ 330 K, being explained in terms of the suppression of cycloid spin configuration by the structural distortion.

  12. Crystal structure and surface characteristics of Sr-doped GdBaCo2O6−δ double perovskites: oxygen evolution reaction and conductivity

    KAUST Repository

    Pramana, Stevin S.

    2017-12-04

    A cheap and direct solution towards engineering better catalysts through identification of novel materials is required for a sustainable energy system. Perovskite oxides have emerged as potential candidates to replace the less economically attractive Pt and IrO2 water splitting catalysts. In this work, excellent electrical conductivity (980 S cm−1) was found for the double perovskite of composition GdBa0.6Sr0.4Co2O6−δ which is consistent with a better oxygen evolution reaction activity with the onset polarisation of 1.51 V with respect to a reversible hydrogen electrode (RHE). GdBa1−xSrxCo2O6−δ with increasing Sr content was found to crystallise in the higher symmetry tetragonal P4/mmm space group in comparison with the undoped GdBaCo2O6−δ which is orthorhombic (Pmmm), and yields higher oxygen uptake, accompanied by higher Co oxidation states. This outstanding electrochemical performance is explained by the wider carrier bandwidth, which is a function of Co–O–Co buckling angles and Co–O bond lengths. Furthermore the higher oxygen evolution activity was observed despite the formation of non-lattice oxides (mainly hydroxide species) and enrichment of alkaline earth ions on the surface.

  13. Crystal structure and surface characteristics of Sr-doped GdBaCo2O6−δ double perovskites: oxygen evolution reaction and conductivity

    KAUST Repository

    Pramana, Stevin S.; Cavallaro, Andrea; Li, Cheng; Handoko, Albertus D.; Chan, Kuang Wen; Walker, Robert J.; Regoutz, Anna; Herrin, Jason S.; Yeo, Boon Siang; Payne, David J.; Kilner, John A.; Ryan, Mary P.; Skinner, Stephen J.

    2017-01-01

    A cheap and direct solution towards engineering better catalysts through identification of novel materials is required for a sustainable energy system. Perovskite oxides have emerged as potential candidates to replace the less economically attractive Pt and IrO2 water splitting catalysts. In this work, excellent electrical conductivity (980 S cm−1) was found for the double perovskite of composition GdBa0.6Sr0.4Co2O6−δ which is consistent with a better oxygen evolution reaction activity with the onset polarisation of 1.51 V with respect to a reversible hydrogen electrode (RHE). GdBa1−xSrxCo2O6−δ with increasing Sr content was found to crystallise in the higher symmetry tetragonal P4/mmm space group in comparison with the undoped GdBaCo2O6−δ which is orthorhombic (Pmmm), and yields higher oxygen uptake, accompanied by higher Co oxidation states. This outstanding electrochemical performance is explained by the wider carrier bandwidth, which is a function of Co–O–Co buckling angles and Co–O bond lengths. Furthermore the higher oxygen evolution activity was observed despite the formation of non-lattice oxides (mainly hydroxide species) and enrichment of alkaline earth ions on the surface.

  14. Crystallographic and electronic structure of the Ca{sub 2}TiMnO{sub 6} double perovskite

    Energy Technology Data Exchange (ETDEWEB)

    López, J.P. Garzón [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Grupo de Estudios de Materiales – GEMA, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Cardona, R. [Grupo de Estudios de Materiales – GEMA, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Santos, A. Sarmiento [Grupo de Superficies, Electroquímica y Corrosión, Universidad Pedagógica y Tecnológica de Colombia, Tunja (Colombia); Téllez, D.A. Landínez [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Roa-Rojas, J., E-mail: jroar@unal.edu.co [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia)

    2014-12-15

    In this work, we report synthesis and crystalline structure study of the Ca{sub 2}TiMnO{sub 6} complex perovskite, by X-ray diffraction experiments and through the application of the Rietveld refinement using the GSAS code. Results revealed the crystallization of the system in a tetragonal perovskite with the characteristic structure given by I4/m (#87) space group and lattice parameters a=5.339(4) Å and c=7.736(6) Å. Ab initio calculations of density of states (DOS) and electronic structure were carried out for this perovskite-like system, by the Density Functional Theory (DFT) and using the Full-potential Linearized Augmented Plane Waves (FP-LAPW) method. The exchange-correlation potential was treated using the Generalized Gradient Approximation (GGA). All calculations were carried-out using spin polarization. For the up spin orientation the compound has a semiconducting behavior and for down spin polarization it behaves like a conductor. The calculated effective magnetic moment in cell was 4.02 μ{sub B}, which is close to the expected value calculated from Hund's rules.

  15. Raman and infrared spectroscopic investigations of a ferroelastic phase transition in B a2ZnTe O6 double perovskite

    Science.gov (United States)

    Moreira, Roberto L.; Lobo, Ricardo P. S. M.; Ramos, Sérgio L. L. M.; Sebastian, Mailadil T.; Matinaga, Franklin M.; Righi, Ariete; Dias, Anderson

    2018-05-01

    The low-temperature vibrational properties of B a2ZnTe O6 double-perovskite ceramics obtained by the solid-state route were investigated by Raman scattering and Fourier-transform infrared reflectivity. We found that this material undergoes a reversible ferroelastic phase transition at around 140 K, well compatible with a recently proposed rhombohedral-to-monoclinic structural change that would occur below 165 K. Complementary calorimetric measurements showed that the phase transition has a first-order character, with an entropy jump compatible with a displacive mechanism. The vibrational spectra show clearly the splitting of the doubly degenerate E modes into nondegenerate representations of the low-symmetry phase. In particular, the lowest-frequency Raman mode presents soft-mode behavior and splits below the critical temperature, confirming the in-plane ferroelastic deformation in the low-temperature phase.

  16. Is the ground state of 5d4 double-perovskite Iridate Ba2YIrO6 magnetic or nonmagnetic?

    Science.gov (United States)

    Gong, Hoshin; Kim, Kyoo; Kim, Beom Hyun; Kim, Bongjae; Kim, Junwon; Min, B. I.

    2018-05-01

    We have investigated electronic structures and magnetic properties of double perovskite Iridate Ba2YIrO6 with 5d4 configuration, employing the exact diagonalization method for multi-site clusters. We have considered a many-body Hamiltonian for all d states (eg and t2g) including all relevant physical parameters such as the Coulomb correlation, spin-orbit coupling, crystal-field effect, and Hund coupling. We have found that the ground state of Ba2YIrO6 is nonmagnetic and that the Hund coupling plays an important role in the magnetic properties of the 5d4 systems, unlike the well-studied 5d5 systems.

  17. Single Crystal Growth of Multiferroic Double Perovskites: Yb2CoMnO6 and Lu2CoMnO6

    Directory of Open Access Journals (Sweden)

    Hwan Young Choi

    2017-02-01

    Full Text Available We report on the growth of multiferroic Yb2CoMnO6 and Lu2CoMnO6 single crystals which were synthesized by the flux method with Bi2O3. Yb2CoMnO6 and Lu2CoMnO6 crystallize in a double-perovskite structure with a monoclinic P21/n space group. Bulk magnetization measurements of both specimens revealed strong magnetic anisotropy and metamagnetic transitions. We observed a dielectric anomaly perpendicular to the c axis. The strongly coupled magnetic and dielectric states resulted in the variation of both the dielectric constant and the magnetization by applying magnetic fields, offering an efficient approach to accomplish intrinsically coupled functionality in multiferroics.

  18. First-principles study on ferromagnetism in double perovskite Sr2AlTaO6 doped with Cu or Zn at B sites

    Science.gov (United States)

    Li, Y. D.; Wang, C. C.; Guo, Y. M.; Yu, Y.; Lu, Q. L.; Huang, S. G.; Li, Q. J.; Wang, H.; Cheng, R. L.; Liu, C. S.

    2018-05-01

    The possibilities of ferromagnetism induced by nonmagnetic dopants (Cu, Zn) in double perovskite Sr2AlTaO6 at B sites are investigated by density functional theory. Calculations reveal that substitutions at Ta-site tend to form high spin electronic configurations and could induce ferromagnetism which can be attributed to the hole-mediated p- d hybridization between Cu (or Zn) eg states and the neighboring O 2p states. The dopants preferably substitute at Al-site and adopt low spin electronic structures. Due to the smaller hole concentration and weaker covalent intensity, Sr2AlTaO6 with dopants at Al-site exhibits p-type metallic semiconductors without spin polarization.

  19. Bandgap engineering of lead-free double perovskite Cs{sub 2}AgBiBr{sub 6} through trivalent metal alloying

    Energy Technology Data Exchange (ETDEWEB)

    Du, Ke-zhao; Mitzi, David B. [Department of Mechanical Engineering and Materials Science, and Department of Chemistry, Duke University, Durham, NC (United States); Meng, Weiwei; Wang, Xiaoming; Yan, Yanfa [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, OH (United States)

    2017-07-03

    The double perovskite family, A{sub 2}M{sup I}M{sup III}X{sub 6}, is a promising route to overcome the lead toxicity issue confronting the current photovoltaic (PV) standout, CH{sub 3}NH{sub 3}PbI{sub 3}. Given the generally large indirect band gap within most known double perovskites, band-gap engineering provides an important approach for targeting outstanding PV performance within this family. Using Cs{sub 2}AgBiBr{sub 6} as host, band-gap engineering through alloying of In{sup III}/Sb{sup III} has been demonstrated in the current work. Cs{sub 2}Ag(Bi{sub 1-x}M{sub x})Br{sub 6} (M=In, Sb) accommodates up to 75 % In{sup III} with increased band gap, and up to 37.5 % Sb{sup III} with reduced band gap; that is, enabling ca. 0.41 eV band gap modulation through introduction of the two metals, with smallest value of 1.86 eV for Cs{sub 2}Ag(Bi{sub 0.625}Sb{sub 0.375})Br{sub 6}. Band structure calculations indicate that opposite band gap shift directions associated with Sb/In substitution arise from different atomic configurations for these atoms. Associated photoluminescence and environmental stability of the three-metal systems are also assessed. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Structural evolution of the double perovskites Sr{sub 2}B'UO{sub 6} (B' = Mn, Fe, Co, Ni, Zn) upon reduction: Magnetic behavior of the uranium cations

    Energy Technology Data Exchange (ETDEWEB)

    Pinacca, R.M., E-mail: rmp@unsl.edu.ar [Area de Quimica General e Inorganica ' Dr. Gabino F. Puelles' , Departamento de Quimica, Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis (Argentina); Viola, M.C.; Pedregosa, J.C. [Area de Quimica General e Inorganica ' Dr. Gabino F. Puelles' , Departamento de Quimica, Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis (Argentina); Carbonio, R.E. [INFIQC (CONICET), Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, X5000HUA Cordoba (Argentina); Lope, M.J. Martinez; Alonso, J.A. [Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco, 28049 Madrid (Spain)

    2011-11-15

    Highlights: {yields} Evolution of the double perovskites Sr{sub 2}B'UO{sub 6} upon reduction were studied by XRPD. {yields} Orthorhombic (Pnma) disordered perovskites SrB'{sub 0.5-x}U{sub 0.5+x}O{sub 3} were obtained at 900 {sup o}C. {yields} U{sup 5+/4+} and Zn{sup 2+} cations are distributed at random over the octahedral positions. {yields} AFM ordering for the perovskite with B' = Zn appears below 30 K. -- Abstract: We describe the preparation of five perovskite oxides obtained upon reduction of Sr{sub 2}B'UO{sub 6} (B' = Mn, Fe, Co, Ni, Zn) with H{sub 2}/N{sub 2} (5%/95%) at 900 {sup o}C during 8 h, and their structural characterization by X-ray powder diffraction (XRPD). During the reduction process there is a partial segregation of the elemental metal when B' = Co, Ni, Fe, and the corresponding B'O oxide when B' = Mn, Zn. Whereas the parent, oxygen stoichiometric double perovskites Sr{sub 2}B'UO{sub 6} are long-range ordered concerning B' and U cations. The crystal structures of the reduced phases, SrB'{sub 0.5-x}U{sub 0.5+x}O{sub 3} with 0.37 < x < 0.27, correspond to simple, disordered perovskites; they are orthorhombic, space group Pnma (No. 62), with a full cationic disorder at the B site. Magnetic measurements performed on the phase with B' = Zn, indicate uncompensated antiferromagnetic ordering of the U{sup 5+}/U{sup 4+} sublattice below 30 K.

  1. Structural phase transitions at high-temperature in double perovskite Sr{sub 2}GdRuO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Triana, C.A.; Corredor, L.T.; Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, A.A. 14490, Bogota D.C (Colombia); Roa-Rojas, J., E-mail: jroar@unal.edu.co [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, A.A. 14490, Bogota D.C (Colombia)

    2012-08-15

    The crystal structure evolution of the Sr{sub 2}GdRuO{sub 6} complex perovskite at high-temperature has been investigated over a wide temperature range between 298 K{<=}T{<=}1273 K. Powder X-ray diffraction measurements at room temperature and Rietveld analysis show that this compounds crystallizes in a monoclinic perovskite-type structure with P2{sub 1}/n (no. 14) space group and the 1:1 ordered arrangement of Ru{sup 5+} and Gd{sup 3+} cations over the six-coordinate M sites, with lattice parameters a=5.81032(8) A, b=5.82341(4) A, c=8.21939(7) A, V=278.11(6) A{sup 3} and angle {beta}=90.311(2){sup o}. The high-temperature analysis shows that this material suffers two-phase transitions. At 373 K it adopts a monoclinic perovskite structure with I2/m space group, and lattice parameters a=5.81383(2) A, b=5.82526(4) A, c=8.22486(1) A, V=278.56(2) A{sup 3} and angle {beta}=90.28(2){sup o}. Above of 773 K, it suffers a phase transition from monoclinic I2/m to tetragonal I4/m, with lattice parameters a=5.84779(1) A, c=8.27261(1) A, V=282.89(5) A{sup 3} and angle {beta}=90.02(9){sup o}. The high-temperature phase transition from monoclinic I2/m to tetragonal I4/m is characterized by strongly anisotropic displacements of the anions.

  2. Structural and magnetic properties of double-perovskite Ba2MnMoO6 by density functional theory

    International Nuclear Information System (INIS)

    Cardona, R.; Landinez Tellez, D.A.; Arbey Rodriguez M, J.; Fajardo, F.; Roa-Rojas, J.

    2008-01-01

    Perovskite-like materials which include magnetic elements have relevance due to the technological perspectives in the spintronics industry. In this work, we report the studies of Ba 2 MnMoO 6 material by using the density functional theory. The interchange-correlation potential was included through the generalized gradient approximation. Our structural calculations are in agreement with the experimental results which show that the material crystallizes in the 225 space group (Fm3-bar m) and has a lattice parameter of about 8070 A. The density of states study was carried out by considering the up and down spin orientations. Results show that Ba 2 MnMoO 6 has a conductor behavior due to dominant Mn spin-up and Mo spin-down contributions. The magnetic moment was calculated to be 2.9 μ B

  3. Calculated g-factors of 5d double perovskites Ba.sub.2./sub.NaOsO.sub.6./sub. and Ba.sub.2./sub.YOsO.sub.6./sub.

    Czech Academy of Sciences Publication Activity Database

    Ahn, K.H.; Pajskr, K.; Lee, K.W.; Kuneš, Jan

    2017-01-01

    Roč. 95, č. 6 (2017), s. 1-5, č. článku 064416. ISSN 2469-9950 R&D Projects: GA ČR GA13-25251S Institutional support: RVO:68378271 Keywords : double perovskite * g-factor Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.836, year: 2016

  4. Magnetodielectric effect in relaxor/ferrimagnetic composites

    Energy Technology Data Exchange (ETDEWEB)

    Naveed Ul-Haq, M., E-mail: naveedulhaq07@gmail.com [Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Institute for Materials Sciences and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Essen 45141 (Germany); Yunus, Tayyaba; Mumtaz, Arif [Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Shvartsman, V.V.; Lupascu, Doru C. [Institute for Materials Sciences and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Essen 45141 (Germany)

    2015-08-15

    Highlights: • Single phase ferroelectric (relaxor)/ferrimagnetic composites are synthesized. • The composite shows magnetodielectric effect. • Effect of interface strain is discussed. • MD is explained via defining a local order parameter q(T). - Abstract: We report on the effect of an applied static magnetic field on the dielectric properties of ferroelectric relaxor/ferrimagnetic composites consisting of [Ba(Sn{sub 0.3}Ti{sub 0.7})O{sub 3}]{sub 0.8}–[CoFe{sub 2}O{sub 4}]{sub 0.2} (BST{sub 0.8}–CFO{sub 0.2}). The pure Ba(Sn{sub 0.3}Ti{sub 0.7})O{sub 3} (BST30) as well as the composites, were synthesized by solid state reaction method. The X-ray diffraction analysis confirmed that BST30 and CFO coexist in the composite without any secondary phase. The real and the imaginary part of the dielectric permittivity were studied as a function of temperature, with and without static magnetic field, respectively. Relaxor characteristics such as dielectric permittivity and its peak temperature are observed to vary with the magnetic field. This is explained in the context that the applied magnetic field creates magnetostriction in the ferrite phase which is transferred to the relaxor phase via the interface coupling. The strain in the relaxor phase results in the reorientation of local polarization entities, polar nano regions (PNRs), which alters the dielectric characteristics of the sample. This effect is explained in relation to local order parameter q(T) which is found to increase in a certain temperature range above the typical ferroelectric temperature regime with the application of magnetic field.

  5. Synthesis, Single Crystal Growth, and Properties of Cobalt Deficient Double Perovskite EuBaCo2−xO6−δ (x = 0–0.1

    Directory of Open Access Journals (Sweden)

    S. V. Telegin

    2017-01-01

    Full Text Available The cobalt deficient double perovskites EuBaCo2−xO6−δ with x=0–0.1 were obtained both as powders and as single crystal. Formation of cobalt vacancies in their crystal lattice was shown to be accompanied by the formation of oxygen ones. Chemical lattice strain caused by this cooperative disordering of cobalt and oxygen sublattices was found to be isotropic contrary to that caused by the formation of oxygen vacancies only. Cobalt deficiency was also shown to lead to lowering overall conductivity and Seebeck coefficient of EuBaCo2−xO6−δ double perovskites as a result of simultaneous decrease of charge carriers’ concentration and their mobility as well as number of sites available for electrons and holes transfer. Strong anisotropy of the overall conductivity of the single crystal double perovskites EuBaCo2−xO6−δ was found and explained on the basis of preferential location of oxygen vacancies in the rare-earth-oxygen- (REO- planes.

  6. An electron diffraction and bond valence sum study of the space group symmetries and structures of the photocatalytic 1:1 ordered A2InNbO6 double perovskites (A=Ca2+, Sr2+, Ba2+)

    International Nuclear Information System (INIS)

    Ting, V.; Liu, Y.; Withers, R.L.; Krausz, E.

    2004-01-01

    A careful investigation has been carried out into the space group symmetries, structures and crystal chemistries of the 1:1 B-site ordered double perovskites A 2 InNbO 6 (A=Ca 2+ , Sr 2+ , Ba 2+ ) using a combination of bond valence sum calculations, powder XRD and electron diffraction. A recent investigation of these compounds by Yin et al. reported a random distribution of In 3+ and Nb 5+ ions onto the perovskite B-site positions of these compounds and hence Pm3-barm (a=a p , subscript p for parent perovskite sub-structure) space group symmetry for the A=Ba and Sr compounds and Pnma (a=a p +b p , b=-a p +b p , c=2c p ) space group symmetry for the A=Ca compound. A careful electron diffraction study, however, shows that both the A=Ca and Sr compounds occur at room temperature in P12 1 /n1 (a=a p +b p , b=-a p +b p , c=2c p ) perovskite-related superstructure phases while the A=Ba compound occurs in the Fm3-barm, a=2a p , elpasolite structure type. Bond valence sum calculations are used to explain why this should be so as well as to provide a useful first-order approximation to the structures of each of the compounds

  7. On the novel double perovskites A2Fe(Mn0.5W0.5)O6 (A= Ca, Sr, Ba). Structural evolution and magnetism from neutron diffraction data

    Science.gov (United States)

    García-Ramos, Crisanto A.; Larrégola, Sebastián; Retuerto, María; Fernández-Díaz, María Teresa; Krezhov, Kiril; Alonso, José Antonio

    2018-06-01

    New A2Fe(Mn0.5W0.5)O6 (A = Ca, Sr, Ba) double perovskite oxides have been prepared by ceramic techniques. X-ray diffraction (XRD) complemented with neutron powder diffraction (NPD) indicate a structural evolution from monoclinic (space group P21/n) for A = Ca to cubic (Fm-3m) for A = Sr and finally to hexagonal (P63/mmc) for A = Ba as the perovskite tolerance factor increases with the A2+ ionic size. The three oxides present different tilting schemes of the FeO6 and (Mn,W)O6 octahedra. NPD data also show evidence in all cases of a considerable anti-site disordering, involving the partial occupancy of Fe positions by Mn atoms, and vice-versa. Magnetic susceptibility data show magnetic transitions below 50 K characterized by a strong irreversibility between ZFC and FC susceptibility curves. The A = Ca perovskite shows a G-type magnetic structure, with weak ordered magnetic moments due to the mentioned antisite disordering. Interesting magnetostrictive effects are observed for the Sr perovskite below 10 K.

  8. Magnetic and dielectric properties of the ruthenium double perovskites La2MRuO6 (M=Mg, Co, Ni, and Zn)

    International Nuclear Information System (INIS)

    Yoshii, Kenji; Ikeda, Naoshi; Mizumaki, Masaichiro

    2006-01-01

    Magnetic and dielectric properties of the ruthenium double perovskites La 2 MRuO 6 (M=Mg, Co, Ni, and Zn) were investigated. The magnetization measurements for M=Co and Ni showed the existence of magnetic order at 20-30 K. Though the oxides with M=Zn and Mg exhibit a deviation from the Curie-Weiss law, magnetic order was not clearly observed. The result of La 2 ZnRuO 6 was different from that previously reported, in which a ferromagnetic transition was found at around 165 K. The AC dielectric measurements for M = Co and Ni showed large dielectric constants (typically larger than 1000) at around room temperature, suggesting both the formation of short-ranged polar regions and the magnetic origin of large dielectric constant. In addition, two peaks were found for the temperature dependence of the tan δ component for La 2 NiRuO 6 . The behavior suggests the existence of two different polar regions. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  9. Observation of semiconductor to metallic transition and polaron hopping in double perovskite Pr{sub 2}CoTiO{sub 6} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Mahato, Dev K., E-mail: drdevkumar@yahoo.com [Department of Physics, National Institute of Technology Patna, Patna 800005 (India); Sinha, T.P. [Department of Physics, Bose Institute, 93/1, APC Road, Kolkata 700009 (India)

    2017-05-01

    This paper describes semiconductor to metal transition and polaron conduction in double perovskite Pr{sub 2}CoTiO{sub 6} (PCTO) ceramics. The XRD pattern recorded at room temperature confirmed the pure phase, single crystalline structure. The semicircle arc in the impedance plot at each temperature can be attributed to the grain boundary contribution, indicating one dominating response in the measurement frequency range. The semiconductor to metallic transition was also confirmed by the variation of grain boundary resistance (R{sub gb}) with temperature. The activation energy estimated from the imaginary part of electrical modulus and impedance are found to be the characteristic of polaron conduction in PCTO. Ac conductivity followed power law dependence σ{sub ac} = Bω{sup n}. The observed variation of the exponent ‘n’ with temperature suggests the typical of charge transport assisted by a hopping process. The observed minimum in the temperature dependence of frequency exponent ‘n’ strongly suggests that the large polaron tunneling is the dominant transport process.

  10. Magnetic and magneto-transport properties of double perovskite Ba{sub 2-x}Sr{sub x}FeMoO{sub 6} system

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Vibhav; Verma, Vivek; Aloysius, R.P. [National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi-110012 (India); Bhalla, G.L. [Department of Physics and Astrophysics, Delhi University, Delhi (India); Awana, V.P.S.; Kishan, H. [National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi-110012 (India); Kotnala, R.K. [National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi-110012 (India)], E-mail: rkkotnala@gmail.com

    2009-07-15

    The structural magnetic and magneto-transport properties of double perovskite system Ba{sub 2-x}Sr{sub x}FeMoO{sub 6} (0{<=}x{<=}1.0) prepared in bulk polycrystalline form are reported in this paper. X-ray diffraction analysis showed that samples are single phase and the lattice constants decreases with increase in the Sr content. The degree of Fe-Mo ordering has been found decreasing in the series with an increase in the Sr content. Parent compound Ba{sub 2}FeMoO{sub 6} exhibits saturation magnetic moment value of 3.54 {mu}{sub B}/f.u. at 85 K in a magnetic field of 6000 Oe. Temperature dependence of resistivity shows metallic behavior for all the samples. The magneto-resistance (MR) of the compound with x=0.4 is higher than that of the other samples. At room temperature this system shows a saturation magnetization value of 1.73 {mu}{sub B}/f.u. and MR value of 7.08% (1 T). The observed variations in the structural and magnetic properties are attributed to the change of chemical pressure due to the substitution of Sr in place of Ba. The effect of antisite disorder (ASD) defects on magneto-transport properties is studied in more detail.

  11. Magnetically frustrated double perovskites: synthesis, structural properties, and magnetic order of Sr{sub 2}BOsO{sub 6} (B = Y, In, Sc)

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Avijit Kumar; Sarapulova, Angelina; Adler, Peter; Kanungo, Sudipta; Mikhailova, Daria; Schnelle, Walter; Hu, Zhiwei; Kuo, Changyang; Yan, Binghai; Felser, Claudia; Tjeng, Liu Hao [Max-Planck-Institut fuer Chemische Physik fester Stoffe,Dresden (Germany); Reehuis, Manfred [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Berlin (Germany); Siruguri, Vasudeva; Rayaprol, Sudhindra [UGC-DAE Consortium for Scientific Research (CSR), Mumbai Centre, Mumbai (India); Soo, Yunlian [Department of Physics, National Tsing Hua University, Hsinchu (China); Jansen, Martin [Max-Planck-Institut fuer Chemische Physik fester Stoffe,Dresden (Germany); Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)

    2015-02-15

    Double perovskites Sr{sub 2}BOsO{sub 6} (B = Y, In, and Sc) were prepared from the respective binary metal oxides, and their structural, magnetic, and electronic properties were investigated. At room temperature all these compounds crystallize in the monoclinic space group P2{sub 1}/n. They contain magnetic osmium (Os{sup 5+}, t{sub 2g}{sup 3}) ions and are antiferromagnetic insulators with Neel temperatures T{sub N} = 53 K, 26 K, and 92 K for B = Y, In, and Sc, respectively. Powder neutron diffraction studies on Sr{sub 2}YOsO{sub 6} and Sr{sub 2}InOsO{sub 6} showed that the crystal structures remain unchanged down to 3 K. The Y and In compounds feature a type I antiferromagnetic spin structure with ordered Os moments of 1.91 μ{sub B} and 1.77 μ{sub B}, respectively. The trend in T{sub N} does not simply follow the development of the lattice parameters, which suggests that d{sup 0} compared to d{sup 10} ions on the B site favor a somewhat different balance of exchange interactions in the frustrated Os{sup 5+} fcc-like lattice. (Copyright copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Photophysical electronic structure of double-perovskites A{sub 2}GdTaO{sub 6} (A = Ba and Sr)

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Binita, E-mail: ghosh.binita@gmail.com [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Dutta, Alo [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Shannigrahi, Santiranjan [Institute of Materials Research and Engineering, Agency for Science Technology and Research, 3 Research Link, Singapore 117602 (Singapore); Sinha, T.P. [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India)

    2015-11-05

    X-ray photoemission spectroscopy (XPS) measurements of double perovskite oxides, Ba{sub 2}GdTaO{sub 6} and Sr{sub 2}GdTaO{sub 6} are performed in the energy window of 0–1300 eV. Density functional theory calculations are initiated with the Vienna ab initio Simulation Package to understand the electronic structure of the systems. The calculated DOS has been compared with the experimental valence band XPS spectra. It has been observed that the Ta-5d and O-2p states are hybridized in the valence band. The chemical shifts of these compounds suggest a mixed ionic and covalent character of the bonds, which has been used to explain the electrical conduction mechanism of the systems. The calculated ratio of the spin-orbit interaction energy for Ba 3d and 4d states matches well with the observed experimental results. - Highlights: • DFT calculations of Ba{sub 2}GdTaO{sub 6} and Sr{sub 2}GdTaO{sub 6} have been performed with VASP. • XPS measurements are performed in the energy window of 0–1300 eV. • The calculated DOS has been compared with the valence band XPS spectra. • Chemical shifts from XPS spectra have been used to explain the conduction mechanism.

  13. A novel double perovskite tellurate Eu3+-doped Sr2MgTeO6 red-emitting phosphor with high thermal stability

    Science.gov (United States)

    Liang, Jingyun; Zhao, Shancang; Yuan, Xuexia; Li, Zengmei

    2018-05-01

    A series of novel double perovskite tellurate red-emitting phosphors Sr2MgTeO6:xEu3+ (x = 0.05-0.40) were successfully synthesized by a high-temperature solid-state reaction method. The phase structure, photoluminescence properties and thermal stability of the phosphor were investigated in detail. The phosphor shows dominant emission peak at 614 nm belonging to the 5D0 → 7F2 electric dipole transition under 465 nm excitation. The luminescence intensity keeps increasing with increasing the content of Eu3+ to 25 mol%, and the critical transfer distance of Eu3+ was calculated to be 12 Å. The quenching temperature for Sr2MgTeO6:0.25Eu3+ was estimated to be above 500 K. This spectral feature reveals high color purity and excellent chromaticity coordinate characteristics. Therefore, Eu3+-doped Sr2MgTeO6 phosphors are potential red phosphors for blue chip-based white light-emitting diode and display devices.

  14. Structures and magnetic properties of rare earth double perovskites containing antimony or bismuth Ba{sub 2}LnMO{sub 6} (Ln=rare earths; M=Sb, Bi)

    Energy Technology Data Exchange (ETDEWEB)

    Otsuka, Shumpei, E-mail: m-nis-s-o@ec.hokudai.ac.jp; Hinatsu, Yukio

    2015-07-15

    A series of double perovskite-type oxides Ba{sub 2}LnMO{sub 6} (Ln=lanthanides; M=Sb, Bi) were synthesized and their structures were studied. The Ln and M are structurally ordered in the rock-salt type at the B-site of the perovskite ABO{sub 3}. For Ba{sub 2}PrBiO{sub 6} and Ba{sub 2}TbBiO{sub 6}, it has been found that the disordering between Ln ion and Bi ion occurs at the B-site of the double perovskite and both the Pr (Tb) and Bi exist in two oxidation state in the same compound from the analysis of the X-ray diffraction and magnetic susceptibility data. Magnetic susceptibility measurements show that all these compounds are paramagnetic and have no magnetic ordering down to 1.8 K. - Graphical abstract: Tolerance factor for Ba{sub 2}LnMO{sub 6} (M=Sb, Bi) plotted against the ionic radius of Ln{sup 3+}. We have found that there is a clear relation between crystal structures and tolerance factors. - Highlights: • The Ln and M ions are structurally ordered in the rock-salt type at the B-site. • The disordering between Pr (Tb) ion and Bi ion occurs at the B-site. • Ba{sub 2}LnMO{sub 6} (M=Sb, Bi) have no magnetic ordering down to 1.8 K.

  15. Rietveld refinement and dielectric relaxation of a new rare earth based double perovskite oxide: BaPrCoNbO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Bharti, Chandrahas, E-mail: bharti.chandrahas@gmail.com [Sensor and Actuator Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja SC Mullick Road, Kolkata 700032 (India); Das, Mrinmoy K.; Sen, A. [Sensor and Actuator Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja SC Mullick Road, Kolkata 700032 (India); Chanda, Sadhan; Sinha, T.P. [Department of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, Kolkata-700009 (India)

    2014-02-15

    A new rare earth based double perovskite oxide barium praseodymium cobalt niobate, BaPrCoNbO{sub 6} (BPCN) is synthesized by solid-state reaction technique. Rietveld analysis of X-ray diffraction (XRD) data shows that the compound crystallizes in a perovskite like tetragonal structure which belongs to the I4/mmm space group with lattice parameters a=b=5.6828(9) Å, c=8.063(2) Å. Structural analysis reveals 1:1 ordered arrangement for the Co{sup 2+} and Nb{sup 5+} cations over the six-coordinate B-sites of BPCN. The superlattice line (1 0 1) at 2θ=19.10° arising from the alternate ordering of Co{sup 2+} and Nb{sup 5+} sites is observed in the XRD pattern which confirms the presence of cation ordering in BPCN. Fourier transform infrared spectrum shows two phonon modes of the sample due to the antisymmetric NbO{sub 6} stretching vibration. The relaxation dynamics of the conductive process in BPCN is investigated in the temperature range 303 to 503 K and in the frequency range 100 Hz to 1 MHz using impedance spectroscopy. The relaxation mechanism of the sample in the framework of electric modulus formalism is modeled by Davidson–Cole model (DCM). The values of α (distribution of relaxation time) for the DCM varies from 0.1 to 0.3 which suggests the asymmetric distribution of relaxation time for BPCN. The activation energy of the sample, calculated from both conductivity and modulus spectra, are found to be almost the same ∼0.4 eV, which indicates that the conduction mechanism for BPCN is polaron hopping. The scaling behaviour of the imaginary part of electric modulus suggests that the relaxation follows the same mechanism at various temperatures. - Graphical abstract: Rietveld refinement plot for BPCN. Inset shows the schematic presentation of the BPCN tetragonal unit cell. The Co{sup 2+} atoms are located at the centers of the CoO{sub 6} (blue) octahedra. The Nb{sup 5+} atoms are located at the centers of the NbO{sub 6} (green) octahedra. Display Omitted

  16. Defect Tolerance to Intolerance in the Vacancy-Ordered Double Perovskite Semiconductors Cs 2 SnI 6 and Cs 2 TeI 6

    Energy Technology Data Exchange (ETDEWEB)

    Maughan, Annalise E.; Ganose, Alex M.; Bordelon, Mitchell M.; Miller, Elisa M.; Scanlon, David O.; Neilson, James R.

    2016-07-13

    Vacancy-ordered double perovskites of the general formula, A2BX6, are a family of perovskite derivatives composed of a face-centered lattice of nearly isolated [BX6] units with A-site cations occupying the cuboctahedral voids. Despite the presence of isolated octahedral units, the close-packed iodide lattice provides significant electronic dispersion, such that Cs2SnI6 has recently been explored for applications in photovoltaic devices. To elucidate the structure-property relationships of these materials, we have synthesized the solid solution Cs2Sn1-xTexI6. However, even though tellurium substitution increases electronic dispersion via closer I-I contact distances, the substitution experimentally yields insulating behavior from a significant decrease in carrier concentration and mobility. Density functional calculations of native defects in Cs2SnI6 reveal that iodine vacancies exhibit a low enthalpy of formation and the defect energy level is a shallow donor to the conduction band, rendering the material tolerant to these defect states. The increased covalency of Te-I bonding renders the formation of iodine vacancy states unfavorable, and is responsible for the reduction in conductivity upon Te substitution. Additionally, Cs2TeI6 is intolerant to the formation of these defects, as the defect level occurs deep within the band gap and thus localizes potential mobile charge carriers. In these vacancy-ordered double perovskites, the close-packed lattice of iodine provides significant electronic dispersion, while the interaction of the B- and X-site ions dictates the properties as they pertain to electronic structure and defect tolerance. This simplified perspective -- based on extensive experimental and theoretical analysis -- provides a platform from which to understand structure-property relationships in functional perovskite halides.

  17. The impact of chemical doping on the magnetic state of the Sr{sub 2}YRuO{sub 6} double perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Kayser, Paula; Ranjbar, Ben; Kennedy, Brendan J. [School of Chemistry, The University of Sydney, Sydney, NSW 2006 (Australia); Avdeev, Maxim [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234 (Australia)

    2017-05-15

    The impact of chemical doping of the type Sr{sub 2−x}A{sub x}YRuO{sub 6} (A=Ca, Ba) on the low temperature magnetic properties of Sr{sub 2}YRuO{sub 6}, probed using variable temperature magnetic susceptibility, neutron diffraction and heat capacity measurements, are described. Specific-heat measurements of un-doped Sr{sub 2}YRuO{sub 6} reveal two features at ∼26 and ∼30 K. Neutron scattering measurements at these temperatures are consistent with a change from a 2D ordered state to the 3D type 1 AFM state. Magnetic and structural studies of a number of doped oxides are described that highlight the unique low temperature behavior of Sr{sub 2}YRuO{sub 6} and demonstrate that doping destabilizes the intermediate 2D ordered state. - Graphical abstract: Neutron diffraction measurements of the ordered double perovskite Sr{sub 2}YRuO{sub 6}reveal a with a change from a 2D ordered state to the 3D type 1 AFM state upon cooling. The impact of chemical doping Sr{sub 2−x}A{sub x}YRuO{sub 6} (A=Ca, Ba) on the low temperature magnetic properties have also been investigated and these highlight the unique low temperature behavior of Sr{sub 2}YRuO{sub 6} with doping destabilizing the intermediate 2D ordered state. - Highlights: • Crystal and Magnetic Structure of Sr{sub 2}YRuO{sub 3} was studied using Neutron Diffraction. • Effect of doping on the magnetic ground state established. • Origin of two low temperature transitions discussed.

  18. Effects of dynamic diffraction conditions on magnetic parameter determination in a double perovskite Sr_2FeMoO_6 using electron energy-loss magnetic chiral dichroism

    International Nuclear Information System (INIS)

    Wang, Z.C.; Zhong, X.Y.; Jin, L.; Chen, X.F.; Moritomo, Y.; Mayer, J.

    2017-01-01

    Electron energy-loss magnetic chiral dichroism (EMCD) spectroscopy, which is similar to the well-established X-ray magnetic circular dichroism spectroscopy (XMCD), can determine the quantitative magnetic parameters of materials with high spatial resolution. One of the major obstacles in quantitative analysis using the EMCD technique is the relatively poor signal-to-noise ratio (SNR), compared to XMCD. Here, in the example of a double perovskite Sr_2FeMoO_6, we predicted the optimal dynamical diffraction conditions such as sample thickness, crystallographic orientation and detection aperture position by theoretical simulations. By using the optimized conditions, we showed that the SNR of experimental EMCD spectra can be significantly improved and the error of quantitative magnetic parameter determined by EMCD technique can be remarkably lowered. Our results demonstrate that, with enhanced SNR, the EMCD technique can be a unique tool to understand the structure-property relationship of magnetic materials particularly in the high-density magnetic recording and spintronic devices by quantitatively determining magnetic structure and properties at the nanometer scale. - Highlights: • We demonstrate how to choose the optimal experimental conditions by using dynamical diffraction calculations in Sr_2FeMoO_6. • With optimized diffraction conditions, the signal-to-noise ratio of experimental EMCD spectra has been significantly improved. • We have determined orbital to spin magnetic moment ratio of Sr_2FeMoO_6 quantitatively. • We have discussed the effects of dynamical diffraction conditions on the error bar of quantitative magnetic parameters.

  19. Resonant Magnon-Phonon Polaritons in a Ferrimagnet

    Science.gov (United States)

    2000-09-29

    UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADPO 11604 TITLE: Resonant Magnon -Phonon Polaritons in a Ferrimagnet...part numbers comprise the compilation report: ADP011588 thru ADP011680 UNCLASSIFIED 75 Resonant Magnon -Phonon Polaritons in a Ferrimagnet I. E...susceptibilities X"aa and X’m << X’m appear, where 77 xem - DPx igEo0 i_ Xxy - hy- C1 (0)2 _ 00t2) 4= -7• 4 3. Phonon and magnon polaritons We solve the

  20. Double functions of porous TiO2 electrodes on CH3NH3PbI3 perovskite solar cells: Enhancement of perovskite crystal transformation and prohibition of short circuiting

    Directory of Open Access Journals (Sweden)

    Govindhasamy Murugadoss

    2014-08-01

    Full Text Available In order to analyze the crystal transformation from hexagonal PbI2 to CH3NH3PbI3 by the sequential (two-step deposition process, perovskite CH3NH3PbI3 layers were deposited on flat and/or porous TiO2 layers. Although the narrower pores using small nanoparticles prohibited the effective transformation, the porous-TiO2 matrix was able to help the crystal transformation of PbI2 to CH3NH3PbI3 by sequential two-step deposition. The resulting PbI2 crystals in porous TiO2 electrodes did not deteriorate the photovoltaic effects. Moreover, it is confirmed that the porous TiO2 electrode had served the function of prohibiting short circuits between working and counter electrodes in perovskite solar cells.

  1. Effect of the internal pressure and the anti-site disorder on the structure and magnetic properties of ALaFeTiO6 (A=Ca, Sr, Ba) double perovskite oxides

    International Nuclear Information System (INIS)

    Elbadawi, A.A.; Yassin, O.A.; Gismelseed, Abbasher A.

    2013-01-01

    Successful preparation of double perovskite oxides of chemical formula ALaFeTiO 6 (A=Ba, Sr and Ca) has been achieved by following the precursor method. The samples were studied by means of X-ray diffraction and Mössbauer spectroscopy. The Rietveld analysis of the X-ray diffraction data showed that all the samples have anti-site disorder. The presence of anti-site disorder has altered the electronic environment around the Fe ion sites which creates electric field gradient between two different sites. Observation of quadruple splitting in the ideal cubic perovskite BaLaFeTiO 6 (its tolerance factor equals 1) is the evidence of this anti-site generated electric field gradient. The valence state of the Fe atom determined from the measurements of the Mössbauer effect of 57 Fe at room temperature and 80 K showed that the iron ion has the Fe 3+ high spin state as extracted from the values of the isomer shift for all the samples. It is evidenced that the anti-site disorder has no appreciable effect on the spin state of the Fe ion, but alters the charge densities at the Fe sites and influences the hyperfine parameters of the present samples. Weak ferromagnetism is observed in CaLaFeTiO 6 and SrLaFeTiO 6 and is related to both the internal pressure and the anti-site effect which facilitate the occurrence of the Fe 3+ ↑−O−Fe 3+ ↓ antiferromagnetic interaction with canted spin. - Highlights: ► Anti-site disorder was revealed in (Ca,Sr,Ba)LaFeTiO 6 double perovskites. ► Mössbauer spectroscopy revealed a dependence of the quadruple splitting and the cation size mismatch. ► Weak ferromagnetism is evidenced due to internal pressure and anti-site disorder.

  2. Electrical properties and scaling behaviour of rare earth based Ho{sub 2}CoZrO{sub 6} double perovskite ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Mahato, Dev K., E-mail: drdevkumar@yahoo.com [Department of Physics, National Institute of Technology Patna, Patna 800005 (India); Dutta, Alo; Sinha, T.P. [Department of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, Kolkata 700 009 (India)

    2012-12-15

    Graphical abstract: The X-ray diffraction analysis suggests that the compound crystallizes in monoclinic phase at room temperature with β = 108.51 ± 0.021° (a = 8.1858 ± 0.0023 Å, b = 5.2599 ± 0.0027 Å, c = 7.9874 ± 0.0031 Å) and cell volume = 324.17 Å{sup 3}. The SEM image indicates the uniformity of the grains in the samples. The grain size of the microstructure of HCZ is found to be ∼0.48 μm on average. Display Omitted Highlights: ► The conduction mechanism in HCZ may be due to hopping of small polaron. ► The material shows semiconducting behaviour. ► Conductivity obeys Jonscher's power law with high frequency dispersion. ► Both long-range and localized relaxation are present. -- Abstract: The Ho{sub 2}CoZrO{sub 6} (HCZ) double perovskite has been prepared in polycrystalline form by solid state reaction technique. The analysis of the X-ray powder diffraction pattern indicates that the crystal structure is monoclinic at room temperature with cell parameters a = 8.1858 ± 0.0023 Å, b = 5.2599 ± 0.0027 Å, c = 7.9874 ± 0.0031 Å and β = 108.51 ± 0.021°. The compound shows significant frequency dispersion in its dielectric properties. The Cole–Cole model is used to determine the polydispersive nature of dielectric relaxation. The scaling behaviour of dielectric loss and imaginary electric modulus suggest that the relaxation describe same mechanism at various temperatures. Impedance data presented in the Nyquist plot (Z″ versus Z′) are used to identify an equivalent circuit and to know the bulk and interface contributions. The complex impedance analysis of HCZ exhibits the appearance of both the grain and the grain-boundary contribution. The frequency dependent conductivity spectra follow the universal power law. The magnitude of the activation energy indicates that the carrier transport is due to the hopping conduction.

  3. Synthesis, structure and magnetic properties of La{sub 3}Co{sub 2}SbO{sub 9}: A double perovskite with competing antiferromagnetic and ferromagnetic interactions

    Energy Technology Data Exchange (ETDEWEB)

    Franco, D.G.; Fuertes, V.C.; Blanco, M.C. [INFIQC (CONICET), Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, X5000HUA Cordoba (Argentina); Fernandez-Diaz, M.T. [Institute Laue-Langevin (ILL) 156X, F-38042 Grenoble Cedex 9 (France); Sanchez, R.D., E-mail: rodo@cab.cnea.gov.ar [Centro Atomico Bariloche, CNEA and Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, 8400 Rio Negro (Argentina); Carbonio, R.E., E-mail: carbonio@fcq.unc.edu.ar [INFIQC (CONICET), Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, X5000HUA Cordoba (Argentina)

    2012-10-15

    The synthesis, structural characterization, and magnetic properties of La{sub 3}Co{sub 2}SbO{sub 9} double perovskite are reported. The crystal structure has been refined by X-ray and neutron powder diffraction data in the monoclinic space group P2{sub 1}/n. Co{sup 2+} and Sb{sup 5+} have the maximum order allowed for the La{sub 3}Co{sub 2}SbO{sub 9} stoichiometry. Rietveld refinements of powder neutron diffraction data show that at room temperature the cell parameters are a=5.6274(2) A, b=5.6842(2) A, c=7.9748(2) A and {beta}=89.999(3) Degree-Sign . Magnetization measurements indicate the presence of ferromagnetic correlations with T{sub C}=55 K attributed to the exchange interactions for non-linear Co{sup 2+}-O-Sb{sup 5+}-O-Co{sup 2+} paths. The effective magnetic moment obtained experimentally is {mu}{sub exp}=4.38 {mu}{sub B} (per mol Co{sup 2+}), between the theoretical one for spin only (3.87 {mu}{sub B}) and spin-orbit value (6.63 {mu}{sub B}), indicating partially unquenched contribution. The low magnetization value at high magnetic field and low temperature (1 {mu}{sub B}/f.u., 5 T and 5 K) and the difference between ZFC and FC magnetization curves (at 5 kOe) indicate that the ferromagnetism do not reach a long range order and that the material has an important magnetic frustration. - Graphical abstract: Co-O-Co (Yellow octahedra only) rich zones (antiferromagnetic) are in contact with Co-O-Sb-O-Co (Red and yellow octahedra) rich zones (Ferromagnetic) to give the peculiar magnetic properties, as a consequence, a complex hysteresis loop can be observed composed by a main and irreversible curve in all the measured range, superimposed with a ferromagnetic component at low fields. Highlights: Black-Right-Pointing-Pointer La{sub 3}Co{sub 2}SbO{sub 9} has small Goldschmidt Tolerance Factor (t) due to the small size of La{sup 3+}. Black-Right-Pointing-Pointer Small t determines an angle for the path Co{sup 2+}-O-Sb{sup 5+}-O-Co{sup 2+} of 153 Degree-Sign . Black

  4. Synthesis, structure and magnetic properties of La3Co2SbO9: A double perovskite with competing antiferromagnetic and ferromagnetic interactions

    International Nuclear Information System (INIS)

    Franco, D.G.; Fuertes, V.C.; Blanco, M.C.; Fernández-Díaz, M.T.; Sánchez, R.D.; Carbonio, R.E.

    2012-01-01

    The synthesis, structural characterization, and magnetic properties of La 3 Co 2 SbO 9 double perovskite are reported. The crystal structure has been refined by X-ray and neutron powder diffraction data in the monoclinic space group P2 1 /n. Co 2+ and Sb 5+ have the maximum order allowed for the La 3 Co 2 SbO 9 stoichiometry. Rietveld refinements of powder neutron diffraction data show that at room temperature the cell parameters are a=5.6274(2) Å, b=5.6842(2) Å, c=7.9748(2) Å and β=89.999(3)°. Magnetization measurements indicate the presence of ferromagnetic correlations with T C =55 K attributed to the exchange interactions for non-linear Co 2+ –O–Sb 5+ –O–Co 2+ paths. The effective magnetic moment obtained experimentally is μ exp =4.38 μ B (per mol Co 2+ ), between the theoretical one for spin only (3.87 μ B ) and spin-orbit value (6.63 μ B ), indicating partially unquenched contribution. The low magnetization value at high magnetic field and low temperature (1 μ B /f.u., 5 T and 5 K) and the difference between ZFC and FC magnetization curves (at 5 kOe) indicate that the ferromagnetism do not reach a long range order and that the material has an important magnetic frustration. - Graphical abstract: Co–O–Co (Yellow octahedra only) rich zones (antiferromagnetic) are in contact with Co–O–Sb–O–Co (Red and yellow octahedra) rich zones (Ferromagnetic) to give the peculiar magnetic properties, as a consequence, a complex hysteresis loop can be observed composed by a main and irreversible curve in all the measured range, superimposed with a ferromagnetic component at low fields. Highlights: ► La 3 Co 2 SbO 9 has small Goldschmidt Tolerance Factor (t) due to the small size of La 3+ . ► Small t determines an angle for the path Co 2+ –O–Sb 5+ –O–Co 2+ of 153°. ► Ferromagnetism is attributed to exchange interactions for Co 2+ –O–Sb 5+ –O–Co 2+ paths. ► Ferromagnetic nanoclusters are embedded in an antiferromagnetic

  5. High-pressure synthesis and magnetic behavior of A-site columnar-ordered double perovskites, LnMn(Ga{sub 0.5}Ti{sub 0.5}){sub 2}O{sub 6} (Ln = Sm, Gd)

    Energy Technology Data Exchange (ETDEWEB)

    Shimura, Gen; Niwa, Ken; Shirako, Yuichi; Hasegawa, Masashi [Department of Crystalline Materials Science, Nagoya University, 464-8601, Nagoya (Japan)

    2017-01-26

    A-site columnar-ordered double perovskites, LnMn(Ga{sub 0.5}Ti{sub 0.5}){sub 2}O{sub 6} (Ln = Sm, Gd), were successfully synthesized under high pressure and high temperature (6 GPa, 1375 K). From the synchrotron powder X-ray diffraction patterns, all of the diffraction peaks can be indexed by the P4{sub 2}/nmc space group with lattice parameters a, c ∼ 2a{sub p} (a{sub p}: primitive cubic perovskite lattice) and no ordering of the B-site cations. Rietveld analysis of the synchrotron powder X-ray diffraction patterns and Curie-Weiss fitting of their magnetizations reveal that the ionic formulae of these perovskites are Ln{sup 3+}Mn{sup 2+}(Ga{sup 3+}{sub 0.5}Ti{sup 4+}{sub 0.5}){sub 2}O{sup 2-}{sub 6}. SmMn(Ga{sub 0.5}Ti{sub 0.5}){sub 2}O{sub 6} shows canted-antiferromagnetic behavior, whereas GdMn(Ga{sub 0.5}Ti{sub 0.5}){sub 2}O{sub 6} exhibits two different magnetic states at low temperature depending on the applied magnetic field and shows an unusual magnetization curve. These magnetic behaviors originate by decreasing the antiferromagnetic interaction by substituting Ga{sup 3+}(d{sup 10}) for Ti{sup 4+}(d{sup 0}) and by decreasing the ferromagnetic interaction between columnar-ordered Ln{sup 3+} and Mn{sup 2+}. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Note on the polishing of small spheres of ferrimagnetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Grunberg, J. G.; Antier, G. [Centre d' etudes nucleaires de Grenoble - C.E.N.G. (France); Seiden, P. E. [Institut Fourier, Universite de Grenoble (France)

    1961-07-01

    This note describes a simple and rapid method that we have used for obtaining a high degree of polish on spheres of ferrimagnetic materials. A high surface polish is of particular importance if one desires to perform ferrimagnetic resonance experiments on very narrow linewidth materials such as Yttrium Iron Garnet. It is not possible to obtain the very narrow linewidths without polishing the sample with a very fine abrasive such as 'Linde A'. Although the methods presently used for the fine polishing of ferrite spheres give satisfactory results, the method described here is of particular interest because of its simplicity and speed. For example with the air-jet tumbling technique it can take as long as three days of polishing to obtain an acceptable surface while our method will give the same results in one to two hours. (author)

  7. Magnetization reversal in weak ferrimagnets and canted antiferromagnets

    International Nuclear Information System (INIS)

    Kageyama, H.; Khomskii, D.I.; Levitin, R.Z.; Markina, M.M.; Okuyama, T.; Uchimoto, T.; Vasil'ev, A.N.

    2003-01-01

    In some ferrimagnets the total magnetization vanishes at a certain compensation temperature T*. In weak magnetic fields, the magnetization can change sign at T* (the magnetization reversal). Much rarer is observation of ferrimagnetic-like response in canted antiferromagnets, where the weak ferromagnetic moment is due to the tilting of the sublattice magnetizations. The latter phenomenon was observed in nickel (II) formate dihydrate Ni(HCOO) 2 ·2H 2 O. The observed weak magnetic moment increases initially below T N =15.5 K, equals zero at T*=8.5 K and increases again at lowering temperature. The sign of the low-field magnetization at any given temperature is determined by the sample's magnetic prehistory and the signs are opposite to each other at T N

  8. Antisite-disorder driven large exchange bias effect in phase separated La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} double perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Sahoo, R.C.; Paladhi, D. [Department of Physics, Indian Institute of Technology Kharagpur, West Bengal 721302 (India); Dasgupta, Papri; Poddar, A. [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, West Bengal (India); Singh, Ripandeep; Das, A. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Nath, T.K., E-mail: tnath@phy.iitkgp.ernet.in [Department of Physics, Indian Institute of Technology Kharagpur, West Bengal 721302 (India)

    2017-04-15

    Investigations of structural and magnetic properties of polycrystalline hole doped double perovskite La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} has clearly revealed the existence of structural antisite-disorder (either, Co–O–Co or Mn–O–Mn) in the system. The ordering of Co{sup 2+} and Mn{sup 4+} gives rise to a ferromagnetic transition around 157 K. A spin-canted antiferromagnetic transition is found in this material at T{sub CAFM} ~9 K. The effect of antisite-disorder in the double perovskite structure is most likely the prime reason for antiferromagnetic interaction. The temperature dependent inverse susceptibility exhibits Curie-Weiss like behaviour and it yields an effective paramagnetic moment of 6.49 μ{sub B}. At very low temperature (Tdouble perovskite material. A phenomenological model has been proposed to explain the exchange coupling between the ferromagnetic and canted-antiferromagnetic interfaces of antisite-disordered La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} mainly on the basis of uncompensated interface spins. - Highlights: • Large exchange bias (EB) effect has been observed in 25% Ca doped La{sub 2}CoMnO{sub 6} antisite-disordered system. • Neutron powder diffraction analysis clearly suggested canted antiferromagnetic spin ordering at low temperature in our phase separated system. • A phenomenological model has been proposed for experimental results. • The results may be useful to acquire enough information about exchange biased interfaces for various magnetic device applications.

  9. Ferrimagnetic ferritin cage nanoparticles used as MRI contrast agent

    Science.gov (United States)

    Cai, Y.; Cao, C.; Zhang, T.; Xu, H.; Pan, Y.

    2017-12-01

    The nano-sized ferrimagnetic ferritin cage nanoparticles are ideal materials for understanding of superparamagnetism, biomimetic synthesis of ultrafine magnetic particles and their application in biomedicine. Ferrimagnetic M-HFn nanoparticles with size of magnetite cores in a mean size ranges from 2.7 nm to 5.3 nm were synthesized through loading different amount of iron into recombinant human H chain ferritin (HFn) shells. Both the saturation magnetization (Ms) and blocking temperature (Tb) were increased with the size of ferrimagnetic cores. In essence, magnetic resonance imaging (MRI) analysis showed that the synthesized M-HFn nanoparticles (5.3 nm magnetite core) has extremely high transverse relaxivity (r2) values up to 320.9 mM-1S-1, which indicate that M-HFn nanoparticles are promising negative contrast agent in early detection of tumors. In addition, the longitudinal relaxivity (r1) (10.4 mM-1S-1) and r2/r1 ratio ( 2.2) of M-HFn nanoparticles ( 2.7 nm magnetite core in diameter) will make it a considerable potential as a positive contrast agent in MRI. This means the M-HFn nanoparticles can be used as dual functional MR contrast agent. Acute toxicity study of M-HFn in rats showed that a dosage of 20 mg Fe/kg makes no abnormalities by serum biochemical and hematological analysis as well as histopathological examination. Compared with a similar commercial contrast agent, combidex (with a clinical dosage of 2.7 mg Fe/kg), it indicates that M-HFn nanoparticle is of a relative safe ferrimagnetic nanoparticle when used in vivo.

  10. Magnon Mode Selective Spin Transport in Compensated Ferrimagnets.

    Science.gov (United States)

    Cramer, Joel; Guo, Er-Jia; Geprägs, Stephan; Kehlberger, Andreas; Ivanov, Yurii P; Ganzhorn, Kathrin; Della Coletta, Francesco; Althammer, Matthias; Huebl, Hans; Gross, Rudolf; Kosel, Jürgen; Kläui, Mathias; Goennenwein, Sebastian T B

    2017-06-14

    We investigate the generation of magnonic thermal spin currents and their mode selective spin transport across interfaces in insulating, compensated ferrimagnet/normal metal bilayer systems. The spin Seebeck effect signal exhibits a nonmonotonic temperature dependence with two sign changes of the detected voltage signals. Using different ferrimagnetic garnets, we demonstrate the universality of the observed complex temperature dependence of the spin Seebeck effect. To understand its origin, we systematically vary the interface between the ferrimagnetic garnet and the metallic layer, and by using different metal layers we establish that interface effects play a dominating role. They do not only modify the magnitude of the spin Seebeck effect signal but in particular also alter its temperature dependence. By varying the temperature, we can select the dominating magnon mode and we analyze our results to reveal the mode selective interface transmission probabilities for different magnon modes and interfaces. The comparison of selected systems reveals semiquantitative details of the interfacial coupling depending on the materials involved, supported by the obtained field dependence of the signal.

  11. Magnon Mode Selective Spin Transport in Compensated Ferrimagnets

    KAUST Repository

    Cramer, Joel

    2017-04-13

    We investigate the generation of magnonic thermal spin currents and their mode selective spin transport across interfaces in insulating, compensated ferrimagnet/normal metal bilayer systems. The spin Seebeck effect signal exhibits a nonmonotonic temperature dependence with two sign changes of the detected voltage signals. Using different ferrimagnetic garnets, we demonstrate the universality of the observed complex temperature dependence of the spin Seebeck effect. To understand its origin, we systematically vary the interface between the ferrimagnetic garnet and the metallic layer, and by using different metal layers we establish that interface effects play a dominating role. They do not only modify the magnitude of the spin Seebeck effect signal but in particular also alter its temperature dependence. By varying the temperature, we can select the dominating magnon mode and we analyze our results to reveal the mode selective interface transmission probabilities for different magnon modes and interfaces. The comparison of selected systems reveals semiquantitative details of the interfacial coupling depending on the materials involved, supported by the obtained field dependence of the signal.

  12. Magnon Mode Selective Spin Transport in Compensated Ferrimagnets

    KAUST Repository

    Cramer, Joel; Guo, Er-Jia; Geprä gs, Stephan; Kehlberger, Andreas; Ivanov, Yurii P.; Ganzhorn, Kathrin; Della Coletta, Francesco; Althammer, Matthias; Huebl, Hans; Gross, Rudolf; Kosel, Jü rgen; Klä ui, Mathias; Goennenwein, Sebastian T. B.

    2017-01-01

    We investigate the generation of magnonic thermal spin currents and their mode selective spin transport across interfaces in insulating, compensated ferrimagnet/normal metal bilayer systems. The spin Seebeck effect signal exhibits a nonmonotonic temperature dependence with two sign changes of the detected voltage signals. Using different ferrimagnetic garnets, we demonstrate the universality of the observed complex temperature dependence of the spin Seebeck effect. To understand its origin, we systematically vary the interface between the ferrimagnetic garnet and the metallic layer, and by using different metal layers we establish that interface effects play a dominating role. They do not only modify the magnitude of the spin Seebeck effect signal but in particular also alter its temperature dependence. By varying the temperature, we can select the dominating magnon mode and we analyze our results to reveal the mode selective interface transmission probabilities for different magnon modes and interfaces. The comparison of selected systems reveals semiquantitative details of the interfacial coupling depending on the materials involved, supported by the obtained field dependence of the signal.

  13. Diffusion test of probe nuclei 111In(111Cd) in the compounds: LaBaMn2O6 'Double Perovskites' for measurements using PAC spectroscopy

    International Nuclear Information System (INIS)

    Nascimento, Natália M.; Bosch-Santos, Brianna; Sciarreta, Beatriz A.; Carbonari, Artur W.; Sandalo, Danilo S.

    2017-01-01

    Double perovskites of type LaBaMn 2 O 6 and LaBaCo 2 O 6 were made using two processes, sol-gel synthesis and solid state reaction, in order to identify which of the methods is best for insertion and diffusion of the 111 In test core ( 111 Cd) used for perturbed gamma-gamma angular correlation (PAC) spectroscopy measurements. The test core diffusion were performed with thermal treatments in air and at temperatures of 550 ° C, 650 ° C and 750 ° C. By the analysis of the results, the synthesis by Sol-Gel is more efficient for the insertion of the radioactive material, together with the heat treatment at 650 ° C. The advantage of this method is that the radioactive material can be added to the compounds of the synthesis process, even in the solid state reaction method the radioactive material can only be inserted after the ready compound

  14. Study of LnBaCo{sub 2}O{sub 6-d}elta (Ln = Pr, Nd, Sm and Gd) double perovskites as new cathode material for IT-SOFC

    Energy Technology Data Exchange (ETDEWEB)

    Chavez, E; Mueller, M; Mogni, L; Caneiro, A, E-mail: mogni@cab.cnea.gov.a [Centro Atomico Bariloche-CNEA, Instituto Balseiro. Av. Bustillo 9500, S. C. de Bariloche 8400 (Argentina)

    2009-05-01

    Oxides with double perovskites structures of general composition LnBaCo{sub 2}O{sub 6-d}elta (Ln = Pr, Nd, Sm and Gd) were synthesized by solid state reaction with the purpose to evaluate new materials to be used as cathodes in intermediate temperature solid oxide fuel cell (IT-SOFC). A preliminary study about electrochemical properties was performed by impedance spectroscopy between 500 and 800 deg. C under atmosphere of pure O{sub 2}. Symmetrical cells were obtained by spray deposition of LnBaCo{sub 2}O{sub 6-d}elta (Ln = Pr, Nd, Sm and Gd) at both sides of a dense ceramic electrolyte. The impedance spectroscopy measurements as a function of temperatures show a hysteresis loop which could be associated to a tetragonal/orthorhombic phase transition. The existence of this transition was corroborated by high temperature X-Ray diffraction and Differential Scanning Calorimetry measurements.

  15. Electrical conductivity of Sr{sub 2−x}VMoO{sub 6−y} (x = 0.0, 0.1, 0.2) double perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Childs, Nicholas B.; Smith, Richard; Key, Camas [Department of Physics, EPS 264, Montana State University, Bozeman, Montana 59717 (United States); Weisenstein, Adam; Sofie, Stephen [Department of Mechanical Engineering, Roberts 220, Montana State University, Bozeman, Montana 59717 (United States)

    2013-06-28

    Electrical conductivity of Sr{sub 2-x}VMoO{sub 6-y} (x = 0.0, 0.1, 0.2) double perovskites has been investigated in a reducing atmosphere at temperatures up to 800 °C. This material has a key application in solid oxide fuel cell anodes as a mixed ion and electron conductor. A solid state synthesis technique was used to fabricate materials and crystal structure was verified through x-ray diffraction. Subsequent to conventional sintering in a reducing environment, elemental valence states were indentified through x-ray photoemission spectroscopy on the double perovskite material before and after annealing in a hydrogen environment. Samples exhibited metallic like conduction with electrical conductivities of 1250 S/cm (Sr{sub 2}VMoO{sub 6-y′}), 2530 S/cm (Sr{sub 1.8}VMoO{sub 6-y″}), and 3610 S/cm (Sr{sub 1.9}VMoO{sub 6-y‴}) at 800 °C in 5% H{sub 2}/95% N{sub 2}, with a substantial increase in conductivity upon cooling to room temperature. Room temperature electrical conductivity values for Sr{sub 1.9}VMoO{sub 6-y‴} make it a candidate as the highest electrically conductive oxide known. Highly insulating secondary surface phases, Sr{sub 3}V{sub 2}O{sub 8}, and SrMoO{sub 4}, begin to reduce at 400 °C in a hydrogen environment, as confirmed by X-ray photoemission and thermal gravimetric analysis. This reduction, from V{sup 5+} and Mo{sup 6+} to lower valence states, leads to a large increase in sample electrical conductivity.

  16. The magnetic properties of a mixed spin-1/2 and spin-1 Heisenberg ferrimagnetic system on a two-dimensional square lattice

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Ai-Yuan, E-mail: huaiyuanhuyuanai@126.com [School of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331 (China); Zhang, A.-Jie [Military Operational Research Teaching Division of the 4th Department, PLA Academy of National Defense Information, Wuhan 430000 (China)

    2016-02-01

    The magnetic properties of a mixed spin-1/2 and spin-1 Heisenberg ferrimagnetic system on a two-dimensional square lattice are investigated by means of the double-time Green's function technique within the random phase decoupling approximation. The role of the nearest-, next-nearest-neighbors interactions and the exchange anisotropy in the Hamiltonian is explored. And their effects on the critical and compensation temperature are discussed in detail. Our investigation indicates that both the next-nearest-neighbor interactions and the anisotropy have a great effect on the phase diagram. - Highlights: • Spin-1/2 and spin-1 ferrimagnetic model is examined. • Green's function technique is used. • The role of the nearest-, next-nearest-neighbors interactions and the exchange anisotropy in the Hamiltonian is explored. • The next-nearest-neighbor interactions and the anisotropy have a great effect on the phase diagram.

  17. Magnetic properties of a single transverse Ising ferrimagnetic nanoparticle

    International Nuclear Information System (INIS)

    Bouhou, S.; El Hamri, M.; Essaoudi, I.; Ainane, A.; Ahuja, R.

    2015-01-01

    Using the effective field theory with a probability distribution technique that accounts for the self-spin correlation function, the thermal and the magnetic properties of a single Ising nanoparticle consisting of a ferromagnetic core, a ferromagnetic surface shell and a ferrimagnetic interface coupling are examined. The effect of the transverse field in the surface shell, the exchange interactions between core/shell and in surface shell on the free energy, thermal magnetization, specific heat and susceptibility are studied. A number of interesting phenomena have been found such as the existence of the compensation phenomenon and the magnetization profiles exhibit P-type, N-type and Q-type behaviors

  18. Magnetization and spin gap in two-dimensional organic ferrimagnet BIPNNBNO

    International Nuclear Information System (INIS)

    Ovchinnikov, A S; Sinitsyn, V E; Bostrem, I G; Hosokoshi, Y; Inoue, K

    2012-01-01

    A magnetization process in the two-dimensional ferrimagnet BIPNNBNO is analyzed. The compound consists of ferrimagnetic (1,1/2) chains coupled by two sorts of antiferromagnetic interaction. Whereas the behavior of the magnetization curve in higher magnetic fields can be understood within a process for the separate ferrimagnetic chain, the appearance of the singlet plateau at lower fields is an example of non-Lieb-Mattis type ferrimagnetism. By using the exact diagonalization technique for finite clusters of size 4 × 6, 4 × 8 and 4 × 10 we show that the interchain frustration coupling plays an essential role in stabilization of the singlet phase. These results are complemented by an analysis of four cylindrically coupled ferrimagnetic (1,1/2) chains via an Abelian bosonization technique and an effective theory based on the XXZ spin-1/2 Heisenberg model when the interchain interactions are sufficiently weak/strong, respectively. (paper)

  19. Angular dependence of spin transfer torque on magnetic tunnel junctions with synthetic ferrimagnetic free layer

    International Nuclear Information System (INIS)

    Ichimura, M; Hamada, T; Imamura, H; Takahashi, S; Maekawa, S

    2010-01-01

    Based on a spin-polarized free-electron model, spin and charge transports are analyzed in magnetic tunnel junctions with synthetic ferrimagnetic layers in the ballistic regime, and the spin transfer torque is derived. We characterize the synthetic ferrimagnetic free layer by extending an arbitrary direction of magnetizations of the two free layers forming the synthetic ferrimagnetic free layer. The synthetic ferrimagnetic configuration exerts the approximately optimum torque for small magnetization angle of the first layer relative to that of the pinned layer. For approximately anti-parallel magnetization of the first layer to that of the pinned layer, the parallel magnetization of two magnetic layers is favorable for magnetization reversal rather than the synthetic ferrimagnetic configuration.

  20. Perovskite-Perovskite Homojunctions via Compositional Doping.

    Science.gov (United States)

    Dänekamp, Benedikt; Müller, Christian; Sendner, Michael; Boix, Pablo P; Sessolo, Michele; Lovrincic, Robert; Bolink, Henk J

    2018-05-11

    One of the most important properties of semiconductors is the possibility of controlling their electronic behavior via intentional doping. Despite the unprecedented progress in the understanding of hybrid metal halide perovskites, extrinsic doping of perovskite remains nearly unexplored and perovskite-perovskite homojunctions have not been reported. Here we present a perovskite-perovskite homojunction obtained by vacuum deposition of stoichiometrically tuned methylammonium lead iodide (MAPI) films. Doping is realized by adjusting the relative deposition rates of MAI and PbI 2 , obtaining p-type (MAI excess) and n-type (MAI defect) MAPI. The successful stoichiometry change in the thin films is confirmed by infrared spectroscopy, which allows us to determine the MA content in the films. We analyzed the resulting thin-film junction by cross-sectional scanning Kelvin probe microscopy (SKPM) and found a contact potential difference (CPD) of 250 mV between the two differently doped perovskite layers. Planar diodes built with the perovskite-perovskite homojunction show the feasibility of our approach for implementation in devices.

  1. Magnetic properties of the ferrimagnetic glass-ceramics for hyperthermia

    International Nuclear Information System (INIS)

    Bretcanu, O.; Verne, E.; Coeisson, M.; Tiberto, P.; Allia, P.

    2006-01-01

    Magnetic materials play a key-role in magnetic induction hyperthermia for the treatment of cancer. In this paper, we analyse the magnetic properties of ferrimagnetic glass-ceramics with the composition in the system SiO 2 -Na 2 O-CaO-P 2 O 5 -FeO-Fe 2 O 3 , as a function of the melting temperature. These materials were obtained by melting of commercial reagents in the temperature range of 1400-1550 o C. Room-temperature magnetic measurements were performed by means of a vibrating sample magnetometer at room temperature. The power loss was determined from calorimetric measurements, using a magnetic induction furnace. The highest power loss (61 W/g) has been obtained for samples melted at 1500 o C. The heat generation of the ferrimagnetic glass-ceramics prepared by two different synthesis methods (traditional melting and coprecipitation-derived) will be compared. These materials are expected to be useful in the localised treatment of cancer

  2. Atomic layer deposition of superparamagnetic and ferrimagnetic magnetite thin films

    International Nuclear Information System (INIS)

    Zhang, Yijun; Liu, Ming; Ren, Wei; Zhang, Yuepeng; Chen, Xing; Ye, Zuo-Guang

    2015-01-01

    One of the key challenges in realizing superparamagnetism in magnetic thin films lies in finding a low-energy growth way to create sufficiently small grains and magnetic domains which allow the magnetization to randomly and rapidly reverse. In this work, well-defined superparamagnetic and ferrimagnetic Fe 3 O 4 thin films are successfully prepared using atomic layer deposition technique by finely controlling the growth condition and post-annealing process. As-grown Fe 3 O 4 thin films exhibit a conformal surface and poly-crystalline nature with an average grain size of 7 nm, resulting in a superparamagnetic behavior with a blocking temperature of 210 K. After post-annealing in H 2 /Ar at 400 °C, the as-grown α−Fe 2 O 3 sample is reduced to Fe 3 O 4 phase, exhibiting a ferrimagnetic ordering and distinct magnetic shape anisotropy. Atomic layer deposition of magnetite thin films with well-controlled morphology and magnetic properties provides great opportunities for integrating with other order parameters to realize magnetic nano-devices with potential applications in spintronics, electronics, and bio-applications

  3. Resonant halide perovskite nanoparticles

    Science.gov (United States)

    Tiguntseva, Ekaterina Y.; Ishteev, Arthur R.; Komissarenko, Filipp E.; Zuev, Dmitry A.; Ushakova, Elena V.; Milichko, Valentin A.; Nesterov-Mueller, Alexander; Makarov, Sergey V.; Zakhidov, Anvar A.

    2017-09-01

    The hybrid halide perovskites is a prospective material for fabrication of cost-effective optical devices. Unique perovskites properties are used for solar cells and different photonic applications. Recently, perovskite-based nanophotonics has emerged. Here, we consider perovskite like a high-refractive index dielectric material, which can be considered to be a basis for nanoparticles fabrication with Mie resonances. As a result, we fabricate and study resonant perovskite nanoparticles with different sizes. We reveal, that spherical nanoparticles show enhanced photoluminescence signal. The achieved results lay a cornerstone in the field of novel types of organic-inorganic nanophotonics devices with optical properties improved by Mie resonances.

  4. Ferrimagnetic properties of Co/(Gd-Co) multilayers

    International Nuclear Information System (INIS)

    Svalov, A.V.; Fernandez, A.; Vas'kovskiy, V.O.; Tejedor, M.; Barandiaran, J.M.; Orue, I.; Kurlyandskaya, G.V.

    2006-01-01

    Co/(Gd-Co) multilayers have been prepared by rf-sputtering and investigated by means of Transverse Magnetooptic Kerr Effect (TMOKE), SQUID and VSM magnetometry. The composition of amorphous Gd 0.36 Co 0.64 layers was chosen so that their saturation magnetization was dominated by Gd moments in all the temperature range. Co and Gd-Co layers formed a macroscopic ferrimagnetically coupled system displaying a compensation temperature. Complete magnetic moment compensation was found at such point. An inversion of TMOKE hysteresis loops and a divergent behaviour of coercivity were also observed. By changing the layers thickness it has been possible to control the magnetic characteristics of the Co/(Gd-Co) structures, in particular the compensation takes place at different temperatures

  5. Hybrid Perovskite/Perovskite Heterojunction Solar Cells.

    Science.gov (United States)

    Hu, Yinghong; Schlipf, Johannes; Wussler, Michael; Petrus, Michiel L; Jaegermann, Wolfram; Bein, Thomas; Müller-Buschbaum, Peter; Docampo, Pablo

    2016-06-28

    Recently developed organic-inorganic hybrid perovskite solar cells combine low-cost fabrication and high power conversion efficiency. Advances in perovskite film optimization have led to an outstanding power conversion efficiency of more than 20%. Looking forward, shifting the focus toward new device architectures holds great potential to induce the next leap in device performance. Here, we demonstrate a perovskite/perovskite heterojunction solar cell. We developed a facile solution-based cation infiltration process to deposit layered perovskite (LPK) structures onto methylammonium lead iodide (MAPI) films. Grazing-incidence wide-angle X-ray scattering experiments were performed to gain insights into the crystallite orientation and the formation process of the perovskite bilayer. Our results show that the self-assembly of the LPK layer on top of an intact MAPI layer is accompanied by a reorganization of the perovskite interface. This leads to an enhancement of the open-circuit voltage and power conversion efficiency due to reduced recombination losses, as well as improved moisture stability in the resulting photovoltaic devices.

  6. DFT study on the crystal, electronic and magnetic structures of tantalum based double perovskite oxides Ba2MTaO6 (M = Cr, Mn, Fe) via GGA and GGA + U

    Science.gov (United States)

    Saad, H.-E.; Musa, M.; Elhag, Ahmed

    2018-06-01

    In this paper, we study the crystal, electronic and magnetic structures of three tantalum based double perovskite oxides Ba2MTaO6 (M = Cr, Mn, Fe). All calculations were performed using the full-potential linear augmented plane-wave (PF-LAPW) method based on the first-principles density functional theory (DFT). For the exchange correlation potential, the generalized gradient approximation (GGA) and GGA plus on-site Coulomb parameter (GGA + U) were employed. The structural optimization reveals that the three compounds are stable in cubic structure (space group Fm-3m; tilt system a0a0a0). The band structure, density of states (DOS), charge density and spin magnetic moments were calculated and analyzed in details. By analysis the band structure and DOS, Ba2MTaO6 exhibits an insulating behavior (M = Cr, Fe) and a half-metallic (HM) nature (M = Mn). GGA + U method yields quite accurate results for the band-gap (Eg) as compared with GGA. We found that all three compounds have stable ferromagnetic (FM) ground state within GGA and GGA + U calculations. The M3+ (3d) ions contribute the majority in the total spin magnetic-moments, while, the empty T5+ (5d) ions carry very small induced magnetic moment via the M (3d)-O (2p)-Ta (5d) hybridization.

  7. In Vitro Evaluation of Some Types of Ferrimagnetic Glass Ceramics

    Directory of Open Access Journals (Sweden)

    S. A. M. Abdel-Hameed

    2014-01-01

    Full Text Available The present study aimed at studying the acceleration of the bioactive layer on the surface of ferrimagnetic glass ceramic with a basic composition 40Fe2O3–15P2O5–20SiO2–5TiO2 through the addition of 20% of different types of metal oxides like MgO or CaO or MnO or CuO or ZnO or CeO2. SEM, EDAX, and ICP were applied to present the results of the study. SEM and EDAX measurements indicated the presence of apatite layer formed on the surface of the prepared glass ceramics after immersion in SBF within 7 to 30 days. The investigation of the results clarified that the addition of CaO or ZnO accelerated the formation of apatite on the surfaces of the samples in the simulated body fluid faster than other metal oxides. Inductive coupled plasma (ICP analysis shows the evolution of ion extraction by the simulated body fluid solution (SBF with time in relation to the elemental composition.

  8. Effects of dynamic diffraction conditions on magnetic parameter determination in a double perovskite Sr{sub 2}FeMoO{sub 6} using electron energy-loss magnetic chiral dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z.C. [National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Zhong, X.Y., E-mail: xyzhong@mail.tsinghua.edu.cn [National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Jin, L. [Peter Grünberg Institute and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Jülich, 52425 Jülich (Germany); Chen, X.F. [National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Moritomo, Y. [Graduate School of Pure & Applied Science and Faculty of Pure & Applied Science, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-7571 (Japan); Mayer, J. [Peter Grünberg Institute and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Jülich, 52425 Jülich (Germany); Central Facility for Electron Microscopy, RWTH Aachen University, 52074 Aachen (Germany)

    2017-05-15

    Electron energy-loss magnetic chiral dichroism (EMCD) spectroscopy, which is similar to the well-established X-ray magnetic circular dichroism spectroscopy (XMCD), can determine the quantitative magnetic parameters of materials with high spatial resolution. One of the major obstacles in quantitative analysis using the EMCD technique is the relatively poor signal-to-noise ratio (SNR), compared to XMCD. Here, in the example of a double perovskite Sr{sub 2}FeMoO{sub 6}, we predicted the optimal dynamical diffraction conditions such as sample thickness, crystallographic orientation and detection aperture position by theoretical simulations. By using the optimized conditions, we showed that the SNR of experimental EMCD spectra can be significantly improved and the error of quantitative magnetic parameter determined by EMCD technique can be remarkably lowered. Our results demonstrate that, with enhanced SNR, the EMCD technique can be a unique tool to understand the structure-property relationship of magnetic materials particularly in the high-density magnetic recording and spintronic devices by quantitatively determining magnetic structure and properties at the nanometer scale. - Highlights: • We demonstrate how to choose the optimal experimental conditions by using dynamical diffraction calculations in Sr{sub 2}FeMoO{sub 6}. • With optimized diffraction conditions, the signal-to-noise ratio of experimental EMCD spectra has been significantly improved. • We have determined orbital to spin magnetic moment ratio of Sr{sub 2}FeMoO{sub 6} quantitatively. • We have discussed the effects of dynamical diffraction conditions on the error bar of quantitative magnetic parameters.

  9. Evidence of spin-glass like ordering and exchange bias effect in antisite-disordered nanometric La1.5Ca0.5CoMnO6 double perovskite

    Science.gov (United States)

    Sahoo, R. C.; Paladhi, D.; Nath, T. K.

    2017-08-01

    Single-phase polycrystalline La1.5Ca0.5CoMnO6 double perovskite nanoparticles (∼25 nm) have been synthesized by chemical sol-gel method. We report here the structural, magnetic and transport properties using X-ray diffraction, dc magnetization, ac susceptibility, exchange bias and dc resistivity measurements. The Rietveld refinement of X-ray diffraction pattern reveals that the La1.5Ca0.5CoMnO6 (LCCMO) system crystallizes in orthorhombic structure with pbnm space group. Mn and Co ions are not completely ordered on the B sites due to the presence of about 30% antisite-disorder in the system. The ordering of Co2+ and Mn4+ gives rise to the ferromagnetism below 145 K. A spin glass like ground state has also been observed near 37.6(4) K, arising mainly due to the presence of competing magnetic interactions and antisite-disorder in the LCCMO nanoparticles. The frequency dependence peak shift of the Ac-susceptibility peak in the glassy state follows the critical slowing down model. The observed memory effect in ac susceptibility data reveals the existence of interacting clusters in a competing magnetic interactions state. The presence of noticeable exchange bias effect can be best explained on the basis of uncompensated interface (ferromagnetic/spin-glass) spins of antisite-disordered LCCMO system. This anti-site disordered nanocompound exhibits semiconducting behavior with variable range hopping kind of electronic conduction mechanism in the temperature range of 200-300 K. We have also observed large negative magnetoresistance (-30% at 100 K and 60 kOe) mainly due to the spin-polarized transport across the grain boundaries.

  10. Perovskite Solar Cell

    Indian Academy of Sciences (India)

    Organic–inorganic halide perovskite, a newcomerin the solar cell industry has proved its potential forincreasing efficiency rapidly from 3.8% in 2009 to 22.1% in2016. High efficiency, flexibility, and cell architecture of theemerging hybrid halide perovskite have caught the attentionof researchers and technologists in the field.

  11. The double-well oscillating potential of oxygen atoms in perovskite system Ba(K)BiO sub 3 : EXAFS - analysis results

    CERN Document Server

    Menushenkov, A P; Konarev, P V; Meshkov, A A; Benazeth, S; Purans, J

    2000-01-01

    Temperature-dependent X-ray absorption investigations were made on the Bi L sub 3 -edge in Ba sub 1 sub - sub x K sub x BiO sub 3 with x=0.0, 0.4 and 0.5. For the superconducting samples (x=0.4 and 0.5) it has been found that the local structure differs from the ideal cubic in contrast to the neutron and X-ray diffraction data. The provided analysis of the EXAFS spectra indicates that the oxygen atoms move in double-well potential produced by the existence of two non-equivalent octahedral types of the oxygen environment of bismuth. The vibrations in such a potential lead to modulations of the Bi-O lengths with low frequency which is determined by the soft oxygen octahedron rotation mode frequency. This induces strong electron-phonon interaction and may be the reason for relatively high-temperature transition (T sub c approx 30 K) to the superconducting state.

  12. Photoconducting hybrid perovskite containing carbazole moiety as the organic layer: Fabrication and characterization

    International Nuclear Information System (INIS)

    Deng Meng; Wu Gang; Cheng Siyuan; Wang Mang; Borghs, Gustaaf; Chen Hongzheng

    2008-01-01

    PbCl 2 -based thin films of perovskite structure with hole-transporting carbazole derivatives as the organic layer were successfully prepared by spin-coating from dimethylformamide solution containing stoichiometric amounts of organic and inorganic moieties. The crystal structure and optical property of the hybrid perovskite were characterized by Fourier transform infrared (FT-IR) spectrum, X-ray diffraction (XRD), UV-vis absorption and photoluminescence (PL). FT-IR spectra confirmed the formation of organic-inorganic hybrid perovskite structure. UV-vis spectra of hybrid perovskite thin films exhibited a wide absorption band in ultraviolet region as well as a sharp peak at 330 nm characteristic of PbCl 2 -based layered perovskite. X-ray diffraction profiles indicated that the layered structure was oriented parallel to the silica glass slide plane. Meanwhile, double-layer photoreceptors of the hybrid perovskite were also fabricated, which showed the enhancement of photoconductivity by carbazole chromophore

  13. TMRG studies on spin alignment in molecule-based ferrimagnetics [rapid communication

    Science.gov (United States)

    Liu, Q. M.; Yao, K. L.; Liu, Z. L.

    2005-05-01

    A physical picture of spin alignment in organic molecule-based ferrimagnets is presented from studying the thermal effective magnetic moment of the sublattice by use of the transfer matrix renormalization group. We conclude that the classical antiparallel spin alignment is not the most stable state. The three-spin system tends to parallel alignment when the exchange interaction between the biradical and the monoradical molecules is much weaker than that within the biradical, which can result in the decrease of the effective magnetic moment upon lowering the temperature. More importantly, we give the theoretical evidence that even the antiparallel spin alignment in the biradical monoradical alternating chain does not necessarily lead to ferrimagnetic spin ordering due to the formation of the spin singlet pairs, which suppresses the ferrimagnetic spin alignment.

  14. Ferroelectric ultrathin perovskite films

    Science.gov (United States)

    Rappe, Andrew M; Kolpak, Alexie Michelle

    2013-12-10

    Disclosed herein are perovskite ferroelectric thin-film. Also disclosed are methods of controlling the properties of ferroelectric thin films. These films can be used in a variety materials and devices, such as catalysts and storage media, respectively.

  15. Entropy in halide perovskites

    Science.gov (United States)

    Katan, Claudine; Mohite, Aditya D.; Even, Jacky

    2018-05-01

    Claudine Katan, Aditya D. Mohite and Jacky Even discuss the possible impact of various entropy contributions (stochastic structural fluctuations, anharmonicity and lattice softness) on the optoelectronic properties of halide perovskite materials and devices.

  16. Perovskites keep on giving

    Science.gov (United States)

    2018-05-01

    Whether you like exploring the mysteries of light-matter interactions, playing with a versatile chemical platform, or developing the most efficient devices, metal halide perovskites could be the materials for you.

  17. Evidence of spin-glass like ordering and exchange bias effect in antisite-disordered nanometric La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} double perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Sahoo, R.C.; Paladhi, D.; Nath, T.K., E-mail: tnath@phy.iitkgp.ernet.in

    2017-08-15

    Highlights: • SG has been observed due to antisite disorder and different magnetic interactions. • The observed EB can be best explained on the basis of uncompensated interface spins. • −30% MR has been observed due to the spin-polarized transport at grain boundaries. - Abstract: Single-phase polycrystalline La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} double perovskite nanoparticles (∼25 nm) have been synthesized by chemical sol-gel method. We report here the structural, magnetic and transport properties using X-ray diffraction, dc magnetization, ac susceptibility, exchange bias and dc resistivity measurements. The Rietveld refinement of X-ray diffraction pattern reveals that the La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} (LCCMO) system crystallizes in orthorhombic structure with pbnm space group. Mn and Co ions are not completely ordered on the B sites due to the presence of about 30% antisite-disorder in the system. The ordering of Co{sup 2+} and Mn{sup 4+} gives rise to the ferromagnetism below 145 K. A spin glass like ground state has also been observed near 37.6(4) K, arising mainly due to the presence of competing magnetic interactions and antisite-disorder in the LCCMO nanoparticles. The frequency dependence peak shift of the Ac-susceptibility peak in the glassy state follows the critical slowing down model. The observed memory effect in ac susceptibility data reveals the existence of interacting clusters in a competing magnetic interactions state. The presence of noticeable exchange bias effect can be best explained on the basis of uncompensated interface (ferromagnetic/spin-glass) spins of antisite-disordered LCCMO system. This anti-site disordered nanocompound exhibits semiconducting behavior with variable range hopping kind of electronic conduction mechanism in the temperature range of 200–300 K. We have also observed large negative magnetoresistance (−30% at 100 K and 60 kOe) mainly due to the spin-polarized transport across the grain boundaries.

  18. Fast vortex oscillations in a ferrimagnetic disk near the angular momentum compensation point

    Science.gov (United States)

    Kim, Se Kwon; Tserkovnyak, Yaroslav

    2017-07-01

    We theoretically study the oscillatory dynamics of a vortex core in a ferrimagnetic disk near its angular momentum compensation point, where the spin density vanishes but the magnetization is finite. Due to the finite magnetostatic energy, a ferrimagnetic disk of suitable geometry can support a vortex as a ground state similar to a ferromagnetic disk. In the vicinity of the angular momentum compensation point, the dynamics of the vortex resemble those of an antiferromagnetic vortex, which is described by equations of motion analogous to Newton's second law for the motion of particles. Owing to the antiferromagnetic nature of the dynamics, the vortex oscillation frequency can be an order of magnitude larger than the frequency of a ferromagnetic vortex, amounting to tens of GHz in common transition-metal based alloys. We show that the frequency can be controlled either by applying an external field or by changing the temperature. In particular, the latter property allows us to detect the angular momentum compensation temperature, at which the lowest eigenfrequency attains its maximum, by performing ferromagnetic resonance measurements on the vortex disk. Our work proposes a ferrimagnetic vortex disk as a tunable source of fast magnetic oscillations and a useful platform to study the properties of ferrimagnets.

  19. Direct observation of ferrimagnetic/ferroelastic domain interactions in magnetite below the Verwey transition

    DEFF Research Database (Denmark)

    Kasama, Takeshi; Church, Nathan S.; Feinberg, Joshua M.

    2010-01-01

    The magnetic behaviour of magnetite at low temperatures is dominated by its transformation to a monoclinic crystal structure that is simultaneously ferrimagnetic, ferroelastic and ferroelectric below similar to 125 K (the Verwey transition). Here we use electron microscopy to reveal the relations...

  20. Perpendicularly magnetized CoFeB multilayers with tunable interlayer exchange for synthetic ferrimagnets

    Energy Technology Data Exchange (ETDEWEB)

    Pirro, P., E-mail: ppirro@physik.uni-kl.de [Institut Jean Lamour, Université de Lorraine, UMR 7198 CNRS, 54506 Vandoeuvre-lés-Nancy (France); Hamadeh, A.; Lavanant-Jambert, M. [Institut Jean Lamour, Université de Lorraine, UMR 7198 CNRS, 54506 Vandoeuvre-lés-Nancy (France); Meyer, T. [Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern (Germany); Tao, B.; Rosario, E.; Lu, Y.; Hehn, M.; Mangin, S.; Petit Watelot, S. [Institut Jean Lamour, Université de Lorraine, UMR 7198 CNRS, 54506 Vandoeuvre-lés-Nancy (France)

    2017-06-15

    Highlights: • MgO/CoFeB/Ta/CoFeB/MgO multilayers as synthetic ferrimagnets. • Comprehensive characterization by measurement of static and dynamic properties. • Different pinning for domain walls with different alignment of the individual layers. - Abstract: A study of the multilayer system MgO/CoFeB(1.1 nm)/Ta(t)/CoFeB(0.8 nm)/MgO is presented, where the two CoFeB layers are separated by a Ta interlayer of varying thickness t. The magnetization properties deduced from complementary techniques such as superconducting quantum interference magnetometry, ferromagnetic resonance frequency measurements and Brillouin light scattering spectroscopy can be tuned by changing the Ta thickness between t = 0.25 nm, 0.5 nm and 0.75 nm. For t = 0.5 nm, a ferromagnetic coupling is observed, whereas for t = 0.75 nm, the antiferromagnetic coupling needed to construct a synthetic ferrimagnet is realized. In the latter case, the shape of magnetic domain walls between two ferrimagnetic alignments or between a ferro- and a ferrimagnetic alignment is very different. This behavior can be interpreted as a result of the change in dipolar as well as interlayer exchange energy and domain wall pinning, which is an important conclusion for the realization of data storage devices based on synthetic ferri- and antiferromagnets.

  1. Synthesis and characterization of the double perovskite BaSrCoFe{sub 1}-{sub x}Ni{sub x}O{sub 5.5} like cathode for solid oxide fuel cells; Sintesis y caracterizacion de la doble perovskita BaSrCoFe{sub 1}-{sub x}Ni{sub x}O{sub 5.5} como catodo para celdas SOFC

    Energy Technology Data Exchange (ETDEWEB)

    Alvarado F, J.; Avalos R, L.; Viramontes G, G. [Universidad Michoacana de San Nicolas de Hidalgo, Facultad de Ingenieria Electrica, Santiago Tapia 403, Morelia 58030, Michoacan (Mexico); Reyes R, A. [Centro de Investigacion en Materiales Avanzados, Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua 31109, Chihuahua (Mexico)

    2013-08-01

    Have been synthesized via sol-gel method and characterized by X-ray diffraction, electrical conductivity and thermal expansion coefficient, new material composites BaSrCoFe{sub 1{sub x}}Ni{sub x}O{sub 5.5} (double perovskite type) with the addition of Ni in solid solution Ni{sub x} (x = 0.025, 0.05, 0.075, 0.1 and 0.2), as alternative cathodes for solid oxide fuel cells of intermediate temperature (Sofc-It). X-ray diffraction confirmed the formation of the tetragonal structure perovskite phase BaSrCoFe{sub 1}-{sub x}Ni{sub x}O{sub 5.5}, with the presence of small peaks identified in 2{theta} values below 30 degrees as BaCO{sub 3} and CoFe{sub 2}O{sub 4}. The electrical conductivity increases with the temperature between 350-470 degrees C and then decreases due to the loss of oxygen in the net, which causes differences in conductivity. Semiconductor behavior was obtained in all compositions. Thermal expansion coefficient determination, showed a linear dependence inversely proportional to the concentration of Ni. Our results of electrical conductivity and thermal expansion coefficient, reach to the conclusion that the cathodes between 0.1 and 0.2 Ni, have the greatest possibility for application in Sofc-It. (Author)

  2. Structural and magnetic characterization of the new GdMn1-xFexO3 perovskite material

    International Nuclear Information System (INIS)

    Vasquez, J A Cardona; Téllez, D A Landínez; Rojas, J Roa; Collazos, C A

    2016-01-01

    In this paper we presents the synthesis process of the GdMn 1-x Fe x O 3 perovskite material by conventional solid state reaction method. Crystalline phase evolution during the synthesis was studied by X-ray Diffraction (XRD) in powder of the materials, observing that the chemical reaction of the precursor oxides was significant above 1000°C. Rietveld refinement of DRX patterns shows a perovskite structure with octahedral distortions (space group Pbnm, # 62) for studied values of x (0, 0.1 and 0.2). The degree of substitution generates an increasing tendency on lattice parameters a and c, while for b is decreasing just as for the volume of the unit cell. The effect of the change in the lattice parameters directly affects the octahedral distortions, ie, with increasing degree of substitution (increased parameter c) octahedra tend to arrange one above the other aligned with the c axis. Magnetization measurements as a function of temperature were performed above room temperature between 300K and 860K with an applied field of 20Oe and below room temperature in Field Cooling (FC) and Zero Field Cooling modes (ZFC) between 4.2K and 300K with an applied field of 200Oe. Magnetic behavior above room temperature is paramagnetic for used values of x, on the other hand at low temperatures (T<30K) magnetic phase transitions associated to the apparition of an antiferromagnetic phase are observed. In addition for x=0.1 the derivative of magnetization shows a peak around 31K, associated to the ferrimagnetic transition for this material. Curie-Weiss fit reveals the antiferromagnetic (ferrimagnetic) behavior of the materials, also shows that the configurations with x=0 and x=0.2 have an effective magnetic moment very similar to the reported value of undoped material, while for x=0.1 a higher value is observed confirming the ferrimagnetic behavior of this configuration. (paper)

  3. Textured perovskite cells

    NARCIS (Netherlands)

    Deelen, J. van; Tezsevin, Y.; Barink, M.

    2017-01-01

    Most research of texturization of solar cells has been devoted to Si based cells. For perovskites, it was assumed that texturization would not have much of an impact because of the relatively low refractive indexes lead to relatively low reflection as compared to the Si based cells. However, our

  4. Structural stability and the electronic and magnetic properties of ferrimagnetic Mn_4N(0 0 1) surfaces

    International Nuclear Information System (INIS)

    Guerrero-Sánchez, J.; Takeuchi, Noboru

    2017-01-01

    Highlights: • Surface formation energy calculations demonstrate a N-dependent stability. • The magnetic alignment of these surfaces remains bulk-like, in a ferrimagnetic fashion. • A ferrimagnetic behavior in both structures is confirmed by density of states calculations. - Abstract: We have carried out spin-polarized first principles calculations to describe the surface stability and the electronic and magnetic properties of Mn_4N(0 0 1) surfaces. Results show two different surface terminations with different N content. The surface formation energies indicate that for manganese rich conditions the most stable structure is a MnN terminated surface. Whereas, from intermediate to nitrogen rich conditions, a MnN terminated surface with excess of nitrogen atoms is the most favorable. The stability of these surfaces can be traced to the formation of Mn–N bonds at the surface. The stable surfaces are Ferrimagnetic along the direction perpendicular to the surface, retaining a bulk-like behavior. However, there is a decrease in the Mn magnetic moments due to the presence of the surface. Density of states shows an asymmetric behavior, inherent of a Ferrimagnetic state. Finally, the surfaces are metallic with the main contributions around the Fermi level coming from the Mn-d orbitals. The knowledge about the atomic arrangements of the Mn_4N surfaces may serve to explain and understand the formation of more complex and technologically applicable ferromagnetic/ferrimagnetic and antiferromagnetic/ferrimagnetic heterostructures.

  5. Structural stability and the electronic and magnetic properties of ferrimagnetic Mn{sub 4}N(0 0 1) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Guerrero-Sánchez, J., E-mail: guerrero@cnyn.unam.mx; Takeuchi, Noboru

    2017-06-15

    Highlights: • Surface formation energy calculations demonstrate a N-dependent stability. • The magnetic alignment of these surfaces remains bulk-like, in a ferrimagnetic fashion. • A ferrimagnetic behavior in both structures is confirmed by density of states calculations. - Abstract: We have carried out spin-polarized first principles calculations to describe the surface stability and the electronic and magnetic properties of Mn{sub 4}N(0 0 1) surfaces. Results show two different surface terminations with different N content. The surface formation energies indicate that for manganese rich conditions the most stable structure is a MnN terminated surface. Whereas, from intermediate to nitrogen rich conditions, a MnN terminated surface with excess of nitrogen atoms is the most favorable. The stability of these surfaces can be traced to the formation of Mn–N bonds at the surface. The stable surfaces are Ferrimagnetic along the direction perpendicular to the surface, retaining a bulk-like behavior. However, there is a decrease in the Mn magnetic moments due to the presence of the surface. Density of states shows an asymmetric behavior, inherent of a Ferrimagnetic state. Finally, the surfaces are metallic with the main contributions around the Fermi level coming from the Mn-d orbitals. The knowledge about the atomic arrangements of the Mn{sub 4}N surfaces may serve to explain and understand the formation of more complex and technologically applicable ferromagnetic/ferrimagnetic and antiferromagnetic/ferrimagnetic heterostructures.

  6. Epitaxial Growth of Hard Ferrimagnetic Mn3Ge Film on Rhodium Buffer Layer

    Directory of Open Access Journals (Sweden)

    Atsushi Sugihara

    2015-06-01

    Full Text Available Mn\\(_3\\Ge has a tetragonal Heusler-like D0\\(_{22}\\ crystal structure, exhibiting a large uniaxial magnetic anisotropy and small saturation magnetization due to its ferrimagnetic spin structure; thus, it is a hard ferrimagnet. In this report, epitaxial growth of a Mn\\(_3\\Ge film on a Rh buffer layer was investigated for comparison with that of a film on a Cr buffer layer in terms of the lattice mismatch between Mn\\(_3\\Ge and the buffer layer. The film grown on Rh had much better crystalline quality than that grown on Cr, which can be attributed to the small lattice mismatch. Epitaxial films of Mn\\(_3\\Ge on Rh show somewhat small coercivity (\\(H_{\\rm c}\\ = 12.6 kOe and a large perpendicular magnetic anisotropy (\\(K_{\\rm u}\\ = 11.6 Merg/cm\\(^3\\, comparable to that of the film grown on Cr.

  7. Ferrimagnetic Properties of Bond Dilution Mixed Blume-Capel Model with Random Single-Ion Anisotropy

    International Nuclear Information System (INIS)

    Liu Lei; Yan Shilei

    2005-01-01

    We study the ferrimagnetic properties of spin 1/2 and spin-1 systems by means of the effective field theory. The system is considered in the framework of bond dilution mixed Blume-Capel model (BCM) with random single-ion anisotropy. The investigation of phase diagrams and magnetization curves indicates the existence of induced magnetic ordering and single or multi-compensation points. Special emphasis is placed on the influence of bond dilution and random single-ion anisotropy on normal or induced magnetic ordering states and single or multi-compensation points. Normal magnetic ordering states take on new phase diagrams with increasing randomness (bond and anisotropy), while anisotropy induced magnetic ordering states are always occurrence no matter whether concentration of anisotropy is large or small. Existence and disappearance of compensation points rely strongly on bond dilution and random single-ion anisotropy. Some results have not been revealed in previous papers and predicted by Neel theory of ferrimagnetism.

  8. Study of the ferrimagnetic and paramagnetic phases of magnetite measured by multiple neutron diffraction

    International Nuclear Information System (INIS)

    Mazzocchi, V.L.

    1992-01-01

    Structural parameters of the ferrimagnetic and paramagnetic phases of magnetite have been refined from neutron multiple diffraction data. Experimental multiple diffraction patterns used in the refinement, were obtained by measuring the 111 primary reflection of a natural single crystal of this compound, at room temperature for the ferrimagnetic phase and 703 0 C for the paramagnetic phase. Corresponding theoretical patterns for both phases have been calculated by the program MULTI which uses the iterative method for the intensity calculations in neutron multiple diffraction. In this method intensities are calculated as Taylor series expansions summed up to a order sufficient for a good approximation. A step by step process has been used in the refinements according to the parameter-shift method. Both isotropic and anisotropic thermal parameters were used in the calculation of the temperature factor. (author)

  9. Magnetism and thermodynamic properties of a spin-1/2 ferrimagnetic diamond XY chain in magnetic fields at finite temperatures

    International Nuclear Information System (INIS)

    Cheng, Tai-Min; Ma, Yan-Ming; Ge, Chong-Yuan; Sun, Shu-Sheng; Jia, Wei-Ye; Li, Qing-Yun; Shi, Xiao-Fei; Li, Lin; Zhu, Lin

    2013-01-01

    The elementary excitation spectra of a one-dimensional ferrimagnetic diamond chain in the spin-1/2 XY model at low temperatures have been calculated by using an invariant eigen-operator (IEO) method, the energies of elementary excitations in different specific cases are discussed, and the analytic solutions of three critical magnetic field intensities (H C1 , H C2 , and H peak ) are given. The magnetization versus external magnetic field curve displays a 1/3 magnetization plateau at low temperatures, in which H C1 is the critical magnetic field intensity from the disappearance of the 1/3 magnetization plateau to spin-flop states, H C2 is the critical magnetic field intensity from spin-flop states to the saturation magnetization, and H peak is the critical magnetic field intensity when the temperature magnetization shows a peak in the external magnetic field. The temperature dependences of the magnetic susceptibility and the specific heat show a double peak structure. The entropy and the magnetic susceptibility versus external magnetic field curves also exhibit a double peak structure, and the positions of the two peaks correspond to H C1 and H C2 , respectively. This derives from the competition among different types of energies: the temperature-dependent thermal disorder energy, the potential energy of the spin magnetic moment, the ferromagnetic exchange interaction energy, and the anti-ferromagnetic exchange interaction energy. However at low temperatures, the specific heat as a function of external magnetic field curve exhibits minima at the above two critical points (H C1 and H C2 ). The origins of the above phenomena are discussed in detail.

  10. Strain-magneto-optics of a magnetostrictive ferrimagnet CoFe2O4

    OpenAIRE

    Sukhorukov, Yu. P.; Telegin, A. V.; Bebenin, N. G.; Nosov, A. P.; Bessonov, V. D.; Buchkevich, A. A.

    2017-01-01

    We experimentally demonstrate that in magnetostrictive ferrimagnetic single crystal of CoFe2O4 there is clear correlation between magnetostriction and magnetoreflection of unpolarized light in the infrared range. The influence of magnetic field on specular reflection is likely to be indirect: application of a magnetic field results in strong strain and deformation of the crystal lattice, which leads to the change in electron energy structure and hence reflection spectrum.

  11. A Direct Bandgap Copper-Antimony Halide Perovskite.

    Science.gov (United States)

    Vargas, Brenda; Ramos, Estrella; Pérez-Gutiérrez, Enrique; Alonso, Juan Carlos; Solis-Ibarra, Diego

    2017-07-12

    Since the establishment of perovskite solar cells (PSCs), there has been an intense search for alternative materials to replace lead and improve their stability toward moisture and light. As single-metal perovskite structures have yielded unsatisfactory performances, an alternative is the use of double perovskites that incorporate a combination of metals. To this day, only a handful of these compounds have been synthesized, but most of them have indirect bandgaps and/or do not have bandgaps energies well-suited for photovoltaic applications. Here we report the synthesis and characterization of a unique mixed metal ⟨111⟩-oriented layered perovskite, Cs 4 CuSb 2 Cl 12 (1), that incorporates Cu 2+ and Sb 3+ into layers that are three octahedra thick (n = 3). In addition to being made of abundant and nontoxic elements, we show that this material behaves as a semiconductor with a direct bandgap of 1.0 eV and its conductivity is 1 order of magnitude greater than that of MAPbI 3 (MA = methylammonium). Furthermore, 1 has high photo- and thermal-stability and is tolerant to humidity. We conclude that 1 is a promising material for photovoltaic applications and represents a new type of layered perovskite structure that incorporates metals in 2+ and 3+ oxidation states, thus significantly widening the possible combinations of metals to replace lead in PSCs.

  12. First-principle investigations of K{sub 2}NiF{sub 4}-type double perovskite oxides La{sub 4}B′B″O{sub 8} (B′B″ = Fe, Co, Ni)

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Hejie; Wei, Yingfen; Gui, Hong; Li, Xin; Zhao, Zhenjie, E-mail: zjzhao@phy.ecnu.edu.cn; Xie, Wenhui, E-mail: whxie@phy.ecnu.edu.cn [Engineering Research Center for Nanophotonics and Advanced Instrument, Department of Physics, East China Normal University, Shanghai 200062 (China)

    2014-06-07

    The K{sub 2}NiF{sub 4}-type structure La{sub 4}CoNiO{sub 8} (LCNO), La{sub 4}FeCoO{sub 8} (LFCO), and La{sub 4}FeNiO{sub 8} (LFNO) are studied by using the first-principle electronic structure calculations. Our results indicate that the ground state of LCNO is a ferrimagnetism (FiM) with a large energy gap about 1.9 eV, LFCO and LFNO are antiferromagnetism with energy gaps about 1.3 and 1.4 eV, respectively. Their orthorhombic distortions, out-of-plane elongation, and tilting of octahedron are discussed. It is indicated that LFCO and LFNO have stronger crystal distortion than LCNO. Our calculations indicate that the in-plane magnetic exchange interaction of LCNO is much stronger than LFCO and LFNO, thus LCNO should have much higher magnetic ordering temperature than LFCO and LFNO.

  13. Diffusion test of probe nuclei {sup 111}In({sup 111}Cd) in the compounds: LaBaMn{sub 2}O{sub 6} 'Double Perovskites' for measurements using PAC spectroscopy; Teste de difusão do núcleo de prova {sup 111}In({sup 111}Cd) nos compostos: LaBaMn{sub 2}0{sub 6} e LaBaCo{sub 2}0{sub 6} 'double perovskites' para a realização de medições utilizando a espectroscopia PAC

    Energy Technology Data Exchange (ETDEWEB)

    Nascimento, Natália M.; Bosch-Santos, Brianna; Sciarreta, Beatriz A.; Carbonari, Artur W., E-mail: nat_mn1@hotmail.com [Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN-SP), São Paulo, SP (Brazil); Sandalo, Danilo S. [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Guaratingueta, SP (Brazil)

    2017-07-01

    Double perovskites of type LaBaMn{sub 2}O{sub 6} and LaBaCo{sub 2}O{sub 6} were made using two processes, sol-gel synthesis and solid state reaction, in order to identify which of the methods is best for insertion and diffusion of the {sup 111}In test core ({sup 111}Cd) used for perturbed gamma-gamma angular correlation (PAC) spectroscopy measurements. The test core diffusion were performed with thermal treatments in air and at temperatures of 550 ° C, 650 ° C and 750 ° C. By the analysis of the results, the synthesis by Sol-Gel is more efficient for the insertion of the radioactive material, together with the heat treatment at 650 ° C. The advantage of this method is that the radioactive material can be added to the compounds of the synthesis process, even in the solid state reaction method the radioactive material can only be inserted after the ready compound.

  14. Topological ferrimagnetic behaviours of coordination polymers containing manganese(II) chains with mixed azide and carboxylate bridges and alternating F/AF/AF'/AF'/AF interactions.

    Science.gov (United States)

    Wang, Yan-Qin; Liu, Hou-Ting; Qi, Yan; Gao, En-Qing

    2014-08-21

    Two Mn(ii) complexes with azide and a new zwitterionic tetracarboxylate ligand 1,2,4,5-tetrakis(4-carboxylatopyridinium-1-methylene)benzene (L(1)), {[Mn5(L(1))2(N3)8(OH)2]·12H2O}n () and {[Mn5(L(1))2(N3)8(H2O)2](ClO4)2·6H2O}n (), have been synthesized and characterized crystallographically and magnetically. and contain similar alternating chains constructed by azide and carboxylate bridges. The independent sets of bridges alternate in an ABCCB sequence between adjacent Mn(ii) ions: (EO-N3)2 double bridges (EO = end-on) (denoted as A), [(EO-N3)(OCO)2] triple bridges (denoted as B) and [(EO-N3)(OCO)] double bridges (denoted as C). The alternating chains are interlinked into 2D coordination networks by the tetrapyridinium spacers. Magnetic studies demonstrate that the magnetic coupling through the double EO azide bridges is ferromagnetic and that through mixed azide/carboxylate bridges is antiferromagnetic. The unprecedented F/AF/AF'/AF'/AF coupling sequence along the chain dictates an uncompensated ground spin state (S = 5/2 per Mn5 unit) and leads to one-dimensional topological ferrimagnetism, which features a minimum in the χT versus T plot.

  15. Interplay of Cation Ordering and Ferroelectricity in Perovskite Tin Iodides: Designing a Polar Halide Perovskite for Photovoltaic Applications

    Energy Technology Data Exchange (ETDEWEB)

    Gou, Gaoyang; Young, Joshua; Liu, Xian; Rondinelli, James M.

    2016-09-28

    Owing to its ideal semiconducting band gap and good carrier transport properties, the fully inorganic perovskite CsSnI3 has been proposed as a visible-light absorber for photovoltaic (PV) applications. However, compared to the organic inorganic lead halide perovskite CH3NH3PbI3, CsSnI3 solar cells display very low energy conversion efficiency. In this work, we propose a potential route to improve the PV properties of CsSnI3. Using first-principles calculations, we examine the crystal structures and electronic properties of CsSnI3, including its structural polymorphs. Next, we purposefully order Cs and Rb cations on the A site to create the double perovskite (CsRb)Sn2I6. We find that a stable ferroelectric polarization arises from the nontrivial coupling between polar displacements and octahedral rotations of the SnI6 network. These ferroelectric double perovskites are predicted to have energy band gaps and carrier effective masses similar to those of CsSnI3. More importantly, unlike nonpolar CsSnI3, the electric polarization present in ferroelectric (CsRb)Sn2I6 can effectively separate the photoexcited carriers, leading to novel ferroelectric PV materials with,potentially enhanced energy conversion efficiency.

  16. Curtailing Perovskite Processing Limitations via Lamination at the Perovskite/Perovskite Interface

    Energy Technology Data Exchange (ETDEWEB)

    Van Hest, Marinus F [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Moore, David [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Klein, Talysa [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Christians, Jeffrey A [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Beard, Matthew C [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Berry, Joseph J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Dunfield, Sean P. [University of Colorado; Fabian, David M. [University of California Irvine; Dixon, Alex G. [University of Colorado; Dou, Benjia [University of Colorado; Ardo, Shane [University of California Irvine; Shaheen, Sean E. [University of Colorado

    2018-04-24

    Standard layer-by-layer solution processing methods constrain lead-halide perovskite device architectures. The layer below the perovskite must be robust to the strong organic solvents used to form the perovskite while the layer above has a limited thermal budget and must be processed in nonpolar solvents to prevent perovskite degradation. To circumvent these limitations, we developed a procedure where two transparent conductive oxide/transport material/perovskite half stacks are independently fabricated and then laminated together at the perovskite/perovskite interface. Using ultraviolet-visible absorption spectroscopy, external quantum efficiency, X-ray diffraction, and time-resolved photoluminesence spectroscopy, we show that this procedure improves photovoltaic properties of the perovskite layer. Applying this procedure, semitransparent devices employing two high-temperature oxide transport layers were fabricated, which realized an average efficiency of 9.6% (maximum: 10.6%) despite series resistance limitations from the substrate design. Overall, the developed lamination procedure curtails processing constraints, enables new device designs, and affords new opportunities for optimization.

  17. Search for fully compensated ferrimagnet in Co substituted Mn2VGa alloy

    International Nuclear Information System (INIS)

    Deka, Bhargab; Singh, R.K.; Srinivasan, A.

    2015-01-01

    Crystallographic and magnetic properties of bulk (Mn 1−x Co x ) 2 VGa alloys with 0≤x≤0.50 are reported in this work. All the alloys exhibit stable L2 1 structure. Unit cell volume of this series of alloys decreased from 207.5 Å 3 to 195.1 Å 3 as x was increased from 0 to 0.50. All the alloys shows ferrimagnetic behavior with Curie temperature decreasing from 763 K to 367 K with increase in x. Saturation magnetization (M s ) measured for the alloys with x=0, 0.25 and 0.50 are 1.84 μ B /f.u., 0.85 μ B /f.u. and 0.30 μ B /f.u., respectively, as compared to the values of 2.00 μ B /f.u., 1.00 μ B /f.u. and 0 μ B /f.u., predicted by the Slater–Pauling (S–P) rule. While explaining the deviations in the M s from the values predicted by the S–P rule, a fully compensated ferrimagnet is expected in an alloy with total number of valance electrons of 24.1. - Highlights: • (Mn 1−x Co x ) 2 VGa alloys with highly ordered L2 1 structure has been obtained • With Co substitution, magnetization of (Mn 1-x Co x ) 2 VGa alloys reduces to 0.3= B /f.u. • Fully compensated ferrimagnet is expected in the alloy with 24.1 valance electrons

  18. Changing the cubic ferrimagnetic domain structure in temperature region of spin flip transition

    International Nuclear Information System (INIS)

    Djuraev, D.R.; Niyazov, L.N.; Saidov, K.S.; Sokolov, B.Yu.

    2011-01-01

    The transformation of cubic ferrimagnetic Tb 0.2 Y 2.8 Fe 5 O 12 domain structure has been studied by magneto optic method in the temperature region of spontaneous spin flip phase transition (SPT). It has been found that SPT occurs in a finite temperature interval where the coexistence of low- and high- temperature magnetic phase domains has observed. A character of domain structure evolution in temperature region of spin flip essentially depends on the presence of mechanical stresses in crystal. Interpretation of experimental results has been carried out within the framework of SPT theory for a cubic crystal. (authors)

  19. Spin dynamics in a molecular ferrimagnetic ring, [Mn(hfac)2NITPh]6

    International Nuclear Information System (INIS)

    Itou, T.; Funahashi, S.; Oyamada, A.; Maegawa, S.; Fujita, K.; Amezawa, K.; Yamaguchi, R.

    2007-01-01

    We studied the spin dynamics of a ferrimagnetic ring [Mn(hfac) 2 NITPh] 6 with an S=12 ground state by means of H-NMR1 experiments under several fields. The spin-lattice relaxation rate increases monotonically with increasing temperature. This monotonous behavior is not reproduced by the calculation based on the lifetimes of eigenstates caused by the spin-phonon interaction. The relaxation rate is possibly caused by the dispersion resulting from the interaction between the clusters, which is far smaller than the interaction in the cluster but comparable to the nuclear Zeeman energy

  20. Influence of ion bombardment induced patterning of exchange bias in pinned artificial ferrimagnets on the interlayer exchange coupling

    Energy Technology Data Exchange (ETDEWEB)

    Schmalhorst, Jan; Reiss, Guenter; Hoenik, V. [Thin Films and Nanostructures, Department of Physics, Univ. Bielefeld (Germany); Weis, Tanja; Engel, Dieter; Ehresmann, Arno [Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology, Kassel Univ. (Germany)

    2007-07-01

    Artificial ferrimagnets (AFi) have many applications as, e.g., pinned reference electrodes in magnetic tunnel junctions. It is known that the application of ion bombardment induced magnetic patterning with He ions on a single layer reference electrode of magnetic tunnel junctions is possible. For some applications a combination of ion bombardment induced magnetic patterning and artificial ferrimagnets as a reference electrode is desirable. The effect of ion bombardment induced magnetic patterning on pinned artificial ferrimagnets with a Ru interlayer which is frequently used in magnetic tunnel junctions as well as pinned AFis with a Cu interlayer has been tested. Special attention has been given to the question whether the antiferromagnetic interlayer exchange coupling can withstand the ion dose necessary to turn the exchange bias.

  1. Coexistence of Velocity Renormalization and Ferrimagnetic Fluctuation in the Organic Dirac Electron System α-(BEDT-TTF)2I3

    Science.gov (United States)

    Matsuno, Genki; Kobayashi, Akito

    2018-05-01

    We evaluate the uniform spin susceptibility in an extended Hubbard model describing α-(BEDT-TTF)2I3. Employing the Fock-type self-energy with the long-range Coulomb interaction and the random phase approximation with the on-site Coulomb interaction, it is clarified that the characteristic energy scales at which ferrimagnetic fluctuation and velocity renormalization emerge are different. This is why these phenomena coexist while the ferrimagnetic fluctuation is disturbed by the velocity renormalization. In addition, it is found that screening effect to the self-energy is irrelevant in the presence of a strong on-site Coulomb interaction U.

  2. Magnetization pole reversal of ferrimagnetic ludwigites Mn{sub 3−x}Ni{sub x}BO{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Bezmaternykh, L.N.; Kolesnikova, E.M., E-mail: ekoles@iph.krasn.ru; Eremin, E.V.; Sofronova, S.N.; Volkov, N.V.; Molokeev, M.S.

    2014-09-01

    The conditions for the flux growth of new Mn–Ni oxyborates with the ludwigite structure are reported. Magnetic measurement data for the samples with nickel and manganese predominance are presented. Magnetization pole reversal of the ferrimagnetic phases is established and analyzed in the framework of a model comprising two antiferromagnetically interacting subsystems, each being ferrimagnetically ordered. - Highlights: • Single crystals of new Mn–Ni oxyborates with ludwigite structure were synthesized. • X-ray study of synthesized single crystals was carried out. • We present magnetic measurement data for the samples with nickel and manganese predominance. • We report two different scenarios of alternative-sign behavior of magnetic susceptibility.

  3. Phase transformation of Ca-perovskite in MORB at D" region

    Science.gov (United States)

    Nishitani, N.; Ohtani, E.; Sakai, T.; Kamada, S.; Miyahara, M.; Hirao, N.

    2012-12-01

    Seismological studies indicate the presence of seismic anomalies in the Earth's deep interior. To investigate the anomaly, the physical property of the major minerals in lower mantle such as MgSiO3-perovskite, MgSiO3 post-perovskite and MgO periclase were studied well. Other candidate, CaSiO3 perovskite (Ca-perovskite) exists in peridotitic mantle and basaltic oceanic crust (mid-ocean ridge basalt; MORB). Previous studies indicate the abundance of Ca-perovskite is up to ~9 vol.% in the pyrolite mantle and ~24 vol.% in the MORB oceanic crust. However, the pressure range of previous works are still not enough to understand the D" region. In this study, natural MORB was compressed in double sided laser heated DAC. Au was used as a pressure maker and a laser absorber. NaCl was used as the thermal insulator and pressure medium. The phase relation of Ca-perovskite in MORB was investigated from 36 to 156 GPa and 300 to 2600 K by the in situ X-ray diffraction measurements at SPring-8 (BL10XU). The transition of Ca-perovskite from a tetragonal structure to a cubic structure occurred at about 1800 K up to about 100 GPa and below 1500 K at pressures above 100 GPa. This suggests that the tetragonal-cubic transition of Ca-perovskite could occur in MORB, associating with Al2O3 contents. The present results suggest that the seismic anomaly at D" layer could be caused by the transition in Ca-perovskite.

  4. Ferrimagnetism and compensation points in a decorated 3D Ising model

    International Nuclear Information System (INIS)

    Oitmaa, J.; Zheng, W.

    2003-01-01

    Full text: Ferrimagnets are materials where ions on different sublattices have opposing magnetic moments which do not exactly cancel even at zero temperature. An intriguing possibility then is the existence of a compensation point, below the Curie temperature, where the net moment changes sign. This has obvious technological significance. Most theoretical studies of such systems have used mean-field approaches, making it difficult to distinguish real properties of the model from artefacts of the approximation. For this reason a number of simpler models have been proposed, where treatments beyond mean-field theory are possible. Of particular interest are decorated systems, which can be mapped exactly onto simpler models and, in this way, either solved exactly or to a high degree of numerical precision. We use this approach to study a ferrimagnetic Ising system with spins 1/2 at the sites of a simple cubic lattice and spins S=1 or 3/2 located on the bonds. Our results, which are exact to high numerical precision, show a number of surprising and interesting features: for S=1 the possibility of zero, one or two compensation points, re-entrant behaviour, and up to three critical points; for S=3/2 always a simple critical point and zero or one compensation point

  5. Kinetics of a mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model

    International Nuclear Information System (INIS)

    Deviren, Bayram; Keskin, Mustafa; Canko, Osman

    2009-01-01

    We present a study, within a mean-field approach, of the kinetics of a mixed ferrimagnetic model on a square lattice in which two interpenetrating square sublattices have spins that can take two values, σ=±1/2 , alternated with spins that can take the four values, S=±3/2 ,±1/2 . We use the Glauber-type stochastic dynamics to describe the time evolution of the system with a crystal-field interaction in the presence of a time-dependent oscillating external magnetic field. The nature (continuous and discontinuous) of transition is characterized by studying the thermal behaviors of average order parameters in a period. The dynamic phase transition points are obtained and the phase diagrams are presented in the reduced magnetic field amplitude (h) and reduced temperature (T) plane, and in the reduced temperature and interaction parameter planes, namely in the (h, T) and (d, T) planes, d is the reduced crystal-field interaction. The phase diagrams always exhibit a tricritical point in (h, T) plane, but do not exhibit in the (d, T) plane for low values of h. The dynamic multicritical point or dynamic critical end point exist in the (d, T) plane for low values of h. Moreover, phase diagrams contain paramagnetic (p), ferromagnetic (f), ferrimagnetic (i) phases, two coexistence or mixed phase regions, (f+p) and (i+p), that strongly depend on interaction parameters

  6. Kinetics of a mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram [Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)], E-mail: keskin@erciyes.edu.tr; Canko, Osman [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2009-03-15

    We present a study, within a mean-field approach, of the kinetics of a mixed ferrimagnetic model on a square lattice in which two interpenetrating square sublattices have spins that can take two values, {sigma}={+-}1/2 , alternated with spins that can take the four values, S={+-}3/2 ,{+-}1/2 . We use the Glauber-type stochastic dynamics to describe the time evolution of the system with a crystal-field interaction in the presence of a time-dependent oscillating external magnetic field. The nature (continuous and discontinuous) of transition is characterized by studying the thermal behaviors of average order parameters in a period. The dynamic phase transition points are obtained and the phase diagrams are presented in the reduced magnetic field amplitude (h) and reduced temperature (T) plane, and in the reduced temperature and interaction parameter planes, namely in the (h, T) and (d, T) planes, d is the reduced crystal-field interaction. The phase diagrams always exhibit a tricritical point in (h, T) plane, but do not exhibit in the (d, T) plane for low values of h. The dynamic multicritical point or dynamic critical end point exist in the (d, T) plane for low values of h. Moreover, phase diagrams contain paramagnetic (p), ferromagnetic (f), ferrimagnetic (i) phases, two coexistence or mixed phase regions, (f+p) and (i+p), that strongly depend on interaction parameters.

  7. Modulating Excitonic Recombination Effects through One-Step Synthesis of Perovskite Nanoparticles for Light-Emitting Diodes.

    Science.gov (United States)

    Kulkarni, Sneha A; Muduli, Subas; Xing, Guichuan; Yantara, Natalia; Li, Mingjie; Chen, Shi; Sum, Tze Chien; Mathews, Nripan; White, Tim J; Mhaisalkar, Subodh G

    2017-10-09

    The primary advantages of halide perovskites for light-emitting diodes (LEDs) are solution processability, direct band gap, good charge-carrier diffusion lengths, low trap density, and reasonable carrier mobility. The luminescence in 3 D halide perovskite thin films originates from free electron-hole bimolecular recombination. However, the slow bimolecular recombination rate is a fundamental performance limitation. Perovskite nanoparticles could result in improved performance but processability and cumbersome synthetic procedures remain challenges. Herein, these constraints are overcome by tailoring the 3 D perovskite as a near monodisperse nanoparticle film prepared through a one-step in situ deposition method. Replacing methyl ammonium bromide (CH 3 NH 3 Br, MABr) partially by octyl ammonium bromide [CH 3 (CH 2 ) 7 NH 3 Br, OABr] in defined mole ratios in the perovskite precursor proved crucial for the nanoparticle formation. Films consisting of the in situ formed nanoparticles displayed signatures associated with excitonic recombination, rather than that of bimolecular recombination associated with 3 D perovskites. This transition was accompanied by enhanced photoluminescence quantum yield (PLQY≈20.5 % vs. 3.40 %). Perovskite LEDs fabricated from the nanoparticle films exhibit a one order of magnitude improvement in current efficiency and doubling in luminance efficiency. The material processing systematics derived from this study provides the means to control perovskite morphologies through the selection and mixing of appropriate additives. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Structural Properties of Ferroelectric Perovskites

    National Research Council Canada - National Science Library

    Vanderbilt, David

    1998-01-01

    Under this research grant, we carried out realistic first-principles computer calculations of the ground-state and finite-temperature structural and dielectric properties of cubic perovskite materials...

  9. Ferrimagnetic-antiferromagnetic phase transition in Mn2–xCrxSb : Electronic structure and electrical and magnetic properties

    NARCIS (Netherlands)

    Wijngaard, Jan; Haas, C.; Groot, R.A. de

    1992-01-01

    Self-consistent spin-polarized energy-band calculations have been performed for Mn2Sb for a ferrimagnetic (FI), ferromagnetic (F), and antiferromagnetic (AF) spin alignment. The calculated local moments on the two types of Mn atoms are in agreement with values obtained from neutron diffraction for

  10. Magnetic phase transitions in ferrimagnetic DyFe.sub.5./sub.Al.sub.7./sub. near the compensation point

    Czech Academy of Sciences Publication Activity Database

    Mushnikov, N. V.; Rozenfeld, E.V.; Gorbunov, Denis; Andreev, Alexander V.

    2014-01-01

    Roč. 115, č. 3 (2014), s. 257-267 ISSN 0031-918X R&D Projects: GA ČR GAP204/12/0150 Institutional support: RVO:68378271 Keywords : rare- earth intermetallic compounds * ferrimagnetism * compensation temperature * magnetic anisotropy * magnetic phase transition Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.761, year: 2014

  11. Multifunctional optoelectronic devices based on perovskites

    KAUST Repository

    Saidaminov, Makhsud I.; Bakr, Osman

    2017-01-01

    Embodiments of the present disclosure provide methods of growing halide films (e.g., single crystal halide perovskites or multi-crystal halide perovskites) on a structure, dual-mode photodetectors, methods of use, and the like.

  12. Photocatalysis: HI-time for perovskites

    DEFF Research Database (Denmark)

    Vesborg, Peter Christian Kjærgaard

    2017-01-01

    Organolead halide perovskite solar absorbers demonstrate high photovoltaic efficiencies but they are notorious for their intolerance to water. Now, methylammonium lead iodide perovskites are used to harvest solar energy — in water — via photocatalytic generation of hydrogen from solutions...

  13. Multifunctional optoelectronic devices based on perovskites

    KAUST Repository

    Saidaminov, Makhsud I.

    2017-10-19

    Embodiments of the present disclosure provide methods of growing halide films (e.g., single crystal halide perovskites or multi-crystal halide perovskites) on a structure, dual-mode photodetectors, methods of use, and the like.

  14. Magnetization reversal and ferrimagnetism in Pr1–xNdxMnO3

    Indian Academy of Sciences (India)

    Detailed magnetic properties of Pr1–NdMnO3 ( = 0.3, 0.5 and 0.7) have been reported. All the samples crystallize in orthorhombic perovskite structure with Pnma space group. Magnetization measurements under field cooled (FC) protocal reveal magnetization reversal at low temperatures and low magnetic field.

  15. Element-resolved x-ray ferrimagnetic and ferromagnetic resonance spectroscopy

    International Nuclear Information System (INIS)

    Boero, G; Mouaziz, S; Rusponi, S; Bencok, P; Nolting, F; Stepanow, S; Gambardella, P

    2008-01-01

    We report on the measurement of element-specific magnetic resonance spectra at gigahertz frequencies using x-ray magnetic circular dichroism (XMCD). We investigate the ferrimagnetic precession of Gd and Fe ions in Gd-substituted yttrium iron garnet, showing that the resonant field and linewidth of Gd precisely coincide with Fe up to the nonlinear regime of parametric excitations. The opposite sign of the Gd x-ray magnetic resonance signal with respect to Fe is consistent with dynamic antiferromagnetic alignment of the two ionic species. Further, we investigate a bilayer metal film, Ni 80 Fe 20 (5 nm)/Ni(50 nm), where the coupled resonance modes of Ni and Ni 80 Fe 20 are separately resolved, revealing shifts in the resonance fields of individual layers but no mutual driving effects. Energy-dependent dynamic XMCD measurements are introduced, combining x-ray absorption and magnetic resonance spectroscopies

  16. Imaging of topological magnetic pinning in superconductor-ferrimagnet bilayer with scanning Hall microscopy

    International Nuclear Information System (INIS)

    Marchevsky, M; Higgins, M J; Bhattacharya, S; Fratello, V J

    2011-01-01

    In a superconducting film deposited on ferromagnetic substrate with perpendicular magnetic anisotropy, vortex matter is confined by the magnetic potential landscape. Using scanning Hall microscopy we visualize flux accumulation and removal in a superconductor-ferrimagnet (S/F) bilayer prepared by rf sputtering of thin niobium film on bismuth-doped rare-earth iron garnet. Penetration of the perpendicular magnetic field in the S/F bilayer follows magnetic domain boundaries and is laterally guided by the garnet magnetization component along the field direction. Upon field removal, localization of the remnant flux at the disclination points of the labyrinthine domain pattern is observed. Our experiments show evidence for strong vortex pinning due the special topology of the domain pattern. Ac magnetic imaging of the transport current distribution in the bilayer reveals complex flow paths commensurate with the magnetic domain boundaries. Topological magnetic pinning can be a useful tool for enhancement and control of critical current in thin film superconductors.

  17. Ferroelectric ferrimagnetic LiFe2F6 : Charge-ordering-mediated magnetoelectricity

    Science.gov (United States)

    Lin, Ling-Fang; Xu, Qiao-Ru; Zhang, Yang; Zhang, Jun-Jie; Liang, Yan-Ping; Dong, Shuai

    2017-12-01

    Trirutile-type LiFe2F6 is a charge-ordered material with an Fe2 +/Fe3 + configuration. Here, its physical properties, including magnetism, electronic structure, phase transition, and charge ordering, are studied theoretically. On one hand, the charge ordering leads to improper ferroelectricity with a large polarization. On the other hand, its magnetic ground state can be tuned from the antiferromagnetic to ferrimagnetic by moderate compressive strain. Thus, LiFe2F6 can be a rare multiferroic with both large magnetization and polarization. Most importantly, since the charge ordering is the common ingredient for both ferroelectricity and magnetization, the net magnetization may be fully switched by flipping the polarization, rendering intrinsically strong magnetoelectric effects and desirable functions.

  18. Crystal structure and crystal growth of the polar ferrimagnet CaBaFe4O7

    Science.gov (United States)

    Perry, R. S.; Kurebayashi, H.; Gibbs, A.; Gutmann, M. J.

    2018-05-01

    Magnetic materials are a cornerstone for developing spintronic devices for the transport of information via magnetic excitations. To date, relatively few materials have been investigated for the purpose of spin transport, mostly due to the paucity of suitable candidates as these materials are often chemically complex and difficult to synthesize. We present the crystal growth and a structure solution on the high-temperature crystal structure of the layered, polar ferrimagnet CaBaFe4O7 , which is a possible new contender for spintronics research. The space group is identified as P 3 by refinement of single crystal and powder neutron diffraction data. At 400 K, the trigonal lattice parameters are a =11.0114 (11 )Å and c =10.330 (3 )Å . The structure is similar to the low-temperature phase with alternating layers of triangular and Kagome-arranged Fe-O tetrahedra. We also present details of the crystal growth by traveling solvent method.

  19. Superparamagnetic and ferrimagnetic behavior of nanocrystalline ZnO(MnO)

    Science.gov (United States)

    Kuryliszyn-Kudelska, I.; Dobrowolski, W.; Arciszewska, M.; Romčević, N.; Romčević, M.; Hadžić, B.; Sibera, D.; Narkiewicz, U.

    2018-04-01

    We have studied the magnetic properties of nanocrystals of ZnO:MnO prepared by traditional wet chemistry method. The detailed structural and morphological characterization was performed. The results of systematic measurements of AC magnetic susceptibility as a function of temperature and frequency as well as DC magnetization are reported. We observed two different types of magnetic behavior depending on the concentration doping. For samples with low nominal content (up to 30 wt% of MnO), superparamagnetic behavior was observed. We attribute the observed superparamagnetism to the presence of nanosized ZnMnO3 phase. For nanocrystals doped above nominal 60 wt% of MnO ferrimagnetism was detected with TC at around 42 K. This magnetic behavior we assign to the presence of nanosized Mn3O4 phase.

  20. Mixed spin-5/2 and spin-2 Ising ferrimagnetic system on the Bethe lattice

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, PB 63 46000, Safi (Morocco); Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Jabar, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Benyoussef, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco)

    2015-11-01

    The magnetic properties of spins-S and σ Ising model on the Bethe lattice have been investigated by using the Monte Carlo simulation. The thermal total magnetization and magnetization of spins S and σ with the different exchange interactions, different external magnetic field and different temperatures have been studied. The critical temperature and compensation temperature have been deduced. The magnetic hysteresis cycle of Ising ferrimagnetic system on the Bethe lattice has been deduced for different values of exchange interactions between the spins S and σ, for different values of crystal field and for different sizes. The magnetic coercive filed has been deduced. - Highlights: • The magnetic properties of Bethe lattice have been investigated. • The critical temperature and compensation temperature have been deduced. • The magnetic coercive filed has been deduced.

  1. A novel ferrimagnetic irido-cuprate: IrSr2GdCu2O8

    International Nuclear Information System (INIS)

    Dos Santos-Garcia, A.J.; Aguirre, Myriam H.; Moran, E.; Saez Puche, R.; Alario-Franco, M.A.

    2006-01-01

    We have performed an investigation of the structural, microstructural and magnetic properties of the new compound IrSr 2 GdCu 2 O 8 . The sample was prepared under high temperature (∼1393K) and high-pressure conditions (∼60Kbars) in a Belt type apparatus. X-ray diffraction (XRD) analysis shows that this irido-cuprate is isostructural with the corresponding Ru-1212 phase. Structurally, this material shows an interesting hierarchy of ordering phenomena, whose observation actually depends on the technique used to analyze the material: from a 'simple' cell a p xa p x3a p which is supported by XRD, through a 'diagonal' one, ∼2a p x2a p x3a p as seen by SAED, to a microdomain texture of this last one cell supported by HREM. A ferrimagnetic Ir IV -Gd III spin ordering is observed below 15K. The iridium oxidation state seems to be +4

  2. Termination layer compensated tunnelling magnetoresistance in ferrimagnetic Heusler compounds with high perpendicular magnetic anisotropy.

    Science.gov (United States)

    Jeong, Jaewoo; Ferrante, Yari; Faleev, Sergey V; Samant, Mahesh G; Felser, Claudia; Parkin, Stuart S P

    2016-01-18

    Although high-tunnelling spin polarization has been observed in soft, ferromagnetic, and predicted for hard, ferrimagnetic Heusler materials, there has been no experimental observation to date of high-tunnelling magnetoresistance in the latter. Here we report the preparation of highly textured, polycrystalline Mn3Ge films on amorphous substrates, with very high magnetic anisotropy fields exceeding 7 T, making them technologically relevant. However, the small and negative tunnelling magnetoresistance that we find is attributed to predominant tunnelling from the lower moment Mn-Ge termination layers that are oppositely magnetized to the higher moment Mn-Mn layers. The net spin polarization of the current reflects the different proportions of the two distinct termination layers and their associated tunnelling matrix elements that result from inevitable atomic scale roughness. We show that by engineering the spin polarization of the two termination layers to be of the same sign, even though these layers are oppositely magnetized, high-tunnelling magnetoresistance is possible.

  3. First-principles prediction of shape memory behavior and ferrimagnetism in Mn2NiSn

    International Nuclear Information System (INIS)

    Paul, Souvik; Ghosh, Subhradip

    2011-01-01

    Using first-principles density functional theory, we show that, in Mn 2 NiSn, an energy lowering phase transition from the cubic to tetragonal phase occurs which indicates a martensitic phase transition. This structural phase transition is nearly volume-conserving, implying that this alloy can exhibit shape memory behavior. The magnetic ground state is a ferrimagnetic one with antiparallel Mn spin moments. The calculated moments with different electronic structure methods in the cubic phase compare well with each other but differ from the experimental values by more than 1 μ B . The reason behind this discrepancy is explored by considering antisite disorder in our calculations, which indicates that the site ordering in this alloy can be quite complex.

  4. Imaging of topological magnetic pinning in superconductor-ferrimagnet bilayer with scanning Hall microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Marchevsky, M [Department of Physics, Syracuse University, Syracuse, NY 12344 (United States); Higgins, M J [Princeton High School, Princeton, NJ 08540 (United States); Bhattacharya, S [Tata Institute of Fundamental Research, Mumbai 400 005 (India); Fratello, V J, E-mail: mmartchevskii@lbl.gov [Integrated Photonics, Inc., Hillsborough, NJ 08844 (United States)

    2011-02-15

    In a superconducting film deposited on ferromagnetic substrate with perpendicular magnetic anisotropy, vortex matter is confined by the magnetic potential landscape. Using scanning Hall microscopy we visualize flux accumulation and removal in a superconductor-ferrimagnet (S/F) bilayer prepared by rf sputtering of thin niobium film on bismuth-doped rare-earth iron garnet. Penetration of the perpendicular magnetic field in the S/F bilayer follows magnetic domain boundaries and is laterally guided by the garnet magnetization component along the field direction. Upon field removal, localization of the remnant flux at the disclination points of the labyrinthine domain pattern is observed. Our experiments show evidence for strong vortex pinning due the special topology of the domain pattern. Ac magnetic imaging of the transport current distribution in the bilayer reveals complex flow paths commensurate with the magnetic domain boundaries. Topological magnetic pinning can be a useful tool for enhancement and control of critical current in thin film superconductors.

  5. Magnetic properties of rare earth oxides with perovskite structure

    International Nuclear Information System (INIS)

    Hinatsu, Yukio

    2008-01-01

    A perovskite composite oxide is represented by the general formula of ABO 3 . Cations at the B site characterize magnetic properties of the oxide. Many studies have been accumulated for transition metal elements at the B sites. In this report the studies of rare earth elements at the B sites are reviewed. In rare elements, tetravalent ions such as Ce 4+ , Pr 4+ and Tb 4+ can occupy the B sites with Ba and Sr ions at the A sites. Both the SrTbO 3 and BaTbO 3 have an orthorhombic structure and show the antiferromagnetic transition at about 33 K, which is originated from terbium ions coupled antiferromagnetically with the six neighboring terbium ions. A tetravalent praseodymium perovskite SrPrO 3 shows no existence of the magnetic ordering down to 2.0 K. This is in contrast to the result of isomorphous BaPrO 3 , which shows an antiferromagnetic transition at 11.5 K. A double perovskite structure is represented by the formula A 2 LnMO 6 (A=Ba, Sr, Ca; M=Ru, Ir). In a double perovskite compound Ba 2 PrRuO 6 , the Pr 3+ and Ru 5+ ions are arranged with regularity over the six-coordinate B sites. This compound transforms to an antiferromagnetic state below 117 K. Antiferromagnetic transition temperatures T N for isomorphous Sr and Ca show a clear tendency, T N (A=Ba)>T N (Sr)>T N (Ca), in the compounds with the same rare earth elements (Ln). The 6H-perovskite structure Ba 3 LnRu 2 O 9 consists of linkages between LnO 6 octahedra and Ru 2 O 9 dimers made from face-shared RuO 6 octahedra. The 6H-perovskite structure Ba 3 MRu 2 O 9 (M=Sc, Y, La, Nd-Gd, Dy-Lu) have the valence state of Ba 3 M 3+ Ru 2 4.5+ O 9 . The magnetic susceptibilities show a broad maximum at 135-370 K. This magnetic behavior is ascribed to the antiferromagnetic coupling between two Ru ions in a Ru 2 O 9 dimer and to the magnetic interaction between the Ru 2 O 9 dimers. (author)

  6. Composite bone cements loaded with a bioactive and ferrimagnetic glass-ceramic: Leaching, bioactivity and cytocompatibility.

    Science.gov (United States)

    Verné, Enrica; Bruno, Matteo; Miola, Marta; Maina, Giovanni; Bianco, Carlotta; Cochis, Andrea; Rimondini, Lia

    2015-08-01

    In this work, composite bone cements, based on a commercial polymethylmethacrylate matrix (Palamed®) loaded with ferrimagnetic bioactive glass-ceramic particles (SC45), were produced and characterized in vitro. The ferrimagnetic bioactive glass-ceramic belongs to the system SiO2-Na2O-CaO-P2O5-FeO-Fe2O3 and contains magnetite (Fe3O4) crystals into a residual amorphous bioactive phase. Three different formulations (containing 10, 15 and 20 wt.% of glass-ceramic particles respectively) have been investigated. These materials are intended to be applied as bone fillers for the hyperthermic treatment of bone tumors. The morphological, compositional, calorimetric and mechanical properties of each formulation have been already discussed in a previous paper. The in vitro properties of the composite bone cements described in the present paper are related to iron ion leaching test (by graphite furnace atomic absorption spectrometer), bioactivity (i.e. the ability to stimulate the formation of a hydroxyapatite - HAp - layer on their surface after soaking in simulated body fluid SBF) and cytocompatibility toward human osteosarcoma cells (ATCC CRL-1427, Mg63). Morphological and chemical characterizations by scanning electron microscopy and energy dispersion spectrometry have been performed on the composite samples after each test. The iron release was negligible and all the tested samples showed the growth of HAp on their surface after 28 days of immersion in a simulated body fluid (SBF). Cells showed good viability, morphology, adhesion, density and the ability to develop bridge-like structures on all investigated samples. A synergistic effect between bioactivity and cell mineralization was also evidenced. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Hybrid Organic-Inorganic Perovskite Photodetectors.

    Science.gov (United States)

    Tian, Wei; Zhou, Huanping; Li, Liang

    2017-11-01

    Hybrid organic-inorganic perovskite materials garner enormous attention for a wide range of optoelectronic devices. Due to their attractive optical and electrical properties including high optical absorption coefficient, high carrier mobility, and long carrier diffusion length, perovskites have opened up a great opportunity for high performance photodetectors. This review aims to give a comprehensive summary of the significant results on perovskite-based photodetectors, focusing on the relationship among the perovskite structures, device configurations, and photodetecting performances. An introduction of recent progress in various perovskite structure-based photodetectors is provided. The emphasis is placed on the correlation between the perovskite structure and the device performance. Next, recent developments of bandgap-tunable perovskite and hybrid photodetectors built from perovskite heterostructures are highlighted. Then, effective approaches to enhance the stability of perovskite photodetector are presented, followed by the introduction of flexible and self-powered perovskite photodetectors. Finally, a summary of the previous results is given, and the major challenges that need to be addressed in the future are outlined. A comprehensive summary of the research status on perovskite photodetectors is hoped to push forward the development of this field. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Stability Issues on Perovskite Solar Cells

    Directory of Open Access Journals (Sweden)

    Xing Zhao

    2015-11-01

    Full Text Available Organo lead halide perovskite materials like methylammonium lead iodide (CH3NH3PbI3 and formamidinium lead iodide (HC(NH22PbI3 show superb opto-electronic properties. Based on these perovskite light absorbers, power conversion efficiencies of the perovskite solar cells employing hole transporting layers have increased from 9.7% to 20.1% within just three years. Thus, it is apparent that perovskite solar cell is a promising next generation photovoltaic technology. However, the unstable nature of perovskite was observed when exposing it to continuous illumination, moisture and high temperature, impeding the commercial development in the long run and thus becoming the main issue that needs to be solved urgently. Here, we discuss the factors affecting instability of perovskite and give some perspectives about further enhancement of stability of perovskite solar cell.

  9. Evidence for non-coaxiality of ferrimagnetic and paramagnetic fabrics, developed during magma flow and cooling in a thick mafic dyke

    Czech Academy of Sciences Publication Activity Database

    Silva, P. F.; Marques, F. O.; Machek, Matěj; Henry, B.; Hirt, A. M.; Roxerová, Zuzana; Madureira, P.; Vratislav, S.

    2014-01-01

    Roč. 629, August (2014), s. 155-164 ISSN 0040-1951 Institutional support: RVO:67985530 Keywords : paramagnetic * ferrimagnetic * fabrics * microstructures * dyke emplacement * stress field Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.872, year: 2014

  10. Patterning of Perovskite Single Crystals

    KAUST Repository

    Corzo, Daniel

    2017-06-12

    As the internet-of-things hardware integration continues to develop and the requirements for electronics keep diversifying and expanding, the necessity for specialized properties other than the classical semiconductor performance becomes apparent. The success of emerging semiconductor materials depends on the manufacturability and cost as much as on the properties and performance they offer. Solution-based semiconductors are an emerging concept that offers the advantage of being compatible with large-scale manufacturing techniques and have the potential to yield high-quality electronic devices at a lower cost than currently available solutions. In this work, patterns of high-quality MAPbBr3 perovskite single crystals in specific locations are achieved through the modification of the substrate properties and solvent engineering. The fabrication of the substrates involved modifying the surface adhesion forces through functionalization with self-assembled monolayers and patterning them by photolithography processes. Spin coating and blade coating were used to deposit the perovskite solution on the modified silicon substrates. While single crystal perovskites were obtained with the modification of substrates alone, solvent engineering helped with improving the Marangoni flows in the deposited droplets by increasing the contact angle and lowering the evaporation rate, therefore controlling and improving the shape of the grown perovskite crystals. The methodology is extended to other types of perovskites such as the transparent MAPbCl3 and the lead-free MABi2I9, demonstrating the adaptability of the process. Adapting the process to electrode arrays opened up the path towards the fabrication of optoelectronic devices including photodetectors and field-effect transistors, for which the first iterations are demonstrated. Overall, manufacturing and integration techniques permitting the fabrication of single crystalline devices, such as the method in this thesis work, are

  11. Morphology modification of perovskite film by a simple post-treatment process in perovskite solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Song, J.; Yang, Y.; Zhao, Y.L., E-mail: sdyulong@cumt.edu.cn; Che, M.; Zhu, L.; Gu, X.Q.; Qiang, Y.H., E-mail: yhqiang@cumt.edu.cn

    2017-03-15

    Highlights: • Perovskite films were post-treated by DMF/CBZ, DMSO/CBZ, or GBL/CBZ blend solvents. • This process could repair pinholes and enhance coverage in perovskite film. • This technique could modify charge transfer process at TiO{sub 2}/perovskite interface. - Abstract: A homogenous perovskite thin film with high coverage is a determining factor for high performance perovskite solar cells. Unlike previous pre-treatments aiming at perovskite precursor, we proposed a simple method to modify the morphology of perovskite films by post-treatment process using mixed solvents of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or 1,4-butyrolactone (GBL) with chlorobenzene (CBZ) in this paper. As good solvent of perovskite, DMF, DMSO, and GBL could dissolve the formed perovskite film. Meanwhile, CBZ, anti-solvent of perovskite film, could decrease the dissolving capacity of these good solvents. Therefore, the perovskite film coverage might be improved by the partial dissolution and recrystallization after solvent post-treatment process. Electrochemical impedance spectrometry (EIS) and time-resolved photoluminescence (TRPL) indicated that this post-treatment process could enhance charge transfer at TiO{sub 2}/perovskite interface. Finally, the conversion efficiency increased from 10.10% to 11.82%, 11.68%, and 10.66% using perovskite films post-treated by DMF/CBZ, DMSO/CBZ, and GBL/CBZ blend solvents, respectively.

  12. Systems and methods for scalable perovskite device fabrication

    Science.gov (United States)

    Huang, Jinsong; Dong, Qingfeng; Sao, Yuchuan

    2017-02-28

    Continuous processes for fabricating a perovskite device are described that include using a doctor blade for continuously forming a perovskite layer and using a conductive tape lamination process to form an anode or a cathode layer on the perovskite device.

  13. Monolithic Perovskite Silicon Tandem Solar Cells with Advanced Optics

    Energy Technology Data Exchange (ETDEWEB)

    Goldschmidt, Jan C.; Bett, Alexander J.; Bivour, Martin; Blasi, Benedikt; Eisenlohr, Johannes; Kohlstadt, Markus; Lee, Seunghun; Mastroianni, Simone; Mundt, Laura; Mundus, Markus; Ndione, Paul; Reichel, Christian; Schubert, Martin; Schulze, Patricia S.; Tucher, Nico; Veit, Clemens; Veurman, Welmoed; Wienands, Karl; Winkler, Kristina; Wurfel, Uli; Glunz, Stefan W.; Hermle, Martin

    2016-11-14

    For high efficiency monolithic perovskite silicon tandem solar cells, we develop low-temperature processes for the perovskite top cell, rear-side light trapping, optimized perovskite growth, transparent contacts and adapted characterization methods.

  14. Composite bone cements loaded with a bioactive and ferrimagnetic glass-ceramic: Leaching, bioactivity and cytocompatibility

    International Nuclear Information System (INIS)

    Verné, Enrica; Bruno, Matteo; Miola, Marta; Maina, Giovanni; Bianco, Carlotta; Cochis, Andrea; Rimondini, Lia

    2015-01-01

    In this work, composite bone cements, based on a commercial polymethylmethacrylate matrix (Palamed®) loaded with ferrimagnetic bioactive glass-ceramic particles (SC45), were produced and characterized in vitro. The ferrimagnetic bioactive glass-ceramic belongs to the system SiO 2 –Na 2 O–CaO–P 2 O 5 –FeO–Fe 2 O 3 and contains magnetite (Fe 3 O 4 ) crystals into a residual amorphous bioactive phase. Three different formulations (containing 10, 15 and 20 wt.% of glass-ceramic particles respectively) have been investigated. These materials are intended to be applied as bone fillers for the hyperthermic treatment of bone tumors. The morphological, compositional, calorimetric and mechanical properties of each formulation have been already discussed in a previous paper. The in vitro properties of the composite bone cements described in the present paper are related to iron ion leaching test (by graphite furnace atomic absorption spectrometer), bioactivity (i.e. the ability to stimulate the formation of a hydroxyapatite – HAp – layer on their surface after soaking in simulated body fluid SBF) and cytocompatibility toward human osteosarcoma cells (ATCC CRL-1427, Mg63). Morphological and chemical characterizations by scanning electron microscopy and energy dispersion spectrometry have been performed on the composite samples after each test. The iron release was negligible and all the tested samples showed the growth of HAp on their surface after 28 days of immersion in a simulated body fluid (SBF). Cells showed good viability, morphology, adhesion, density and the ability to develop bridge-like structures on all investigated samples. A synergistic effect between bioactivity and cell mineralization was also evidenced. - Highlights: • An in vitro biological characterization was carried out on ferromagnetic and bioactive composite cements. • No release of iron was revealed in the physiological solution. • Bioactivity tests show hydroxyapatite precipitates

  15. In vitro biocompatibility of a ferrimagnetic glass-ceramic for hyperthermia application

    Energy Technology Data Exchange (ETDEWEB)

    Bretcanu, Oana; Miola, Marta [Applied Science and Technology Department, Institute of Materials Physics and Engineering, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino (Italy); Bianchi, Claudia L. [Department of Chemistry, University of Milan, Via Golgi 19, 20133 Milan (Italy); Marangi, Ida; Carbone, Roberta [Department of Experimental Oncology, European Institute of Oncology, Milan, Italy. (Italy); Corazzari, Ingrid [Department of Chemistry, University of Torino, Via Pietro Giuria 7, 10125 Torino (Italy); “G. Scansetti” Interdepartmental Centre for Studies on Asbestos and other Toxic Particulates, Via Pietro Giuria 7, 10125 Torino (Italy); Cannas, Mario [Department of Medical Science, Human Anatomy, University of Eastern Piedmont, Novara (Italy); Verné, Enrica, E-mail: enrica.verne@polito.it [Applied Science and Technology Department, Institute of Materials Physics and Engineering, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino (Italy)

    2017-04-01

    Ferrimagnetic glass-ceramics containing magnetite crystals were developed for hyperthermia applications of solid neoplastic tissue. The present work is focused on in vitro evaluation of the biocompatibility of these materials, before and after soaking in a simulated body fluid (SBF). X-ray diffraction, scanning electron microscopy, atomic absorption spectrophotometry, X-ray photoelectron spectrometry and pH measurements were employed in glass-ceramic characterisation. The free-radical mediated reactivity of the glass-ceramic was evaluated by Electron Paramagnetic Resonance (EPR) spin trapping. Cell adhesion and proliferation tests were carried out by using 3T3 murine fibroblasts. Cytotoxicity was performed by qualitative evaluation of human bone osteosarcoma cells U2OS cell line. The results show that almost two times more 3T3 cells proliferated on the samples pre-treated in SBF, compared with the untreated specimens. Moreover a decrease of confluence was observed at 48 and 72 h for U2OS cells exposed to the untreated glass-ceramic, while the powder suspensions of glass-ceramic pre-treated in SBF did not influence the cell morphology up to 72 h of exposition. The untreated glass-ceramic exhibited Fenton-like reactivity, as well as reactivity towards formate molecule. After pre-treatment with SBF the reactivity towards formate was completely suppressed. The concentration of iron released into the SBF solution was below 0.1 ppm at 37 °C, during one month of soaking. The different in vitro behaviour of the samples before and after SBF treatment has been correlated to the bioactive glass-ceramic surface modifications as detected by morphological, structural and compositional analyses. - Highlights: • In vitro characterization of a ferrimagnetic glass-ceramic has been performed, before and after treatment in SBF. • The SBF pre-treatment stimulates the cellular function and acts as a surface activation process, increasing cells activity. • Pre-treatment with SBF

  16. Composite bone cements loaded with a bioactive and ferrimagnetic glass-ceramic: Leaching, bioactivity and cytocompatibility

    Energy Technology Data Exchange (ETDEWEB)

    Verné, Enrica, E-mail: enrica.verne@polito.it [Institute of Materials Physics and Engineering, Applied Science and Technology Department, Politecnico di Torino, C. so Duca degli Abruzzi 24, 10129 Torino (Italy); Bruno, Matteo [Institute of Materials Physics and Engineering, Applied Science and Technology Department, Politecnico di Torino, C. so Duca degli Abruzzi 24, 10129 Torino (Italy); Miola, Marta [Institute of Materials Physics and Engineering, Applied Science and Technology Department, Politecnico di Torino, C. so Duca degli Abruzzi 24, 10129 Torino (Italy); Department of Health Sciences, Università del Piemonte Orientale “Amedeo Avogadro”, Via Solaroli 17, 28100 Novara (Italy); Maina, Giovanni; Bianco, Carlotta [Traumatology Orthopedics and Occupational Medicine Dept., Università di Torino, Via G. Zuretti 29, 10126 Torino (Italy); Cochis, Andrea [Department of Health Sciences, Università del Piemonte Orientale “Amedeo Avogadro”, Via Solaroli 17, 28100 Novara (Italy); Rimondini, Lia [Department of Health Sciences, Università del Piemonte Orientale “Amedeo Avogadro”, Via Solaroli 17, 28100 Novara (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali, Via G. Giusti, 9, 50121 Firenze (Italy)

    2015-08-01

    In this work, composite bone cements, based on a commercial polymethylmethacrylate matrix (Palamed®) loaded with ferrimagnetic bioactive glass-ceramic particles (SC45), were produced and characterized in vitro. The ferrimagnetic bioactive glass-ceramic belongs to the system SiO{sub 2}–Na{sub 2}O–CaO–P{sub 2}O{sub 5}–FeO–Fe{sub 2}O{sub 3} and contains magnetite (Fe{sub 3}O{sub 4}) crystals into a residual amorphous bioactive phase. Three different formulations (containing 10, 15 and 20 wt.% of glass-ceramic particles respectively) have been investigated. These materials are intended to be applied as bone fillers for the hyperthermic treatment of bone tumors. The morphological, compositional, calorimetric and mechanical properties of each formulation have been already discussed in a previous paper. The in vitro properties of the composite bone cements described in the present paper are related to iron ion leaching test (by graphite furnace atomic absorption spectrometer), bioactivity (i.e. the ability to stimulate the formation of a hydroxyapatite – HAp – layer on their surface after soaking in simulated body fluid SBF) and cytocompatibility toward human osteosarcoma cells (ATCC CRL-1427, Mg63). Morphological and chemical characterizations by scanning electron microscopy and energy dispersion spectrometry have been performed on the composite samples after each test. The iron release was negligible and all the tested samples showed the growth of HAp on their surface after 28 days of immersion in a simulated body fluid (SBF). Cells showed good viability, morphology, adhesion, density and the ability to develop bridge-like structures on all investigated samples. A synergistic effect between bioactivity and cell mineralization was also evidenced. - Highlights: • An in vitro biological characterization was carried out on ferromagnetic and bioactive composite cements. • No release of iron was revealed in the physiological solution. • Bioactivity tests

  17. Vibrational spectra of ordered perovskites

    NARCIS (Netherlands)

    Corsmit, A.F.; Hoefdraad, H.E.; Blasse, G.

    1972-01-01

    The vibrational spectra of the molecular M6+O6 (M = Mo, Te, W) group in ordered perovskites of the type Ba2M2+M6+O6 are reported. These groups have symmetry Oh, whereas their site symmetry is also Oh. An assignment of the internal vibrations is presented.

  18. Thermochromic halide perovskite solar cells

    Science.gov (United States)

    Lin, Jia; Lai, Minliang; Dou, Letian; Kley, Christopher S.; Chen, Hong; Peng, Fei; Sun, Junliang; Lu, Dylan; Hawks, Steven A.; Xie, Chenlu; Cui, Fan; Alivisatos, A. Paul; Limmer, David T.; Yang, Peidong

    2018-03-01

    Smart photovoltaic windows represent a promising green technology featuring tunable transparency and electrical power generation under external stimuli to control the light transmission and manage the solar energy. Here, we demonstrate a thermochromic solar cell for smart photovoltaic window applications utilizing the structural phase transitions in inorganic halide perovskite caesium lead iodide/bromide. The solar cells undergo thermally-driven, moisture-mediated reversible transitions between a transparent non-perovskite phase (81.7% visible transparency) with low power output and a deeply coloured perovskite phase (35.4% visible transparency) with high power output. The inorganic perovskites exhibit tunable colours and transparencies, a peak device efficiency above 7%, and a phase transition temperature as low as 105 °C. We demonstrate excellent device stability over repeated phase transition cycles without colour fade or performance degradation. The photovoltaic windows showing both photoactivity and thermochromic features represent key stepping-stones for integration with buildings, automobiles, information displays, and potentially many other technologies.

  19. Thermochromic halide perovskite solar cells.

    Science.gov (United States)

    Lin, Jia; Lai, Minliang; Dou, Letian; Kley, Christopher S; Chen, Hong; Peng, Fei; Sun, Junliang; Lu, Dylan; Hawks, Steven A; Xie, Chenlu; Cui, Fan; Alivisatos, A Paul; Limmer, David T; Yang, Peidong

    2018-03-01

    Smart photovoltaic windows represent a promising green technology featuring tunable transparency and electrical power generation under external stimuli to control the light transmission and manage the solar energy. Here, we demonstrate a thermochromic solar cell for smart photovoltaic window applications utilizing the structural phase transitions in inorganic halide perovskite caesium lead iodide/bromide. The solar cells undergo thermally-driven, moisture-mediated reversible transitions between a transparent non-perovskite phase (81.7% visible transparency) with low power output and a deeply coloured perovskite phase (35.4% visible transparency) with high power output. The inorganic perovskites exhibit tunable colours and transparencies, a peak device efficiency above 7%, and a phase transition temperature as low as 105 °C. We demonstrate excellent device stability over repeated phase transition cycles without colour fade or performance degradation. The photovoltaic windows showing both photoactivity and thermochromic features represent key stepping-stones for integration with buildings, automobiles, information displays, and potentially many other technologies.

  20. Perovskite catalysts for oxidative coupling

    Science.gov (United States)

    Campbell, Kenneth D.

    1991-01-01

    Perovskites of the structure A.sub.2 B.sub.2 C.sub.3 O.sub.10 are useful as catalysts for the oxidative coupling of lower alkane to heavier hydrocarbons. A is alkali metal; B is lanthanide or lanthanum, cerium, neodymium, samarium, praseodymium, gadolinium or dysprosium; and C is titanium.

  1. Planar-integrated single-crystalline perovskite photodetectors

    KAUST Repository

    Saidaminov, Makhsud I.; Adinolfi, Valerio; Comin, Riccardo; Abdelhady, Ahmed L.; Peng, Wei; Dursun, Ibrahim; Yuan, Mingjian; Hoogland, Sjoerd; Sargent, Edward H.; Bakr, Osman

    2015-01-01

    Hybrid perovskites are promising semiconductors for optoelectronic applications. However, they suffer from morphological disorder that limits their optoelectronic properties and, ultimately, device performance. Recently, perovskite single crystals

  2. Slow-Photon-Effect-Induced Photoelectrical-Conversion Efficiency Enhancement for Carbon-Quantum-Dot-Sensitized Inorganic CsPbBr3 Inverse Opal Perovskite Solar Cells.

    Science.gov (United States)

    Zhou, Shujie; Tang, Rui; Yin, Longwei

    2017-11-01

    All-inorganic cesium lead halide perovskite is suggested as a promising candidate for perovskite solar cells due to its prominent thermal stability and comparable light absorption ability. Designing textured perovskite films rather than using planar-architectural perovskites can indeed optimize the optical and photoelectrical conversion performance of perovskite photovoltaics. Herein, for the first time, this study demonstrates a rational strategy for fabricating carbon quantum dot (CQD-) sensitized all-inorganic CsPbBr 3 perovskite inverse opal (IO) films via a template-assisted, spin-coating method. CsPbBr 3 IO introduces slow-photon effect from tunable photonic band gaps, displaying novel optical response property visible to naked eyes, while CQD inlaid among the IO frameworks not only broadens the light absorption range but also improves the charge transfer process. Applied in the perovskite solar cells, compared with planar CsPbBr 3 , slow-photon effect of CsPbBr 3 IO greatly enhances the light utilization, while CQD effectively facilitates the electron-hole extraction and injection process, prolongs the carrier lifetime, jointly contributing to a double-boosted power conversion efficiency (PCE) of 8.29% and an increased incident photon-to-electron conversion efficiency of up to 76.9%. The present strategy on CsPbBr 3 IO to enhance perovskite PCE can be extended to rationally design other novel optoelectronic devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. New ferrimagnetic biocomposite film based in collagen and yttrium iron garnet

    Directory of Open Access Journals (Sweden)

    2010-12-01

    Full Text Available In recent years a great interest in the study of the association of magnetic with biological material for bioapplications has been observed in the literature. This work analyses the development of new magnetic biocomposite films from a magnetic ferrite and a biopolymer. Magnetic and dielectric properties of Y3Fe5O12 (YIG/collagen composite films were studied as a function of the YIG concentration. This biocomposite was also characterized by Infrared Spectroscopy (IR, Thermal Analysis (DSC and TG and scanning electron microspcopic (SEM methods. The magnetization and dielectric measurements were performed at room temperature. The results demonstrated that ferrimagnetic garnet (YIG and collagen (Col can be used to obtain a homogeneous composite. All the composite films showed a ferromagnetic behavior and they were characterized as a soft magnet material. These results show that Col-YIG biocomposites are biological films with magnetic properties that can be employed as a versatile performance materials, due to their flexible dielectric and magnetic features. They could be used as electronic devices in biological applications.

  4. Origin of Ferrimagnetism and Ferroelectricity in Room-Temperature Multiferroic ɛ -Fe2O3

    Science.gov (United States)

    Xu, K.; Feng, J. S.; Liu, Z. P.; Xiang, H. J.

    2018-04-01

    Exploring and identifying room-temperature multiferroics is critical for developing better nonvolatile random-access memory devices. Recently, ɛ -Fe2O3 was found to be a promising room-temperature multiferroic with a large polarization and magnetization. However, the origin of the multiferroicity in ɛ -Fe2O3 is still puzzling. In this work, we perform density-functional-theory calculations to reveal that the spin frustration between tetrahedral-site Fe3 + spins gives rise to the unexpected ferrimagnetism. For the ferroelectricity, we identify a low-energy polarization switching path with an energy barrier of 85 meV /f .u . by performing a stochastic surface walking simulation. The switching of the ferroelectric polarization is achieved by swapping the tetrahedral Fe ion with the octahedral Fe ion, different from the usual case (e.g., in BaTiO3 and BiFeO3 ) where the coordination number remains unchanged after the switching. Our results not only confirm that ɛ -Fe2O3 is a promising room-temperature multiferroic but also provide guiding principles to design high-performance multiferroics.

  5. Synthesis and dielectric properties of ferroelectric-ferrimagnetic PZT-SFMO composites

    Directory of Open Access Journals (Sweden)

    Alexander V. Petrov

    2017-03-01

    Full Text Available Ferrimagnetic-ferroelectric composite materials on the base of Pb0.85Zr0.53Ti0.47O3– Sr2FeMoO6–δ (PZT-SFMO compounds have been prepared by a complex ceramic technology and a modified sol-gel synthesis. The dielectric properties of the PZT-SFMO composites with the PZT concentrations of 55 wt% and less, as well as of pure SFMO, are caused by the Maxwell-Wagner relaxation and a huge electrical conductivity. In contrast, in pure PZT the ferroelectric phase transition is clearly expressed in the static dielectric permittivity anomaly. Moreover, in all investigated composites, similarly to pure SFMO, the electrical conductivity anomaly is observed in the range from 560–540 K. This indicates that the composites with PZT concentrations of 55 wt% and higher are above the electrical and magnetic percolation threshold, in a good agreement with the excluded volume theory. In PZT-SFMO composites the DC electrical conductivity increases with SFMO concentration almost in a power law fashion, while the activation energy of the DC conductivity decreases under certain conditions.

  6. GMAG Dissertation Award Talk: Zero-moment Half-Metallic Ferrimagnetic Semiconductors

    Science.gov (United States)

    Jamer, Michelle E.

    2015-03-01

    Low- and zero-moment half-metallic ferrimagnetic semiconductors have been proposed for advanced applications, such as nonvolatile RAM memory and quantum computing. These inverse-Heusler materials could be used to generate spin-polarized electron or hole currents without the associated harmful fringing magnetic fields. Such materials are expected to exhibit low to zero magnetic moment at room temperature, which makes them well-positioned for future spin-based devices. However, these compounds have been shown to suffer from disorder. This work focuses on the synthesis of these compounds and the investigation of their structural, magnetic, and transport properties. Cr2CoGa and Mn3Al thin films were synthesized by molecular beam epitaxy, and V3Al and Cr2CoAl were synthesized via arc-melting. Rietveld analysis was used to determine the degree of ordering in the sublattices as a function of annealing. The atomic moments were measured by X-ray magnetic circular and linear dichroism confirmed antiferromagnetic alignment of sublattices and the desired near-zero moment in several compounds. In collaboration with George E. Sterbinsky, Photon Sciences Directorate, Brookhaven National Laboratory; Dario Arena Photon Sciences Directorate, Brookhaven National Laboratory; Laura H. Lewis, Chemical Engineering, Northeastern University; and Don Heiman, Physics, Northeastern University. NSF-ECCS-1402738, NSF-DMR-0907007.

  7. Study of synthetic ferrimagnet-synthetic antiferromagnet structures for magnetic sensor application

    Science.gov (United States)

    Guedes, A.; Mendes, M. J.; Freitas, P. P.; Martins, J. L.

    2006-04-01

    There has been a growing interest in using both synthetic ferrimagnet (SF) free and synthetic antiferromagnet (SAF) pinned layers for head and memory applications. In particular, for linear sensor applications, these structures lower the magnetostatic fields present at the free layer through the reduction of its effective thickness (teffSF). This allows higher sensitivity but at the expense of an increased offset field H0(Néel coupling field Hf+interlayer demagnetizing field HdSAF). In this work, results on a series of patterned 3×1 and 6×2 μm2 top-pinned SF-SAF spin valves are analyzed and compared with a three-dimensional micromagnetic simulation in order to clarify the role of the different ferromagnetic layers in the overall offset field and sensitivity. H0 varies as 1/teffSF[teffSF=(Mata-Mbtb)/MeffSF]. The magnetostatic field acting on the SF coming from the SAF (HdSAF) can act as a biasing field, partially counterbalancing the Néel coupling field (Hf) leading to a reduction of H0. In this work the offset field was reduced from an initial value of 25 Oe in a quasicompensated SAF to a value of -6 Oe, by unbalancing the SAF and consequently increasing its effective moment (teffSF=15 A˚).

  8. Compensation phenomena of a mixed spin-2 and spin-12 Heisenberg ferrimagnetic model: Green function study

    International Nuclear Information System (INIS)

    Li Jun; Wei Guozhu; Du An

    2005-01-01

    The compensation and critical behaviors of a mixed spin-2 and spin-12 Heisenberg ferrimagnetic system on a square lattice are investigated theoretically by the two-time Green's function technique, which takes into account the quantum nature of Heisenberg spins. The model can be relevant for understanding the magnetic behavior of the new class of organometallic ferromagnetic materials that exhibit spontaneous magnetic properties at room temperature. We carry out the calculation of the sublattice magnetizations and the spin-wave spectra of the ground state. In particular, we have studied the effects of the nearest, next-nearest-neighbor interactions, the crystal field and the external magnetic field on the compensation temperature and the critical temperature. When only the nearest-neighbor interactions and the crystal field are included, no compensation temperature exists; when the next-nearest-neighbor interaction between spin-12 is taken into account and exceeds a minimum value, a compensation point appears and it is basically unchanged for other parameters in Hamiltonian fixed. The next-nearest-neighbor interactions between spin-2 and the external magnetic field have the effects of changing the compensation temperature and there is a narrow range of parameters of the Hamiltonian for which the model has the compensation temperatures and compensation temperature exists only for a small value of them

  9. Ligand-Stabilized Reduced-Dimensionality Perovskites

    KAUST Repository

    Quan, Li Na; Yuan, Mingjian; Comin, Riccardo; Voznyy, Oleksandr; Beauregard, Eric M.; Hoogland, Sjoerd; Buin, Andrei; Kirmani, Ahmad R.; Zhao, Kui; Amassian, Aram; Kim, Dong Ha; Sargent, Edward H.

    2016-01-01

    Metal halide perovskites have rapidly advanced thin film photovoltaic performance; as a result, the materials’ observed instabilities urgently require a solution. Using density functional theory (DFT), we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers introduces quantitatively appreciable van der Waals interactions; and these drive an increased formation energy and should therefore improve material stability. Here we report the reduced-dimensionality (quasi-2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three-dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoichiometry in materials synthesis. We achieved the first certified hysteresis-free solar power conversion in a planar perovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity.

  10. Ligand-Stabilized Reduced-Dimensionality Perovskites

    KAUST Repository

    Quan, Li Na

    2016-02-03

    Metal halide perovskites have rapidly advanced thin film photovoltaic performance; as a result, the materials’ observed instabilities urgently require a solution. Using density functional theory (DFT), we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers introduces quantitatively appreciable van der Waals interactions; and these drive an increased formation energy and should therefore improve material stability. Here we report the reduced-dimensionality (quasi-2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three-dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoichiometry in materials synthesis. We achieved the first certified hysteresis-free solar power conversion in a planar perovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity.

  11. Cerium luminescence in nd0 perovskites

    International Nuclear Information System (INIS)

    Setlur, A.A.; Happek, U.

    2010-01-01

    The luminescence of Ce 3+ in perovskite (ABO 3 ) hosts with nd 0 B-site cations, specifically Ca(Hf,Zr)O 3 and (La,Gd)ScO 3 , is investigated in this report. The energy position of the Ce 3+ excitation and emission bands in these perovskites is compared to those of typical Al 3+ perovskites; we find a Ce 3+ 5d 1 centroid shift and Stokes shift that are larger versus the corresponding values for the Al 3+ perovskites. It is also shown that Ce 3+ luminescence quenching is due to Ce 3+ photoionization. The comparison between these perovskites shows reasonable correlations between Ce 3+ luminescence quenching, the energy position of the Ce 3+ 5d 1 excited state with respect to the host conduction band, and the host composition. - Graphical abstract: Ce 3+ decay times versus temperature for perovskites with nd 0 B-site cations.

  12. Design of Lead-Free Inorganic Halide Perovskites for Solar Cells via Cation-Transmutation.

    Science.gov (United States)

    Zhao, Xin-Gang; Yang, Ji-Hui; Fu, Yuhao; Yang, Dongwen; Xu, Qiaoling; Yu, Liping; Wei, Su-Huai; Zhang, Lijun

    2017-02-22

    Hybrid organic-inorganic halide perovskites with the prototype material of CH 3 NH 3 PbI 3 have recently attracted intense interest as low-cost and high-performance photovoltaic absorbers. Despite the high power conversion efficiency exceeding 20% achieved by their solar cells, two key issues-the poor device stabilities associated with their intrinsic material instability and the toxicity due to water-soluble Pb 2+ -need to be resolved before large-scale commercialization. Here, we address these issues by exploiting the strategy of cation-transmutation to design stable inorganic Pb-free halide perovskites for solar cells. The idea is to convert two divalent Pb 2+ ions into one monovalent M + and one trivalent M 3+ ions, forming a rich class of quaternary halides in double-perovskite structure. We find through first-principles calculations this class of materials have good phase stability against decomposition and wide-range tunable optoelectronic properties. With photovoltaic-functionality-directed materials screening, we identify 11 optimal materials with intrinsic thermodynamic stability, suitable band gaps, small carrier effective masses, and low excitons binding energies as promising candidates to replace Pb-based photovoltaic absorbers in perovskite solar cells. The chemical trends of phase stabilities and electronic properties are also established for this class of materials, offering useful guidance for the development of perovskite solar cells fabricated with them.

  13. Ferroic properties in bi-component perovskites: artificial superlattices and naturally forming compounds

    International Nuclear Information System (INIS)

    Saha-Dasgupta, T

    2014-01-01

    The use of four different metal cations in a bi-component perovskite ABO 3 structure with 50 : 50 substitution at A sublattice as well as B sublattice, opens up the door for materials designing, with the aim to improve ferroic properties. This can be achieved following two different routes; one using the concept of artificially grown superlattices with alternating layers of ABO 3 and A′B′O 3 perovskites in a periodic set-up and another, through synthesis of naturally grown bulk double perovskites with ordered arrangement of A and A′ cations, simultaneously with that of B and B′ cations. The tremendous progress in layered deposition techniques as well as advances in solid state chemistry methods, has made both routes equally plausible and an area of much activity. This review summarizes some of the recent progress in this field, with a special emphasis on two computational studies, (i) one on ultra-thin 1–1 superlattices built out of paraelectric and ferroelectric components, showing tunable piezoelectric properties, and (ii) another on CrOs-based double perovskites which show multiferroic behavior, achieved through layered ordering of A and A′ cations. (topical review)

  14. Perovskites synthesis to SOFC anodes

    International Nuclear Information System (INIS)

    Wendler, L.P.; Chinelatto, A.L.; Chinelatto, A.S.A.; Ramos, K.

    2012-01-01

    Perovskite structure materials containing lanthanum have been widely applied as solid oxide fuel cells (SOFCs) electrodes, due to its electrical properties. Was investigated the obtain of the perovskite structure LaCr 0,5 Ni 0,5 O 3 , by Pechini method, and its suitability as SOFC anode. The choice of this composition was based on the stability provided by chromium and the catalytic properties of nickel. After preparing the resins, the samples were calcined at 300 deg C, 600 deg C, 700 deg C and 850 deg C. The resulting powders were characterized by X-ray diffraction to determine the existing phases. Furthermore, were performed other analysis, like X-ray fluorescence, He pycnometry, specific surface area by BET isotherm and scanning electronic microscopy (author)

  15. Enhanced Exciton and Photon Confinement in Ruddlesden-Popper Perovskite Microplatelets for Highly Stable Low-Threshold Polarized Lasing.

    Science.gov (United States)

    Li, Mingjie; Wei, Qi; Muduli, Subas Kumar; Yantara, Natalia; Xu, Qiang; Mathews, Nripan; Mhaisalkar, Subodh G; Xing, Guichuan; Sum, Tze Chien

    2018-06-01

    At the heart of electrically driven semiconductors lasers lies their gain medium that typically comprises epitaxially grown double heterostuctures or multiple quantum wells. The simultaneous spatial confinement of charge carriers and photons afforded by the smaller bandgaps and higher refractive index of the active layers as compared to the cladding layers in these structures is essential for the optical-gain enhancement favorable for device operation. Emulating these inorganic gain media, superb properties of highly stable low-threshold (as low as ≈8 µJ cm -2 ) linearly polarized lasing from solution-processed Ruddlesden-Popper (RP) perovskite microplatelets are realized. Detailed investigations using microarea transient spectroscopies together with finite-difference time-domain simulations validate that the mixed lower-dimensional RP perovskites (functioning as cladding layers) within the microplatelets provide both enhanced exciton and photon confinement for the higher-dimensional RP perovskites (functioning as the active gain media). Furthermore, structure-lasing-threshold relationship (i.e., correlating the content of lower-dimensional RP perovskites in a single microplatelet) vital for design and performance optimization is established. Dual-wavelength lasing from these quasi-2D RP perovskite microplatelets can also be achieved. These unique properties distinguish RP perovskite microplatelets as a new family of self-assembled multilayer planar waveguide gain media favorable for developing efficient lasers. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Element selective X-ray magnetic circular and linear dichroisms in ferrimagnetic yttrium iron garnet films

    Energy Technology Data Exchange (ETDEWEB)

    Rogalev, A. [European Synchrotron Radiation Facility (ESRF), B.P. 220, F-38043 Grenoble Cedex (France); Goulon, J. [European Synchrotron Radiation Facility (ESRF), B.P. 220, F-38043 Grenoble Cedex (France)], E-mail: goulon@esrf.fr; Wilhelm, F. [European Synchrotron Radiation Facility (ESRF), B.P. 220, F-38043 Grenoble Cedex (France); Brouder, Ch. [Institut de Mineralogie et de Physique des Milieux Condenses, UMR-CNRS 7590, Universite Paris VI-VII, 4 place Jussieu, F-75252 Paris Cedex 05 (France); Yaresko, A. [Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart (Germany); Ben Youssef, J.; Indenbom, M.V. [Laboratoire de Magnetisme de Bretagne, CNRS FRE 2697, UFR Sciences et Techniques, F-29328 Brest Cedex (France)

    2009-12-15

    X-ray magnetic circular dichroism (XMCD) was used to probe the existence of induced magnetic moments in yttrium iron garnet (YIG) films in which yttrium is partly substituted with lanthanum, lutetium or bismuth. Spin polarization of the 4d states of yttrium and of the 5d states of lanthanum or lutetium was clearly demonstrated. Angular momentum resolved d-DOS of yttrium and lanthanun was shown to be split by the crystal field, the two resolved substructures having opposite magnetic polarization. The existence of a weak orbital moment involving the 6p states of bismuth was definitely established with the detection of a small XMCD signal at the Bi M{sub 1}-edge. Difference spectra also enhanced the visibility of subtle changes in the Fe K-edge XMCD spectra of YIG and {l_brace}Y, Bi{r_brace}IG films. Weak natural X-ray linear dichroism signatures were systematically observed with all iron garnet films and with a bulk YIG single crystal cut parallel to the (1 1 1) plane: this proved that, at room temperature, the crystal cannot satisfy all requirements of perfect cubic symmetry (space group: Ia3-bar d), crystal distortions preserving at best trigonal symmetry (R3-bar or R3m). For the first time, a very weak X-ray magnetic linear dichroism (XMLD) was also measured in the iron K-edge pre-peak of YIG and revealed the presence of a tiny electric quadrupole moment in the ground-state charge distribution of iron atoms. Band-structure calculations carried out with fully relativistic LMTO-LSDA methods support our interpretation that ferrimagnetically coupled spins at the iron sites induce a spin polarization of the yttrium d-DOS and reproduce the observed crystal field splitting of the XMCD signal.

  17. Element selective X-ray magnetic circular and linear dichroisms in ferrimagnetic yttrium iron garnet films

    International Nuclear Information System (INIS)

    Rogalev, A.; Goulon, J.; Wilhelm, F.; Brouder, Ch.; Yaresko, A.; Ben Youssef, J.; Indenbom, M.V.

    2009-01-01

    X-ray magnetic circular dichroism (XMCD) was used to probe the existence of induced magnetic moments in yttrium iron garnet (YIG) films in which yttrium is partly substituted with lanthanum, lutetium or bismuth. Spin polarization of the 4d states of yttrium and of the 5d states of lanthanum or lutetium was clearly demonstrated. Angular momentum resolved d-DOS of yttrium and lanthanun was shown to be split by the crystal field, the two resolved substructures having opposite magnetic polarization. The existence of a weak orbital moment involving the 6p states of bismuth was definitely established with the detection of a small XMCD signal at the Bi M 1 -edge. Difference spectra also enhanced the visibility of subtle changes in the Fe K-edge XMCD spectra of YIG and {Y, Bi}IG films. Weak natural X-ray linear dichroism signatures were systematically observed with all iron garnet films and with a bulk YIG single crystal cut parallel to the (1 1 1) plane: this proved that, at room temperature, the crystal cannot satisfy all requirements of perfect cubic symmetry (space group: Ia3-bar d), crystal distortions preserving at best trigonal symmetry (R3-bar or R3m). For the first time, a very weak X-ray magnetic linear dichroism (XMLD) was also measured in the iron K-edge pre-peak of YIG and revealed the presence of a tiny electric quadrupole moment in the ground-state charge distribution of iron atoms. Band-structure calculations carried out with fully relativistic LMTO-LSDA methods support our interpretation that ferrimagnetically coupled spins at the iron sites induce a spin polarization of the yttrium d-DOS and reproduce the observed crystal field splitting of the XMCD signal.

  18. BaZrO3 perovskite nanoparticles as emissive material for organic/inorganic hybrid light-emitting diodes

    DEFF Research Database (Denmark)

    Tamulevičius, S.; Ivaniuk, K.; Cherpak, V.

    2017-01-01

    In the present work we have demonstrated double-channel emission from organic exciplexes coupled to inorganic nanoparticles. The process is demonstrated by yellow-green emission in light-emitting diodes based on organic exciplexes hybridized with perovskite-type dispersed BaZrO3 nanoparticles...

  19. Weak ferrimagnetism, compensation point and magnetization reversal in Ni(HCOO)2x2H2O

    International Nuclear Information System (INIS)

    Kageyama, H.; Khomskii, D.I.; Levitin, R.Z.; Vasiliev, A.N.

    2003-01-01

    Nickel (II) format dihydrate Ni(HCOO) 2 x2H 2 O shows peculiar magnetic response at T N =15.5 K. The magnitude of weak magnetic moment increases initially below T N , equals zero at T*=8.5 K and increases again at lowering temperature. The sign of low field magnetization at any given temperature is determined by the sample's magnetic prehistory and the signs are opposite to each other at T N . This behavior suggests that Ni(HCOO) 2 x2H 2 O is a weak ferrimagnet and T* is a compensation point

  20. Inhomogeneous ferrimagnetic-like behavior in Gd2/3Ca1/3MnO3 single crystals

    International Nuclear Information System (INIS)

    Haberkorn, N.; Larregola, S.; Franco, D.; Nieva, G.

    2009-01-01

    We present a study of the magnetic properties of Gd 2/3 Ca 1/3 MnO 3 single crystals at low temperatures, showing that this material behaves as an inhomogeneous ferrimagnet. In addition to small saturation magnetization at 5 K, we have found history dependent effects in the magnetization and the presence of exchange bias. These features are compatible with microscopic phase separation in the clean Gd 2/3 Ca 1/3 MnO 3 system studied

  1. Efficient Luminescence from Perovskite Quantum Dot Solids

    KAUST Repository

    Kim, Younghoon; Yassitepe, Emre; Voznyy, Oleksandr; Comin, Riccardo; Walters, Grant; Gong, Xiwen; Kanjanaboos, Pongsakorn; Nogueira, Ana F.; Sargent, Edward H.

    2015-01-01

    © 2015 American Chemical Society. Nanocrystals of CsPbX3 perovskites are promising materials for light-emitting optoelectronics because of their colloidal stability, optically tunable bandgap, bright photoluminescence, and excellent photoluminescence quantum yield. Despite their promise, nanocrystal-only films of CsPbX3 perovskites have not yet been fabricated; instead, highly insulating polymers have been relied upon to compensate for nanocrystals' unstable surfaces. We develop solution chemistry that enables single-step casting of perovskite nanocrystal films and overcomes problems in both perovskite quantum dot purification and film fabrication. Centrifugally cast films retain bright photoluminescence and achieve dense and homogeneous morphologies. The new materials offer a platform for optoelectronic applications of perovskite quantum dot solids.

  2. Oxyfluoride Chemistry of Layered Perovskite Compounds

    Directory of Open Access Journals (Sweden)

    Yoshihiro Tsujimoto

    2012-03-01

    Full Text Available In this paper, we review recent progress and new challenges in the area of oxyfluoride perovskite, especially layered systems including Ruddlesden-Popper (RP, Dion-Jacobson (DJ and Aurivillius (AV type perovskite families. It is difficult to synthesize oxyfluoride perovskite using a conventional solid-state reaction because of the high chemical stability of the simple fluoride starting materials. Nevertheless, persistent efforts made by solid-state chemists have led to a major breakthrough in stabilizing such a mixed anion system. In particular, it is known that layered perovskite compounds exhibit a rich variety of O/F site occupation according to the synthesis used. We also present the synthetic strategies to further extend RP type perovskite compounds, with particular reference to newly synthesized oxyfluorides, Sr2CoO3F and Sr3Fe2O5+xF2−x (x ~ 0.44.

  3. Non-collinear magnetism in multiferroic perovskites.

    Science.gov (United States)

    Bousquet, Eric; Cano, Andrés

    2016-03-31

    We present an overview of the current interest in non-collinear magnetism in multiferroic perovskite crystals. We first describe the different microscopic mechanisms giving rise to the non-collinearity of spins in this class of materials. We discuss, in particular, the interplay between non-collinear magnetism and ferroelectric and antiferrodistortive distortions of the perovskite structure, and how this can promote magnetoelectric responses. We then provide a literature survey on non-collinear multiferroic perovskites. We discuss numerous examples of spin cantings driving weak ferromagnetism in transition metal perovskites, and of spin-induced ferroelectricity as observed in the rare-earth based perovskites. These examples are chosen to best illustrate the fundamental role of non-collinear magnetism in the design of multiferroicity.

  4. Efficient Luminescence from Perovskite Quantum Dot Solids

    KAUST Repository

    Kim, Younghoon

    2015-11-18

    © 2015 American Chemical Society. Nanocrystals of CsPbX3 perovskites are promising materials for light-emitting optoelectronics because of their colloidal stability, optically tunable bandgap, bright photoluminescence, and excellent photoluminescence quantum yield. Despite their promise, nanocrystal-only films of CsPbX3 perovskites have not yet been fabricated; instead, highly insulating polymers have been relied upon to compensate for nanocrystals\\' unstable surfaces. We develop solution chemistry that enables single-step casting of perovskite nanocrystal films and overcomes problems in both perovskite quantum dot purification and film fabrication. Centrifugally cast films retain bright photoluminescence and achieve dense and homogeneous morphologies. The new materials offer a platform for optoelectronic applications of perovskite quantum dot solids.

  5. Perovskite Superlattices as Tunable Microwave Devices

    Science.gov (United States)

    Christen, H. M.; Harshavardhan, K. S.

    2003-01-01

    Experiments have shown that superlattices that comprise alternating epitaxial layers of dissimilar paraelectric perovskites can exhibit large changes in permittivity with the application of electric fields. The superlattices are potentially useful as electrically tunable dielectric components of such microwave devices as filters and phase shifters. The present superlattice approach differs fundamentally from the prior use of homogeneous, isotropic mixtures of base materials and dopants. A superlattice can comprise layers of two or more perovskites in any suitable sequence (e.g., ABAB..., ABCDABCD..., ABACABACA...). Even though a single layer of one of the perovskites by itself is not tunable, the compositions and sequence of the layers can be chosen so that (1) the superlattice exhibits low microwave loss and (2) the interfacial interaction between at least two of the perovskites in the superlattice renders either the entire superlattice or else at least one of the perovskites tunable.

  6. CaCu3Ti4O12: A Bifunctional Perovskite Electrocatalyst for Oxygen Evolution and Reduction Reaction in Alkaline Medium

    International Nuclear Information System (INIS)

    Kushwaha, H.S.; Halder, Aditi; Thomas, P.; Vaish, Rahul

    2017-01-01

    Highlights: •A cost effective double perovskite CaCu 3 Ti 4 O 12 have been synthesized using oxalate precursor method. •CCTO electrocatalyst exhibit enhanced bifunctional electrocatalytic activities. •CCTO electrocatalyst have lower overpotential and higher mass activity as compared to noble metal oxide and well-known perovskite catalysts. •Electrochemical impedance spectroscopy investigations of oxygen reactions on perovskite surfaces. -- Abstract: Perovskite oxides are prominent materials as the bifunctional electrocatalysts for both oxygen reduction/evolution reactions (ORR/OER) for the electrochemical energy conversion and storage using regenerative fuel cells and rechargeable metal-air batteries. In this work, a quadruple perovskite CaCu 3 Ti 4 O 12 has been synthesized oxalate precursor route. X-ray diffraction pattern shows phase purity of the synthesized electrocatalyst. The synthesized CCTO electrocatalyst have crystallite size of 26 nm. Electrochemical investigations reveal that CCTO exhibit efficient catalytic activity. More interestingly, an extremely high OER activity is observed for CCTO electrocatalysts which is found superior than similar class of perovskites. Additionally, CCTO shows efficient ORR activity with an onset potential of 0.83 V which is better than that of Pt/C catalyst (≈0.94 V). These results demonstrate the significant potential of CCTO perovskite as a bifunctional electrode material for alkaline fuel cells and metal-air batteries.

  7. Magnetoelectric and transport properties of (GaMn)Sb thin films: A ferrimagnetic phase in dilute alloys

    Energy Technology Data Exchange (ETDEWEB)

    Calderón, Jorge A. [Universidad Nacional de Colombia – Bogotá, Dpto. de Física, Grupo de Materiales Nanoestructurados y sus Aplicaciones, Cra. 30 No. 45-03 Edificio 404 Lab. 121C Ciudad Universitaria, Bogotá (Colombia); Mesa, F., E-mail: fredy.mesa@urosario.edu.co [Grupo NanoTech, Facultad de Ciencias Naturales y Matemáticas, Universidad del Rosario, Cra. 24 No. 63C-69, Bogotá (Colombia); Dussan, A. [Universidad Nacional de Colombia – Bogotá, Dpto. de Física, Grupo de Materiales Nanoestructurados y sus Aplicaciones, Cra. 30 No. 45-03 Edificio 404 Lab. 121C Ciudad Universitaria, Bogotá (Colombia)

    2017-02-28

    Highlights: • (GaMn)Sb thin films were fabricated using the direct current (DC) magnetron co-sputtering. • Presence of ferrimagnetic (Mn{sub 2}Sb) and ferromagnetic (Mn{sub 2}Sb{sub 2}) phases. • A minor difference of 1% was found with respect to percolation theory, which confirmed the validity of the diffusional model in semiconductor alloys with magnetic properties. • Increase in the localized states density (N{sub F}) with increasing substrate temperature. - Abstract: We studied the electrical, magnetic, and transport properties of (GaMn)Sb thin films fabricated by the direct current magnetron co-sputtering method. Using X-ray powder diffraction measurements, we identified the presence of ferrimagnetic (Mn{sub 2}Sb) and ferromagnetic (Mn{sub 2}Sb{sub 2}) phases within the films. We also measured the magnetization of the films versus an applied magnetic field as well as their hysteresis curves at room temperature. We determined the electrical and transport properties of the films through temperature-dependent resistivity measurements using the Van Der Pauw method. The main contribution to the transport process was variable range hopping. Hopping parameters were calculated using percolation theory and refined using the diffusional model. In addition, we determined that all samples had p type semiconductor behavior, that there was an increase in the density of localized states near the Fermi level, and that the binary magnetic phases influenced the electrical properties and transport mechanisms.

  8. Magnetic anisotropy and chemical long-range order in epitaxial ferrimagnetic CrPt sub 3 films

    CERN Document Server

    Maret, M; Köhler, J; Poinsot, R; Ulhaq-Bouillet, C; Tonnerre, J M; Berar, J F; Bucher, E

    2000-01-01

    Thin films of CrPt sub 3 were prepared by molecular beam epitaxy on both Al sub 2 O sub 3 (0 0 0 1) and MgO(0 0 1) substrates, either directly by co-deposition of Cr and Pt at high temperatures or after in situ annealing of superlattices [Cr(2 A)/Pt(7 A)]. In situ RHEED observations and X-ray diffraction measurements have allowed us to check the single-crystal quality of CrPt sub 3 films and to determine the degree of L1 sub 2 -type long-range order (LRO). In films co-deposited between 850 deg. C and 950 deg. C a nearly perfect LRO has been observed. As in bulk alloys, such ordering yields a ferrimagnetic order, while the disordered films are non-magnetic. In contrast with the ferromagnetic L1 sub 2 -type ordered CoPt sub 3 (1 1 1) films, the ferrimagnetic CrPt sub 3 (1 1 1) films exhibit perpendicular magnetic anisotropy with quality factors, K sub u /K sub d , as large as 5 and large coercivities around 450 kA/m. Such anisotropy could be related to the arrangement of Cr atoms, which owing to their large mag...

  9. Perovskite Solar Cells: Progress and Advancements

    Directory of Open Access Journals (Sweden)

    Naveen Kumar Elumalai

    2016-10-01

    Full Text Available Organic–inorganic hybrid perovskite solar cells (PSCs have emerged as a new class of optoelectronic semiconductors that revolutionized the photovoltaic research in the recent years. The perovskite solar cells present numerous advantages include unique electronic structure, bandgap tunability, superior charge transport properties, facile processing, and low cost. Perovskite solar cells have demonstrated unprecedented progress in efficiency and its architecture evolved over the period of the last 5–6 years, achieving a high power conversion efficiency of about 22% in 2016, serving as a promising candidate with the potential to replace the existing commercial PV technologies. This review discusses the progress of perovskite solar cells focusing on aspects such as superior electronic properties and unique features of halide perovskite materials compared to that of conventional light absorbing semiconductors. The review also presents a brief overview of device architectures, fabrication methods, and interface engineering of perovskite solar cells. The last part of the review elaborates on the major challenges such as hysteresis and stability issues in perovskite solar cells that serve as a bottleneck for successful commercialization of this promising PV technology.

  10. Oxygen permeation modelling of perovskites

    NARCIS (Netherlands)

    van Hassel, Bart A.; van Hassel, B.A.; Kawada, Tatsuya; Sakai, Natsuko; Yokokawa, Harumi; Dokiya, Masayuki; Bouwmeester, Henricus J.M.

    1993-01-01

    A point defect model was used to describe the oxygen nonstoichiometry of the perovskites La0.75Sr0.25CrO3, La0.9Sr0.1FeO3, La0.9Sr0.1CoO3 and La0.8Sr0.2MnO3 as a function of the oxygen partial pressure. Form the oxygen vacancy concentration predicte by the point defect model, the ionic conductivity

  11. Phonon model of perovskite thermal capacity

    International Nuclear Information System (INIS)

    Kesler, Ya.A.; Poloznikova, M.Eh.; Petrov, K.I.

    1983-01-01

    A model for calculating the temperature curve of thermal capacity of perovskite family crystals on the basis of vibrational spectra is proposed. Different representatives of the perovskite family: cubic SrTiO 3 , tetragonal BaTiO 3 and orthorbombic CaTiO 3 and LaCrO 3 are considered. The total frequency set is used in thermal capacity calcUlations. Comparison of the thermal capacity values of compounds calculated on the basis of the proposed model with the experimental values shows their good agreement. The method is also recommended for other compounds with the perovskite-like structure

  12. Photovoltaic Effect of 2D Homologous Perovskites

    International Nuclear Information System (INIS)

    Jung, Mi-Hee

    2017-01-01

    Highlights: • The mixed perovskite was prepared by exposure of MAI gas on the BAPbI_4 film. • The increased dimensional perovskite shows a smaller band gap than 2D perovskite. • The mixed perovskite system shows the vertical crystal orientation. • The mixed perovskite cell exhibits the higher Jsc and FF than 2D perovskite cell. - Abstract: The controlled growth of mixed dimensional perovskite structures, (C_6H_5CH_2NH_2)(CH_3NH_3)_n_-_1Pb_nI_3_n_+_1, through the introduction of CH_3NH_3I molecule vapor into the two-dimensional perovskite C_6H_5CH_2NH_3PbI_4 structure and its application in photovoltaic devices is reported. The dimensionality of (C_6H_5CH_2NH_2)(CH_3NH_3)_n_-_1Pb_nI_3_n_+_1 is controlled using the exposure time to the CH_3NH_3I vapor on the C_6H_5CH_2NH_3PbI_4 perovskite film. As the stacking of the lead iodide lattice increases, the crystallographic planes of the inorganic perovskite compound exhibit vertical growth in order to facilitate efficient charge transport. Furthermore, the devices have a smaller band gap, which offers broader absorption and the potential to increase the photocurrent density in the solar cell. As a result, the photovoltaic device based on the (C_6H_5CH_2NH_2)(CH_3NH_3)_n_-_1Pb_nI_3_n_+_1 perovskite exhibits a power conversion efficiency of 5.43% with a short circuit current density of 14.49 mA cm"−"2, an open circuit voltage of 0.85 V, and a fill factor of 44.30 for the best power conversion efficiency under AM 1.5G solar irradiation (100 mW cm"−"2), which is significantly higher than the 0.34% of the pure two-dimensional BAPbI_4 perovskite-based solar cell.

  13. Calculated optical absorption of different perovskite phases

    DEFF Research Database (Denmark)

    Castelli, Ivano Eligio; Thygesen, Kristian Sommer; Jacobsen, Karsten Wedel

    2015-01-01

    We present calculations of the optical properties of a set of around 80 oxides, oxynitrides, and organometal halide cubic and layered perovskites (Ruddlesden-Popper and Dion-Jacobson phases) with a bandgap in the visible part of the solar spectrum. The calculations show that for different classes...... of perovskites the solar light absorption efficiency varies greatly depending not only on bandgap size and character (direct/indirect) but also on the dipole matrix elements. The oxides exhibit generally a fairly weak absorption efficiency due to indirect bandgaps while the most efficient absorbers are found...... in the classes of oxynitride and organometal halide perovskites with strong direct transitions....

  14. Strongly correlated perovskite fuel cells

    Science.gov (United States)

    Zhou, You; Guan, Xiaofei; Zhou, Hua; Ramadoss, Koushik; Adam, Suhare; Liu, Huajun; Lee, Sungsik; Shi, Jian; Tsuchiya, Masaru; Fong, Dillon D.; Ramanathan, Shriram

    2016-06-01

    Fuel cells convert chemical energy directly into electrical energy with high efficiencies and environmental benefits, as compared with traditional heat engines. Yttria-stabilized zirconia is perhaps the material with the most potential as an electrolyte in solid oxide fuel cells (SOFCs), owing to its stability and near-unity ionic transference number. Although there exist materials with superior ionic conductivity, they are often limited by their ability to suppress electronic leakage when exposed to the reducing environment at the fuel interface. Such electronic leakage reduces fuel cell power output and the associated chemo-mechanical stresses can also lead to catastrophic fracture of electrolyte membranes. Here we depart from traditional electrolyte design that relies on cation substitution to sustain ionic conduction. Instead, we use a perovskite nickelate as an electrolyte with high initial ionic and electronic conductivity. Since many such oxides are also correlated electron systems, we can suppress the electronic conduction through a filling-controlled Mott transition induced by spontaneous hydrogen incorporation. Using such a nickelate as the electrolyte in free-standing membrane geometry, we demonstrate a low-temperature micro-fabricated SOFC with high performance. The ionic conductivity of the nickelate perovskite is comparable to the best-performing solid electrolytes in the same temperature range, with a very low activation energy. The results present a design strategy for high-performance materials exhibiting emergent properties arising from strong electron correlations.

  15. Layered B-site cation ordering: A key factor in ferrimagnetism of Y{sub 2}MnCrO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Lin [Department of Physics, University of Science and Technology of China, Hefei, Anhui (China); Yang, Lei [Collaborative Innovation Center for Magnetoelectric Industry, China Three Gorges University, Yichang, Hubei (China); Lee, Ming-Hsien; Lin, Tseh-Hsing [Department of Physics, Tamkang University, Taipei, Taiwan (China); Zhang, ZhongFeng; Xie, XiangNan [Department of Physics, University of Science and Technology of China, Hefei, Anhui (China); Zhu, Hong, E-mail: zhuh@ustc.edu.cn [Department of Physics, University of Science and Technology of China, Hefei, Anhui (China)

    2014-07-15

    Highlights: • Rietveld refinement and first-principles calculations are performed for Y{sub 2}MnCrO{sub 6}. • The layered B-site cation ordering is a more reliable structure for Y{sub 2}MnCrO{sub 6}. • Y{sub 2}MnCrO{sub 6} has an insulating ferrimagnetism (0 0 1)-ordered ground state. • The layered ordered pattern plays a key role for the ferrimagnetism in Y{sub 2}MnCrO{sub 6}. - Abstract: We report the Rietveld refinement of powder X-ray diffraction (XRD) pattern and first-principles calculations for the half-Cr{sup 3+} doped YMnO{sub 3} compound. The Rietveld refinement results suggest that the compound has a monoclinic structure with the Mn{sup 3+}/Cr{sup 3+} layers alternately stacking along the [0 0 1] direction. The first-principles calculations show that the structure with layered B-site cation ordering has the lowest total energy; meanwhile, the insulating ferrimagnetic state is more favored compared to the ferromagnetic state, which is in agreement with the reported experimental results. Based upon Goodenough’s model of semi-covalent exchange, we argue that the anisotropic magnetic couplings between the Mn{sup 3+}/Cr{sup 3+} cations ordered in layered pattern play an important role for the ferrimagnetism in the compound.

  16. Cubic Re6+ (5d1) Double Perovskites, Ba2MgReO6, Ba2ZnReO6, and Ba2Y2/3ReO6: Magnetism, Heat Capacity, μSR, and Neutron Scattering Studies and Comparison with Theory.

    Science.gov (United States)

    Marjerrison, Casey A; Thompson, Corey M; Sala, Gabrielle; Maharaj, Dalini D; Kermarrec, Edwin; Cai, Yipeng; Hallas, Alannah M; Wilson, Murray N; Munsie, Timothy J S; Granroth, Garrett E; Flacau, Roxana; Greedan, John E; Gaulin, Bruce D; Luke, Graeme M

    2016-10-04

    Double perovskites (DP) of the general formula Ba 2 MReO 6 , where M = Mg, Zn, and Y 2/3 , all based on Re 6+ (5d 1 , t 2g 1 ), were synthesized and studied using magnetization, heat capacity, muon spin relaxation, and neutron-scattering techniques. All are cubic, Fm3̅m, at ambient temperature to within the resolution of the X-ray and neutron diffraction data, although the muon data suggest the possibility of a local distortion for M = Mg. The M = Mg DP is a ferromagnet, T c = 18 K, with a saturation moment ∼0.3 bohr magnetons at 3 K. There are two anomalies in the heat capacity: a sharp feature at 18 K and a broad maximum centered near 33 K. The total entropy loss below 45 K is 9.68 e.u., which approaches R ln 4 (11.52 e.u.) supporting a j = 3/2 ground state. The unit cell constants of Ba 2 MgReO 6 and the isostructural, isoelectronic analogue, Ba 2 LiOsO 6 , differ by only 0.1%, yet the latter is an anti-ferromagnet. The M = Zn DP also appears to be a ferromagnet, T c = 11 K, μ sat (Re) = 0.1 μ B . In this case the heat capacity shows a somewhat broad peak near 10 K and a broader maximum at ∼33 K, behavior that can be traced to a smaller particle size, ∼30 nm, for this sample. For both M = Mg and Zn, the low-temperature magnetic heat capacity follows a T 3/2 behavior, consistent with a ferromagnetic spin wave. An attempt to attribute the broad 33 K heat capacity anomalies to a splitting of the j = 3/2 state by a crystal distortion is not supported by inelastic neutron scattering, which shows no transition at the expected energy of ∼7 meV nor any transition up to 100 meV. However, the results for the two ferromagnets are compared to the theory of Chen, Pereira, and Balents, and the computed heat capacity predicts the two maxima observed experimentally. The M = Y 2/3 DP, with a significantly larger cell constant (3%) than the ferromagnets, shows predominantly anti-ferromagnetic correlations, and the ground state is complex with a spin frozen component T

  17. Neutral Color Semitransparent Microstructured Perovskite Solar Cells

    KAUST Repository

    Eperon, Giles E.; Burlakov, Victor M.; Goriely, Alain; Snaith, Henry J.

    2014-01-01

    Neutral-colored semitransparent solar cells are commercially desired to integrate solar cells into the windows and cladding of buildings and automotive applications. Here, we report the use of morphological control of perovskite thin films to form

  18. Ambipolar solution-processed hybrid perovskite phototransistors

    KAUST Repository

    Li, Feng; Ma, Chun; Wang, Hong; Hu, Weijin; Yu, Weili; Sheikh, Arif D.; Wu, Tao

    2015-01-01

    Organolead halide perovskites have attracted substantial attention because of their excellent physical properties, which enable them to serve as the active material in emerging hybrid solid-state solar cells. Here we investigate the phototransistors

  19. Perovskites As Electrocatalysts for Alkaline Water Electrolysis

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey Valerievich; De La Osa Puebla, Ana Raquel; Jensen, Jens Oluf

    2014-01-01

    such as X-ray diffraction, electrical conductivity, scanning electron microscopy (SEM), energy dispersive microscopy (EDX) and rotating disk electrode. The perovskites tested in this work were both produced by a ball-milling technique and by an auto-combustion synthesis, which appeared to be a fast...... and robust method for synthesis of perovskites with various chemical compositions1. The electrochemical performance of the materials was tested through pellet pressing of the perovskite powders. This involved in some case a time consuming preparation process. Furthermore the technique should show...... the adequate reproducibility.2 In this work we show the development of the method, which was further used to compare the activity of various electrocatalysts (Figures 1,2). The electrocatalytic activity of all prepared perovskites was tested in 1M KOH at 80 °C, using an ink consisting of potassium exchanged...

  20. Making and Breaking of Lead Halide Perovskites

    KAUST Repository

    Manser, Joseph S.; Saidaminov, Makhsud I.; Christians, Jeffrey A.; Bakr, Osman; Kamat, Prashant V.

    2016-01-01

    To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice

  1. Scalable fabrication of perovskite solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhen; Klein, Talysa R.; Kim, Dong Hoe; Yang, Mengjin; Berry, Joseph J.; van Hest, Maikel F. A. M.; Zhu, Kai

    2018-03-27

    Perovskite materials use earth-abundant elements, have low formation energies for deposition and are compatible with roll-to-roll and other high-volume manufacturing techniques. These features make perovskite solar cells (PSCs) suitable for terawatt-scale energy production with low production costs and low capital expenditure. Demonstrations of performance comparable to that of other thin-film photovoltaics (PVs) and improvements in laboratory-scale cell stability have recently made scale up of this PV technology an intense area of research focus. Here, we review recent progress and challenges in scaling up PSCs and related efforts to enable the terawatt-scale manufacturing and deployment of this PV technology. We discuss common device and module architectures, scalable deposition methods and progress in the scalable deposition of perovskite and charge-transport layers. We also provide an overview of device and module stability, module-level characterization techniques and techno-economic analyses of perovskite PV modules.

  2. Oxygen excess in the '114' cobaltite hexagonal structure: The ferrimagnet CaBaCo4O7.50

    International Nuclear Information System (INIS)

    Pralong, V.; Caignaert, V.; Sarkar, T.; Lebedev, O.I.; Duffort, V.; Raveau, B.

    2011-01-01

    The study of the oxidation of the '114' orthorhombic cobaltite CaBaCo 4 O 7 , using first electrochemistry and then soft chemistry based on oxidation by NaClO, has allowed a new phase, CaBaCo 4 O 7.50 , to be prepared topotactically. The structural study of this phase shows that its hexagonal structure, closely related to that of orthorhombic CaBaCo 4 O 7 , is curiously similar to that of the members of the LnBaCo 4 O 7 series, in spite of its excess oxygen. Its magnetic study shows that this phase, like CaBaCo 4 O 7 , is ferrimagnetic with the same T C (60 K), but differently exhibits an unusual magnetic hysteresis. This exceptional behavior of CaBaCo 4 O 7 with respect to oxidation as well as the magnetic properties of CaBaCo 4 O 7.50 is interpreted in terms of the presence of defects due to oxidation. - Graphical Abstract: The study of the oxidation of the '114' orthorhombic cobaltite CaBaCo 4 O 7 , using first electrochemistry and then soft chemistry based on oxidation by NaClO, has allowed a new phase, CaBaCo 4 O 7.50 , to be prepared topotactically. The structural study of this phase shows that its hexagonal structure, closely related to that of orthorhombic CaBaCo 4 O 7 , is curiously similar to that of the members of the LnBaCo 4 O 7 series, in spite of its oxygen excess. Its magnetic study shows that this phase, like CaBaCo 4 O 7 , is ferrimagnetic. Highlights: → Topotactic oxidation by means of electrochemistry and soft chemistry of the '114' orthorhombic cobaltite CaBaCo 4 O 7 . → This new phase, CaBaCo 4 O 7.5 shows an hexagonal structure, is closely related to that of orthorhombic mother phase CaBaCo 4 O 7 . → CaBaCo 4 O 7.5 is ferrimagnetic and exhibits an unusual magnetic hysteresis, due to defect pinning centers.

  3. Multicomponent, peptide-targeted glycol chitosan nanoparticles containing ferrimagnetic iron oxide nanocubes for bladder cancer multimodal imaging

    Directory of Open Access Journals (Sweden)

    Key J

    2016-08-01

    Full Text Available Jaehong Key,1,2 Deepika Dhawan,3 Christy L Cooper,3,4 Deborah W Knapp,3 Kwangmeyung Kim,5 Ick Chan Kwon,5 Kuiwon Choi,5 Kinam Park,1,6 Paolo Decuzzi,7–9 James F Leary1,3,41Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA; 2Department of Biomedical Engineering, Yonsei University, Wonju, Republic of Korea; 3School of Veterinary Medicine-Department of Basic Medical Sciences, Purdue University, West Lafayette, 4Birck Nanotechnology Center at Discovery Park, Purdue University, West Lafayette, IN, USA; 5Biomedical Research Center, Korea Institute of Science and Technology, Sungbook-Gu, Seoul, Republic of Korea; 6Department of Pharmaceutics, Purdue University, West Lafayette, IN, 7Department of Translational Imaging, 8Department of Nanomedicine, Houston Methodist Research Institute, Houston, TX USA; 9Laboratory of Nanotechnology for Precision Medicine, Fondazione Istituto Italiano di Tecnologia (IIT, Genova, Italy Abstract: While current imaging modalities, such as magnetic resonance imaging (MRI, computed tomography, and positron emission tomography, play an important role in detecting tumors in the body, no single-modality imaging possesses all the functions needed for a complete diagnostic imaging, such as spatial resolution, signal sensitivity, and tissue penetration depth. For this reason, multimodal imaging strategies have become promising tools for advanced biomedical research and cancer diagnostics and therapeutics. In designing multimodal nanoparticles, the physicochemical properties of the nanoparticles should be engineered so that they successfully accumulate at the tumor site and minimize nonspecific uptake by other organs. Finely altering the nano-scale properties can dramatically change the biodistribution and tumor accumulation of nanoparticles in the body. In this study, we engineered multimodal nanoparticles for both MRI, by using ferrimagnetic nanocubes (NCs, and near infrared fluorescence imaging

  4. Perovskite Thin Films via Atomic Layer Deposition

    KAUST Repository

    Sutherland, Brandon R.; Hoogland, Sjoerd; Adachi, Michael M.; Kanjanaboos, Pongsakorn; Wong, Chris T. O.; McDowell, Jeffrey J.; Xu, Jixian; Voznyy, Oleksandr; Ning, Zhijun; Houtepen, Arjan J.; Sargent, Edward H.

    2014-01-01

    © 2014 Wiley-VCH Verlag GmbH & Co. KGaA. (Graph Presented) A new method to deposit perovskite thin films that benefit from the thickness control and conformality of atomic layer deposition (ALD) is detailed. A seed layer of ALD PbS is place-exchanged with PbI2 and subsequently CH3NH3PbI3 perovskite. These films show promising optical properties, with gain coefficients of 3200 ± 830 cm-1.

  5. Thermodynamic stability and kinetics of perovskite dissolution

    Energy Technology Data Exchange (ETDEWEB)

    Nesbitt, H W; Bancroft, G M; Fyfe, W S; Karkhanis, S N; Nishijima, A [Western Ontario Univ., London (Canada); Shin, S [National Chemical Lab. for Industry, Tsukuba (Japan)

    1981-01-29

    Perovskite, a SYNROC host mineral for nuclear wastes, is thermodynamically unstable in natural waters and in association with common minerals. Leach experiments demonstrate that CaTiO/sub 3/ (perovskite), SrTiO/sub 3/ and BaTiO/sub 3/ are as reactive as some silicate glasses below 100/sup 0/C, but leach much more slowly than glasses above 100/sup 0/C.

  6. Perovskite Thin Films via Atomic Layer Deposition

    KAUST Repository

    Sutherland, Brandon R.

    2014-10-30

    © 2014 Wiley-VCH Verlag GmbH & Co. KGaA. (Graph Presented) A new method to deposit perovskite thin films that benefit from the thickness control and conformality of atomic layer deposition (ALD) is detailed. A seed layer of ALD PbS is place-exchanged with PbI2 and subsequently CH3NH3PbI3 perovskite. These films show promising optical properties, with gain coefficients of 3200 ± 830 cm-1.

  7. Ambipolar solution-processed hybrid perovskite phototransistors

    KAUST Repository

    Li, Feng

    2015-09-08

    Organolead halide perovskites have attracted substantial attention because of their excellent physical properties, which enable them to serve as the active material in emerging hybrid solid-state solar cells. Here we investigate the phototransistors based on hybrid perovskite films and provide direct evidence for their superior carrier transport property with ambipolar characteristics. The field-effect mobilities for triiodide perovskites at room temperature are measured as 0.18 (0.17) cm2 V−1 s−1 for holes (electrons), which increase to 1.24 (1.01) cm2 V−1 s−1 for mixed-halide perovskites. The photoresponsivity of our hybrid perovskite devices reaches 320 A W−1, which is among the largest values reported for phototransistors. Importantly, the phototransistors exhibit an ultrafast photoresponse speed of less than 10 μs. The solution-based process and excellent device performance strongly underscore hybrid perovskites as promising material candidates for photoelectronic applications.

  8. Planar structured perovskite solar cells by hybrid physical chemical vapor deposition with optimized perovskite film thickness

    Science.gov (United States)

    Wei, Xiangyang; Peng, Yanke; Jing, Gaoshan; Cui, Tianhong

    2018-05-01

    The thickness of perovskite absorber layer is a critical parameter to determine a planar structured perovskite solar cell’s performance. By modifying the spin coating speed and PbI2/N,N-dimethylformamide (DMF) solution concentration, the thickness of perovskite absorber layer was optimized to obtain high-performance solar cells. Using a PbI2/DMF solution of 1.3 mol/L, maximum power conversion efficiency (PCE) of a perovskite solar cell is 15.5% with a perovskite film of 413 nm at 5000 rpm, and PCE of 14.3% was also obtained for a solar cell with a perovskite film of 182 nm thick. It is derived that higher concentration of PbI2/DMF will result in better perovskite solar cells. Additionally, these perovskite solar cells are highly uniform. In 14 sets of solar cells, standard deviations of 11 sets of solar cells were less than 0.50% and the smallest standard deviation was 0.25%, which demonstrates the reliability and effectiveness of hybrid physical chemical vapor deposition (HPCVD) method.

  9. Constructing Efficient and Stable Perovskite Solar Cells via Interconnecting Perovskite Grains.

    Science.gov (United States)

    Hou, Xian; Huang, Sumei; Ou-Yang, Wei; Pan, Likun; Sun, Zhuo; Chen, Xiaohong

    2017-10-11

    A high-quality perovskite film with interconnected perovskite grains was obtained by incorporating terephthalic acid (TPA) additive into the perovskite precursor solution. The presence of TPA changed the crystallization kinetics of the perovskite film and promoted lateral growth of grains in the vicinity of crystal boundaries. As a result, sheet-shaped perovskite was formed and covered onto the bottom grains, which made some adjacent grains partly merge together to form grains-interconnected perovskite film. Perovskite solar cells (PSCs) with TPA additive exhibited a power conversion efficiency (PCE) of 18.51% with less hysteresis, which is obviously higher than that of pristine cells (15.53%). PSCs without and with TPA additive retain 18 and 51% of the initial PCE value, respectively, aging for 35 days exposed to relative humidity 30% in air without encapsulation. Furthermore, MAPbI 3 film with TPA additive shows superior thermal stability to the pristine one under 100 °C baking. The results indicate that the presence of TPA in perovskite film can greatly improve the performance of PSCs as well as their moisture resistance and thermal stability.

  10. Magnetization switching diagram of a perpendicular synthetic ferrimagnet CoFeB/Ta/CoFeB bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Koplak, O. [Immanuel Kant Baltic Federal University, 236041 Kaliningrad (Russian Federation); Institute of Problems of Chemical Physics, 142432 Chernogolovka, Moscow (Russian Federation); Talantsev, A. [Institute of Problems of Chemical Physics, 142432 Chernogolovka, Moscow (Russian Federation); Lu, Y.; Hamadeh, A.; Pirro, P.; Hauet, T. [Institut Jean Lamour, UMR 7198 CNRS, Université de Lorraine (France); Morgunov, R., E-mail: morgunov2005@yandex.ru [Institute of Problems of Chemical Physics, 142432 Chernogolovka, Moscow (Russian Federation); Tambov State Technical University, 392000 Tambov (Russian Federation); Mangin, S. [Institut Jean Lamour, UMR 7198 CNRS, Université de Lorraine (France)

    2017-07-01

    Highlights: • Anisotropy, Zeeman and exchange energy determine sequence of magnetic transitions. • Three temperature ranges manifest different shapes of the hysteresis loop. • The critical transition fields are temperature dependent. - Abstract: Magnetic configurations in synthetic ferrimagnet CoFeB/Ta/CoFeB bilayer with strong perpendicular anisotropy have been systematically studied. Magnetization versus field hysteresis loop has been measured for different temperature ranging from 5 to 300 K. The applied field – temperature (H-T) magnetization switching diagram has been constructed by extracting the different switching fields as a function of temperature. This switching diagram can be well explained by considering the competition between energy barrier of layer’s magnetization reversal, interlayer exchange coupling, and Zeeman energy.

  11. Magnetization switching diagram of a perpendicular synthetic ferrimagnet CoFeB/Ta/CoFeB bilayer

    International Nuclear Information System (INIS)

    Koplak, O.; Talantsev, A.; Lu, Y.; Hamadeh, A.; Pirro, P.; Hauet, T.; Morgunov, R.; Mangin, S.

    2017-01-01

    Highlights: • Anisotropy, Zeeman and exchange energy determine sequence of magnetic transitions. • Three temperature ranges manifest different shapes of the hysteresis loop. • The critical transition fields are temperature dependent. - Abstract: Magnetic configurations in synthetic ferrimagnet CoFeB/Ta/CoFeB bilayer with strong perpendicular anisotropy have been systematically studied. Magnetization versus field hysteresis loop has been measured for different temperature ranging from 5 to 300 K. The applied field – temperature (H-T) magnetization switching diagram has been constructed by extracting the different switching fields as a function of temperature. This switching diagram can be well explained by considering the competition between energy barrier of layer’s magnetization reversal, interlayer exchange coupling, and Zeeman energy.

  12. Mixed spin-((1)/(2)) and spin-1 Blume-Capel Ising ferrimagnetic system on the Bethe lattice

    International Nuclear Information System (INIS)

    Albayrak, Erhan; Keskin, Mustafa

    2003-01-01

    The mixed spin-((1)/(2)) and spin-1 Blume-Capel Ising ferrimagnetic system is studied on the Bethe lattice by using the exact recursion equations. Exact expressions for the magnetization, the quadrupolar moment, the Curie temperature and the free energy are found and the phase diagrams are constructed on the Bethe lattice with the coordination numbers q=3, 4, 5 and 6. The existence of a tricritical point is investigated for different values of q. The results are compared with those of other approximate methods and with the exact result on the Bethe lattice by using a discrete nonlinear map and also the exact results that are available for the case of the honeycomb lattice

  13. The effective-field study of a mixed spin-1 and spin-5/2 Ising ferrimagnetic system

    International Nuclear Information System (INIS)

    Deviren, Bayram; Bati, Mehmet; Keskin, Mustafa

    2009-01-01

    An effective-field theory with correlations is developed for a mixed spin-1 and spin-5/2 Ising ferrimagnetic system on the honeycomb (δ=3) and square (δ=4) lattices in the absence and presence of a longitudinal magnetic field. The ground-state phase diagram of the model is obtained in the longitudinal magnetic field (h) and a single-ion potential or crystal-field interaction (Δ) plane. We also investigate the thermal variations of the sublattice magnetizations, and present the phase diagrams in the (Δ/|J|,k B T/|J|) plane. The susceptibility, internal energy and specific heat of the system are numerically examined, and some interesting phenomena in these quantities are found due to the absence and presence of the applied longitudinal magnetic field. Moreover, the system undergoes second- and first-order phase transition; hence, the system gives a tricritical point. The system also exhibits reentrant behavior.

  14. The effective-field study of a mixed spin-1 and spin-5/2 Ising ferrimagnetic system

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram; Bati, Mehmet [Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)], E-mail: keskin@erciyes.edu.tr

    2009-06-15

    An effective-field theory with correlations is developed for a mixed spin-1 and spin-5/2 Ising ferrimagnetic system on the honeycomb ({delta}=3) and square ({delta}=4) lattices in the absence and presence of a longitudinal magnetic field. The ground-state phase diagram of the model is obtained in the longitudinal magnetic field (h) and a single-ion potential or crystal-field interaction ({delta}) plane. We also investigate the thermal variations of the sublattice magnetizations, and present the phase diagrams in the ({delta}/|J|,k{sub B}T/|J|) plane. The susceptibility, internal energy and specific heat of the system are numerically examined, and some interesting phenomena in these quantities are found due to the absence and presence of the applied longitudinal magnetic field. Moreover, the system undergoes second- and first-order phase transition; hence, the system gives a tricritical point. The system also exhibits reentrant behavior.

  15. Narrow-band tunable terahertz emission from ferrimagnetic Mn{sub 3-x}Ga thin films

    Energy Technology Data Exchange (ETDEWEB)

    Awari, N. [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden (Germany); University of Groningen, 9747 AG Groningen (Netherlands); Kovalev, S., E-mail: s.kovalev@hzdr.de, E-mail: c.fowley@hzdr.de, E-mail: rodek@tcd.ie; Fowley, C., E-mail: s.kovalev@hzdr.de, E-mail: c.fowley@hzdr.de, E-mail: rodek@tcd.ie; Green, B.; Yildirim, O.; Lindner, J.; Fassbender, J.; Deac, A. M.; Gensch, M. [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden (Germany); Rode, K., E-mail: s.kovalev@hzdr.de, E-mail: c.fowley@hzdr.de, E-mail: rodek@tcd.ie; Lau, Y.-C.; Betto, D.; Thiyagarajah, N.; Coey, J. M. D. [CRANN, AMBER and School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Gallardo, R. A. [Departamento de Física, Universidad Técnica Federico Santa María, Avenida España 1680, 2390123 Valparíso (Chile)

    2016-07-18

    Narrow-band terahertz emission from coherently excited spin precession in metallic ferrimagnetic Mn{sub 3-x}Ga Heusler alloy nanofilms has been observed. The efficiency of the emission, per nanometer film thickness, is comparable or higher than that of classical laser-driven terahertz sources based on optical rectification. The center frequency of the emission from the films can be tuned precisely via the film composition in the range of 0.20–0.35 THz, making this type of metallic film a candidate for efficient on-chip terahertz emitters. Terahertz emission spectroscopy is furthermore shown to be a sensitive probe of magnetic properties of ultra-thin films.

  16. Metallic transport and large anomalous Hall effect at room temperature in ferrimagnetic Mn{sub 4}N epitaxial thin film

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Xi; Shigematsu, Kei [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); Chikamatsu, Akira, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp; Fukumura, Tomoteru [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); CREST, Japan Science and Technology Agency (JST), Tokyo 113-0033 (Japan); Hirose, Yasushi; Hasegawa, Tetsuya [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); CREST, Japan Science and Technology Agency (JST), Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan)

    2014-08-18

    We report the electrical transport properties of ferrimagnetic Mn{sub 4}N (001) epitaxial thin films grown by pulsed laser deposition on MgO (001) substrates. The Mn{sub 4}N thin films were tetragonally distorted with a ratio of out-of-plane to in-plane lattice constants of 0.987 and showed perpendicular magnetic anisotropy with an effective magnetic anisotropy constant of 0.16 MJ/m{sup 3}, which is comparable with that of a recently reported molecular-beam-epitaxy-grown film. The thin films exhibited metallic transport with a room temperature resistivity of 125 μΩ cm in addition to a large anomalous Hall effect with a Hall angle tangent of 0.023.

  17. Metallic transport and large anomalous Hall effect at room temperature in ferrimagnetic Mn4N epitaxial thin film

    International Nuclear Information System (INIS)

    Shen, Xi; Shigematsu, Kei; Chikamatsu, Akira; Fukumura, Tomoteru; Hirose, Yasushi; Hasegawa, Tetsuya

    2014-01-01

    We report the electrical transport properties of ferrimagnetic Mn 4 N (001) epitaxial thin films grown by pulsed laser deposition on MgO (001) substrates. The Mn 4 N thin films were tetragonally distorted with a ratio of out-of-plane to in-plane lattice constants of 0.987 and showed perpendicular magnetic anisotropy with an effective magnetic anisotropy constant of 0.16 MJ/m 3 , which is comparable with that of a recently reported molecular-beam-epitaxy-grown film. The thin films exhibited metallic transport with a room temperature resistivity of 125 μΩ cm in addition to a large anomalous Hall effect with a Hall angle tangent of 0.023.

  18. Green function study of a mixed spin-((3)/(2)) and spin-((1)/(2)) Heisenberg ferrimagnetic model

    International Nuclear Information System (INIS)

    Li Jun; Wei Guozhu; Du An

    2004-01-01

    The magnetic properties of a mixed spin-((3)/(2)) and spin-((1)/(2)) Heisenberg ferrimagnetic system on a square lattice are investigated theoretically by a multisublattice Green-function technique which takes into account the quantum nature of Heisenberg spins. This model can be relevant for understanding the magnetic behavior of the new class of organometallic materials that exhibit spontaneous magnetic moments at room temperature. We discuss the spontaneous magnetic moments and the finite-temperature phase diagram. We find that there is no compensation point at finite temperature when only the nearest-neighbor interaction and the single-ion anisotropy are included. When the next-nearest-neighbor interaction between spin-((1)/(2)) is taken into account and exceeds a minimum value, a compensation point appears and it is basically unchanged for other values in Hamiltonian fixed. The next-nearest-neighbor interaction between spin-((3)/(2)) has the effect of changing the compensation temperature

  19. Oxygen perovskites with tetravalent neodymium

    Energy Technology Data Exchange (ETDEWEB)

    Brauer, G; Kristen, H [Freiburg Univ. (Germany, F.R.)

    1979-09-01

    Neodymium could be stabilized by incorporating it in host-lattices with the perovskite structure. BaCeO/sub 3/, BaPrO/sub 3/, BaThO/sub 3/, and BaZrO/sub 3/ have been used for host-lattices. The samples were prepared by heating the corresponding oxides on air and at 1250-1400 /sup 0/C. X-ray diffraction and chemical analysis showed that Nd(IV) has been stabilized in different rates by these four host-lattices. BaCeO/sub 3/ is able to incorporate Nd(IV) up to 30%. BaPrO/sub 3/ up to 18%, BaThO/sub 3/ up to 17% and BaZrO/sub 3/ up to 4%.

  20. Ordered meso- and macroporous perovskite oxide catalysts for emerging applications

    DEFF Research Database (Denmark)

    Arandiyan, Hamidreza; Wang, Yuan; Sun, Hongyu

    2018-01-01

    This feature article summarizes the recent progress in porous perovskite oxides as advanced catalysts for both energy conversion applications and various heterogeneous reactions. Recently, research has been focused on specifically designing porous perovskite materials so that large surface areas ...

  1. Design, Structure, and Optical Properties of Organic-Inorganic Perovskites Containing an Oligothiophene Chromophore.

    Science.gov (United States)

    Mitzi, David B.; Chondroudis, Konstantinos; Kagan, Cherie R.

    1999-12-27

    A quaterthiophene derivative, 5,5' "-bis(aminoethyl)-2,2':5',2' ':5' ',2' "-quaterthiophene (AEQT), has been selected for incorporation within the layered organic-inorganic perovskite structure. In addition to having an appropriate molecular shape and two tethering aminoethyl groups to bond to the inorganic framework, AEQT is also a dye and can influence the optical properties of lead(II) halide-based perovskites. Crystals of C(20)H(22)S(4)N(2)PbBr(4) were grown from a slowly cooled aqueous solution containing lead(II) bromide and quaterthiophene derivative (AEQT.2HBr) salts. The new layered perovskite adopts a monoclinic (C2/c) subcell with the lattice parameters a = 39.741(2) Å, b = 5.8420(3) Å, c = 11.5734(6) Å, beta = 92.360(1) degrees, and Z = 4. Broad superstructure peaks are observed in the X-ray diffraction data, indicative of a poorly ordered, doubled supercell along both the a and b axes. The quaterthiophene segment of AEQT(2+) is nearly planar, with a syn-anti-syn relationship between adjacent thiophene rings. Each quaterthiophene chromophore is ordered between nearest-neighbor lead(II) bromide sheets in a herringbone arrangement with respect to neighboring quaterthiophenes. Room temperature optical absorption spectra for thermally ablated films of the perovskites (AEQT)PbX(4) (X = Cl, Br, I) exhibit an exciton peak arising from the lead(II) halide sheets, along with absorption from the quaterthiophene moiety. No evidence of the inorganic sheet excitonic transition is observed in the photoluminescence spectra for any of the chromophore-containing perovskites. However, strong quaterthiophene photoluminescence is observed for X = Cl, with an emission peak at approximately lambda(max) = 532 nm. Similar photoluminescence is observed for the X = Br and I materials, but with substantial quenching, as the inorganic layer band gap decreases relative to the chromophore HOMO-LUMO gap.

  2. Highly Efficient Perovskite-Perovskite Tandem Solar Cells Reaching 80% of the Theoretical Limit in Photovoltage.

    Science.gov (United States)

    Rajagopal, Adharsh; Yang, Zhibin; Jo, Sae Byeok; Braly, Ian L; Liang, Po-Wei; Hillhouse, Hugh W; Jen, Alex K-Y

    2017-09-01

    Organic-inorganic hybrid perovskite multijunction solar cells have immense potential to realize power conversion efficiencies (PCEs) beyond the Shockley-Queisser limit of single-junction solar cells; however, they are limited by large nonideal photovoltage loss (V oc,loss ) in small- and large-bandgap subcells. Here, an integrated approach is utilized to improve the V oc of subcells with optimized bandgaps and fabricate perovskite-perovskite tandem solar cells with small V oc,loss . A fullerene variant, Indene-C 60 bis-adduct, is used to achieve optimized interfacial contact in a small-bandgap (≈1.2 eV) subcell, which facilitates higher quasi-Fermi level splitting, reduces nonradiative recombination, alleviates hysteresis instabilities, and improves V oc to 0.84 V. Compositional engineering of large-bandgap (≈1.8 eV) perovskite is employed to realize a subcell with a transparent top electrode and photostabilized V oc of 1.22 V. The resultant monolithic perovskite-perovskite tandem solar cell shows a high V oc of 1.98 V (approaching 80% of the theoretical limit) and a stabilized PCE of 18.5%. The significantly minimized nonideal V oc,loss is better than state-of-the-art silicon-perovskite tandem solar cells, which highlights the prospects of using perovskite-perovskite tandems for solar-energy generation. It also unlocks opportunities for solar water splitting using hybrid perovskites with solar-to-hydrogen efficiencies beyond 15%. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Charge disproportionation of mixed-valent Cr triggered by Bi lone-pair effect in the A -site-ordered perovskite BiC u3C r4O12

    Science.gov (United States)

    Etter, Martin; Isobe, Masahiko; Sakurai, Hiroya; Yaresko, Alexander; Dinnebier, Robert E.; Takagi, Hidenori

    2018-05-01

    A new A -site-ordered perovskite BiC u3C r4O12 is synthesized under a high pressure of 7.7 GPa. A phase transition from a paramagnetic metal to a ferrimagnetic metal is observed at Tc=190 K accompanied with a structural change from cubic to monoclinic. Structural analysis of the low-temperature monoclinic phase reveals that this transition represents a charge disproportionation of C r3.75 + into C r4 + and C r3.5 + . We argue that the asymmetric displacement of Bi caused by a lone-pair effect triggers the formation of a dimeric Cr4+2O5 unit and leads to an ordering of C r4 + and C r3.5 + below the transition.

  4. Making and Breaking of Lead Halide Perovskites

    KAUST Repository

    Manser, Joseph S.

    2016-02-16

    A new front-runner has emerged in the field of next-generation photovoltaics. A unique class of materials, known as organic metal halide perovskites, bridges the gap between low-cost fabrication and exceptional device performance. These compounds can be processed at low temperature (typically in the range 80–150 °C) and readily self-assemble from the solution phase into high-quality semiconductor thin films. The low energetic barrier for crystal formation has mixed consequences. On one hand, it enables inexpensive processing and both optical and electronic tunability. The caveat, however, is that many as-formed lead halide perovskite thin films lack chemical and structural stability, undergoing rapid degradation in the presence of moisture or heat. To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice of solvent treatment. Proper characterization and tuning of processing parameters can aid in rational optimization of perovskite devices. Likewise, gaining a comprehensive understanding of the degradation mechanism and identifying components of the perovskite structure that may be particularly susceptible to attack by moisture are vital to mitigate device degradation under operating conditions. This Account provides insight into the lifecycle of organic–inorganic lead halide perovskites, including (i) the nature of the precursor solution, (ii) formation of solid-state perovskite thin films and single crystals, and (iii) transformation of perovskites into hydrated phases upon exposure to moisture. In particular, spectroscopic and structural characterization techniques shed light on the thermally driven evolution of the perovskite structure. By tuning precursor stoichiometry and chemistry, and thus the lead halide charge-transfer complexes present in solution, crystallization

  5. Halide-Dependent Electronic Structure of Organolead Perovskite Materials

    KAUST Repository

    Buin, Andrei; Comin, Riccardo; Xu, Jixian; Ip, Alexander H.; Sargent, Edward H.

    2015-01-01

    -based perovskites, in line with recent experimental data. As a result, the optimal growth conditions are also different for the distinct halide perovskites: growth should be halide-rich for Br and Cl, and halide-poor for I-based perovskites. We discuss stability

  6. Mixed Valence Perovskite Cs2 Au2 I6 : A Potential Material for Thin-Film Pb-Free Photovoltaic Cells with Ultrahigh Efficiency.

    Science.gov (United States)

    Debbichi, Lamjed; Lee, Songju; Cho, Hyunyoung; Rappe, Andrew M; Hong, Ki-Ha; Jang, Min Seok; Kim, Hyungjun

    2018-03-01

    New light is shed on the previously known perovskite material, Cs 2 Au 2 I 6 , as a potential active material for high-efficiency thin-film Pb-free photovoltaic cells. First-principles calculations demonstrate that Cs 2 Au 2 I 6 has an optimal band gap that is close to the Shockley-Queisser value. The band gap size is governed by intermediate band formation. Charge disproportionation on Au makes Cs 2 Au 2 I 6 a double-perovskite material, although it is stoichiometrically a single perovskite. In contrast to most previously discussed double perovskites, Cs 2 Au 2 I 6 has a direct-band-gap feature, and optical simulation predicts that a very thin layer of active material is sufficient to achieve a high photoconversion efficiency using a polycrystalline film layer. The already confirmed synthesizability of this material, coupled with the state-of-the-art multiscale simulations connecting from the material to the device, strongly suggests that Cs 2 Au 2 I 6 will serve as the active material in highly efficient, nontoxic, and thin-film perovskite solar cells in the very near future. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Rational Strategies for Efficient Perovskite Solar Cells.

    Science.gov (United States)

    Seo, Jangwon; Noh, Jun Hong; Seok, Sang Il

    2016-03-15

    A long-standing dream in the large scale application of solar energy conversion is the fabrication of solar cells with high-efficiency and long-term stability at low cost. The realization of such practical goals depends on the architecture, process and key materials because solar cells are typically constructed from multilayer heterostructures of light harvesters, with electron and hole transporting layers as a major component. Recently, inorganic-organic hybrid lead halide perovskites have attracted significant attention as light absorbers for the fabrication of low-cost and high-efficiency solar cells via a solution process. This mainly stems from long-range ambipolar charge transport properties, low exciton binding energies, and suitable band gap tuning by managing the chemical composition. In our pioneering work, a new photovoltaic platform for efficient perovskite solar cells (PSCs) was proposed, which yielded a high power conversion efficiency (PCE) of 12%. The platform consisted of a pillared architecture of a three-dimensional nanocomposite of perovskites fully infiltrating mesoporous TiO2, resulting in the formation of continuous phases and perovskite domains overlaid with a polymeric hole conductor. Since then, the PCE of our PSCs has been rapidly increased from 3% to over 20% certified efficiency. The unprecedented increase in the PCE can be attributed to the effective integration of the advantageous attributes of the refined bicontinuous architecture, deposition process, and composition of perovskite materials. Specifically, the bicontinuous architectures used in the high efficiency comprise a layer of perovskite sandwiched between mesoporous metal-oxide layer, which is a very thinner than that of used in conventional dye-sensitized solar cells, and hole-conducting contact materials with a metal back contact. The mesoporous scaffold can affect the hysteresis under different scan direction in measurements of PSCs. The hysteresis also greatly depends on

  8. Molecular behavior of zero-dimensional perovskites

    KAUST Repository

    Yin, Jun

    2017-12-16

    Low-dimensional perovskites offer a rare opportunity to investigate lattice dynamics and charge carrier behavior in bulk quantum-confined solids, in addition to them being the leading materials in optoelectronic applications. In particular, zero-dimensional (0D) inorganic perovskites of the Cs4PbX6 (X = Cl, Br, or I) kind have crystal structures with isolated lead halide octahedra [PbX6]4− surrounded by Cs+ cations, allowing the 0D crystals to exhibit the intrinsic properties of an individual octahedron. Using both experimental and theoretical approaches, we studied the electronic and optical properties of the prototypical 0D perovskite Cs4PbBr6. Our results underline that this 0D perovskite behaves akin to a molecule, demonstrating low electrical conductivity and mobility as well as large polaron binding energy. Density functional theory calculations and transient absorption measurements of Cs4PbBr6 perovskite films reveal the polaron band absorption and strong polaron localization features of the material. A short polaron lifetime of ~2 ps is observed in femtosecond transient absorption experiments, which can be attributed to the fast lattice relaxation of the octahedra and the weak interactions among them.

  9. Hybrid Perovskites: Prospects for Concentrator Solar Cells.

    Science.gov (United States)

    Lin, Qianqian; Wang, Zhiping; Snaith, Henry J; Johnston, Michael B; Herz, Laura M

    2018-04-01

    Perovskite solar cells have shown a meteoric rise of power conversion efficiency and a steady pace of improvements in their stability of operation. Such rapid progress has triggered research into approaches that can boost efficiencies beyond the Shockley-Queisser limit stipulated for a single-junction cell under normal solar illumination conditions. The tandem solar cell architecture is one concept here that has recently been successfully implemented. However, the approach of solar concentration has not been sufficiently explored so far for perovskite photovoltaics, despite its frequent use in the area of inorganic semiconductor solar cells. Here, the prospects of hybrid perovskites are assessed for use in concentrator solar cells. Solar cell performance parameters are theoretically predicted as a function of solar concentration levels, based on representative assumptions of charge-carrier recombination and extraction rates in the device. It is demonstrated that perovskite solar cells can fundamentally exhibit appreciably higher energy-conversion efficiencies under solar concentration, where they are able to exceed the Shockley-Queisser limit and exhibit strongly elevated open-circuit voltages. It is therefore concluded that sufficient material and device stability under increased illumination levels will be the only significant challenge to perovskite concentrator solar cell applications.

  10. Quantum-dot-in-perovskite solids

    KAUST Repository

    Ning, Zhijun; Gong, Xiwen; Comin, Riccardo; Walters, Grant; Fan, Fengjia; Voznyy, Oleksandr; Yassitepe, Emre; Buin, Andrei; Hoogland, Sjoerd; Sargent, Edward H.

    2015-01-01

    © 2015 Macmillan Publishers Limited. All rights reserved. Heteroepitaxy - atomically aligned growth of a crystalline film atop a different crystalline substrate - is the basis of electrically driven lasers, multijunction solar cells, and blue-light-emitting diodes. Crystalline coherence is preserved even when atomic identity is modulated, a fact that is the critical enabler of quantum wells, wires, and dots. The interfacial quality achieved as a result of heteroepitaxial growth allows new combinations of materials with complementary properties, which enables the design and realization of functionalities that are not available in the single-phase constituents. Here we show that organohalide perovskites and preformed colloidal quantum dots, combined in the solution phase, produce epitaxially aligned 'dots-in-a-matrix' crystals. Using transmission electron microscopy and electron diffraction, we reveal heterocrystals as large as about 60 nanometres and containing at least 20 mutually aligned dots that inherit the crystalline orientation of the perovskite matrix. The heterocrystals exhibit remarkable optoelectronic properties that are traceable to their atom-scale crystalline coherence: photoelectrons and holes generated in the larger-bandgap perovskites are transferred with 80% efficiency to become excitons in the quantum dot nanocrystals, which exploit the excellent photocarrier diffusion of perovskites to produce bright-light emission from infrared-bandgap quantum-tuned materials. By combining the electrical transport properties of the perovskite matrix with the high radiative efficiency of the quantum dots, we engineer a new platform to advance solution-processed infrared optoelectronics.

  11. Quantum-dot-in-perovskite solids

    KAUST Repository

    Ning, Zhijun

    2015-07-15

    © 2015 Macmillan Publishers Limited. All rights reserved. Heteroepitaxy - atomically aligned growth of a crystalline film atop a different crystalline substrate - is the basis of electrically driven lasers, multijunction solar cells, and blue-light-emitting diodes. Crystalline coherence is preserved even when atomic identity is modulated, a fact that is the critical enabler of quantum wells, wires, and dots. The interfacial quality achieved as a result of heteroepitaxial growth allows new combinations of materials with complementary properties, which enables the design and realization of functionalities that are not available in the single-phase constituents. Here we show that organohalide perovskites and preformed colloidal quantum dots, combined in the solution phase, produce epitaxially aligned \\'dots-in-a-matrix\\' crystals. Using transmission electron microscopy and electron diffraction, we reveal heterocrystals as large as about 60 nanometres and containing at least 20 mutually aligned dots that inherit the crystalline orientation of the perovskite matrix. The heterocrystals exhibit remarkable optoelectronic properties that are traceable to their atom-scale crystalline coherence: photoelectrons and holes generated in the larger-bandgap perovskites are transferred with 80% efficiency to become excitons in the quantum dot nanocrystals, which exploit the excellent photocarrier diffusion of perovskites to produce bright-light emission from infrared-bandgap quantum-tuned materials. By combining the electrical transport properties of the perovskite matrix with the high radiative efficiency of the quantum dots, we engineer a new platform to advance solution-processed infrared optoelectronics.

  12. Phase diagrams of a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system under a time-dependent oscillating magnetic field

    International Nuclear Information System (INIS)

    Keskin, M.; Canko, O.; Gueldal, S.

    2009-01-01

    We present phase diagrams for a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system on a square lattice in the presence of a time dependent oscillating external magnetic field. We employ the Glauber transition rates to construct the mean-field dynamical equations. The time variation of the average magnetizations and the thermal behavior of the dynamic magnetizations are investigated, extensively. The nature (continuous or discontinuous) of the transitions is characterized by studying the thermal behaviors of the dynamic magnetizations. The dynamic phase transition points are obtained and the phase diagrams are presented in two different planes. Phase diagrams contain paramagnetic (p) and ferrimagnetic (i) phases, and one coexistence or mixed phase region, namely the i+p, that strongly depend on interaction parameters. The system exhibits the dynamic tricritical point and the reentrant behaviors.

  13. Phase diagrams of a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system under a time-dependent oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Keskin, M., E-mail: keskin@erciyes.edu.t [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Canko, O. [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Gueldal, S. [Institute of Science, Erciyes University, 38039 Kayseri (Turkey)

    2009-12-14

    We present phase diagrams for a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system on a square lattice in the presence of a time dependent oscillating external magnetic field. We employ the Glauber transition rates to construct the mean-field dynamical equations. The time variation of the average magnetizations and the thermal behavior of the dynamic magnetizations are investigated, extensively. The nature (continuous or discontinuous) of the transitions is characterized by studying the thermal behaviors of the dynamic magnetizations. The dynamic phase transition points are obtained and the phase diagrams are presented in two different planes. Phase diagrams contain paramagnetic (p) and ferrimagnetic (i) phases, and one coexistence or mixed phase region, namely the i+p, that strongly depend on interaction parameters. The system exhibits the dynamic tricritical point and the reentrant behaviors.

  14. Giant magnetoresistance associated with a first-order transition between two ferrimagnetic states in Mn2-xZnxSb (x < 0.3) compounds

    International Nuclear Information System (INIS)

    Zhang, Q; Zhang, Y Q; Li, Y B; Du, J; Feng, W J; Li, D; Zhang, Z D

    2008-01-01

    A giant magnetoresistance (GMR) is observed in the Mn 2-x Zn x Sb (x 1.9 Zn 0.1 Sb compound. Different from other Mn 2 Sb-based compounds, the GMR in Mn 2-x Zn x Sb is closely correlated with a field-induced transition from a weak ferrimagnetic (WFI) state to a ferrimagnetic (FI) state. It is understood that the influences of both super-zone gap and spin-dependent scattering are responsible for GMR in the present system. Magnetic hysteresis and phase coexistence of the WFI and the FI phases suggest that this WFI-FI transition is of first order. The different mechanisms responsible for butterfly loops of magnetization/resistivity curves in different magnetic states are discussed

  15. Autothermal reforming catalyst having perovskite structure

    Science.gov (United States)

    Krumpel, Michael [Naperville, IL; Liu, Di-Jia [Naperville, IL

    2009-03-24

    The invention addressed two critical issues in fuel processing for fuel cell application, i.e. catalyst cost and operating stability. The existing state-of-the-art fuel reforming catalyst uses Rh and platinum supported over refractory oxide which add significant cost to the fuel cell system. Supported metals agglomerate under elevated temperature during reforming and decrease the catalyst activity. The catalyst is a perovskite oxide or a Ruddlesden-Popper type oxide containing rare-earth elements, catalytically active firs row transition metal elements, and stabilizing elements, such that the catalyst is a single phase in high temperature oxidizing conditions and maintains a primarily perovskite or Ruddlesden-Popper structure under high temperature reducing conditions. The catalyst can also contain alkaline earth dopants, which enhance the catalytic activity of the catalyst, but do not compromise the stability of the perovskite structure.

  16. Aqueous-Containing Precursor Solutions for Efficient Perovskite Solar Cells.

    Science.gov (United States)

    Liu, Dianyi; Traverse, Christopher J; Chen, Pei; Elinski, Mark; Yang, Chenchen; Wang, Lili; Young, Margaret; Lunt, Richard R

    2018-01-01

    Perovskite semiconductors have emerged as competitive candidates for photovoltaic applications due to their exceptional optoelectronic properties. However, the impact of moisture instability on perovskite films is still a key challenge for perovskite devices. While substantial effort is focused on preventing moisture interaction during the fabrication process, it is demonstrated that low moisture sensitivity, enhanced crystallization, and high performance can actually be achieved by exposure to high water content (up to 25 vol%) during fabrication with an aqueous-containing perovskite precursor. The perovskite solar cells fabricated by this aqueous method show good reproducibility of high efficiency with average power conversion efficiency (PCE) of 18.7% and champion PCE of 20.1% under solar simulation. This study shows that water-perovskite interactions do not necessarily negatively impact the perovskite film preparation process even at the highest efficiencies and that exposure to high contents of water can actually enable humidity tolerance during fabrication in air.

  17. Coherent intergrowth of simple cubic and quintuple tetragonal perovskites in the system Nd{sub 2−ε}Ba{sub 3+ε}(Fe{sub ,}Co){sub 5}O{sub 15−δ}

    Energy Technology Data Exchange (ETDEWEB)

    Kundu, Asish K. [Laboratoire CRISMAT, ENSICAEN UMR6508, 6 Bd Maréchal Juin, Cedex 4, Caen 14050 (France); Yu Mychinko, Mikhail [Laboratoire CRISMAT, ENSICAEN UMR6508, 6 Bd Maréchal Juin, Cedex 4, Caen 14050 (France); Department of Chemistry, Institute of Natural Sciences, Ural Federal University, Lenin av. 51, Yekaterinburg 620000 (Russian Federation); Caignaert, Vincent; Lebedev, Oleg I. [Laboratoire CRISMAT, ENSICAEN UMR6508, 6 Bd Maréchal Juin, Cedex 4, Caen 14050 (France); Volkova, Nadezhda E.; Deryabina, Ksenia M.; Cherepanov, Vladimir A. [Department of Chemistry, Institute of Natural Sciences, Ural Federal University, Lenin av. 51, Yekaterinburg 620000 (Russian Federation); Raveau, Bernard, E-mail: bernard.raveau@ensicaen.fr [Laboratoire CRISMAT, ENSICAEN UMR6508, 6 Bd Maréchal Juin, Cedex 4, Caen 14050 (France)

    2015-11-15

    Investigation of the Nd{sub 2−ε}Ba{sub 3+ε}(Fe,Co){sub 5}O{sub 15−δ} system, combining X-ray diffraction and electron microscopy, has allowed a tetragonal quintuple ordered perovskite “a{sub p}×a{sub p}×5a{sub p}” phasoid inter-grown within a single cubic perovskite matrix to be evidenced for ε=0. This nanoscale chemically twinned perovskite is compared with other members, Ln=Sm, Eu, Pr. The unusual long range ordering of the layers develops strains due to size mismatch between Ba{sup 2+} and Ln{sup 3+} cations. Importantly, two factors allow the strains to be decreased: (i) special intergrowths of double (LnBaFe{sub 2}O{sub 6−δ}) and triple (LnBa{sub 2}Fe{sub 3}O{sub 9−δ}) perovskite ribbons/layers oriented at 90°, (ii) nanoscale chemical twinning. The spin locking effect of the nano-domain boundaries upon the magnetic properties of these perovskites is discussed. - Graphical abstract: Nd{sub 2}Ba{sub 3}Fe{sub 5}O{sub 14.54} is a tetragonal quintuple perovskite phasoid embedded in a simple cubic perovskite matrix, which shows collinear antiferromagnetic behavior.

  18. Coherent intergrowth of simple cubic and quintuple tetragonal perovskites in the system Nd_2_−_εBa_3_+_ε(Fe_,Co)_5O_1_5_−_δ

    International Nuclear Information System (INIS)

    Kundu, Asish K.; Yu Mychinko, Mikhail; Caignaert, Vincent; Lebedev, Oleg I.; Volkova, Nadezhda E.; Deryabina, Ksenia M.; Cherepanov, Vladimir A.; Raveau, Bernard

    2015-01-01

    Investigation of the Nd_2_−_εBa_3_+_ε(Fe,Co)_5O_1_5_−_δ system, combining X-ray diffraction and electron microscopy, has allowed a tetragonal quintuple ordered perovskite “a_p×a_p×5a_p” phasoid inter-grown within a single cubic perovskite matrix to be evidenced for ε=0. This nanoscale chemically twinned perovskite is compared with other members, Ln=Sm, Eu, Pr. The unusual long range ordering of the layers develops strains due to size mismatch between Ba"2"+ and Ln"3"+ cations. Importantly, two factors allow the strains to be decreased: (i) special intergrowths of double (LnBaFe_2O_6_−_δ) and triple (LnBa_2Fe_3O_9_−_δ) perovskite ribbons/layers oriented at 90°, (ii) nanoscale chemical twinning. The spin locking effect of the nano-domain boundaries upon the magnetic properties of these perovskites is discussed. - Graphical abstract: Nd_2Ba_3Fe_5O_1_4_._5_4 is a tetragonal quintuple perovskite phasoid embedded in a simple cubic perovskite matrix, which shows collinear antiferromagnetic behavior.

  19. Perovskite Solar Cells—Towards Commercialization

    International Nuclear Information System (INIS)

    Ono, Luis K.; Park, Nam-Gyu; Zhu, Kai; Huang, Wei; Qi, Yabing

    2017-01-01

    The Symposium ES1, Perovskite Solar Cells - Towards Commercialization, held at the 2017 Materials Research Society (MRS) Spring Meeting in Phoenix, Arizona (April 17-21, 2017) received ~200 abstracts. The 23 invited talks and 72 contributed oral presentations as well as 3 poster presentation sessions were organized into 13 principal themes according to the contents of the received abstracts. This Energy Focus article provides a concise summary of the opinions from the scientists and engineers who participated in this symposium regarding the recent progresses, challenges, and future directions for perovskite solar cells as well as other optoelectronic devices.

  20. Research Update: Luminescence in lead halide perovskites

    Directory of Open Access Journals (Sweden)

    Ajay Ram Srimath Kandada

    2016-09-01

    Full Text Available Efficiency and dynamics of radiative recombination of carriers are crucial figures of merit for optoelectronic materials. Following the recent success of lead halide perovskites in efficient photovoltaic and light emitting technologies, here we review some of the noted literature on the luminescence of this emerging class of materials. After outlining the theoretical formalism that is currently used to explain the carrier recombination dynamics, we review a few significant works which use photoluminescence as a tool to understand and optimize the operation of perovskite based optoelectronic devices.

  1. Partial oxidation of 2-propanol on perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Sumathi, R.; Viswanathan, B.; Varadarajan, T.K. [Indian Inst. of Tech., Madras (India). Dept. of Chemistry

    1998-12-31

    Partial oxidation of 2-propanol was carried out on AB{sub 1-x}B`{sub x}O{sub 3} (A=Ba, B=Pb, Ce, Ti; B`=Bi, Sb and Cu) type perovskite oxides. Acetone was the major product observed on all the catalysts. All the catalysts underwent partial reduction during the reaction depending on the composition of the reactant, nature of the B site cation and the extent of substitution at B site. The catalytic activity has been correlated with the reducibility of the perovskite oxides determined from Temperature Programmed Reduction (TPR) studies. (orig.)

  2. Large polarons in lead halide perovskites

    OpenAIRE

    Miyata, Kiyoshi; Meggiolaro, Daniele; Trinh, M. Tuan; Joshi, Prakriti P.; Mosconi, Edoardo; Jones, Skyler C.; De Angelis, Filippo; Zhu, X.-Y.

    2017-01-01

    Lead halide perovskites show marked defect tolerance responsible for their excellent optoelectronic properties. These properties might be explained by the formation of large polarons, but how they are formed and whether organic cations are essential remain open questions. We provide a direct time domain view of large polaron formation in single-crystal lead bromide perovskites CH3NH3PbBr3 and CsPbBr3. We found that large polaron forms predominantly from the deformation of the PbBr3 ? framewor...

  3. Ultrafast Magnetism of Multi-component Ferromagnets and Ferrimagnets on the Time Scale of the Exchange Interaction

    Science.gov (United States)

    Radu, Ilie

    2012-02-01

    Revealing the ultimate speed limit at which magnetic order can be controlled, is a fundamental challenge of modern magnetism having far reaching implications for the magnetic recording industry [1]. Exchange interaction is the strongest force in magnetism, being ultimately responsible for ferromagnetic or antiferromagnetic spin order. How do spins react after being optically excited on a timescale of or even faster than the exchange interaction? Here, we demonstrate that femtosecond (fs) measurements of ferrimagnetic and ferromagnetic alloys using X-ray magnetic circular dichroism provide revolutionary new insights into the problem of ultrafast magnetism on timescales pertinent to the exchange interaction. In particular, we show that upon fs optical excitation the ultrafast spin reversal of GdFeCo - a material with antiferromagnetic coupling of spins - occurs via a transient ferromagnetic state [2]. The latter emerges due to different dynamics of the Gd and Fe magnetic moments: Gd switches within 1.5 ps while it takes only 300 fs for Fe. Thus, by using a single fs laser pulse one can force the spin system to evolve via an energetically unfavorable way and temporarily switch from an antiferromagnetic to a ferromagnetic type of ordering. In order to understand whether the observation of this temporarily decoupled and element-specific dynamics is a general phenomenon or just something strictly related to the case of ferrimagnetic GdFeCo, we have investigated the demagnetization of the archetypal ferromagnetic NiFe alloys. Essentially, we observe the same distinct magnetization dynamics of the constituent magnetic moments: Ni demagnetizes within ˜300 fs being much faster than the demagnetization of Fe of ˜800 fs. This distinct demagnetization behavior leads to an apparent decoupling of the Fe and Ni magnetic moments on a few hundreds of fs time scale, despite the strong exchange interaction of 260meV (˜16 fs) that couples them. These observations supported by

  4. Novel Solvent-free Perovskite Deposition in Fabrication of Normal and Inverted Architectures of Perovskite Solar Cells

    Science.gov (United States)

    Nejand, Bahram Abdollahi; Gharibzadeh, Saba; Ahmadi, Vahid; Shahverdi, H. Reza

    2016-01-01

    We introduced a new approach to deposit perovskite layer with no need for dissolving perovskite precursors. Deposition of Solution-free perovskite (SFP) layer is a key method for deposition of perovskite layer on the hole or electron transport layers that are strongly sensitive to perovskite precursors. Using deposition of SFP layer in the perovskite solar cells would extend possibility of using many electron and hole transport materials in both normal and invert architectures of perovskite solar cells. In the present work, we synthesized crystalline perovskite powder followed by successful deposition on TiO2 and cuprous iodide as the non-sensitve and sensitive charge transport layers to PbI2 and CH3NH3I solution in DMF. The post compressing step enhanced the efficiency of the devices by increasing the interface area between perovskite and charge transport layers. The 9.07% and 7.71% cell efficiencies of the device prepared by SFP layer was achieved in respective normal (using TiO2 as a deposition substrate) and inverted structure (using CuI as deposition substrate) of perovskite solar cell. This method can be efficient in large-scale and low cost fabrication of new generation perovskite solar cells. PMID:27640991

  5. Enhanced planar perovskite solar cell efficiency and stability using a perovskite/PCBM heterojunction formed in one step.

    Science.gov (United States)

    Zhou, Long; Chang, Jingjing; Liu, Ziye; Sun, Xu; Lin, Zhenhua; Chen, Dazheng; Zhang, Chunfu; Zhang, Jincheng; Hao, Yue

    2018-02-08

    Perovskite/PCBM heterojunctions are efficient for fabricating perovskite solar cells with high performance and long-term stability. In this study, an efficient perovskite/PCBM heterojunction was formed via conventional sequential deposition and one-step formation processes. Compared with conventional deposition, the one-step process was more facile, and produced a perovskite thin film of substantially improved quality due to fullerene passivation. Moreover, the resulting perovskite/PCBM heterojunction exhibited more efficient carrier transfer and extraction, and reduced carrier recombination. The perovskite solar cell device based on one-step perovskite/PCBM heterojunction formation exhibited a higher maximum PCE of 17.8% compared with that from the conventional method (13.7%). The device also showed exceptional stability, retaining 83% of initial PCE after 60 days of storage under ambient conditions.

  6. Amine treatment induced perovskite nanowire network in perovskite solar cells: efficient surface passivation and carrier transport

    Science.gov (United States)

    Xiao, Ke; Cui, Can; Wang, Peng; Lin, Ping; Qiang, Yaping; Xu, Lingbo; Xie, Jiangsheng; Yang, Zhengrui; Zhu, Xiaodong; Yu, Xuegong; Yang, Deren

    2018-02-01

    In the fabrication of high efficiency organic-inorganic metal halide perovskite solar cells (PSCs), an additional interface modifier is usually applied for enhancing the interface passivation and carrier transport. In this paper, we develop an innovative method with in-situ growth of one-dimensional perovskite nanowire (1D PNW) network triggered by Lewis amine over the perovskite films. To our knowledge, this is the first time to fabricate PSCs with shape-controlled perovskite surface morphology, which improved power conversion efficiency (PCE) from 14.32% to 16.66% with negligible hysteresis. The amine molecule can passivate the trap states on the polycrystalline perovskite surface to reduce trap-state density. Meanwhile, as a fast channel, the 1D PNWs would promote carrier transport from the bulk perovskite film to the electron transport layer. The PSCs with 1D PNW modification not only exhibit excellent photovoltaic performances, but also show good stability with only 4% PCE loss within 30 days in the ambient air without encapsulation. Our results strongly suggest that in-situ grown 1D PNW network provides a feasible and effective strategy for nanostructured optoelectronic devices such as PSCs to achieve superior performances.

  7. Light-Independent Ionic Transport in Inorganic Perovskite and Ultrastable Cs-Based Perovskite Solar Cells.

    Science.gov (United States)

    Zhou, Wenke; Zhao, Yicheng; Zhou, Xu; Fu, Rui; Li, Qi; Zhao, Yao; Liu, Kaihui; Yu, Dapeng; Zhao, Qing

    2017-09-07

    Due to light-induced effects in CH 3 NH 3 -based perovskites, such as ion migration, defects formation, and halide segregation, the degradation of CH 3 NH 3 -based perovskite solar cells under maximum power point is generally implicated. Here we demonstrated that the effect of light-enhanced ion migration in CH 3 NH 3 PbI 3 can be eliminated by inorganic Cs substitution, leading to an ultrastable perovskite solar cell. Quantitatively, the ion migration barrier for CH 3 NH 3 PbI 3 is 0.62 eV under dark conditions, larger than that of CsPbI 2 Br (0.45 eV); however, it reduces to 0.07 eV for CH 3 NH 3 PbI 3 under illumination, smaller than that for CsPbI 2 Br (0.43 eV). Meanwhile, photoinduced halide segregation is also suppressed in Cs-based perovskites. Cs-based perovskite solar cells retained >99% of the initial efficiency (10.3%) after 1500 h of maximum power point tracking under AM1.5G illumination, while CH 3 NH 3 PbI 3 solar cells degraded severely after 50 h of operation. Our work reveals an uncovered mechanism for stability improvement by inorganic cation substitution in perovskite-based optoelectronic devices.

  8. Ferrimagnetic resonance study on photo-induced magnetism in hybrid magnetic semiconductor V(TCNE)x, x ˜2 film

    Science.gov (United States)

    Yoo, Jung-Woo; Shima Edelstein, R.; Lincoln, D. M.; Epstein, A. J.

    2007-03-01

    The V(TCNE)x, x˜2 is a fully spin-polarized magnetic semiconductor, whose magnetic order exceeds room temperature (Tc > 350 K), and electronic transport follows hopping mechanism through the Coulomb energy split &*circ; subband. In addition, it was determined that this material has thermally reversible persistent change in both magnetism and conductivity driven by the optical excitation [1]. Here, we report detailed investigation on photo-induced magnetism in V(TCNE)x by employing ferrimagnetic resonance (PIFMR) study with an in-situ light illumination. Upon optical excitation (λ˜ 457.9 nm), the FMR spectra display substantial change in their linewidth and resonance field. Angular dependence analyses of line shift indicate the increase of unixial anisotropy field in the film caused by the light irradiation. The results demonstrated that the change in overall magnetic anisotropy by the illumination plays an important role in inducing photo- induced magnetism in (TCNE) class magnet. [1] J.-W. Yoo, et al. to be published in Phys. Rev. Lett.

  9. Ferrimagnetism and spin excitation in a Ni–Mn partially inverted spinel prepared using a modified polymeric precursor method

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Rafael A. [Programa de Pos-Graduação em Ciência e Tecnologia de Materiais (POSMAT), Universidade Estadual Paulista, Faculdade de Ciências, Caixa Postal 473, 17033-360 Bauru, São Paulo (Brazil); Institut des Sciences Chimiques de Rennes – UMR 6226, Université de Rennes 1, F-35042 Rennes (France); Tedesco, Julio C.G.; Birk, Jonas O. [The Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark); Kalceff, Walter, E-mail: wkalceff@uts.edu.au [School of Physics and Advanced Materials, University of Technology Sydney (UTS), P.O. Box 123, Broadway, NSW 2007 (Australia); Yokaichiya, Fabiano [Laboratório Nacional de Luz Síncrotron (LNLS), Caixa Postal 6192, CEP 13083-970 Campinas, São Paulo (Brazil); Comissao Nacional de Energia Nuclear (CNEN), Instituto de Pesquisas Energeticas e Nucleares (IPEN), Reactor Multiproposito Brasileiro - RMB, Avenida Lineo Prestes 2242, Bloco A, Cidade Universitaria Armando Salles de Oliveira, Sao Paulo (Brazil); Rasmussen, Nina [The Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark); Peña, Octavio [Institut des Sciences Chimiques de Rennes – UMR 6226, Université de Rennes 1, F-35042 Rennes (France); Henry, Paul F. [European Spallation Source ESS AB, Box 176, 22100 Lund (Sweden); Simeoni, Giovanna G. [Heinz Maier-Leibnitz Zentrum (MLZ) and Physics Department, Technische Universität München, Lichtenbergstr. 1, 85748 Garching (Germany); Bordallo, Heloisa N. [The Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark); European Spallation Source ESS AB, Box 176, 22100 Lund (Sweden); and others

    2014-07-01

    We demonstrate that a Ni–Mn oxide partially inverted spinel (Ni{sub 1−ν}Mn{sub ν})[Ni{sub ν}Mn{sub 2−ν}]O{sub 4} having inversion degree ν ≈ 0.8 and produced by a modified polymeric precursor method exhibits behaviour previously reported only in monophased samples. The structure of the specimen was determined using Rietveld analysis of X-ray and neutron powder diffraction data, showing that at room temperature the material crystallizes in the Fd3{sup ¯}m space group with a lattice constant a = 8.392 Å. Combining magnetization measurements with neutron powder diffraction, we show that the magnetic structure of this spinel is associated with the interplay between the ferromagnetic and antiferromagnetic lattices which coexist due to the cations' presence on both tetrahedral and octahedral sites. Our analysis of the neutron diffraction data confirms the postulated magnetic structure involving a star-like moment arrangement, arising from competition for the B (octahedral) spinel sites by the Ni and Mn cations. Finally, we show that strong magnetic fluctuations are observed in the inelastic neutron scattering data. - Highlights: • Ni–Mn oxide partially-inverted spinel made by modified polymeric precursor method. • Magnetic measurements showed a ferrimagnetic and a parasitic magnetic transition. • NPD revealed a magnetic structure consistent with a star-like moment arrangement. • INS measurements indicated four distinct temperature-dependent magnetic regimes.

  10. Ferrimagnetic Tb-Fe Alloy Thin Films: Composition and Thickness Dependence of Magnetic Properties and All-Optical Switching

    Directory of Open Access Journals (Sweden)

    Birgit eHebler

    2016-02-01

    Full Text Available Ferrimagnetic rare earth - transition metal Tb-Fe alloy thin films exhibit a variety of different magnetic properties, which depends strongly on composition and temperature. In this study, first the influence of the film thickness (5 - 85 nm on the sample magnetic properties was investigated in a wide composition range between 15 at.% and 38 at.% of Tb. From our results, we find that the compensation point, remanent magnetization, and magnetic anisotropy of the Tb-Fe films depend not only on the composition but also on the thickness of the magnetic film up to a critical thickness of about 20-30 nm. Beyond this critical thickness, only slight changes in magnetic properties are observed. This behavior can be attributed to a growth-induced modification of the microstructure of the amorphous films, which affects the short range order. As a result, a more collinear alignment of the distributed magnetic moments of Tb along the out-of-plane direction with film thickness is obtained. This increasing contribution of the Tb sublattice magnetization to the total sample magnetization is equivalent to a sample becoming richer in Tb and can be referred to as an effective composition. Furthermore, the possibility of all-optical switching, where the magnetization orientation of Tb-Fe can be reversed solely by circularly polarized laser pulses, was analyzed for a broad range of compositions and film thicknesses and correlated to the underlying magnetic properties.

  11. Improved perovskite phototransistor prepared using multi-step annealing method

    Science.gov (United States)

    Cao, Mingxuan; Zhang, Yating; Yu, Yu; Yao, Jianquan

    2018-02-01

    Organic-inorganic hybrid perovskites with good intrinsic physical properties have received substantial interest for solar cell and optoelectronic applications. However, perovskite film always suffers from a low carrier mobility due to its structural imperfection including sharp grain boundaries and pinholes, restricting their device performance and application potential. Here we demonstrate a straightforward strategy based on multi-step annealing process to improve the performance of perovskite photodetector. Annealing temperature and duration greatly affects the surface morphology and optoelectrical properties of perovskites which determines the device property of phototransistor. The perovskite films treated with multi-step annealing method tend to form highly uniform, well-crystallized and high surface coverage perovskite film, which exhibit stronger ultraviolet-visible absorption and photoluminescence spectrum compare to the perovskites prepared by conventional one-step annealing process. The field-effect mobilities of perovskite photodetector treated by one-step direct annealing method shows mobility as 0.121 (0.062) cm2V-1s-1 for holes (electrons), which increases to 1.01 (0.54) cm2V-1s-1 for that treated with muti-step slow annealing method. Moreover, the perovskite phototransistors exhibit a fast photoresponse speed of 78 μs. In general, this work focuses on the influence of annealing methods on perovskite phototransistor, instead of obtains best parameters of it. These findings prove that Multi-step annealing methods is feasible to prepared high performance based photodetector.

  12. Highly Efficient Spectrally Stable Red Perovskite Light-Emitting Diodes.

    Science.gov (United States)

    Tian, Yu; Zhou, Chenkun; Worku, Michael; Wang, Xi; Ling, Yichuan; Gao, Hanwei; Zhou, Yan; Miao, Yu; Guan, Jingjiao; Ma, Biwu

    2018-05-01

    Perovskite light-emitting diodes (LEDs) have recently attracted great research interest for their narrow emissions and solution processability. Remarkable progress has been achieved in green perovskite LEDs in recent years, but not blue or red ones. Here, highly efficient and spectrally stable red perovskite LEDs with quasi-2D perovskite/poly(ethylene oxide) (PEO) composite thin films as the light-emitting layer are reported. By controlling the molar ratios of organic salt (benzylammonium iodide) to inorganic salts (cesium iodide and lead iodide), luminescent quasi-2D perovskite thin films are obtained with tunable emission colors from red to deep red. The perovskite/polymer composite approach enables quasi-2D perovskite/PEO composite thin films to possess much higher photoluminescence quantum efficiencies and smoothness than their neat quasi-2D perovskite counterparts. Electrically driven LEDs with emissions peaked at 638, 664, 680, and 690 nm have been fabricated to exhibit high brightness and external quantum efficiencies (EQEs). For instance, the perovskite LED with an emission peaked at 680 nm exhibits a brightness of 1392 cd m -2 and an EQE of 6.23%. Moreover, exceptional electroluminescence spectral stability under continuous device operation has been achieved for these red perovskite LEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Molecular behavior of zero-dimensional perovskites

    KAUST Repository

    Yin, Jun; Maity, Partha; de Bastiani, Michele; Dursun, Ibrahim; Bakr, Osman; Bredas, Jean-Luc; Mohammed, Omar F.

    2017-01-01

    -dimensional (0D) inorganic perovskites of the Cs4PbX6 (X = Cl, Br, or I) kind have crystal structures with isolated lead halide octahedra [PbX6]4− surrounded by Cs+ cations, allowing the 0D crystals to exhibit the intrinsic properties of an individual octahedron

  14. Elastic softness of hybrid lead halide perovskites

    KAUST Repository

    Ferreira, A. C.; Lé toublon, A.; Paofai, S.; Raymond, S.; Ecolivet, C.; Rufflé , B.; Cordier, S.; Katan, C.; Saidaminov, Makhsud I.; Zhumekenov, A. A.; Bakr, Osman; Even, J.; Bourges, Ph.

    2018-01-01

    scattering, low frequency acoustic phonons in four different hybrid perovskite single crystals: MAPbBr3, FAPbBr3, MAPbI3 and α-FAPbI3 (MA: methylammonium, FA: formamidinium). We report a complete set of elastic constants caracterized by a very soft shear

  15. Combustion synthesis and characterization of porous perovskite ...

    Indian Academy of Sciences (India)

    TECS

    But those perovskite-structural complex oxides produced via ... and cobalt nitrates in a desired molar ratio were dis- solved in a ... At pH 6-7 (ammonia adjustor), ... areas were measured by nitrogen adsorption-desorp- .... The obtained oxide.

  16. High performance magnetocaloric perovskites for magnetic refrigeration

    DEFF Research Database (Denmark)

    Bahl, Christian R. H.; Velazquez, David; Nielsen, Kaspar K.

    2012-01-01

    We have applied mixed valance manganite perovskites as magnetocaloric materials in a magnetic refrigeration device. Relying on exact control of the composition and a technique to process the materials into single adjoined pieces, we have observed temperature spans above 9 K with two materials...

  17. Tilts and Ionic Shifts in Rhombohedral Perovskites

    NARCIS (Netherlands)

    Noheda, Beatriz; Duan, Ning; Cereceda, Noé; Gonzalo, Julio A.

    1998-01-01

    We make a comparative analysis of rhombohedral perovskites (ABO3) with/without oxygen rotations and ionic shifts, within the framework of a generalised effective field approach. We analyse available data on LaAlO3 and LiTaO3 and new data on Zr-rich PZT, examples of three different ways of structural

  18. Hybrid solar cells : Perovskites under the Sun

    NARCIS (Netherlands)

    Loi, Maria Antonietta; Hummelen, Jan C.

    2013-01-01

    Mixed-halide organic–inorganic hybrid perovskites are reported to display electron–hole diffusion lengths over 1 μm. This observation provides important insight into the charge-carrier dynamics of this class of semiconductors and increases the expectations for highly efficient and cheap solar cells.

  19. Calculated optical absorption of different perovskite phases

    Energy Technology Data Exchange (ETDEWEB)

    Castelli, Ivano E. [Center for Atomic-scale Materials Design; Department of Physics; Technical University of Denmark; DK 2800, Kongens Lyngby; Denmark; Thygesen, Kristian S. [Center for Atomic-scale Materials Design; Department of Physics; Technical University of Denmark; DK 2800, Kongens Lyngby; Denmark; Jacobsen, Karsten W. [Center for Atomic-scale Materials Design; Department of Physics; Technical University of Denmark; DK 2800, Kongens Lyngby; Denmark

    2015-01-01

    We present calculations of the optical properties of a set of around 80 oxides, oxynitrides, and organometal halide cubic and layered perovskites (Ruddlesden–Popper and Dion–Jacobson phases) with a bandgap in the visible part of the solar spectrum.

  20. Small polarons in 2D perovskites

    KAUST Repository

    Cortecchia, Daniele

    2017-11-02

    We demonstrate that white light luminescence in two-dimensional (2D) perovskites stems from photoinduced formation of small polarons confined at specific sites of the inorganic framework in the form of self-trapped electrons and holes. We discuss their application in white light emitting devices and X-ray scintillators.

  1. Small polarons in 2D perovskites

    KAUST Repository

    Cortecchia, Daniele; Yin, Jun; Birowosuto, Muhammad D.; Lo, Shu-Zee A.; Gurzadyan, Gagik G.; Bruno, Annalisa; Bredas, Jean-Luc; Soci, Cesare

    2017-01-01

    We demonstrate that white light luminescence in two-dimensional (2D) perovskites stems from photoinduced formation of small polarons confined at specific sites of the inorganic framework in the form of self-trapped electrons and holes. We discuss their application in white light emitting devices and X-ray scintillators.

  2. Spontaneous emission enhancement of colloidal perovskite nanocrystals

    Science.gov (United States)

    Yang, Zhili; Waks, Edo

    Halide perovskite semiconductors have emerged as prominent photovoltaic materials since their high conversion efficiency and promising light emitting materials in optoelectronics. In particular, easy-to-fabricated colloidal perovskite nanocrystals based on CsPbX3 quantum dots has been intensively investigated recently. Their luminescent wavelength could be tuned precisely by their chemical composition and size of growth. This opens new applications including light-emitting diodes, optical amplifiers and lasing since their promising performance as emitters. However, this potentially high-efficient emitter and gain material has not been fully investigated and realized in integrated photonic structures. Here we demonstrate Purcell enhancement effect of CsPbBr3 perovskite nanocrystals by coupling to an optimized photonic crystal nanobeam cavity as a first crucial step towards realization of integrated on-chip coherent light source with low energy consumption. We show clearly highly-enhanced photoluminescent spectrum and an averaged Purcell enhancement factor of 2.9 is achieved when they are coupled to nanobeam photonic crystal cavities compared to the ones on unpatterned surface in our lifetime measurement. Our success in enhancement of emission from CsPbX3 perovskite nanocrystals paves the way towards the realization of efficient light sources for integrated optoelectronic devices with low energy consumption.

  3. Monocrystalline halide perovskite nanostructures for optoelectronic applications

    NARCIS (Netherlands)

    Khoram, P.

    2018-01-01

    Halide perovskites are a promising class of materials for incorporation in optoelectronics with higher efficiency and lower cost. The solution processability of these materials provides unique opportunities for simple nanostructure fabrication. In the first half of the thesis (chapter 2 and 3) we

  4. Photovoltaic Rudorffites: Lead-Free Silver Bismuth Halides Alternative to Hybrid Lead Halide Perovskites.

    Science.gov (United States)

    Turkevych, Ivan; Kazaoui, Said; Ito, Eisuke; Urano, Toshiyuki; Yamada, Koji; Tomiyasu, Hiroshi; Yamagishi, Hideo; Kondo, Michio; Aramaki, Shinji

    2017-10-09

    Hybrid CPbX 3 (C: Cs, CH 3 NH 3 ; X: Br, I) perovskites possess excellent photovoltaic properties but are highly toxic, which hinders their practical application. Unfortunately, all Pb-free alternatives based on Sn and Ge are extremely unstable. Although stable and non-toxic C 2 ABX 6 double perovskites based on alternating corner-shared AX 6 and BX 6 octahedra (A=Ag, Cu; B=Bi, Sb) are possible, they have indirect and wide band gaps of over 2 eV. However, is it necessary to keep the corner-shared perovskite structure to retain good photovoltaic properties? Here, we demonstrate another family of photovoltaic halides based on edge-shared AX 6 and BX 6 octahedra with the general formula A a B b X x (x=a+3 b) such as Ag 3 BiI 6 , Ag 2 BiI 5 , AgBiI 4 , AgBi 2 I 7 . As perovskites were named after their prototype oxide CaTiO 3 discovered by Lev Perovski, we propose to name these new ABX halides as rudorffites after Walter Rüdorff, who discovered their prototype oxide NaVO 2 . We studied structural and optoelectronic properties of several highly stable and promising Ag-Bi-I photovoltaic rudorffites that feature direct band gaps in the range of 1.79-1.83 eV and demonstrated a proof-of-concept FTO/c-m-TiO 2 /Ag 3 BiI 6 /PTAA/Au (FTO: fluorine-doped tin oxide, PTAA: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], c: compact, m: mesoporous) solar cell with photoconversion efficiency of 4.3 %. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. New perovskite-based manganite Pb2Mn2O5

    International Nuclear Information System (INIS)

    Hadermann, Joke; Abakumov, Artem M.; Perkisas, Tyche; D'Hondt, Hans; Tan Haiyan; Verbeeck, Johan; Filonenko, Vladimir P.; Antipov, Evgeny V.; Van Tendeloo, Gustaaf

    2010-01-01

    A new perovskite based compound Pb 2 Mn 2 O 5 has been synthesized using a high pressure high temperature technique. The structure model of Pb 2 Mn 2 O 5 is proposed based on electron diffraction, high angle annular dark field scanning transmission electron microscopy and high resolution transmission electron microscopy. The compound crystallizes in an orthorhombic unit cell with parameters a=5.736(1) A∼√2a p , b=3.800(1) A∼a p , c=21.562(6) A∼4√2a p (a p -the parameter of the perovskite subcell) and space group Pnma. The Pb 2 Mn 2 O 5 structure consists of quasi two-dimensional perovskite blocks separated by 1/2[110] p (101) p crystallographic shear planes. The blocks are connected to each other by chains of edge-sharing MnO 5 distorted tetragonal pyramids. The chains of MnO 5 pyramids and the MnO 6 octahedra of the perovskite blocks delimit six-sided tunnels accommodating double chains of Pb atoms. The tunnels and pyramidal chains adopt two mirror-related configurations ('left' L and 'right' R) and layers consisting of chains and tunnels of the same configuration alternate in the structure according to an -L-R-L-R-sequence. The sequence is sometimes locally violated by the appearance of -L-L- or -R-R-fragments. A scheme is proposed with a Jahn-Teller distortion of the MnO 6 octahedra with two long and two short bonds lying in the a-c plane, along two perpendicular orientations within this plane, forming a d-type pattern. - Graphical abstract: Order of the Jahn-Teller distorted MnO 6 octahedra in Pb 2 Mn 2 O 5 . Two long and two short bonds lie in the a-c plane, along two perpendicular orientations within this plane, forming a d-type pattern.

  6. Conducting Layered Organic-inorganic Halides Containing -Oriented Perovskite Sheets.

    Science.gov (United States)

    Mitzi, D B; Wang, S; Feild, C A; Chess, C A; Guloy, A M

    1995-03-10

    Single crystals of the layered organic-inorganic perovskites, [NH(2)C(I=NH(2)](2)(CH(3)NH(3))m SnmI3m+2, were prepared by an aqueous solution growth technique. In contrast to the recently discovered family, (C(4)H(9)NH(3))(2)(CH(3)NH(3))n-1SnnI3n+1, which consists of (100)-terminated perovskite layers, structure determination reveals an unusual structural class with sets of m -oriented CH(3)NH(3)SnI(3) perovskite sheets separated by iodoformamidinium cations. Whereas the m = 2 compound is semiconducting with a band gap of 0.33 +/- 0.05 electron volt, increasing m leads to more metallic character. The ability to control perovskite sheet orientation through the choice of organic cation demonstrates the flexibility provided by organic-inorganic perovskites and adds an important handle for tailoring and understanding lower dimensional transport in layered perovskites.

  7. Morphology-Controlled Synthesis of Organometal Halide Perovskite Inverse Opals.

    Science.gov (United States)

    Chen, Kun; Tüysüz, Harun

    2015-11-09

    The booming development of organometal halide perovskites in recent years has prompted the exploration of morphology-control strategies to improve their performance in photovoltaic, photonic, and optoelectronic applications. However, the preparation of organometal halide perovskites with high hierarchical architecture is still highly challenging and a general morphology-control method for various organometal halide perovskites has not been achieved. A mild and scalable method to prepare organometal halide perovskites in inverse opal morphology is presented that uses a polystyrene-based artificial opal as hard template. Our method is flexible and compatible with different halides and organic ammonium compositions. Thus, the perovskite inverse opal maintains the advantage of straightforward structure and band gap engineering. Furthermore, optoelectronic investigations reveal that morphology exerted influence on the conducting nature of organometal halide perovskites. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Hybrid perovskites: Approaches towards light-emitting devices

    KAUST Repository

    Alias, Mohd Sharizal

    2016-10-06

    The high optical gain and absorption of organic-inorganic hybrid perovskites have attracted extensive research for photonic device applications. Using the bromide halide as an example, we present key approaches of our work towards realizing efficient perovskites based light-emitters. The approaches involved determination of optical constants for the hybrid perovskites thin films, fabrication of photonic nanostructures in the form of subwavelength grating reflector patterned directly on the hybrid perovskites as light manipulation layer, and enhancing the emission property of the hybrid perovskites by using microcavity structure. Our results provide a platform for realization of hybrid perovskites based light-emitting devices for solid-state lighting and display applications. © 2016 IEEE.

  9. Generalized trends in the formation energies of perovskite oxides

    DEFF Research Database (Denmark)

    Zeng, Zhenhua; Calle-Vallejo, Federico; Mogensen, Mogens Bjerg

    2013-01-01

    Generalized trends in the formation energies of several families of perovskite oxides (ABO3) and plausible explanations to their existence are provided in this study through a combination of DFT calculations, solid-state physics analyses and simple physical/chemical descriptors. The studied...... elements at the A site of perovskites comprise rare-earth, alkaline-earth and alkaline metals, whereas 3d and 5d metals were studied at the B site. We also include ReO3-type compounds, which have the same crystal structure of cubic ABO3 perovskites except without A-site elements. From the observations we...... extract the following four conclusions for the perovskites studied in the present paper: for a given cation at the B site, (I) perovskites with cations of identical oxidation state at the A site possess close formation energies; and (II) perovskites with cations of different oxidation states at the A site...

  10. Hybrid perovskites: Approaches towards light-emitting devices

    KAUST Repository

    Alias, Mohd Sharizal; Dursun, Ibrahim; Priante, Davide; Saidaminov, Makhsud I.; Ng, Tien Khee; Bakr, Osman; Ooi, Boon S.

    2016-01-01

    The high optical gain and absorption of organic-inorganic hybrid perovskites have attracted extensive research for photonic device applications. Using the bromide halide as an example, we present key approaches of our work towards realizing efficient perovskites based light-emitters. The approaches involved determination of optical constants for the hybrid perovskites thin films, fabrication of photonic nanostructures in the form of subwavelength grating reflector patterned directly on the hybrid perovskites as light manipulation layer, and enhancing the emission property of the hybrid perovskites by using microcavity structure. Our results provide a platform for realization of hybrid perovskites based light-emitting devices for solid-state lighting and display applications. © 2016 IEEE.

  11. Water-Induced Dimensionality Reduction in Metal-Halide Perovskites

    KAUST Repository

    Turedi, Bekir

    2018-03-30

    Metal-halide perovskite materials are highly attractive materials for optoelectronic applications. However, the instability of perovskite materials caused by moisture and heat-induced degradation impairs future prospects of using these materials. Here we employ water to directly transform films of the three-dimensional (3D) perovskite CsPbBr3 to stable two-dimensional (2D) perovskite-related CsPb2Br5. A sequential dissolution-recrystallization process governs this water induced transformation under PbBr2 rich condition. We find that these post-synthesized 2D perovskite-related material films exhibit excellent stability against humidity and high photoluminescence quantum yield. We believe that our results provide a new synthetic method to generate stable 2D perovskite-related materials that could be applicable for light emitting device applications.

  12. Neutral- and Multi-Colored Semitransparent Perovskite Solar Cells.

    Science.gov (United States)

    Lee, Kyu-Tae; Guo, L Jay; Park, Hui Joon

    2016-04-11

    In this review, we summarize recent works on perovskite solar cells with neutral- and multi-colored semitransparency for building-integrated photovoltaics and tandem solar cells. The perovskite solar cells exploiting microstructured arrays of perovskite "islands" and transparent electrodes-the latter of which include thin metallic films, metal nanowires, carbon nanotubes, graphenes, and transparent conductive oxides for achieving optical transparency-are investigated. Moreover, the perovskite solar cells with distinctive color generation, which are enabled by engineering the band gap of the perovskite light-harvesting semiconductors with chemical management and integrating with photonic nanostructures, including microcavity, are discussed. We conclude by providing future research directions toward further performance improvements of the semitransparent perovskite solar cells.

  13. Band gap engineering strategy via polarization rotation in perovskite ferroelectrics

    International Nuclear Information System (INIS)

    Wang, Fenggong; Grinberg, Ilya; Rappe, Andrew M.

    2014-01-01

    We propose a strategy to engineer the band gaps of perovskite oxide ferroelectrics, supported by first principles calculations. We find that the band gaps of perovskites can be substantially reduced by as much as 1.2 eV through local rhombohedral-to-tetragonal structural transition. Furthermore, the strong polarization of the rhombohedral perovskite is largely preserved by its tetragonal counterpart. The B-cation off-center displacements and the resulting enhancement of the antibonding character in the conduction band give rise to the wider band gaps of the rhombohedral perovskites. The correlation between the structure, polarization orientation, and electronic structure lays a good foundation for understanding the physics of more complex perovskite solid solutions and provides a route for the design of photovoltaic perovskite ferroelectrics

  14. Ceramic materials on perovskite-type structure for electronic applications

    International Nuclear Information System (INIS)

    Surowiak, Z.

    2003-01-01

    Ceramic materials exhibiting the perovskite-type structure constitute among others, resource base for many fields of widely understood electronics (i.e., piezoelectronics, accustoelectronics, optoelectronics, computer science, tele- and radioelectronics etc.). Most often they are used for fabrication of different type sensors (detectors), transducers, ferroelectric memories, limiters of the electronic current intensity, etc., and hence they are numbered among so-called intelligent materials. Prototype structure of this group of materials is the structure of the mineral called perovskite (CaTiO 3 ). By means of right choice of the chemical composition of ABO 3 and deforming the regular perovskite structure (m3m) more than 5000 different chemical compounds and solid solutions exhibiting the perovskite-type structure have been fabricated. The concept of perovskite functional ceramics among often things ferroelectric ceramics, pyroelectric ceramics, piezoelectric ceramics, electrostrictive ceramics, posistor ceramics, superconductive ceramics and ferromagnetic ceramics. New possibilities of application of the perovskite-type ceramics are opened by nanotechnology. (author)

  15. Double Trouble

    NARCIS (Netherlands)

    Elsaesser, Thomas; Kievit, Robert; Simons, Jan

    1994-01-01

    Double Trouble highlights the career of Dutch scriptwriter and television producer Chiem van Houweninge, well-known for his long-running TV comedy series and as author of episodes for TV detective series. Double Trouble gives Van Houweninge's own views on writing and filming in television prime

  16. Perovskite type nanopowders and thin films obtained by chemical methods

    Directory of Open Access Journals (Sweden)

    Viktor Fruth

    2010-09-01

    Full Text Available The review presents the contribution of the authors, to the preparation of two types of perovskites, namely BiFeO3 and LaCoO3, by innovative methods. The studied perovskites were obtained as powders, films and sintered bodies. Their complex structural and morphological characterization is also presented. The obtained results have underlined the important influence of the method of preparation on the properties of the synthesized perovskites.

  17. High-pressure stability relations, crystal structures, and physical properties of perovskite and post-perovskite of NaNiF3

    International Nuclear Information System (INIS)

    Shirako, Y.; Shi, Y.G.; Aimi, A.; Mori, D.; Kojitani, H.; Yamaura, K.; Inaguma, Y.; Akaogi, M.

    2012-01-01

    NaNiF 3 perovskite was found to transform to post-perovskite at 16–18 GPa and 1273–1473 K. The equilibrium transition boundary is expressed as P (GPa)=−2.0+0.014×T (K). Structure refinements indicated that NaNiF 3 perovskite and post-perovskite have almost regular NiF 6 octahedra consistent with absence of the first-order Jahn–Teller active ions. Both NaNiF 3 perovskite and post-perovskite are insulators. The perovskite underwent a canted antiferromagnetic transition at 156 K, and the post-perovskite antiferromagnetic transition at 22 K. Magnetic exchange interaction of NaNiF 3 post-perovskite is smaller than that of perovskite, reflecting larger distortion of Ni–F–Ni network and lower dimension of octahedral arrangement in post-perovskite than those in perovskite. - Graphical abstract: Perovskite–post-perovskite transition in NaNiF 3 at high pressure Highlights: ► NaNiF 3 perovskite (Pv) transforms to post-perovskite (pPv) at 16 GPa and 1300 K. ► The equilibrium transition boundary is expressed as P (GPa)=−2.0+0.014 T (K). ► Antiferromagnetic transition occurs at 156 K in Pv and 22 K in pPv.

  18. Development of Perovskite-Type Materials for Thermoelectric Application

    Directory of Open Access Journals (Sweden)

    Tingjun Wu

    2018-06-01

    Full Text Available Oxide perovskite materials have a long history of being investigated for thermoelectric applications. Compared to the state-of-the-art tin and lead chalcogenides, these perovskite compounds have advantages of low toxicity, eco-friendliness, and high elemental abundance. However, because of low electrical conductivity and high thermal conductivity, the total thermoelectric performance of oxide perovskites is relatively poor. Variety of methods were used to enhance the TE properties of oxide perovskite materials, such as doping, inducing oxygen vacancy, embedding crystal imperfection, and so on. Recently, hybrid perovskite materials started to draw attention for thermoelectric application. Due to the low thermal conductivity and high Seebeck coefficient feature of hybrid perovskites materials, they can be promising thermoelectric materials and hold the potential for the application of wearable energy generators and cooling devices. This mini-review will build a bridge between oxide perovskites and burgeoning hybrid halide perovskites in the research of thermoelectric properties with an aim to further enhance the relevant performance of perovskite-type materials.

  19. Impact of Ultrathin C60 on Perovskite Photovoltaic Devices.

    Science.gov (United States)

    Liu, Dianyi; Wang, Qiong; Traverse, Christopher J; Yang, Chenchen; Young, Margaret; Kuttipillai, Padmanaban S; Lunt, Sophia Y; Hamann, Thomas W; Lunt, Richard R

    2018-01-23

    Halide perovskite solar cells have seen dramatic progress in performance over the past several years. Certified efficiencies of inverted structure (p-i-n) devices have now exceeded 20%. In these p-i-n devices, fullerene compounds are the most popular electron-transfer materials. However, the full function of fullerenes in perovskite solar cells is still under investigation, and the mechanism of photocurrent hysteresis suppression by fullerene remains unclear. In previous reports, thick fullerene layers (>20 nm) were necessary to fully cover the perovskite film surface to make good contact with perovskite film and avoid large leakage currents. In addition, the solution-processed fullerene layer has been broadly thought to infiltrate into the perovskite film to passivate traps on grain boundary surfaces, causing suppressed photocurrent hysteresis. In this work, we demonstrate an efficient perovskite photovoltaic device with only 1 nm C 60 deposited by vapor deposition as the electron-selective material. Utilizing a combination of fluorescence microscopy and impedance spectroscopy, we show that the ultrathin C 60 predominately acts to extract electrons from the perovskite film while concomitantly suppressing the photocurrent hysteresis by reducing space charge accumulation at the interface. This work ultimately helps to clarify the dominant role of fullerenes in perovskite solar cells while simplifying perovskite solar cell design to reduce manufacturing costs.

  20. Coexistence of spin glass and superparamagnetism with ferrimagnetic order in polycrystalline spinel Co{sub 0.2}Zn{sub 0.8}Fe{sub 1.95}Ho{sub 0.05}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Bhowmik, R.N. [Experimental Condensed Matter Physics Dvision, Saha Institute of Nuclear Physics, Kolkata-70064 (India)]. E-mail: rnb@cmp.saha.ernet.in; Ranganathan, R. [Experimental Condensed Matter Physics Dvision, Saha Institute of Nuclear Physics, Kolkata-70064 (India)]. E-mail: ranga@cmp.saha.ernet.in; Nagarajan, R. [Tata Institute of Fundamental Research, Department of Condensed Matter Physics and Materials Science, Colaba Road, Mumbai (India)

    2006-04-15

    We discuss our investigation of DC magnetization, as a function of time, temperature and magnetic field, and explore some distinct magnetic behaviour in the polycrystalline spinel Co{sub 0.2}Zn{sub 0.8}Fe{sub 1.95}Ho{sub 0.05}O{sub 4}. The system is essentially to be a ferrimagnet and the ferrimagnetic order (spontaneous magnetization) is identified using Arrot plot of M(H) data. Application of some scaling laws have shown the coexistence of spin glass (SG) and superparamagnetism (SPM) with ferrimagnetic order (FIMO) at low and high temperature, respectively, in the system. The coexistence of SG and SPM with FIMO shows paramagnetic to ferrimagnetic state at T{sub C}{approx}225K and ferrimagnetic to cluster spin glass state below T{sub m}{approx}120K. The non-linear increase, without hysteresis, of M(H) data above T{sub C} indicates the existence of short range interacting clusters in the paramagnetic state. In addition, the anisotropy effect of Ho{sup 3+} has shown some interesting magnetic features, such as, spin glass of Ising nature and an unusual maximum in the thermoremanent magnetization about 180K.

  1. A first-principle investigation of spin-gapless semiconductivity, half-metallicity, and fully-compensated ferrimagnetism property in Mn{sub 2}ZnMg inverse Heusler compound

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaotian [School of Material Sciences and Engineering, Hebei University of Technology, Tianjin 300130 (China); Institute for Superconducting & Electronic Materials (ISEM), University of Wollongong, Wollongong 2500 (Australia); Cheng, Zhenxiang, E-mail: cheng@uow.edu.au [Institute for Superconducting & Electronic Materials (ISEM), University of Wollongong, Wollongong 2500 (Australia); Khenata, Rabah [Laboratoire de Physique Quantique, de la Matière et de la Modélisation Mathématique (LPQ3M), Université de Mascara, Mascara 29000 (Algeria); Rozale, Habib [Condensed Matter and Sustainable Development Laboratory, Physics Department, University of Sidi-Bel-Abbès, 22000 Sidi-Bel-Abbès (Algeria); Wang, Jianli [Institute for Superconducting & Electronic Materials (ISEM), University of Wollongong, Wollongong 2500 (Australia); Wang, Liying; Guo, Ruikang [School of Material Sciences and Engineering, Hebei University of Technology, Tianjin 300130 (China); Liu, Guodong, E-mail: gdliu1978@126.com [School of Material Sciences and Engineering, Hebei University of Technology, Tianjin 300130 (China)

    2017-02-01

    Recently, spin-gapless semiconductors (SGSs) and half-metallic materials (HMMs) have received considerable interest in the fields of materials sciences and solid-state physics because they can provide a high degree of spin polarization in electron transport. The results on band structure calculations reveal that the metallic fully-compensated ferrimagnet (M-FCF) Mn{sub 2}ZnMg becomes half-metallic fully-compensated ferrimagnet (HM-FCF), fully-compensated ferrimagnetic semiconductor (FCF-S) and fully-compensated ferrimagnetic spin-gapless semiconductor (FCF-SGS) if the uniform strain applied. However, the metallic fully-compensated ferrimagnetism property of the Mn{sub 2}ZnMg is robust to the tetragonalization. The structure stability based on the calculations of the cohesion energy and the formation energy of this compound has been tested. Furthermore, a magnetic state transition from antiferromagentic (AFM) state to non-magnetic (NM) state can be observed at the lattice constant of 5.20 Å. - Highlights: • Mn{sub 2}ZnMg is a M-FCF at its equilibrium lattice constant. • We study the effect of uniform strain on the physical nature transition of Mn{sub 2}ZnMg. • The M-FCF property of the Mn{sub 2}ZnMg is robust to the tetragonalization. • A magnetic phase transition occurs at 5.20 Å.

  2. Organohalide Perovskites for Solar Energy Conversion.

    Science.gov (United States)

    Lin, Qianqian; Armin, Ardalan; Burn, Paul L; Meredith, Paul

    2016-03-15

    Lead-based organohalide perovskites have recently emerged as arguably the most promising of all next generation thin film solar cell technologies. Power conversion efficiencies have reached 20% in less than 5 years, and their application to other optoelectronic device platforms such as photodetectors and light emitting diodes is being increasingly reported. Organohalide perovskites can be solution processed or evaporated at low temperatures to form simple thin film photojunctions, thus delivering the potential for the holy grail of high efficiency, low embedded energy, and low cost photovoltaics. The initial device-driven "perovskite fever" has more recently given way to efforts to better understand how these materials work in solar cells, and deeper elucidation of their structure-property relationships. In this Account, we focus on this element of organohalide perovskite chemistry and physics in particular examining critical electro-optical, morphological, and architectural phenomena. We first examine basic crystal and chemical structure, and how this impacts important solar-cell related properties such as the optical gap. We then turn to deeper electronic phenomena such as carrier mobilities, trap densities, and recombination dynamics, as well as examining ionic and dielectric properties and how these two types of physics impact each other. The issue of whether organohalide perovskites are predominantly nonexcitonic at room temperature is currently a matter of some debate, and we summarize the evidence for what appears to be the emerging field consensus: an exciton binding energy of order 10 meV. Having discussed the important basic chemistry and physics we turn to more device-related considerations including processing, morphology, architecture, thin film electro-optics and interfacial energetics. These phenomena directly impact solar cell performance parameters such as open circuit voltage, short circuit current density, internal and external quantum efficiency

  3. Post-perovskite transitions in CaB4+O3 at high pressure

    International Nuclear Information System (INIS)

    Akaogi, M; Shirako, Y; Kojitani, H; Takamori, S; Yamaura, K; Takayama-Muromachi, E

    2010-01-01

    High-pressure phase transitions in CaRhO 3 were examined using a multianvil apparatus up to 27 GPa and 1930 o C. CaRhO 3 perovskite transforms to post-perovskite via a monoclinic intermediate phase with increasing pressure. Volume changes for the transitions of perovskite - intermediate phase and of intermediate phase - post-perovskite are -1.1 and -0.7 %, respectively. CaRhO 3 post-perovskite is the fourth quenchable post-perovskite oxide found so far. By high-temperature calorimetric experiments, enthalpy of the perovskite - post-perovskite transition in CaRuO 3 was measured as 15.2±3.3 kJ/mol. Combining the datum with those of CaIrO 3 , it is shown that CaIrO 3 perovskite is energetically less stable than CaRuO 3 perovskite. This is consistent with the fact that orthorhombic distortion of CaIrO 3 perovskite is larger than CaRuO 3 , as indicated with the tilt-angle of octahedral framework of perovskite structure. The transition pressure from perovskite to post-perovskite in CaBO 3 (B = Ru, Rh, Ir) increases almost linearly with decreasing the tilt-angle, suggesting that the perovskite - post-perovskite transition may result from instability of the perovskite structure with pressure.

  4. Preparation and studies on surface modifications of calcium-silico-phosphate ferrimagnetic glass-ceramics in simulated body fluid

    International Nuclear Information System (INIS)

    Sharma, K.; Dixit, A.; Singh, Sher; Jagannath,; Bhattacharya, S.; Prajapat, C.L.; Sharma, P.K.; Yusuf, S.M.; Tyagi, A.K.; Kothiyal, G.P.

    2009-01-01

    The structure and magnetic behaviour of 34SiO 2 -(45 - x) CaO-16P 2 O 5 -4.5 MgO-0.5 CaF 2 - x Fe 2 O 3 (where x = 5, 10, 15, 20 wt.%) glasses have been investigated. Ferrimagnetic glass-ceramics are prepared by melt quench followed by controlled crystallization. The surface modification and dissolution behaviour of these glass-ceramics in simulated body fluid (SBF) have also been studied. Phase formation and magnetic behaviour have been studied using XRD and SQUID magnetometer. The room temperature Moessbauer study has been done to monitor the local environment around Fe cations and valence state of Fe ions. X-ray photoelectron spectroscopy (XPS) was used to study the surface modification in glass-ceramics when immersed in simulated body fluid. Formation of bioactive layer in SBF has been ascertained using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The SBF solutions were analyzed using an absorption spectrophotometer. The magnetic measurements indicated that all these glasses possess paramagnetic character and the [Fe 2+ /Fe 3+ ] ions ratio depends on the composition of glass and varied with Fe 2 O 3 concentration in glass matrix. In glass-ceramics saturation magnetization increases with increase in amount of Fe 2 O 3 . The nanostructure of hematite and magnetite is formed in the glass-ceramics with 15 and 20 wt.% Fe 2 O 3 , which is responsible for the magnetic property of these glass-ceramics. Introduction of Fe 2 O 3 induces several modifications at the glass-ceramics surface when immersed in SBF solution and thereby affecting the surface dissolution and the formation of the bioactive layer.

  5. New hybrid lead iodides: From one-dimensional chain to two-dimensional layered perovskite structure

    International Nuclear Information System (INIS)

    Xiong, Kecai; Liu, Wei; Teat, Simon J.; An, Litao; Wang, Hao; Emge, Thomas J.; Li, Jing

    2015-01-01

    Two new hybrid lead halides (H 2 BDA)[PbI 4 ] (1) (H 2 BDA=1,4-butanediammonium dication) and (HNPEIM)[PbI 3 ] (2) (HNPEIM=N-​phenyl-ethanimidamidine cation) have been synthesized and structurally characterized. X-ray diffraction analyses reveal that compound 1 features a two-dimensional corner-sharing perovskite layer whereas compound 2 contains one-dimensional edge-sharing double chains. The N-​phenyl-ethanimidamidine cation within compound 2 was generated in-situ under solvothermal conditions. The optical absorption spectra collected at room temperature suggest that both compounds are semiconductors having direct band gaps, with estimated values of 2.64 and 2.73 eV for 1 and 2, respectively. Results from the density functional theory (DFT) calculations are consistent with the experimental data. Density of states (DOS) analysis reveals that in both compounds 1 and 2, the energy states in the valence band maximum region are iodine 5p atomic orbitals with a small contribution from lead 6s, while in the region of conduction band minimum, the major contributions are from the inorganic (Pb 6p atomic orbitals) and organic components (C and N 2p atomic orbitals) in compound 1 and 2, respectively. - Graphical abstract: Two new hybrid lead halides built on one-dimensional edge-sharing double chains and two-dimensional corner-sharing perovskite layers are synthesized and their structural and electronic properties are analyzed. - Highlights: • Two new hybrid lead iodides are designed, synthesized, and characterized. • They are closely related to, but different from, perovskite structures. • The electronic properties of both compounds are analyzed by DFT calculations

  6. New hybrid lead iodides: From one-dimensional chain to two-dimensional layered perovskite structure

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Kecai; Liu, Wei [Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854 (United States); Teat, Simon J. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); An, Litao; Wang, Hao; Emge, Thomas J. [Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854 (United States); Li, Jing, E-mail: jingli@rutgers.edu [Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854 (United States)

    2015-10-15

    Two new hybrid lead halides (H{sub 2}BDA)[PbI{sub 4}] (1) (H{sub 2}BDA=1,4-butanediammonium dication) and (HNPEIM)[PbI{sub 3}] (2) (HNPEIM=N-​phenyl-ethanimidamidine cation) have been synthesized and structurally characterized. X-ray diffraction analyses reveal that compound 1 features a two-dimensional corner-sharing perovskite layer whereas compound 2 contains one-dimensional edge-sharing double chains. The N-​phenyl-ethanimidamidine cation within compound 2 was generated in-situ under solvothermal conditions. The optical absorption spectra collected at room temperature suggest that both compounds are semiconductors having direct band gaps, with estimated values of 2.64 and 2.73 eV for 1 and 2, respectively. Results from the density functional theory (DFT) calculations are consistent with the experimental data. Density of states (DOS) analysis reveals that in both compounds 1 and 2, the energy states in the valence band maximum region are iodine 5p atomic orbitals with a small contribution from lead 6s, while in the region of conduction band minimum, the major contributions are from the inorganic (Pb 6p atomic orbitals) and organic components (C and N 2p atomic orbitals) in compound 1 and 2, respectively. - Graphical abstract: Two new hybrid lead halides built on one-dimensional edge-sharing double chains and two-dimensional corner-sharing perovskite layers are synthesized and their structural and electronic properties are analyzed. - Highlights: • Two new hybrid lead iodides are designed, synthesized, and characterized. • They are closely related to, but different from, perovskite structures. • The electronic properties of both compounds are analyzed by DFT calculations.

  7. Improved Efficiency and Stability of Perovskite Solar Cells Induced by CO Functionalized Hydrophobic Ammonium-Based Additives.

    Science.gov (United States)

    Wu, Zhifang; Raga, Sonia R; Juarez-Perez, Emilio J; Yao, Xuyang; Jiang, Yan; Ono, Luis K; Ning, Zhijun; Tian, He; Qi, Yabing

    2018-01-01

    Because of the rapid rise of the efficiency, perovskite solar cells are currently considered as the most promising next-generation photovoltaic technology. Much effort has been made to improve the efficiency and stability of perovskite solar cells. Here, it is demonstrated that the addition of a novel organic cation of 2-(6-bromo-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)ethan-1-ammonium iodide (2-NAM), which has strong Lewis acid and base interaction (between CO and Pb) with perovskite, can effectively increase crystalline grain size and reduce charge carrier recombination of the double cation FA 0.83 MA 0.17 PbI 2.51 Br 0.49 perovskite film, thus boosting the efficiency from 17.1 ± 0.8% to 18.6 ± 0.9% for the 0.1 cm 2 cell and from 15.5 ± 0.5% to 16.5 ± 0.6% for the 1.0 cm 2 cell. The champion cell shows efficiencies of 20.0% and 17.6% with active areas of 0.1 and 1.0 cm 2 , respectively. Moreover, the hysteresis behavior is suppressed and the stability is improved. The result provides a promising route to further elevate efficiency and stability of perovskite solar cells by the fine tuning of triple organic cations. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. The different climatic response of pedogenic hematite and ferrimagnetic minerals: Evidence from particle-sized modern soils over the Chinese Loess Plateau

    Science.gov (United States)

    Gao, Xinbo; Hao, Qingzhen; Wang, Luo; Oldfield, Frank; Bloemendal, Jan; Deng, Chenglong; Song, Yang; Ge, Junyi; Wu, Haibin; Xu, Bing; Li, Fengjiang; Han, Long; Fu, Yu; Guo, Zhengtang

    2018-01-01

    In recent years, increasing interest in loess studies has focused on qualitative and quantitative paleoclimatic reconstruction using the imperfect antiferromagnetic mineral hematite. However, the linkage between the hematite formation and climatic variables remains controversial. Here we present the results of a comprehensive investigation of the magnetic properties and statistical analysis of a suite of clay and silt fractions of modern soil samples from 179 sites across the Chinese Loess Plateau (CLP) and adjacent regions. Our objective was to clarify the relationships between modern climatic variables and pedogenic hematite, as well as pedogenic ferrimagnetic minerals. First-order reversal curve measurements were also conducted on representative particle-sized subsamples from a N-S transect to understand the differences in magnetic mineralogy between the two fractions. Our results show that pipette extraction separates the fine-grained superparamagnetic (SP) and most of the single-domain (SD) magnetic grains into the clay fraction, and that the remaining silt fraction displays the magnetic properties of coarse pseudo-single domain (PSD) or a mixture of multidomain (MD)/PSD and a few SD particles. Only the pedogenic clay fraction shows a strong correlation with climatic variables. The application of redundancy analysis helps to distinguish the climate variables controlling the formation of ferrimagnetic minerals and hematite during pedogenesis. On the CLP, pedogenic ferrimagnetic minerals are sensitive to mean annual precipitation, while pedogenic hematite formation is preferentially dependent on mean annual temperature. The confirmation of the temperature-dependent nature of hematite on the CLP provides a new possibility for quantitatively reconstructing the paleotemperature history of Chinese loess/paleosol sequences.

  9. Investigating in vitro bioactivity and magnetic properties of the ferrimagnetic bioactive glass–ceramic fabricated using soda-lime–silica waste glass

    Energy Technology Data Exchange (ETDEWEB)

    Abbasi, M. [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Zand Street, Shiraz (Iran, Islamic Republic of); Hashemi, B., E-mail: hashemib@shirazu.ac.ir [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Zand Street, Shiraz (Iran, Islamic Republic of); Shokrollahi, H. [Electroceramics Group, Materials Science and Engineering Department, Shiraz University of Technology, Shiraz (Iran, Islamic Republic of)

    2014-04-01

    The main purpose of the current research is the production and characterization of a ferrimagnetic bioactive glass–ceramic prepared through the solid-state reaction method using soda-lime–silica waste glass as the main raw material. In comparison with the conventional route, that is, the melt-quenching and subsequent heat treatment, the present work is an economical technique. Structural, thermal and magnetic properties of the samples were examined by X-ray diffraction (XRD), differential thermal analysis (DTA) and vibrating sample magnetometer (VSM). The in vitro test was utilized to assess the bioactivity level of the samples by Hanks' solution as simulated body fluid (SBF). The apatite surface layer formation was examined by the scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). The calcium ion concentration in the solutions was measured by atomic absorption spectroscopy (AAS). VSM results revealed that with the addition of 5–20 wt% strontium hexaferrite to bioactive glass–ceramics, the ferrimagnetic bioactive glass–ceramics with hysteresis losses between 7024 and 75,852 erg/g were obtained. The in vitro test showed that the onset formation time of hydroxyapatite layer on the surface of the samples was 14 days and after 30 days, this layer was completed. - Highlights: • A novel ferrimagnetic bioactive glass–ceramic was synthesized by an incorporation method. • The bioactive part was synthesized by the solid-state reaction method using soda-lime–silica waste glass. • The doping of SrFe{sub 12}O{sub 19} to Bioglass{sup ®} 45S5 glass–ceramic is likely to decrease bioactivity.

  10. What makes the difference in perovskite titanates?

    Science.gov (United States)

    Bussmann-Holder, Annette; Roleder, Krystian; Ko, Jae-Hyeon

    2018-06-01

    We have investigated in detail the lattice dynamics of five different perovskite titanates ATiO3 (A = Ca, Sr, Ba, Pb, Eu) where the A sites are occupied by +2 ions. In spite of the largely ionic character of these ions, the properties of these compounds differ substantially. They range from order/disorder like, to displacive ferroelectric, quantum paraelectric, and antiferromagnetic. All compounds crystallize in the cubic structure at high temperature and undergo structural phase transitions to tetragonal symmetry, partly followed by further transitions to lower symmetries. Since the TiO6 moiety is the essential electronic and structural unit, the question arises, what makes the significant difference between them. It is shown that the lattice dynamics of these compounds are very different, and that mode-mode coupling effects give rise to many distinct properties. In addition, the oxygen ion nonlinear polarizability plays a key role since it dominates the anharmonicity of these perovskites and determines the structural instability.

  11. Elastic softness of hybrid lead halide perovskites

    KAUST Repository

    Ferreira, A. C.

    2018-01-26

    Much recent attention has been devoted towards unravelling the microscopic optoelectronic properties of hybrid organic-inorganic perovskites (HOP). Here we investigate by coherent inelastic neutron scattering spectroscopy and Brillouin light scattering, low frequency acoustic phonons in four different hybrid perovskite single crystals: MAPbBr3, FAPbBr3, MAPbI3 and α-FAPbI3 (MA: methylammonium, FA: formamidinium). We report a complete set of elastic constants caracterized by a very soft shear modulus C44. Further, a tendency towards an incipient ferroelastic transition is observed in FAPbBr3. We observe a systematic lower sound group velocity in the technologically important iodide-based compounds compared to the bromide-based ones. The findings suggest that low thermal conductivity and hot phonon bottleneck phenomena are expected to be enhanced by low elastic stiffness, particularly in the case of the ultrasoft α-FAPbI3.

  12. Perovskite Materials: Solar Cell and Optoelectronic Applications

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Bin [ORNL; Geohegan, David B [ORNL; Xiao, Kai [ORNL

    2017-01-01

    Hybrid organometallic trihalide perovskites are promising candidates in the applications for next-generation, high-performance, low-cost optoelectronic devices, including photovoltaics, light emitting diodes, and photodetectors. Particularly, the solar cells based on this type of materials have reached 22% lab scale power conversion efficiency in only about seven years, comparable to the other thin film photovoltaic technologies. Hybrid perovskite materials not only exhibit superior optoelectronic properties, but also show many interesting physical properties such as ion migration and defect physics, which may allow the exploration of more device functionalities. In this article, the fundamental understanding of the interrelationships between crystal structure, electronic structure, and material properties is discussed. Various chemical synthesis and processing methods for superior device performance in solar cells and optoelectronic devices are reviewed.

  13. Effect of the Hamiltonian parameters on the hysteresis properties of the kinetic mixed spin (1/2, 1) Ising ferrimagnetic model on a hexagonal lattice

    Energy Technology Data Exchange (ETDEWEB)

    Batı, Mehmet, E-mail: mehmet.bati@erdogan.edu.tr [Department of Physics, Recep Tayyip Erdoğan University, 53100 Rize (Turkey); Ertaş, Mehmet [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2017-05-15

    The hysteresis properties of a kinetic mixed spin (1/2, 1) Ising ferrimagnetic system on a hexagonal lattice are studied by means of the dynamic mean field theory. In the present study, the effects of the nearest-neighbor interaction, temperature, frequency of oscillating magnetic field and the exchange anisotropy on the hysteresis properties of the kinetic system are discussed in detail. A number of interesting phenomena such as the shape of hysteresis loops with one, two, three and inverted-hysteresis/proteresis (butterfly shape hysteresis) have been obtained. Finally, the obtained results are compared with some experimental and theoretical results and a qualitatively good agreement is found.

  14. Quasiparticle Interference on Cubic Perovskite Oxide Surfaces.

    Science.gov (United States)

    Okada, Yoshinori; Shiau, Shiue-Yuan; Chang, Tay-Rong; Chang, Guoqing; Kobayashi, Masaki; Shimizu, Ryota; Jeng, Horng-Tay; Shiraki, Susumu; Kumigashira, Hiroshi; Bansil, Arun; Lin, Hsin; Hitosugi, Taro

    2017-08-25

    We report the observation of coherent surface states on cubic perovskite oxide SrVO_{3}(001) thin films through spectroscopic-imaging scanning tunneling microscopy. A direct link between the observed quasiparticle interference patterns and the formation of a d_{xy}-derived surface state is supported by first-principles calculations. We show that the apical oxygens on the topmost VO_{2} plane play a critical role in controlling the coherent surface state via modulating orbital state.

  15. Dynamics of photoinduced degradation of perovskite photovoltaics

    DEFF Research Database (Denmark)

    Khenkin, M. V.; Anoop, K. M.; Visoly-Fischer, I.

    2018-01-01

    The operational stability of perovskite solar cells (PSCs) remains a limiting factor in their commercial implementation. We studied the long-term outdoor stability of ITO/SnO2/Cs0.05((CH3NH3)0.15(CH(NH2)2)0.85)0.95PbI2.55Br0.45/spiro-OMeTAD/Au cells, as well as the dynamics of their degradation...

  16. Magnetotransport in doped manganate perovskites (invited) (abstract)

    International Nuclear Information System (INIS)

    Sun, J.Z.; Krusin-Elbaum, L.; Gupta, A.; Xiao, G.; Duncombe, P.R.; Gallagher, W.J.; Parkin, S.S.

    1997-01-01

    Recent progress in oxide perovskite thin-film technology has led to the discovery of a large negative magnetoresistance at room temperature in the doped manganate perovskite thin films. For applications such as magnetic-field sensing, the saturation magnetic field for large magnetoresistance has to be significantly lowered. The magnetic and transport properties of the doped manganates involve a curious magnetic-field scale, on the order of 1 endash 10 T. Upon the application of a field on this scale, the magnetoresistance saturates, and a significant broadening of the temperature-dependent magnetization is seen. An understanding of the materials physics that underlie such behavior can point to new ways of lowering the saturation field in this class of materials. We argue that this characteristic field is suggestive of an inhomogeneous magnetic state in the system. We will discuss the basic phenomena and physics of magnetotransport in this class of materials. We will also report the successful fabrication of a trilayer thin-film pillar structure made using the doped manganate perovskites in which a magnetoresistance change by about a factor of 2 was observed at temperatures below 100 K in a field less than 200 Oe, proving that large magnetoresistance in low field can be obtained in these materials. copyright 1997 American Institute of Physics

  17. Modified titanate perovskites in photocatalytic water splitting

    Energy Technology Data Exchange (ETDEWEB)

    Wlodarczak, M.; Ludwiczak, M.; Laniecki, M. [A. Mickiewicz Univ. (Poland)

    2010-07-01

    Received materials have structure of perovskite, what was shown by XRD diffraction patterns. Perovskite structure is present in all samples with strontium, barium and one sample with calcium. Moreover, received barium and strontium titanate are very similar to pattern materials. XRD results show, that temperature 500 C is too low to create perovskite structure in CaTiO{sub 3}. However, it is high enough in case of SrTiO{sub 3} and BaTiO{sub 3}. One regularity is obvious, surface area increases for samples calcined in lower temperature. There is a connection between surface area and dispersion of platinum. Both of them reach the greatest value to the calcium titanate. Catalytic activity was shown by all of received samples. Measurable values were received to samples calcined in 700 C. Calcium titanate had the best catalytic activity, both an amount of hydrogen and a ratio of hydrogen to platinum. There is one regularity to all samples, the ration of hydrogen to platinum increase when amount of platinum decrease. (orig.)

  18. PbBr3 Perovskite Crystals

    KAUST Repository

    Wei, Tzu-Chiao

    2018-01-31

    Researchers have recently revealed that hybrid lead halide perovskites exhibit ferroelectricity, which is often associated with other physical characteristics, such as a large nonlinear optical response. In this work, the nonlinear optical properties of single crystal inorganic–organic hybrid perovskite CH3NH3PbBr3 are studied. By exciting the material with a 1044 nm laser, strong two-photon absorption-induced photoluminescence in the green spectral region is observed. Using the transmission open-aperture Z-scan technique, the values of the two-photon absorption coefficient are observed to be 8.5 cm GW−1, which is much higher than that of standard two-photon absorbing materials that are industrially used in nonlinear optical applications, such as lithium niobate (LiNbO3), LiTaO3, KTiOPO4, and KH2PO4. Such a strong two-photon absorption effect in CH3NH3PbBr3 can be used to modulate the spectral and spatial profiles of laser pulses, as well as to reduce noise, and can be used to strongly control the intensity of incident light. In this study, the superior optical limiting, pulse reshaping, and stabilization properties of CH3NH3PbBr3 are demonstrated, opening new applications for perovskites in nonlinear optics.

  19. Light-trapping in perovskite solar cells

    Directory of Open Access Journals (Sweden)

    Qing Guo Du

    2016-06-01

    Full Text Available We numerically demonstrate enhanced light harvesting efficiency in both CH3NH3PbI3 and CH(NH22PbI3-based perovskite solar cells using inverted vertical-cone photonic-crystal nanostructures. For CH3NH3PbI3 perovskite solar cells, the maximum achievable photocurrent density (MAPD reaches 25.1 mA/cm2, corresponding to 92% of the total available photocurrent in the absorption range of 300 nm to 800 nm. Our cell shows 6% absorption enhancement compared to the Lambertian limit (23.7 mA/cm2 and has a projected power conversion efficiency of 12.9%. Excellent solar absorption is numerically demonstrated over a broad angular range from 0 to 60 degree for both S- and P- polarizations. For the corresponding CH(NH22PbI3 based perovskite solar cell, with absorption range of 300 nm to 850 nm, we find a MAPD of 29.1 mA/cm2, corresponding to 95.4% of the total available photocurrent. The projected power conversion efficiency of the CH(NH22PbI3 based photonic crystal solar cell is 23.4%, well above the current world record efficiency of 20.1%.

  20. Resistance switching memory in perovskite oxides

    International Nuclear Information System (INIS)

    Yan, Z.B.; Liu, J.-M.

    2015-01-01

    The resistance switching behavior has recently attracted great attentions for its application as resistive random access memories (RRAMs) due to a variety of advantages such as simple structure, high-density, high-speed and low-power. As a leading storage media, the transition metal perovskite oxide owns the strong correlation of electrons and the stable crystal structure, which brings out multifunctionality such as ferroelectric, multiferroic, superconductor, and colossal magnetoresistance/electroresistance effect, etc. The existence of rich electronic phases, metal–insulator transition and the nonstoichiometric oxygen in perovskite oxide provides good platforms to insight into the resistive switching mechanisms. In this review, we first introduce the general characteristics of the resistance switching effects, the operation methods and the storage media. Then, the experimental evidences of conductive filaments, the transport and switching mechanisms, and the memory performances and enhancing methods of perovskite oxide based filamentary RRAM cells have been summarized and discussed. Subsequently, the switching mechanisms and the performances of the uniform RRAM cells associating with the carrier trapping/detrapping and the ferroelectric polarization switching have been discussed. Finally, the advices and outlook for further investigating the resistance switching and enhancing the memory performances are given

  1. Magnetic field effects in hybrid perovskite devices

    Science.gov (United States)

    Zhang, C.; Sun, D.; Sheng, C.-X.; Zhai, Y. X.; Mielczarek, K.; Zakhidov, A.; Vardeny, Z. V.

    2015-05-01

    Magnetic field effects have been a successful tool for studying carrier dynamics in organic semiconductors as the weak spin-orbit coupling in these materials gives rise to long spin relaxation times. As the spin-orbit coupling is strong in organic-inorganic hybrid perovskites, which are promising materials for photovoltaic and light-emitting applications, magnetic field effects are expected to be negligible in these optoelectronic devices. We measured significant magneto-photocurrent, magneto-electroluminescence and magneto-photoluminescence responses in hybrid perovskite devices and thin films, where the amplitude and shape are correlated to each other through the electron-hole lifetime, which depends on the perovskite film morphology. We attribute these responses to magnetic-field-induced spin-mixing of the photogenerated electron-hole pairs with different g-factors--the Δg model. We validate this model by measuring large Δg (~ 0.65) using field-induced circularly polarized photoluminescence, and electron-hole pair lifetime using picosecond pump-probe spectroscopy.

  2. Surface Restructuring of Hybrid Perovskite Crystals

    KAUST Repository

    Banavoth, Murali

    2016-11-07

    Hybrid perovskite crystals have emerged as an important class of semiconductors because of their remarkable performance in optoelectronics devices. The interface structure and chemistry of these crystals are key determinants of the device\\'s performance. Unfortunately, little is known about the intrinsic properties of the surfaces of perovskite materials because extrinsic effects, such as complex microstructures, processing conditions, and hydration under ambient conditions, are thought to cause resistive losses and high leakage current in solar cells. We reveal the intrinsic structural and optoelectronic properties of both pristinely cleaved and aged surfaces of single crystals. We identify surface restructuring on the aged surfaces (visualized on the atomic-scale by scanning tunneling microscopy) that lead to compositional and optical bandgap changes as well as degradation of carrier dynamics, photocurrent, and solar cell device performance. The insights reported herein clarify the key variables involved in the performance of perovskite-based solar cells and fabrication of high-quality surface single crystals, thus paving the way toward their future exploitation in highly efficient solar cells.

  3. Light-trapping in perovskite solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Du, Qing Guo, E-mail: duqi0001@e.ntu.edu.sg [Department of Physics, University of Toronto, 60 ST. George St., Toronto, Ontario, M5S 1A7 (Canada); Institute of High Performance Computing, A* STAR, Singapore, 138632 (Singapore); Shen, Guansheng [Department of Physics, University of Toronto, 60 ST. George St., Toronto, Ontario, M5S 1A7 (Canada); School of Information and Communication Engineering, Beijing University of Posts and Telecommunications, Beijing 100876 (China); John, Sajeev [Department of Physics, University of Toronto, 60 ST. George St., Toronto, Ontario, M5S 1A7 (Canada); Department of Physics, Soochow University, Suzhou (China)

    2016-06-15

    We numerically demonstrate enhanced light harvesting efficiency in both CH{sub 3}NH{sub 3}PbI{sub 3} and CH(NH{sub 2}){sub 2}PbI{sub 3}-based perovskite solar cells using inverted vertical-cone photonic-crystal nanostructures. For CH{sub 3}NH{sub 3}PbI{sub 3} perovskite solar cells, the maximum achievable photocurrent density (MAPD) reaches 25.1 mA/cm{sup 2}, corresponding to 92% of the total available photocurrent in the absorption range of 300 nm to 800 nm. Our cell shows 6% absorption enhancement compared to the Lambertian limit (23.7 mA/cm{sup 2}) and has a projected power conversion efficiency of 12.9%. Excellent solar absorption is numerically demonstrated over a broad angular range from 0 to 60 degree for both S- and P- polarizations. For the corresponding CH(NH{sub 2}){sub 2}PbI{sub 3} based perovskite solar cell, with absorption range of 300 nm to 850 nm, we find a MAPD of 29.1 mA/cm{sup 2}, corresponding to 95.4% of the total available photocurrent. The projected power conversion efficiency of the CH(NH{sub 2}){sub 2}PbI{sub 3} based photonic crystal solar cell is 23.4%, well above the current world record efficiency of 20.1%.

  4. Large polarons in lead halide perovskites

    Science.gov (United States)

    Miyata, Kiyoshi; Meggiolaro, Daniele; Trinh, M. Tuan; Joshi, Prakriti P.; Mosconi, Edoardo; Jones, Skyler C.; De Angelis, Filippo; Zhu, X.-Y.

    2017-01-01

    Lead halide perovskites show marked defect tolerance responsible for their excellent optoelectronic properties. These properties might be explained by the formation of large polarons, but how they are formed and whether organic cations are essential remain open questions. We provide a direct time domain view of large polaron formation in single-crystal lead bromide perovskites CH3NH3PbBr3 and CsPbBr3. We found that large polaron forms predominantly from the deformation of the PbBr3− frameworks, irrespective of the cation type. The difference lies in the polaron formation time, which, in CH3NH3PbBr3 (0.3 ps), is less than half of that in CsPbBr3 (0.7 ps). First-principles calculations confirm large polaron formation, identify the Pb-Br-Pb deformation modes as responsible, and explain quantitatively the rate difference between CH3NH3PbBr3 and CsPbBr3. The findings reveal the general advantage of the soft [PbX3]− sublattice in charge carrier protection and suggest that there is likely no mechanistic limitations in using all-inorganic or mixed-cation lead halide perovskites to overcome instability problems and to tune the balance between charge carrier protection and mobility. PMID:28819647

  5. Lattice effects on ferromagnetism in perovskite ruthenates

    Science.gov (United States)

    Cheng, J.-G.; Zhou, J.-S.; Goodenough, John B.

    2013-01-01

    Ferromagnetism and its evolution in the orthorhombic perovskite system Sr1–xCaxRuO3 have been widely believed to correlate with structural distortion. The recent development of high-pressure synthesis of the Ba-substituted Sr1–yBayRuO3 makes it possible to study ferromagnetism over a broader phase diagram, which includes the orthorhombic Imma and the cubic phases. However, the chemical substitutions introduce the A-site disorder effect on Tc, which complicates determination of the relationship between ferromagnetism and structural distortion. By clarifying the site disorder effect on Tc in several unique series of ruthenates in which the average bond length 〈A–O〉 remains the same but the bond-length variance varies, we are able to demonstrate a parabolic curve of Tc versus mean bond length 〈A–O〉. A much higher Tc ∼ 177 K than that found in orthorhombic SrRuO3 can be obtained from the curve at a bond length 〈A–O〉, which makes the geometric factor t = 〈A–O〉/(√2〈Ru–O〉) ∼ 1. This result reveals not only that the ferromagnetism in the ruthenates is extremely sensitive to the lattice strain, but also that it has an important implication for exploring the structure–property relationship in a broad range of oxides with perovskite or a perovskite-related structure. PMID:23904477

  6. The A-cation deficient perovskite series La2-xCoTiO6-δ (0 ≤ x ≤ 0.20): new components for potential SOFC composite cathodes

    DEFF Research Database (Denmark)

    Gomez-Perez, Alejandro; Teresa Azcondo, M.; Yuste, Mercedes

    2016-01-01

    La2-xCoTiO6-delta/Ce0.9Gd0.1O2-delta composites are presented as promising new cathodes for solid oxide fuel cells. The B-site ordering characteristic of double perovskites is present in the whole series. Additionally, increasing amounts of La-vacancies give rise to ordering of alternating La...

  7. Probing anisotropic magnetotransport in manganese perovskites using Raman spectroscopy

    International Nuclear Information System (INIS)

    Liu, H.L.; Yoon, S.; Cooper, S.L.; Cheong, S.; Han, P.D.; Payne, D.A.

    1998-01-01

    We report an electronic Raman scattering study of the colossal magnetoresistance (CMR) manganese perovskites as a function of temperature, magnetic field, symmetry, and doping. The low-frequency electronic Raman spectrum in the paramagnetic-insulating phase of these materials is characterized by a diffusive Raman-scattering response, while a nearly flat continuum response is observed in the ferromagnetic-metallic state. We found that the B 1g -symmetry electronic scattering intensity is significantly reduced with applied magnetic field near T C , in a manner reminiscent of the dc magnetoresistivity. The strongly field-dependent scattering rate in the B 1g channel appears to reflect the highly field-dependent mobility along the Mn-O bond direction expected in the double exchange mechanism. In addition, we observe a persistent field dependence in the B 1g electronic scattering response for T C , suggesting that the ferromagnetic phase is inhomogeneous, perhaps consisting of both metallic and insulating components. copyright 1998 The American Physical Society

  8. Anharmonicity and Disorder in the Black Phases of Cesium Lead Iodide Used for Stable Inorganic Perovskite Solar Cells.

    Science.gov (United States)

    Marronnier, Arthur; Roma, Guido; Boyer-Richard, Soline; Pedesseau, Laurent; Jancu, Jean-Marc; Bonnassieux, Yvan; Katan, Claudine; Stoumpos, Constantinos C; Kanatzidis, Mercouri G; Even, Jacky

    2018-04-24

    Hybrid organic-inorganic perovskites emerged as a new generation of absorber materials for high-efficiency low-cost solar cells in 2009. Very recently, fully inorganic perovskite quantum dots also led to promising efficiencies, making them a potentially stable and efficient alternative to their hybrid cousins. Currently, the record efficiency is obtained with CsPbI 3 , whose crystallographical characterization is still limited. Here, we show through high-resolution in situ synchrotron XRD measurements that CsPbI 3 can be undercooled below its transition temperature and temporarily maintained in its perovskite structure down to room temperature, stabilizing a metastable perovskite polytype (black γ-phase) crucial for photovoltaic applications. Our analysis of the structural phase transitions reveals a highly anisotropic evolution of the individual lattice parameters versus temperature. Structural, vibrational, and electronic properties of all the experimentally observed black phases are further inspected based on several theoretical approaches. Whereas the black γ-phase is shown to behave harmonically around equilibrium, for the tetragonal phase, density functional theory reveals the same anharmonic behavior, with a Brillouin zone-centered double-well instability, as for the cubic phase. Using total energy and vibrational entropy calculations, we highlight the competition between all the low-temperature phases of CsPbI 3 (γ, δ, β) and show that avoiding the order-disorder entropy term arising from double-well instabilities is key to preventing the formation of the yellow perovskitoid phase. A symmetry-based tight-binding model, validated by self-consistent GW calculations including spin-orbit coupling, affords further insight into their electronic properties, with evidence of Rashba effect for both cubic and tetragonal phases when using the symmetry-breaking structures obtained through frozen phonon calculations.

  9. Water-Induced Dimensionality Reduction in Metal-Halide Perovskites

    KAUST Repository

    Turedi, Bekir; Lee, Kwangjae; Dursun, Ibrahim; Alamer, Badriah Jaber; Wu, Zhennan; Alarousu, Erkki; Mohammed, Omar F.; Cho, Namchul; Bakr, Osman

    2018-01-01

    . Here we employ water to directly transform films of the three-dimensional (3D) perovskite CsPbBr3 to stable two-dimensional (2D) perovskite-related CsPb2Br5. A sequential dissolution-recrystallization process governs this water induced transformation

  10. Progress, challenges and perspectives in flexible perovskite solar cells

    NARCIS (Netherlands)

    Di Giacomo, F.; Fakharuddin, A.; Jose, R.; Brown, T.M.

    2016-01-01

    Perovskite solar cells have attracted enormous interest since their discovery only a few years ago because they are able to combine the benefits of high efficiency and remarkable ease of processing over large areas. Whereas most of research has been carried out on glass, perovskite deposition and

  11. On the luminescence of perovskite type rare earth gallates

    International Nuclear Information System (INIS)

    Jianmei, Y.; Qingyuan, W.; Shuzhen, L.; Lianren, S.; Mingyu, C.

    1985-01-01

    It has been reported that perovskite type lanthanum gallates may be a good host material for laser and luminescence, but in the rare earth gallates studied, the numbers of perovskite type are less than that of the garnet type and there is less report on their spectroscopic properties in the literature. In this paper synthesis and spectroscopic properties of these compounds are studied

  12. Bandgap calculations and trends of organometal halide perovskites

    DEFF Research Database (Denmark)

    Castelli, Ivano Eligio; García Lastra, Juan Maria; Thygesen, Kristian Sommer

    2014-01-01

    Energy production from the Sun requires a stable efficient light absorber. Promising candidates in this respect are organometal perovskites (ABX3), which have been intensely investigated during the last years. Here, we have performed electronic structure calculations of 240 perovskites composed...

  13. Temperature Dependent Charge Carrier Dynamics in Formamidinium Lead Iodide Perovskite

    NARCIS (Netherlands)

    Gelvez Rueda, M.C.; Renaud, N.; Grozema, F.C.

    2017-01-01

    The fundamental opto-electronic properties of organic-inorganic hybrid perovskites are strongly affected by their structural parameters. These parameters are particularly critical in formamidinium lead iodide (FAPbI3), in which its large structural disorder leads to a non-perovskite

  14. NREL Research Pushes Perovskites Closer to Market | News | NREL

    Science.gov (United States)

    even get close-to the above-20% efficiencies dominated by silicon solar panels. NREL researcher Kai Zhu ; Perovskites have a couple of major benefits over silicon solar panels. The silicon technology requires a high as excellent semiconductors. This means perovskite panels are more flexible than rigid silicon panels

  15. Impact of Interfacial Layers in Perovskite Solar Cells.

    Science.gov (United States)

    Cho, An-Na; Park, Nam-Gyu

    2017-10-09

    Perovskite solar cells (PCSs) are composed of organic-inorganic lead halide perovskite as the light harvester. Since the first report on a long-term-durable, 9.7 % efficient, solid-state perovskite solar cell, organic-inorganic halide perovskites have received considerable attention because of their excellent optoelectronic properties. As a result, a power conversion efficiency (PCE) exceeding 22 % was certified. Controlling the grain size, grain boundary, morphology, and defects of the perovskite layer is important for achieving high efficiency. In addition, interfacial engineering is equally or more important to further improve the PCE through better charge collection and a reduction in charge recombination. In this Review, the type of interfacial layers and their impact on photovoltaic performance are investigated for both the normal and the inverted cell architectures. Four different interfaces of fluorine-doped tin oxide (FTO)/electron-transport layer (ETL), ETL/perovskite, perovskite/hole-transport layer (HTL), and HTL/metal are classified, and their roles are investigated. The effects of interfacial engineering with organic or inorganic materials on photovoltaic performance are described in detail. Grain-boundary engineering is also included because it is related to interfacial engineering and the grain boundary in the perovskite layer plays an important role in charge conduction, recombination, and chargecarrier life time. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. NaIrO3-A pentavalent post-perovskite

    International Nuclear Information System (INIS)

    Bremholm, M.; Dutton, S.E.; Stephens, P.W.; Cava, R.J.

    2011-01-01

    Sodium iridium (V) oxide, NaIrO 3, was synthesized by a high pressure solid state method and recovered to ambient conditions. It is found to be isostructural with CaIrO 3 , the much-studied structural analog of the high-pressure post-perovskite phase of MgSiO 3 . Among the oxide post-perovskites, NaIrO 3 is the first example with a pentavalent cation. The structure consists of layers of corner- and edge-sharing IrO 6 octahedra separated by layers of NaO 8 bicapped trigonal prisms. NaIrO 3 shows no magnetic ordering and resistivity measurements show non-metallic behavior. The crystal structure, electrical and magnetic properties are discussed and compared to known post-perovskites and pentavalent perovskite metal oxides. -- Graphical abstract: Sodium iridium(V) oxide, NaIrO 3 , synthesized by a high pressure solid state method and recovered to ambient conditions is found to crystallize as the post-perovskite structure and is the first example of a pentavalent ABO 3 post-perovskite. Research highlights: → NaIrO 3 post-perovskite stabilized by pressure. → First example of a pentavalent oxide post-perovskite. → Non-metallic and non-magnetic behavior of NaIrO 3 .

  17. Dissolution-recrystallization method for high efficiency perovskite solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Han, Fei; Luo, Junsheng; Wan, Zhongquan; Liu, Xingzhao; Jia, Chunyang, E-mail: cyjia@uestc.edu.cn

    2017-06-30

    Highlights: • Dissolution-recrystallization method can improve perovskite crystallization. • Dissolution-recrystallization method can improve TiO{sub 2}/perovskite interface. • The optimal perovskite solar cell obtains the champion PCE of 16.76%. • The optimal devices are of high reproducibility. - Abstract: In this work, a dissolution-recrystallization method (DRM) with chlorobenzene and dimethylsulfoxide treating the perovskite films during the spin-coating process is reported. This is the first time that DRM is used to control perovskite crystallization and improve the device performance. Furthermore, the DRM is good for reducing defects and grain boundaries, improving perovskite crystallization and even improving TiO{sub 2}/perovskite interface. By optimizing, the DRM2-treated perovskite solar cell (PSC) obtains the best photoelectric conversion efficiency (PCE) of 16.76% under AM 1.5 G illumination (100 mW cm{sup −2}) with enhanced J{sub sc} and V{sub oc} compared to CB-treated PSC.

  18. Miscellaneous Lasing Actions in Organo-Lead Halide Perovskite Films.

    Science.gov (United States)

    Duan, Zonghui; Wang, Shuai; Yi, Ningbo; Gu, Zhiyuan; Gao, Yisheng; Song, Qinghai; Xiao, Shumin

    2017-06-21

    Lasing actions in organo-lead halide perovskite films have been heavily studied in the past few years. However, due to the disordered nature of synthesized perovskite films, the lasing actions are usually understood as random lasers that are formed by multiple scattering. Herein, we demonstrate the miscellaneous lasing actions in organo-lead halide perovskite films. In addition to the random lasers, we show that a single or a few perovskite microparticles can generate laser emissions with their internal resonances instead of multiple scattering among them. We experimentally observed and numerically confirmed whispering gallery (WG)-like microlasers in polygon shaped and other deformed microparticles. Meanwhile, owing to the nature of total internal reflection and the novel shape of the nanoparticle, the size of the perovskite WG laser can be significantly decreased to a few hundred nanometers. Thus, wavelength-scale lead halide perovskite lasers were realized for the first time. All of these laser behaviors are complementary to typical random lasers in perovskite film and will help the understanding of lasing actions in complex lead halide perovskite systems.

  19. Determining the energetics of vicinal perovskite oxide surfaces

    NARCIS (Netherlands)

    Wessels, W.A.; Bollmann, Tjeerd Rogier Johannes; Koster, Gertjan; Zandvliet, Henricus J.W.; Rijnders, Augustinus J.H.M.

    2017-01-01

    The energetics of vicinal SrTiO3(001) and DyScO3(110), prototypical perovskite vicinal surfaces, has been studied using topographic atomic force microscopy imaging. The kink formation and strain relaxation energies are extracted from a statistical analysis of the step meandering. Both perovskite

  20. Highly efficient light management for perovskite solar cells.

    Science.gov (United States)

    Wang, Dong-Lin; Cui, Hui-Juan; Hou, Guo-Jiao; Zhu, Zhen-Gang; Yan, Qing-Bo; Su, Gang

    2016-01-06

    Organic-inorganic halide perovskite solar cells have enormous potential to impact the existing photovoltaic industry. As realizing a higher conversion efficiency of the solar cell is still the most crucial task, a great number of schemes were proposed to minimize the carrier loss by optimizing the electrical properties of the perovskite solar cells. Here, we focus on another significant aspect that is to minimize the light loss by optimizing the light management to gain a high efficiency for perovskite solar cells. In our scheme, the slotted and inverted prism structured SiO2 layers are adopted to trap more light into the solar cells, and a better transparent conducting oxide layer is employed to reduce the parasitic absorption. For such an implementation, the efficiency and the serviceable angle of the perovskite solar cell can be promoted impressively. This proposal would shed new light on developing the high-performance perovskite solar cells.

  1. Self-Assembled PbSe Nanowire:Perovskite Hybrids

    KAUST Repository

    Yang, Zhenyu

    2015-12-02

    © 2015 American Chemical Society. Inorganic semiconductor nanowires are of interest in nano- and microscale photonic and electronic applications. Here we report the formation of PbSe nanowires based on directional quantum dot alignment and fusion regulated by hybrid organic-inorganic perovskite surface ligands. All material synthesis is carried out at mild temperatures. Passivation of PbSe quantum dots was achieved via a new perovskite ligand exchange. Subsequent in situ ammonium/amine substitution by butylamine enables quantum dots to be capped by butylammonium lead iodide, and this further drives the formation of a PbSe nanowire superlattice in a two-dimensional (2D) perovskite matrix. The average spacing between two adjacent nanowires agrees well with the thickness of single atomic layer of 2D perovskite, consistent with the formation of a new self-assembled semiconductor nanowire:perovskite heterocrystal hybrid.

  2. Planar-integrated single-crystalline perovskite photodetectors

    KAUST Repository

    Saidaminov, Makhsud I.

    2015-11-09

    Hybrid perovskites are promising semiconductors for optoelectronic applications. However, they suffer from morphological disorder that limits their optoelectronic properties and, ultimately, device performance. Recently, perovskite single crystals have been shown to overcome this problem and exhibit impressive improvements: low trap density, low intrinsic carrier concentration, high mobility, and long diffusion length that outperform perovskite-based thin films. These characteristics make the material ideal for realizing photodetection that is simultaneously fast and sensitive; unfortunately, these macroscopic single crystals cannot be grown on a planar substrate, curtailing their potential for optoelectronic integration. Here we produce large-area planar-integrated films made up of large perovskite single crystals. These crystalline films exhibit mobility and diffusion length comparable with those of single crystals. Using this technique, we produced a high-performance light detector showing high gain (above 104 electrons per photon) and high gain-bandwidth product (above 108 Hz) relative to other perovskite-based optical sensors.

  3. Performance of planar heterojunction perovskite solar cells under light concentration

    Directory of Open Access Journals (Sweden)

    Aaesha Alnuaimi

    2016-11-01

    Full Text Available In this work, we present 2D simulation of planar heterojunction perovskite solar cells under high concentration using physics-based TCAD. The performance of planar perovskite heterojunction solar cells is examined up to 1000 suns. We analyze the effect of HTM mobility and band structure, surface recombination velocities at interfaces and the effect of series resistance under concentrated light. The simulation results revealed that the low mobility of HTM material limits the improvement in power conversation efficiency of perovskite solar cells under concentration. In addition, large band offset at perovskite/HTM interface contributes to the high series resistance. Moreover, losses due to high surface recombination at interfaces and the high series resistance deteriorate significantly the performance of perovskite solar cells under concentration.

  4. Reconditioning perovskite films in vapor environments through repeated cation doping

    Science.gov (United States)

    Boonthum, Chirapa; Pinsuwan, Kusuma; Ponchai, Jitprabhat; Srikhirin, Toemsak; Kanjanaboos, Pongsakorn

    2018-06-01

    Perovskites have attracted considerable attention for application as high-efficiency photovoltaic devices owing to their low-cost and low-temperature fabrication. A good surface and high crystallinity are necessary for high-performance devices. We examine the negative effects of chemical ambiences on the perovskite crystal formation and morphology. The repeated cation doping (RCD) technique was developed to remedy these issues by gradually dropping methylammonium ions on top of about-to-form perovskite surfaces to cause recrystallization. RCD promotes pinhole-free, compact, and polygonal-like surfaces under various vapor conditions. Furthermore, it enhances the electronic properties and crystallization. The benefits of RCD extend beyond perovskites under vapor ambiences, as it can improve regular and wasted perovskites.

  5. Perovskite-fullerene hybrid materials suppress hysteresis in planar diodes.

    KAUST Repository

    Xu, Jixian

    2015-05-08

    Solution-processed planar perovskite devices are highly desirable in a wide variety of optoelectronic applications; however, they are prone to hysteresis and current instabilities. Here we report the first perovskite-PCBM hybrid solid with significantly reduced hysteresis and recombination loss achieved in a single step. This new material displays an efficient electrically coupled microstructure: PCBM is homogeneously distributed throughout the film at perovskite grain boundaries. The PCBM passivates the key PbI3(-) antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar solar cells that feature low hysteresis and enhanced photovoltage. Using conductive AFM studies, we reveal the memristive properties of perovskite films. We close by positing that PCBM, by tying up both halide-rich antisites and unincorporated halides, reduces electric field-induced anion migration that may give rise to hysteresis and unstable diode behaviour.

  6. Two-Dimensional Perovskite Activation with an Organic Luminophore.

    Science.gov (United States)

    Jemli, Khaoula; Audebert, Pierre; Galmiche, Laurent; Trippé-Allard, Gaelle; Garrot, Damien; Lauret, Jean-Sébastien; Deleporte, Emmanuelle

    2015-10-07

    A great advantage of the hybrid organic-inorganic perovskites is the chemical flexibility and the possibility of a molecular engineering of each part of the material (the inorganic part and the organic part respectively) in order to improve or add some functionalities. An adequately chosen organic luminophore has been introduced inside a lead bromide type organic-inorganic perovskite, while respecting the two-dimensional perovskite structure. A substantial increase of the brilliance of the perovskite is obtained. This activation of the perovskite luminescence by the adequate engineering of the organic part is an original approach, and is particularly interesting in the framework of the light-emitting devices such as organic light-emitting diodes (OLEDs) or lasers.

  7. Perovskite-fullerene hybrid materials suppress hysteresis in planar diodes

    Science.gov (United States)

    Xu, Jixian; Buin, Andrei; Ip, Alexander H.; Li, Wei; Voznyy, Oleksandr; Comin, Riccardo; Yuan, Mingjian; Jeon, Seokmin; Ning, Zhijun; McDowell, Jeffrey J.; Kanjanaboos, Pongsakorn; Sun, Jon-Paul; Lan, Xinzheng; Quan, Li Na; Kim, Dong Ha; Hill, Ian G.; Maksymovych, Peter; Sargent, Edward H.

    2015-05-01

    Solution-processed planar perovskite devices are highly desirable in a wide variety of optoelectronic applications; however, they are prone to hysteresis and current instabilities. Here we report the first perovskite-PCBM hybrid solid with significantly reduced hysteresis and recombination loss achieved in a single step. This new material displays an efficient electrically coupled microstructure: PCBM is homogeneously distributed throughout the film at perovskite grain boundaries. The PCBM passivates the key PbI3- antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar solar cells that feature low hysteresis and enhanced photovoltage. Using conductive AFM studies, we reveal the memristive properties of perovskite films. We close by positing that PCBM, by tying up both halide-rich antisites and unincorporated halides, reduces electric field-induced anion migration that may give rise to hysteresis and unstable diode behaviour.

  8. Two-Dimensional Halide Perovskites for Emerging New- Generation Photodetectors

    DEFF Research Database (Denmark)

    Tang, Yingying; Cao, Xianyi; Chi, Qijin

    2018-01-01

    Compared to their conventional three-dimensional (3D) counterparts, two-dimensional (2D) halide perovskites have attracted more interests recently in a variety of areas related to optoelectronics because of their unique structural characteristics and enhanced performances. In general, there are two...... distinct types of 2D halide perovskites. One represents those perovskites with an intrinsic layered crystal structure (i.e. MX6 layers, M = metal and X = Cl, Br, I), the other defines the perovskites with a 2D nanostructured morphology such as nanoplatelets and nanosheets. Recent studies have shown that 2D...... halide perovskites hold promising potential for the development of new-generation photodetectors, mainly arising from their highly efficient photoluminescence and absorbance, color tunability in the visible-light range and relatively high stability. In this chapter, we present the summary and highlights...

  9. Perovskite Catalysts—A Special Issue on Versatile Oxide Catalysts

    Directory of Open Access Journals (Sweden)

    Yu-Chuan Lin

    2014-08-01

    Full Text Available Perovskite-type catalysts have been prominent oxide catalysts for many years due to attributes such as flexibility in choosing cations, significant thermal stability, and the unique nature of lattice oxygen. Nearly 90% metallic elements of the Periodic Table can be stabilized in perovskite’s crystalline framework [1]. Moreover, by following the Goldschmidt rule [2], the A- and/or B-site elements can be partially substituted, making perovskites extremely flexible in catalyst design. One successful example is the commercialization of noble metal-incorporated perovskites (e.g., LaFe0.57Co0.38Pd0.05O3 for automotive emission control used by Daihatsu Motor Co. Ltd. [3]. Thus, growing interest in, and application of perovskites in the fields of material sciences, heterogeneous catalysis, and energy storage have prompted this Special Issue on perovskite catalysts. [...

  10. Self-Assembled PbSe Nanowire:Perovskite Hybrids

    KAUST Repository

    Yang, Zhenyu; Yassitepe, Emre; Voznyy, Oleksandr; Janmohamed, Alyf; Lan, Xinzheng; Levina, Larissa; Comin, Riccardo; Sargent, Edward H.

    2015-01-01

    © 2015 American Chemical Society. Inorganic semiconductor nanowires are of interest in nano- and microscale photonic and electronic applications. Here we report the formation of PbSe nanowires based on directional quantum dot alignment and fusion regulated by hybrid organic-inorganic perovskite surface ligands. All material synthesis is carried out at mild temperatures. Passivation of PbSe quantum dots was achieved via a new perovskite ligand exchange. Subsequent in situ ammonium/amine substitution by butylamine enables quantum dots to be capped by butylammonium lead iodide, and this further drives the formation of a PbSe nanowire superlattice in a two-dimensional (2D) perovskite matrix. The average spacing between two adjacent nanowires agrees well with the thickness of single atomic layer of 2D perovskite, consistent with the formation of a new self-assembled semiconductor nanowire:perovskite heterocrystal hybrid.

  11. Group theoretical analysis of octahedral tilting in perovskites

    International Nuclear Information System (INIS)

    Howard, C.J.; Stokes, H.T.

    1998-01-01

    Full text: Structures of the perovskite family, ABX 3 , have interested crystallographers over many years, and continue to attract attention on account of their fascinating electrical and magnetic properties, for example the giant magnetoresistive effects exhibited by certain perovskite materials. The ideal perovskite (cubic, space group Pm -/3 m) is a particularly simple structure, but also a demanding one, since aside from the lattice parameter there are no variable parameters in the structure. Consequently, the majority of perovskite structures are distorted perovskites (hettotypes), the most common distortion being the corner-linked tilting of the practically rigid BX 6 octahedral units. In this work, group theoretical methods have been applied to the study of octahedral tilting in perovskites. The only irreducible representations of the parent group (Pm -/3 m) which produce octahedral tilting subject to corner-linking constraints are M + / 3 and R 4 ' + . A six-dimensional order parameter in the reducible representation space of M + / 3 + R + / 4 describes the different possible tilting patterns. The space groups for the different perovskites are then simply the isotropy subgroups, comprising those operations which leave the order parameter invariant. The isotropy subgroups are obtained from a computer program or tabulations. The analysis yields a list of fifteen possible space groups for perovskites derived through octahedral tilting. A connection is made to the (twenty-three) tilt systems given previously by Glazer. The group-subgroup relationships have been derived and displayed. It is interesting to note that all known perovskites based on octahedral tilting conform with the fifteen space groups on our list, with the exception of one perovskite at high temperature, the structure of which seems poorly determined

  12. Generalized trends in the formation energies of perovskite oxides.

    Science.gov (United States)

    Zeng, ZhenHua; Calle-Vallejo, Federico; Mogensen, Mogens B; Rossmeisl, Jan

    2013-05-28

    Generalized trends in the formation energies of several families of perovskite oxides (ABO3) and plausible explanations to their existence are provided in this study through a combination of DFT calculations, solid-state physics analyses and simple physical/chemical descriptors. The studied elements at the A site of perovskites comprise rare-earth, alkaline-earth and alkaline metals, whereas 3d and 5d metals were studied at the B site. We also include ReO3-type compounds, which have the same crystal structure of cubic ABO3 perovskites except without A-site elements. From the observations we extract the following four conclusions for the perovskites studied in the present paper: for a given cation at the B site, (I) perovskites with cations of identical oxidation state at the A site possess close formation energies; and (II) perovskites with cations of different oxidation states at the A site usually have quite different but ordered formation energies. On the other hand, for a given A-site cation, (III) the formation energies of perovskites vary linearly with respect to the atomic number of the elements at the B site within the same period of the periodic table, and the slopes depend systematically on the oxidation state of the A-site cation; and (IV) the trends in formation energies of perovskites with elements from different periods at the B site depend on the oxidation state of A-site cations. Since the energetics of perovskites is shown to be the superposition of the individual contributions of their constituent oxides, the trends can be rationalized in terms of A-O and B-O interactions in the ionic crystal. These findings reveal the existence of general systematic trends in the formation energies of perovskites and provide further insight into the role of ion-ion interactions in the properties of ternary compounds.

  13. Dynamic hysteresis behaviors for the two-dimensional mixed spin (2, 5/2) ferrimagnetic Ising model in an oscillating magnetic field

    Science.gov (United States)

    Ertaş, Mehmet

    2015-09-01

    Keskin and Ertaş (2009) presented a study of the magnetic properties of a mixed spin (2, 5/2) ferrimagnetic Ising model within an oscillating magnetic field. They employed dynamic mean-field calculations to find the dynamic phase transition temperatures, the dynamic compensation points of the model and to present the dynamic phase diagrams. In this work, we extend the study and investigate the dynamic hysteresis behaviors for the two-dimensional (2D) mixed spin (2, 5/2) ferrimagnetic Ising model on a hexagonal lattice in an oscillating magnetic field within the framework of dynamic mean-field calculations. The dynamic hysteresis curves are obtained for both the ferromagnetic and antiferromagnetic interactions and the effects of the Hamiltonian parameters on the dynamic hysteresis behaviors are discussed in detail. The thermal behaviors of the coercivity and remanent magnetizations are also investigated. The results are compared with some theoretical and experimental works and a qualitatively good agreement is found. Finally, the dynamic phase diagrams depending on the frequency of an oscillating magnetic field in the plane of the reduced temperature versus magnetic field amplitude is examined and it is found that the dynamic phase diagrams display richer dynamic critical behavior for higher values of frequency than for lower values.

  14. Nonequilibrium dynamics of a mixed spin-1/2 and spin-3/2 Ising ferrimagnetic system with a time dependent oscillating magnetic field source

    Energy Technology Data Exchange (ETDEWEB)

    Vatansever, Erol [Dokuz Eylül University, Graduate School of Natural and Applied Sciences, TR-35160 Izmir (Turkey); Polat, Hamza, E-mail: hamza.polat@deu.edu.tr [Department of Physics, Dokuz Eylül University, TR-35160 Izmir (Turkey)

    2015-10-15

    Nonequilibrium phase transition properties of a mixed Ising ferrimagnetic model consisting of spin-1/2 and spin-3/2 on a square lattice under the existence of a time dependent oscillating magnetic field have been investigated by making use of Monte Carlo simulations with a single-spin flip Metropolis algorithm. A complete picture of dynamic phase boundary and magnetization profiles have been illustrated and the conditions of a dynamic compensation behavior have been discussed in detail. According to our simulation results, the considered system does not point out a dynamic compensation behavior, when it only includes the nearest-neighbor interaction, single-ion anisotropy and an oscillating magnetic field source. As the next-nearest-neighbor interaction between the spins-1/2 takes into account and exceeds a characteristic value which sensitively depends upon values of single-ion anisotropy and only of amplitude of external magnetic field, a dynamic compensation behavior occurs in the system. Finally, it is reported that it has not been found any evidence of dynamically first-order phase transition between dynamically ordered and disordered phases, which conflicts with the recently published molecular field investigation, for a wide range of selected system parameters. - Highlights: • Spin-1/2 and spin-3/2 Ising ferrimagnetic model is examined. • The system is exposed to time-dependent magnetic field. • Kinetic Monte Carlo simulation technique is used. • Any evidence of first-order phase transition has not been found.

  15. Improving the Morphology of the Perovskite Absorber Layer in Hybrid Organic/Inorganic Halide Perovskite MAPbI3 Solar Cells

    Directory of Open Access Journals (Sweden)

    I. J. Ogundana

    2017-01-01

    Full Text Available Recently, perovskite solar cells have attracted tremendous attention due to their excellent power conversion efficiency, low cost, simple fabrications, and high photovoltaic performance. Furthermore, the perovskite solar cells are lightweight and possess thin film and semitransparency. However, the nonuniformity in perovskite layer constitutes a major setback to the operation mechanism, performance, reproducibility, and degradation of perovskite solar cells. Therefore, one of the main challenges in planar perovskite devices is the fabrication of high quality films with controlled morphology and least amount of pin-holes for high performance thin film perovskite devices. The poor reproducibility in perovskite solar cells hinders the accurate fabrication of practical devices for use in real world applications, and this is primarily as a result of the inability to control the morphology of perovskites, leading to large variability in the characteristics of perovskite solar cells. Hence, the focus of research in perovskites has been mostly geared towards improving the morphology and crystallization of perovskite absorber by selecting the optimal annealing condition considering the effect of humidity. Here we report a controlled ambient condition that is necessary to grow uniform perovskite crystals. A best PCE of 7.5% was achieved along with a short-circuit current density of 15.2 mA/cm2, an open-circuit voltage of 0.81 V, and a fill factor of 0.612 from the perovskite solar cell prepared under 60% relative humidity.

  16. Structures of ordered tungsten- or molybdenum-containing quaternary perovskite oxides

    International Nuclear Information System (INIS)

    Day, Bradley E.; Bley, Nicholas D.; Jones, Heather R.; McCullough, Ryan M.; Eng, Hank W.; Porter, Spencer H.; Woodward, Patrick M.; Barnes, Paris W.

    2012-01-01

    The room temperature crystal structures of six A 2 MMoO 6 and A 2 MWO 6 ordered double perovskites were determined from X-ray and neutron powder diffraction data. Ba 2 MgWO 6 and Ba 2 CaMoO 6 both adopt cubic symmetry (space group Fm3-bar m, tilt system a 0 a 0 a 0 ). Ba 2 CaWO 6 has nearly the same tolerance factor (t=0.972) as Ba 2 CaMoO 6 (t=0.974), yet it surprisingly crystallizes with I4/m symmetry indicative of out-of-phase rotations of the MO 6 octahedra about the c-axis (a 0 a 0 c − ). Sr 2 ZnMoO 6 (t=0.979) also adopts I4/m symmetry; whereas, Sr 2 ZnWO 6 (t=0.976) crystallizes with monoclinic symmetry (P2 1 /n) with out-of-phase octahedral tilting distortions about the a- and b-axes, and in-phase tilting about the c-axis (a − a − c + ). Ca 2 CaWO 6 (t=0.867) also has P2 1 /n symmetry with large tilting distortions about all three crystallographic axes and distorted CaO 6 octahedra. Analysis of 93 double perovskites and their crystal structures showed that while the type and magnitude of the octahedral tilting distortions are controlled primarily by the tolerance factor, the identity of the A-cation acts as the secondary structure directing factor. When A=Ba 2+ the boundary between cubic and tetragonal symmetries falls near t=0.97, whereas when A=Sr 2+ this boundary falls somewhere between t=1.018 and t=0.992. - Graphical abstract: A survey of the tolerance factor of 41 Mo/W- and 52 Nb/Ta-containing quaternary perovskites plotted as a function of the difference between the two six-coordinate M-cation ionic radii. Compounds with cubic symmetry are represented by diamonds, those with tetragonal symmetry are represented by squares, those with I2/m monoclinic symmetry are represented by ×, and those with P2 1 /n monoclinic symmetry are represented by triangles. White symbols represent compositions where A=Ba 2+ , gray symbols represent compositions where A=Sr 2+ , and black symbols represent where A=Ca 2+ . The filled circle represents rhombohedral Ba 2

  17. Characterization and thermal expansion of Sr2FexMo2−xO6 double ...

    Indian Academy of Sciences (India)

    in SFMO.21 The tolerance factor of SFMO double perovskite is given by t = rSr + rO ..... project OU-DST-PURSE-Scheme No. A.60. We express our ... Zhang L, Zhou Q, He Q and He T 2010 J. Power Sources 195. 6356. 12. Mostafa M F ...

  18. Improving the photovoltaic performance of perovskite solar cells with acetate

    Science.gov (United States)

    Zhao, Qian; Li, G. R.; Song, Jian; Zhao, Yulong; Qiang, Yinghuai; Gao, X. P.

    2016-01-01

    In an all-solid-state perovskite solar cell, methylammonium lead halide film is in charge of generating photo-excited electrons, thus its quality can directly influence the final photovoltaic performance of the solar cell. This paper accentuates a very simple chemical approach to improving the quality of a perovskite film with a suitable amount of acetic acid. With introduction of acetate ions, a homogeneous, continual and hole-free perovskite film comprised of high-crystallinity grains is obtained. UV-visible spectra, steady-state and time-resolved photoluminescence (PL) spectra reveal that the obtained perovskite film under the optimized conditions shows a higher light absorption, more efficient electron transport, and faster electron extraction to the adjoining electron transport layer. The features result in the optimized perovskite film can provide an improved short-circuit current. The corresponding solar cells with a planar configuration achieves an improved power conversion efficiency of 13.80%, and the highest power conversion efficiency in the photovoltaic measurements is up to 14.71%. The results not only provide a simple approach to optimizing perovskite films but also present a novel angle of view on fabricating high-performance perovskite solar cells. PMID:27934924

  19. Perovskite-Based Solar Cells: Materials, Methods, and Future Perspectives

    Directory of Open Access Journals (Sweden)

    Di Zhou

    2018-01-01

    Full Text Available A novel all-solid-state, hybrid solar cell based on organic-inorganic metal halide perovskite (CH3NH3PbX3 materials has attracted great attention from the researchers all over the world and is considered to be one of the top 10 scientific breakthroughs in 2013. The perovskite materials can be used not only as light-absorbing layer, but also as an electron/hole transport layer due to the advantages of its high extinction coefficient, high charge mobility, long carrier lifetime, and long carrier diffusion distance. The photoelectric power conversion efficiency of the perovskite solar cells has increased from 3.8% in 2009 to 22.1% in 2016, making perovskite solar cells the best potential candidate for the new generation of solar cells to replace traditional silicon solar cells in the future. In this paper, we introduce the development and mechanism of perovskite solar cells, describe the specific function of each layer, and focus on the improvement in the function of such layers and its influence on the cell performance. Next, the synthesis methods of the perovskite light-absorbing layer and the performance characteristics are discussed. Finally, the challenges and prospects for the development of perovskite solar cells are also briefly presented.

  20. Perovskite Materials for Light-Emitting Diodes and Lasers.

    Science.gov (United States)

    Veldhuis, Sjoerd A; Boix, Pablo P; Yantara, Natalia; Li, Mingjie; Sum, Tze Chien; Mathews, Nripan; Mhaisalkar, Subodh G

    2016-08-01

    Organic-inorganic hybrid perovskites have cemented their position as an exceptional class of optoelectronic materials thanks to record photovoltaic efficiencies of 22.1%, as well as promising demonstrations of light-emitting diodes, lasers, and light-emitting transistors. Perovskite materials with photoluminescence quantum yields close to 100% and perovskite light-emitting diodes with external quantum efficiencies of 8% and current efficiencies of 43 cd A(-1) have been achieved. Although perovskite light-emitting devices are yet to become industrially relevant, in merely two years these devices have achieved the brightness and efficiencies that organic light-emitting diodes accomplished in two decades. Further advances will rely decisively on the multitude of compositional, structural variants that enable the formation of lower-dimensionality layered and three-dimensional perovskites, nanostructures, charge-transport materials, and device processing with architectural innovations. Here, the rapid advancements in perovskite light-emitting devices and lasers are reviewed. The key challenges in materials development, device fabrication, operational stability are addressed, and an outlook is presented that will address market viability of perovskite light-emitting devices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Improving the photovoltaic performance of perovskite solar cells with acetate.

    Science.gov (United States)

    Zhao, Qian; Li, G R; Song, Jian; Zhao, Yulong; Qiang, Yinghuai; Gao, X P

    2016-12-09

    In an all-solid-state perovskite solar cell, methylammonium lead halide film is in charge of generating photo-excited electrons, thus its quality can directly influence the final photovoltaic performance of the solar cell. This paper accentuates a very simple chemical approach to improving the quality of a perovskite film with a suitable amount of acetic acid. With introduction of acetate ions, a homogeneous, continual and hole-free perovskite film comprised of high-crystallinity grains is obtained. UV-visible spectra, steady-state and time-resolved photoluminescence (PL) spectra reveal that the obtained perovskite film under the optimized conditions shows a higher light absorption, more efficient electron transport, and faster electron extraction to the adjoining electron transport layer. The features result in the optimized perovskite film can provide an improved short-circuit current. The corresponding solar cells with a planar configuration achieves an improved power conversion efficiency of 13.80%, and the highest power conversion efficiency in the photovoltaic measurements is up to 14.71%. The results not only provide a simple approach to optimizing perovskite films but also present a novel angle of view on fabricating high-performance perovskite solar cells.

  2. Random lasing actions in self-assembled perovskite nanoparticles

    Science.gov (United States)

    Liu, Shuai; Sun, Wenzhao; Li, Jiankai; Gu, Zhiyuan; Wang, Kaiyang; Xiao, Shumin; Song, Qinghai

    2016-05-01

    Solution-based perovskite nanoparticles have been intensively studied in the past few years due to their applications in both photovoltaic and optoelectronic devices. Here, based on the common ground between solution-based perovskite and random lasers, we have studied the mirrorless lasing actions in self-assembled perovskite nanoparticles. After synthesis from a solution, discrete lasing peaks have been observed from optically pumped perovskites without any well-defined cavity boundaries. We have demonstrated that the origin of the random lasing emissions is the scattering between the nanostructures in the perovskite microplates. The obtained quality (Q) factors and thresholds of random lasers are around 500 and 60 μJ/cm2, respectively. Both values are comparable to the conventional perovskite microdisk lasers with polygon-shaped cavity boundaries. From the corresponding studies on laser spectra and fluorescence microscope images, the lasing actions are considered random lasers that are generated by strong multiple scattering in random gain media. In additional to conventional single-photon excitation, due to the strong nonlinear effects of perovskites, two-photon pumped random lasers have also been demonstrated for the first time. We believe this research will find its potential applications in low-cost coherent light sources and biomedical detection.

  3. Properties of perovskites and other oxides

    CERN Document Server

    Müller, K Alex

    2010-01-01

    In this book some 50 papers published by K A Muller as author or co-author over several decades, amplified by more recent work mainly by T W Kool with collaborators, are reproduced. The main subject is Electron Paramagnetic Resonance (EPR) applied to the study of perovskites and other oxides with related subjects. This wealth of papers is organized into eleven chapters, each with an introductory text written in the light of current understanding. The contributions of the first author on structural phase transitions have been immense, and because K A Muller and J C Fayet have published a review

  4. Superconductivity in multilayer perovskite. Weak coupling analysis

    International Nuclear Information System (INIS)

    Koikegami, Shigeru; Yanagisawa, Takashi

    2006-01-01

    We investigate the superconductivity of a three-dimensional d-p model with a multilayer perovskite structure on the basis of the second-order perturbation theory within the weak coupling framework. Our model has been designed with multilayer high-T c superconducting cuprates in mind. In our model, multiple Fermi surfaces appear, and the component of a superconducting gap function develops on each band. We have found that the multilayer structure can stabilize the superconductivity in a wide doping range. (author)

  5. Halide-Dependent Electronic Structure of Organolead Perovskite Materials

    KAUST Repository

    Buin, Andrei

    2015-06-23

    © 2015 American Chemical Society. Organometal halide perovskites have recently attracted tremendous attention both at the experimental and theoretical levels. These materials, in particular methylammonium triiodide, are still limited by poor chemical and structural stability under ambient conditions. Today this represents one of the major challenges for polycrystalline perovskite-based photovoltaic technology. In addition to this, the performance of perovskite-based devices is degraded by deep localized states, or traps. To achieve better-performing devices, it is necessary to understand the nature of these states and the mechanisms that lead to their formation. Here we show that the major sources of deep traps in the different halide systems have different origin and character. Halide vacancies are shallow donors in I-based perovskites, whereas they evolve into a major source of traps in Cl-based perovskites. Lead interstitials, which can form lead dimers, are the dominant source of defects in Br-based perovskites, in line with recent experimental data. As a result, the optimal growth conditions are also different for the distinct halide perovskites: growth should be halide-rich for Br and Cl, and halide-poor for I-based perovskites. We discuss stability in relation to the reaction enthalpies of mixtures of bulk precursors with respect to final perovskite product. Methylammonium lead triiodide is characterized by the lowest reaction enthalpy, explaining its low stability. At the opposite end, the highest stability was found for the methylammonium lead trichloride, also consistent with our experimental findings which show no observable structural variations over an extended period of time.

  6. Prospect for tunneling anisotropic magneto-resistance in ferrimagnets: spin-orbit coupling effects in Mn.sub.3./sub.Ge and Mn.sub.3./sub.Ga

    Czech Academy of Sciences Publication Activity Database

    Khmelevskyi, S.; Shick, Alexander; Mohn, P.

    2016-01-01

    Roč. 109, č. 22 (2016), s. 1-4, č. článku 222402. ISSN 0003-6951 R&D Projects: GA ČR GB14-37427G Institutional support: RVO:68378271 Keywords : magneto-resistance * ferrimagnets Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.411, year: 2016

  7. Pressure-Induced Bandgap Optimization in Lead-Based Perovskites with Prolonged Carrier Lifetime and Ambient Retainability

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Gang [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 China; Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015 USA; Kong, Lingping [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 China; Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015 USA; Gong, Jue [Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb IL 60115 USA; Yang, Wenge [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 China; Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015 USA; Mao, Ho-kwang [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 China; Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015 USA; Hu, Qingyang [Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015 USA; Liu, Zhenxian [Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015 USA; Schaller, Richard D. [Center for Nanoscale Materials, Argonne National Laboratory, Argonne IL 60439 USA; Zhang, Dongzhou [Hawai' i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai' i at Manoa, Honolulu HI 96822 USA; Xu, Tao [Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb IL 60115 USA

    2016-12-05

    Bond length and bond angle exhibited by valence electrons is essential to the core of chemistry. Using lead-based organic–inorganic perovskite compounds as an exploratory platform, it is demonstrated that the modulation of valence electrons by compression can lead to discovery of new properties of known compounds. Yet, despite its unprecedented progress, further efficiency boost of lead-based organic–inorganic perovskite solar cells is hampered by their wider bandgap than the optimum value according to the Shockley–Queisser limit. By modulating the valence electron wavefunction with modest hydraulic pressure up to 2.1 GPa, the optimized bandgap for single-junction solar cells in lead-based perovskites, for the first time, is achieved by narrowing the bandgap of formamidinium lead triiodide (HC(NH2)2PbI3) from 1.489 to 1.337 eV. Strikingly, such bandgap narrowing is partially retained after the release of pressure to ambient, and the bandgap narrowing is also accompanied with double-prolonged carrier lifetime. With First-principles simulation, this work opens a new dimension in basic chemical understanding of structural photonics and electronics and paves an alternative pathway toward better photovoltaic materials-by-design.

  8. Pressure-Induced Bandgap Optimization in Lead-Based Perovskites with Prolonged Carrier Lifetime and Ambient Retainability

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Gang [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 China; Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015 USA; Kong, Lingping [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 China; Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015 USA; Gong, Jue [Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb IL 60115 USA; Yang, Wenge [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 China; Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015 USA; Mao, Ho-kwang [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 China; Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015 USA; Hu, Qingyang [Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015 USA; Liu, Zhenxian [Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015 USA; Schaller, Richard D. [Center for Nanoscale Materials, Argonne National Laboratory, Argonne IL 60439 USA; Zhang, Dongzhou [Hawai' i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai' i at Manoa, Honolulu HI 96822 USA; Xu, Tao [Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb IL 60115 USA

    2016-12-05

    Bond length and bond angle exhibited by valence electrons is essential to the core of chemistry. Using lead-based organic–inorganic perovskite compounds as an exploratory platform, it is demonstrated that the modulation of valence electrons by compression can lead to discovery of new properties of known compounds. Yet, despite its unprecedented progress, further efficiency boost of lead-based organic–inorganic perovskite solar cells is hampered by their wider bandgap than the optimum value according to the Shockley–Queisser limit. By modulating the valence electron wavefunction with modest hydraulic pressure up to 2.1 GPa, the optimized bandgap for single-junction solar cells in lead-based perovskites, for the first time, is achieved by narrowing the bandgap of formamidinium lead triiodide (HC(NH2)2PbI3) from 1.489 to 1.337 eV. Strikingly, such bandgap narrowing is partially retained after the release of pressure to ambient, and the bandgap narrowing is also accompanied with double-prolonged carrier lifetime. With First-principles simulation, this work opens a new dimension in basic chemical understanding of structural photonics and electronics and paves an alternative pathway toward better photovoltaic materials-by-design.

  9. Simulation design of P–I–N-type all-perovskite solar cells with high efficiency

    International Nuclear Information System (INIS)

    Du Hui-Jing; Wang Wei-Chao; Gu Yi-Fan

    2017-01-01

    According to the good charge transporting property of perovskite, we design and simulate a p–i–n-type all-perovskite solar cell by using one-dimensional device simulator. The perovskite charge transporting layers and the perovskite absorber constitute the all-perovskite cell. By modulating the cell parameters, such as layer thickness values, doping concentrations and energy bands of n-, i-, and p-type perovskite layers, the all-perovskite solar cell obtains a high power conversion efficiency of 25.84%. The band matched cell shows appreciably improved performance with widen absorption spectrum and lowered recombination rate, so weobtain a high J sc of 32.47 mA/cm 2 . The small series resistance of the all-perovskite solar cell also benefits the high J sc . The simulation provides a novel thought of designing perovskite solar cells with simple producing process, low production cost and high efficient structure to solve the energy problem. (paper)

  10. Theoretical calculations on layered perovskites: implications for photocatalysis

    Directory of Open Access Journals (Sweden)

    Xiang Liu

    2014-12-01

    Full Text Available The application of first-principles calculations to the study of layered perovskites is reviewed here, with an emphasis on properties relevant to the use of these materials in photocatalysis. First, the accuracies of the theoretical methods in common use for the study of layered perovskites are compared. The main body of the article then reviews studies of the bulk atomic and electronic structures of pure and doped perovskites; first-principles thermodynamics studies; studies of surfaces and studies of adsorption on surfaces.

  11. Magnetic and structural investigations on La0.6Sr0.4MnO3 nanostructured manganite: Evidence of a ferrimagnetic shell

    International Nuclear Information System (INIS)

    Andrade, V.M.; Caraballo-Vivas, R.J.; Costas-Soares, T.; Pedro, S.S.; Rocco, D.L.; Reis, M.S.; Campos, A.P.C.; Coelho, A.A.

    2014-01-01

    This paper presents the structural and magnetic properties of La 0.6 Sr 0.4 MnO 3 nanoparticles with sizes from 21 to 106 nm, which have been prepared using the sol–gel method. The reduction of the nanoparticles' size tends to broaden the paramagnetic to ferromagnetic transition, as well as to promote magnetic hysteresis and a remarkable change on the magnetic saturation. In order to better understand the magnetic behavior of those nanoparticles, a simple model based on a ferromagnetic core and a ferrimagnetic shell was considered, where the magnetization was described in terms of the standard mean-field Brillouin function. This model matches the experimental data, leading to conclusion the nanoparticles with size <40nm are single magnetic domain. In addition, the output fitting parameters give information on the Landé factor of the core and shell. - Graphical abstract: Core–shell model: The core has a ferromagnetic character, while the shell is ferrimagnetic. Each one has two sub-lattices (Mn 3+ and Mn 4+ ) that interact through a mean-field (see Eq. (6)). Interactions strength and signals are also represented in this figure. In this figure the arrows (or vectors) represent the magnetic moment of ions Mn 3+ (s=2) and Mn 4+ (s=3/2). βλ's describe the ferromagnetic interaction between Mn 4+ ions into the core (βλ co ) and into the shell (βλ sh ), while αλ's represent ferromagnetic interaction between Mn 3+ ions into the core (αλ co ) and into the shell (αλ sh ). The −λ sh and +λ co co are associated to the mean field parameter of interaction between Mn 3+ and Mn 4+ sub-lattices in the shell (ferrimagnetic, negative sign) and core (ferromagnetic, positive sign), respectively. - Highlights: • Evidences of ferromagnetic shell in La 0.6 Sr 0.4 MnO 3 ferromagnetic nanoparticles. • Core(ferromagnetic)–shell(ferromagnetic) model for nanostructured manganite. • Sol–gel method was successfully used to obtain nanostructured

  12. Double Chooz

    Energy Technology Data Exchange (ETDEWEB)

    Buck, Christian [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

    2006-05-15

    The goal of the Double Chooz reactor neutrino experiment is to search for the neutrino mixing parameter {theta}{sub 13}. Double Chooz will use two identical detectors at 150 m and 1.05 km distance from the reactor cores. The near detector is used to monitor the reactor {nu}-bar {sub e} flux while the second is dedicated to the search for a deviation from the expected (1/distance){sup 2} behavior. This two detector concept will allow a relative normalization systematic error of ca. 0.6 %. The expected sensitivity for sin{sup 2}2{theta}{sub 13} is then in the range 0.02 - 0.03 after three years of data taking. The antineutrinos will be detected in a liquid scintillator through the capture on protons followed by a gamma cascade, produced by the neutron capture on Gd.

  13. Double supergeometry

    Energy Technology Data Exchange (ETDEWEB)

    Cederwall, Martin [Division for Theoretical Physics, Department of Physics, Chalmers University of Technology,SE 412 96 Gothenburg (Sweden)

    2016-06-27

    A geometry of superspace corresponding to double field theory is developed, with type I I supergravity in D=10 as the main example. The formalism is based on an orthosymplectic extension OSp(d,d|2s) of the continuous T-duality group. Covariance under generalised super-diffeomorphisms is manifest. Ordinary superspace is obtained as a solution of the orthosymplectic section condition. A systematic study of curved superspace Bianchi identities is performed, and a relation to a double pure spinor superfield cohomology is established. A Ramond-Ramond superfield is constructed as an infinite-dimensional orthosymplectic spinor. Such objects in minimal orbits under the OSp supergroup (“pure spinors”) define super-sections.

  14. Double ambidexterity

    DEFF Research Database (Denmark)

    Kaulio, Matti; Thorén, Kent; Rohrbeck, René

    2017-01-01

    We leverage the business model innovation and ambidexterity literature to investigate a contradictory case, the Swedish-Finnish Telecom operator TeliaSonera. Despite being challenged by three major disruptions, the company not only still exists but also enjoys remarkably good financial performance....... Building on extant archival data and interviews, we carefully identify and map 26 organizational responses during 1992–2016. We find that the firm has overcome three critical phases by experimenting and pioneering with portfolios of business models and/or technological innovations. We describe...... this behaviour as double ambidexterity. We use an in-depth case study to conceptualize double ambidexterity and discuss its impact on the business's survival and enduring success....

  15. Dimensional scaling of perovskite ferroelectric thin films

    Science.gov (United States)

    Keech, Ryan R.

    Dimensional size reduction has been the cornerstone of the exponential improvement in silicon based logic devices for decades. However, fundamental limits in the device physics were reached ˜2003, halting further reductions in clock speed without significant penalties in power consumption. This has motivated the research into next generation transistors and switching devices to reinstate the scaling laws for clock speed. This dissertation aims to support the scaling of devices that are based on ferroelectricity and piezoelectricity and to provide a roadmap for the corresponding materials performance. First, a scalable growth process to obtain highly {001}-oriented lead magnesium niobate - lead titanate (PMN-PT) thin films was developed, motivated by the high piezoelectric responses observed in bulk single crystals. It was found that deposition of a 2-3 nm thick PbO buffer layer on {111} Pt thin film bottom electrodes, prior to chemical solution deposition of PMN-PT reduces the driving force for Pb diffusion from the PMN-PT to the bottom electrode, and facilitates nucleation of {001}-oriented perovskite grains. Energy dispersive spectroscopy demonstrated that up to 10% of the Pb from a PMN-PT precursor solution may diffuse into the bottom electrode. PMN-PT grains with a mixed {101}/{111} orientation in a matrix of Pb-deficient pyrochlore phase were then promoted near the interface. When this is prevented, phase pure films with {001} orientation with Lotgering factors of 0.98-1.0, can be achieved. The resulting films of only 300 nm in thickness exhibit longitudinal effective d33,f coefficients of ˜90 pm/V and strain values of ˜1% prior to breakdown. 300 nm thick epitaxial and polycrystalline lead magnesium niobate - lead titanate (70PMN-30PT) blanket thin films were studied for the relative contributions to property thickness dependence from interfacial and grain boundary low permittivity layers. Epitaxial PMN-PT films were grown on SrRuO 3 /(001)SrTiO3, while

  16. Neutral Color Semitransparent Microstructured Perovskite Solar Cells

    KAUST Repository

    Eperon, Giles E.

    2014-01-28

    Neutral-colored semitransparent solar cells are commercially desired to integrate solar cells into the windows and cladding of buildings and automotive applications. Here, we report the use of morphological control of perovskite thin films to form semitransparent planar heterojunction solar cells with neutral color and comparatively high efficiencies. We take advantage of spontaneous dewetting to create microstructured arrays of perovskite "islands", on a length-scale small enough to appear continuous to the eye yet large enough to enable unattenuated transmission of light between the islands. The islands are thick enough to absorb most visible light, and the combination of completely absorbing and completely transparent regions results in neutral transmission of light. Using these films, we fabricate thin-film solar cells with respectable power conversion efficiencies. Remarkably, we find that such discontinuous films still have good rectification behavior and relatively high open-circuit voltages due to the inherent rectification between the n- and p-type charge collection layers. Furthermore, we demonstrate the ease of "color-tinting" such microstructured perovksite solar cells with no reduction in performance, by incorporation of a dye within the hole transport medium. © 2013 American Chemical Society.

  17. Electrically Anisotropic Layered Perovskite Single Crystal

    KAUST Repository

    Li, Ting-You

    2016-04-01

    Organic-inorganic hybrid perovskites (OIHPs), which are promising materials for electronic and optoelectronic applications (1-10), have made into layered organic-inorganic hybrid perovskites (LOIHPs). These LOIHPs have been applied to thin-film transistors, solar cells and tunable wavelength phosphors (11-18). It is known that devices fabricated with single crystal exhibit the superior performance, which makes the growth of large-sized single crystals critical for future device applications (19-23). However, the difficulty in growing large-sized LOIHPs single crystal with superior electrical properties limits their practical applications. Here, we report a method to grow the centimeter-scaled LOIHP single crystal of [(HOC2H4NH3)2PbI4], demonstrating the potentials in mass production. After that, we reveal anisotropic electrical and optoelectronic properties which proved the carrier propagating along inorganic framework. The carrier mobility of in-inorganic-plane (in-plane) devices shows the average value of 45 cm2 V–1 s–1 which is about 100 times greater than the record of LOIHP devices (15), showing the importance of single crystal in device application. Moreover, the LOIHP single crystals show its ultra-short carrier lifetime of 42.7 ps and photoluminescence quantum efficiency (PLQE) of 25.4 %. We expect this report to be a start of LOIHPs for advanced applications in which the anisotropic properties are needed (24-25), and meets the demand of high-speed applications and fast-response applications.

  18. Finding New Perovskite Halides via Machine learning

    Directory of Open Access Journals (Sweden)

    Ghanshyam ePilania

    2016-04-01

    Full Text Available Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach towards rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning via building a support vector machine (SVM based classifier that uses elemental features (or descriptors to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br or I anion in the perovskite crystal structure. The classification model is built by learning from a dataset of 181 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. The trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

  19. Magnetic and Electric Properties of , ( Layered Perovskites

    Directory of Open Access Journals (Sweden)

    A. I. Ali

    2013-01-01

    Full Text Available The electric and magnetic properties of layered perovskites have been investigated systematically over the doping range . It was found that both Sr1.5Y0.5CoO4 and Sr1.4Y0.6CoO4 undergo ferromagnetic (FM transition around 145 K and 120 K, respectively. On the other hand, Sr1.3Y0.7CoO4 and Sr1.2Y0.8CoO4 compounds showed paramagnetic behavior over a wide range of temperatures. In addition, spin-glass transition ( was observed at 10 K for Sr1.3Y0.7CoO4. All investigated samples are semiconducting-like within the temperature range of 10–300 K. The temperature dependence of the electrical resistivity, , was described by two-dimensional variable range hopping (2D-VRH model at 50 K < ≤ 300 K. Comparison with other layered perovskites was discussed in this work.

  20. Finding New Perovskite Halides via Machine learning

    Science.gov (United States)

    Pilania, Ghanshyam; Balachandran, Prasanna V.; Kim, Chiho; Lookman, Turab

    2016-04-01

    Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach towards rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning) via building a support vector machine (SVM) based classifier that uses elemental features (or descriptors) to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br or I anion) in the perovskite crystal structure. The classification model is built by learning from a dataset of 181 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. The trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

  1. Local polar fluctuations in lead halide perovskites

    Science.gov (United States)

    Tan, Liang; Yaffe, Omer; Guo, Yinsheng; Brus, Louis; Rappe, Andrew; Egger, David; Kronik, Leeor

    The lead halide perovskites have recently attracted much attention because of their large and growing photovoltaic power conversion efficiencies. However, questions remain regarding the temporal and spatial correlations of the structural fluctuations, their atomistic nature, and how they affect electronic and photovoltaic properties. To address these questions, we have performed a combined ab initio molecular dynamics (MD) and density functional theory (DFT) study on CsPbBr3. We have observed prevalent anharmonic motion in our MD trajectories, with local polar fluctuations involving head-to-head motion of A-site Cs cations coupled with Br window opening. We calculate Raman spectra from the polarizability auto-correlation functions obtained from these trajectories and show that anharmonic A-site cation motion manifests as a broad central peak in the Raman spectrum, which increases in intensity with temperature. A comparison of the experimental Raman spectrum of hybrid organometallic MAPbBr3 and fully inorganic CsPbBr3 suggests that structural fluctuations in lead-halide perovskites is more general than rotation of polar organic cations and is intimately coupled to the inorganic framework.

  2. Perovskite oxides: Oxygen electrocatalysis and bulk structure

    Science.gov (United States)

    Carbonio, R. E.; Fierro, C.; Tryk, D.; Scherson, D.; Yeager, Ernest

    1987-01-01

    Perovskite type oxides were considered for use as oxygen reduction and generation electrocatalysts in alkaline electrolytes. Perovskite stability and electrocatalytic activity are studied along with possible relationships of the latter with the bulk solid state properties. A series of compounds of the type LaFe(x)Ni1(-x)O3 was used as a model system to gain information on the possible relationships between surface catalytic activity and bulk structure. Hydrogen peroxide decomposition rate constants were measured for these compounds. Ex situ Mossbauer effect spectroscopy (MES), and magnetic susceptibility measurements were used to study the solid state properties. X ray photoelectron spectroscopy (XPS) was used to examine the surface. MES has indicated the presence of a paramagnetic to magnetically ordered phase transition for values of x between 0.4 and 0.5. A correlation was found between the values of the MES isomer shift and the catalytic activity for peroxide decomposition. Thus, the catalytic activity can be correlated to the d-electron density for the transition metal cations.

  3. Evaluation of covalency of ions in lead-free perovskite-type dielectric oxides

    Directory of Open Access Journals (Sweden)

    Naohisa Takesue

    2017-10-01

    Full Text Available Electronic states of ions in lead-free perovskite-type dielectric oxides have been investigated with a first-principle cluster calculation. For this calculation a double-perovskite cluster model based upon the simple cubic ABO3 was used; A and B are both the cations, and O is the oxygen anion. Systematic variations of ionic species for A and B, and lengths of the model cube edge were given to the model. Results of charge transfers of the ions show that their magnitudes depend on the edge length; the lager length leads to the higher transfer magnitude. This tendency implies spatial tolerance of the ions to the clusters, and are expected to correlate with electric polarizability and dipole reversibility of this kind of oxides. The density of states and the overlap population indicate that the higher cation valence causes the higher covalency of the anions. Considering all results together provides us an idea to obtain lead-free high-performance ferroelectrics, as high as the lead-based solid solutions.

  4. Dielectric behaviour of (Ba,Sr)TiO3 perovskite borosilicate glass ceramics

    International Nuclear Information System (INIS)

    Yadav, Avadhesh Kumar; Gautam, C.R.

    2013-01-01

    Various perovskite (Ba,Sr)TiO 3 borosilicate glasses were prepared by rapid melt-quench technique in the glass system ((Ba 1-x Sr x ).TiO 3 )-(2SiO 2 .B 2 O 3 )-(K 2 O)-(La 2 O 3 ). On the basis of differential thermal analysis results, glasses were converted into glass ceramic samples by regulated heat treatment schedules. The dielectric behaviour of crystallized barium strontium titanate borosilicate glass ceramic samples shows diffuse phase transition. The study depicts the dielectric behaviour of glass ceramic sample BST5K1L0.2S814. The double relaxation was observed in glass ceramic samples corresponding 80/20% Ba/Sr due to change in crystal structure from orthorhombic to tetragonal and tetragonal to cubic with variation of temperature. The highest value of dielectric constant was found to be 48289 for the glass ceramic sample BST5K1L0.2S814. The high value of dielectric constant attributed to space charge polarization between the glassy phase and perovskite phase. Due to very high value of dielectric constant, such glass ceramics are used for high energy storage devices. La 2 O 3 acts as nucleating agent for crystallization of glass to glass ceramics and enhances the dielectric constant and retarded dielectric loss. Such glass ceramics can be used in high energy storage devices such as barrier layer capacitors, multilayer capacitors etc. (author)

  5. All-inorganic inverse perovskite solar cells using zinc oxide nanocolloids on spin coated perovskite layer

    Science.gov (United States)

    Shibayama, Naoyuki; Kanda, Hiroyuki; Yusa, Shin-ichi; Fukumoto, Shota; Baranwal, Ajay K.; Segawa, Hiroshi; Miyasaka, Tsutomu; Ito, Seigo

    2017-07-01

    We confirmed the influence of ZnO nanoparticle size and residual water on performance of all inorganic perovskite solar cells. By decreasing the size of the ZnO nanoparticles, the short-circuit current density ( Jsc) and open circuit photovoltage ( Voc) values are increased and the conversion efficiency is improved. Although the Voc value is not affected by the influence of residual water in the solution for preparing the ZnO layer, the Jsc value drops greatly. As a result, it was found that it is important to use the oxide nanoparticles with a small particle diameter and to reduce the water content in the oxide forming material in order to manufacture a highly efficient all inorganic perovskite solar cells.

  6. Ferri-magnetic order in Mn induced spinel Co3-xMnxO4 (0.1≤x≤1.0) ceramic compositions

    Science.gov (United States)

    Meena, P. L.; Sreenivas, K.; Singh, M. R.; Kumar, Ashok; Singh, S. P.; Kumar, Ravi

    2016-04-01

    We report structural and magnetic properties of spinel Co3-xMnxO4 (x=0.1-1.0) synthesized by solid state reaction technique. Rietveld refinement analysis of X-ray diffraction (XRD) data, revealed the formation of polycrystalline single phase Co3-xMnxO4 without any significant structural change in cubic crystal symmetry with Mn substitution, except change in lattice parameter. Temperature dependent magnetization data show changes in magnetic ordering temperature, indicating formation of antiferromagnetic (AFM) and ferrimagnetic (FM) phase at low Mn concentration (x≤0.3) and well-defined FM phase at high Mn concentration (x≥0.5). The isothermal magnetization records established an AFM/FM mixed phase for composition ranging 0.10.5.

  7. Magnetic properties of a mixed spin-3/2 and spin-2 Ising ferrimagnetic system within the effective-field theory

    International Nuclear Information System (INIS)

    Deviren, Bayram; Kantar, Ersin; Keskin, Mustafa

    2010-01-01

    The magnetic properties of the ferrimagnetic mixed spin-3/2 and spin-2 Ising model with a crystal field in a longitudinal magnetic field on a honeycomb (δ = 3) and a square lattice (δ = 4) are studied by using the effective-field theory with correlations. The ground-state phase diagram of the model is obtained in a longitudinal magnetic field (h) for a single-ion potential or a crystal-field interaction (Δ) plane. We also investigate the thermal variations of the sublattice magnetization, and present the phase diagrams in the (Δ/|J|, k B T/|J|) plane. The susceptibility, internal energy, and specific heat of the system are numerically examined, and some interesting phenomena in these quantities are found due to the applied longitudinal magnetic field. Moreover, the system undergoes first- and second-order phase transitions; hence, the system has a tricritical point. The system also exhibits reentrant behaviors.

  8. Magnetic properties of a mixed spin-3/2 and spin-2 Ising ferrimagnetic system within the effective-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram [Nevsehir University, Nevsehir (Turkmenistan); Kantar, Ersin; Keskin, Mustafa [Erciyes University, Kayseri (Turkmenistan)

    2010-06-15

    The magnetic properties of the ferrimagnetic mixed spin-3/2 and spin-2 Ising model with a crystal field in a longitudinal magnetic field on a honeycomb ({delta} = 3) and a square lattice ({delta} = 4) are studied by using the effective-field theory with correlations. The ground-state phase diagram of the model is obtained in a longitudinal magnetic field (h) for a single-ion potential or a crystal-field interaction ({Delta}) plane. We also investigate the thermal variations of the sublattice magnetization, and present the phase diagrams in the ({Delta}/|J|, k{sub B}T/|J|) plane. The susceptibility, internal energy, and specific heat of the system are numerically examined, and some interesting phenomena in these quantities are found due to the applied longitudinal magnetic field. Moreover, the system undergoes first- and second-order phase transitions; hence, the system has a tricritical point. The system also exhibits reentrant behaviors.

  9. Thermal properties of the mixed spin-1 and spin-3/2 Ising ferrimagnetic system with two different random single-ion anisotropies

    Science.gov (United States)

    Pereira, J. R. V.; Tunes, T. M.; de Arruda, A. S.; Godoy, M.

    2018-06-01

    In this work, we have performed Monte Carlo simulations to study a mixed spin-1 and spin-3/2 Ising ferrimagnetic system on a square lattice with two different random single-ion anisotropies. This lattice is divided in two interpenetrating sublattices with spins SA = 1 in the sublattice A and SB = 3 / 2 in the sublattice B. The exchange interaction between the spins on the sublattices is antiferromagnetic (J single-ion anisotropies, DiA and DjB , on the sublattices A and B, respectively. We have determined the phase diagram of the model in the critical temperature Tc versus strength of the random single-ion anisotropy D plane and we shown that it exhibits only second-order phase transition lines. We also shown that this system displays compensation temperatures for some cases of the random single-ion distribution.

  10. Monte Carlo study of a ferrimagnetic mixed-spin (2, 5/2) system with the nearest and next-nearest neighbors exchange couplings

    Science.gov (United States)

    Bi, Jiang-lin; Wang, Wei; Li, Qi

    2017-07-01

    In this paper, the effects of the next-nearest neighbors exchange couplings on the magnetic and thermal properties of the ferrimagnetic mixed-spin (2, 5/2) Ising model on a 3D honeycomb lattice have been investigated by the use of Monte Carlo simulation. In particular, the influences of exchange couplings (Ja, Jb, Jan) and the single-ion anisotropy(Da) on the phase diagrams, the total magnetization, the sublattice magnetization, the total susceptibility, the internal energy and the specific heat have been discussed in detail. The results clearly show that the system can express the critical and compensation behavior within the next-nearest neighbors exchange coupling. Great deals of the M curves such as N-, Q-, P- and L-types have been discovered, owing to the competition between the exchange coupling and the temperature. Compared with other theoretical and experimental works, our results have an excellent consistency with theirs.

  11. High pressure Moessbauer spectroscopy of perovskite iron oxide

    CERN Document Server

    Nasu, S; Morimoto, S; Kawakami, T; Kuzushita, K; Takano, M

    2003-01-01

    High-pressure sup 5 sup 7 Fe Moessbauer spectroscopy using a diamond anvil cell has been performed for perovskite iron oxides SrFeO sub 3 , CaFeO sub 3 and La sub 1 sub / sub 3 Sr sub 2 sub / sub 3 O sub 3. The charge states and the magnetic dependency to pressure were determined. Pressure magnetic phase diagrams of these perovskite iron oxides are determined up to about 70 GPa. To be clear the magnetic ordered state, they are measured up to 7.8 T external magnetic fields at 4.5K. The phase transition of these perovskite oxides to ferromagnetisms with high magnetic ordered temperature is observed. In higher pressure, high spin-low spin transition of oxides besides CaFeO sub 3 is generated. The feature of Moessbauer spectroscopy, perovskite iron oxide and Moessbauer spectroscopy under high pressure are explained. (S.Y.)

  12. The Surface of Hybrid Perovskite Crystals: A Boon or Bane

    KAUST Repository

    Banavoth, Murali; Yengel, Emre; Yang, Chen; Peng, Wei; Alarousu, Erkki; Bakr, Osman; Mohammed, Omar F.

    2017-01-01

    Hybrid perovskite single crystals have garnered tremendous research attention and are expected to be next-generation materials for high-efficiency photoactive devices. Therefore, it is fundamentally important to understand the 8 relationship between

  13. Single Crystals of Organolead Halide Perovskites: Growth, Characterization, and Applications

    KAUST Repository

    Peng, Wei

    2017-01-01

    Despite their outstanding charge transport characteristics, organolead halide perovskite single crystals grown by hitherto reported crystallization methods are not suitable for most optoelectronic devices due to their small aspect ratios

  14. Present status and future prospects of perovskite photovoltaics

    Science.gov (United States)

    Snaith, Henry J.

    2018-05-01

    Solar cells based on metal halide perovskites continue to approach their theoretical performance limits thanks to worldwide research efforts. Mastering the materials properties and addressing stability may allow this technology to bring profound transformations to the electric power generation industry.

  15. Perovskite-fullerene hybrid materials suppress hysteresis in planar diodes.

    KAUST Repository

    Xu, Jixian; Buin, Andrei; Ip, Alexander H; Li, Wei; Voznyy, Oleksandr; Comin, Riccardo; Yuan, Mingjian; Jeon, Seokmin; Ning, Zhijun; McDowell, Jeffrey J; Kanjanaboos, Pongsakorn; Sun, Jon-Paul; Lan, Xinzheng; Quan, Li Na; Kim, Dong Ha; Hill, Ian G; Maksymovych, Peter; Sargent, Edward H

    2015-01-01

    passivates the key PbI3(-) antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar

  16. Manganites in Perovskite Superlattices: Structural and Electronic Properties

    KAUST Repository

    Jiwuer, Jilili

    2016-01-01

    Perovskite manganites are widely investigated compounds due to the discovery of the colossal magnetoresistance effect in 1994. They have a broad range of structural, electronic, magnetic properties and potential device applications in sensors

  17. Chemically Addressable Perovskite Nanocrystals for Light-Emitting Applications

    KAUST Repository

    Sun, Haizhu; Yang, Zhenyu; Wei, Mingyang; Sun, Wei; Li, Xiyan; Ye, Shuyang; Zhao, Yongbiao; Tan, Hairen; Kynaston, Emily L.; Schon, Tyler B.; Yan, Han; Lu, Zheng-Hong; Ozin, Geoffrey A.; Sargent, Edward H.; Seferos, Dwight S.

    2017-01-01

    Whereas organic–inorganic hybrid perovskite nanocrystals (PNCs) have remarkable potential in the development of optoelectronic materials, their relatively poor chemical and colloidal stability undermines their performance in optoelectronic devices

  18. Pyridine-induced Dimensionality Change in Hybrid Perovskite Nanocrystals

    KAUST Repository

    Ahmed, Ghada H.; Yin, Jun; Bose, Riya; Sinatra, Lutfan; Alarousu, Erkki; Yengel, Emre; AlYami, Noktan; Saidaminov, Makhsud I.; Zhang, Yuhai; Hedhili, Mohamed N.; Bakr, Osman; Bredas, Jean-Luc; Mohammed, Omar F.

    2017-01-01

    of pyridine during the synthesis of methylammonium lead bromide (MAPbBr) perovskite nanocrystals can transform three-dimensional (3D) cubes into two-dimensional (2D) nanostructures. Density functional theory (DFT) calculations show that pyridine preferentially

  19. Hydrogen Bonding and Stability of Hybrid Organic-Inorganic Perovskites

    KAUST Repository

    El-Mellouhi, Fedwa

    2016-09-08

    In the past few years, the efficiency of solar cells based on hybrid organic–inorganic perovskites has exceeded the level needed for commercialization. However, existing perovskites solar cells (PSCs) suffer from several intrinsic instabilities, which prevent them from reaching industrial maturity, and stabilizing PSCs has become a critically important problem. Here we propose to stabilize PSCs chemically by strengthening the interactions between the organic cation and inorganic anion of the perovskite framework. In particular, we show that replacing the methylammonium cation with alternative protonated cations allows an increase in the stability of the perovskite by forming strong hydrogen bonds with the halide anions. This interaction also provides opportunities for tuning the electronic states near the bandgap. These mechanisms should have a universal character in different hybrid organic–inorganic framework materials that are widely used.

  20. Metal Halide Perovskite Single Crystals: From Growth Process to Application

    Directory of Open Access Journals (Sweden)

    Shuigen Li

    2018-05-01

    Full Text Available As a strong competitor in the field of optoelectronic applications, organic-inorganic metal hybrid perovskites have been paid much attention because of their superior characteristics, which include broad absorption from visible to near-infrared region, tunable optical and electronic properties, high charge mobility, long exciton diffusion length and carrier recombination lifetime, etc. It is noted that perovskite single crystals show remarkably low trap-state densities and long carrier diffusion lengths, which are even comparable with the best photovoltaic-quality silicon, and thus are expected to provide better optoelectronic performance. This paper reviews the recent development of crystal growth in single-, mixed-organic-cation and fully inorganic halide perovskite single crystals, in particular the solution approach. Furthermore, the application of metal hybrid perovskite single crystals and future perspectives are also highlighted.

  1. Preparation of manganese-based perovskite nanoparticles using a ...

    Indian Academy of Sciences (India)

    Preparation of manganese-based perovskite nanoparticles using a reverse microemulsion method: ... ted much attention in various fields of medicine and pharma- cology such as .... In addition, the SAR value of sample was calculated through ...

  2. Working Mechanism for Flexible Perovskite Solar Cells with Simplified Architecture.

    Science.gov (United States)

    Xu, Xiaobao; Chen, Qi; Hong, Ziruo; Zhou, Huanping; Liu, Zonghao; Chang, Wei-Hsuan; Sun, Pengyu; Chen, Huajun; De Marco, Nicholas; Wang, Mingkui; Yang, Yang

    2015-10-14

    In this communication, we report an efficient and flexible perovskite solar cell based on formamidinium lead trihalide (FAPbI3) with simplified configuration. The device achieved a champion efficiency of 12.70%, utilizing direct contact between metallic indium tin oxide (ITO) electrode and perovskite absorber. The underlying working mechanism is proposed subsequently, via a systematic investigation focusing on the heterojunction within this device. A significant charge storage has been observed in the perovskite, which is believed to generate photovoltage and serves as the driving force for charge transferring from the absorber to ITO electrode as well. More importantly, this simplified device structure on flexible substrates suggests its compatibility for scale-up fabrication, which paves the way for commercialization of perovskite photovoltaic technology.

  3. A general approach for monodisperse colloidal perovskites, Chemistry of Materials

    NARCIS (Netherlands)

    Demirors, A.F.; Imhof, A.

    2009-01-01

    We describe a novel general method for synthesizing monodisperse colloidal perovskite particles at room temperature by postsynthesis addition of metal hydroxides to amorphous titania colloids. In previous work, we used titania particles to synthesize homogenously mixed silica-titania composite

  4. High pressure Moessbauer spectroscopy of perovskite iron oxide

    International Nuclear Information System (INIS)

    Nasu, Saburo; Suenaga, Tomoya; Morimoto, Shotaro; Kawakami, Takateru; Kuzushita, Kaori; Takano, Mikio

    2003-01-01

    High-pressure 57 Fe Moessbauer spectroscopy using a diamond anvil cell has been performed for perovskite iron oxides SrFeO 3 , CaFeO 3 and La 1/3 Sr 2/3 O 3 . The charge states and the magnetic dependency to pressure were determined. Pressure magnetic phase diagrams of these perovskite iron oxides are determined up to about 70 GPa. To be clear the magnetic ordered state, they are measured up to 7.8 T external magnetic fields at 4.5K. The phase transition of these perovskite oxides to ferromagnetisms with high magnetic ordered temperature is observed. In higher pressure, high spin-low spin transition of oxides besides CaFeO 3 is generated. The feature of Moessbauer spectroscopy, perovskite iron oxide and Moessbauer spectroscopy under high pressure are explained. (S.Y.)

  5. Hydrogen Bonding and Stability of Hybrid Organic-Inorganic Perovskites

    KAUST Repository

    El-Mellouhi, Fedwa; Marzouk, Asma; Bentria, El Tayeb; Rashkeev, Sergey N.; Kais, Sabre; Alharbi, Fahhad H.

    2016-01-01

    In the past few years, the efficiency of solar cells based on hybrid organic–inorganic perovskites has exceeded the level needed for commercialization. However, existing perovskites solar cells (PSCs) suffer from several intrinsic instabilities, which prevent them from reaching industrial maturity, and stabilizing PSCs has become a critically important problem. Here we propose to stabilize PSCs chemically by strengthening the interactions between the organic cation and inorganic anion of the perovskite framework. In particular, we show that replacing the methylammonium cation with alternative protonated cations allows an increase in the stability of the perovskite by forming strong hydrogen bonds with the halide anions. This interaction also provides opportunities for tuning the electronic states near the bandgap. These mechanisms should have a universal character in different hybrid organic–inorganic framework materials that are widely used.

  6. Magnetic and bioactivity evaluation of ferrimagnetic ZnFe 2O 4 containing glass ceramics for the hyperthermia treatment of cancer

    Science.gov (United States)

    Shah, Saqlain A.; Hashmi, M. U.; Alam, S.; Shamim, A.

    2010-02-01

    Glass ceramics of the composition xZnO·25Fe 2O 3·(40- x)SiO 2·25CaO·7P 2O 5·3Na 2O were prepared by the melt-quench method using oxy-acetylene flame. Glass-powder compacts were sintered at 1100 °C for 3 h and then rapidly cooled at -10 °C. X-ray diffraction (XRD) revealed 3 prominent crystalline phases: ZnFe 2O 4, CaSiO 3 and Ca 10(PO 4) 6(OH) 2. Vibrating sample magnetometer (VSM) data at 10 KOe and 500 Oe showed that saturation magnetization, coercivity and hence hysteresis area increased with the increase in ZnO content. Nano-sized ZnFe 2O 4 crystallites were of pseudo-single domain structure and thus coercivity increased with the increase in crystallite size. ZnFe 2O 4 exhibited ferrimagnetism due to the random distribution of Zn 2+ and Fe 3+ cations at tetrahedral A sites and octahedral B sites. This inversion/random distribution of cations was probably due to the surface effects of nano-ZnFe 2O 4 and rapid cooling of the material from 1100 °C (thus preserving the high temperature state of the random distribution of cations). Calorimetric measurements were carried out using magnetic induction furnace at 500 Oe magnetic field and 400 KHz frequency. The data showed that maximum specific power loss and temperature increase after 2 min were 26 W/g and 37 °C, respectively for the sample containing 10% ZnO. The samples were immersed in simulated body fluid (SBF) for 3 weeks. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDX) and XRD results confirmed the growth of precipitated hydroxyapatite phase after immersion in SBF, suggesting that the ferrimagnetic glass ceramics were bioactive and could bond to the living tissues in physiological environment.

  7. Magnetic and bioactivity evaluation of ferrimagnetic ZnFe2O4 containing glass ceramics for the hyperthermia treatment of cancer

    International Nuclear Information System (INIS)

    Shah, Saqlain A.; Hashmi, M.U.; Alam, S.; Shamim, A.

    2010-01-01

    Glass ceramics of the composition xZnO.25Fe 2 O 3 .(40-x)SiO 2 .25CaO.7P 2 O 5 .3Na 2 O were prepared by the melt-quench method using oxy-acetylene flame. Glass-powder compacts were sintered at 1100 deg. C for 3 h and then rapidly cooled at -10 deg. C. X-ray diffraction (XRD) revealed 3 prominent crystalline phases: ZnFe 2 O 4 , CaSiO 3 and Ca 10 (PO 4 ) 6 (OH) 2 . Vibrating sample magnetometer (VSM) data at 10 KOe and 500 Oe showed that saturation magnetization, coercivity and hence hysteresis area increased with the increase in ZnO content. Nano-sized ZnFe 2 O 4 crystallites were of pseudo-single domain structure and thus coercivity increased with the increase in crystallite size. ZnFe 2 O 4 exhibited ferrimagnetism due to the random distribution of Zn 2+ and Fe 3+ cations at tetrahedral A sites and octahedral B sites. This inversion/random distribution of cations was probably due to the surface effects of nano-ZnFe 2 O 4 and rapid cooling of the material from 1100 deg. C (thus preserving the high temperature state of the random distribution of cations). Calorimetric measurements were carried out using magnetic induction furnace at 500 Oe magnetic field and 400 KHz frequency. The data showed that maximum specific power loss and temperature increase after 2 min were 26 W/g and 37 deg. C, respectively for the sample containing 10% ZnO. The samples were immersed in simulated body fluid (SBF) for 3 weeks. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDX) and XRD results confirmed the growth of precipitated hydroxyapatite phase after immersion in SBF, suggesting that the ferrimagnetic glass ceramics were bioactive and could bond to the living tissues in physiological environment.

  8. Enhanced Charge Collection with Passivation Layers in Perovskite Solar Cells.

    Science.gov (United States)

    Lee, Yong Hui; Luo, Jingshan; Son, Min-Kyu; Gao, Peng; Cho, Kyung Taek; Seo, Jiyoun; Zakeeruddin, Shaik M; Grätzel, Michael; Nazeeruddin, Mohammad Khaja

    2016-05-01

    The Al2 O3 passivation layer is beneficial for mesoporous TiO2 -based perovskite solar cells when it is deposited selectively on the compact TiO2 surface. Such a passivation layer suppressing surface recombination can be formed by thermal decomposition of the perovskite layer during post-annealing. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Topological Crystalline Insulators and Dirac Octets in Anti-perovskites

    OpenAIRE

    Hsieh, Timothy H.; Liu, Junwei; Fu, Liang

    2014-01-01

    We predict a new class of topological crystalline insulators (TCI) in the anti-perovskite material family with the chemical formula A$_3$BX. Here the nontrivial topology arises from band inversion between two $J=3/2$ quartets, which is described by a generalized Dirac equation for a "Dirac octet". Our work suggests that anti-perovskites are a promising new venue for exploring the cooperative interplay between band topology, crystal symmetry and electron correlation.

  10. Maximizing and stabilizing luminescence from halide perovskites with potassium passivation

    Science.gov (United States)

    Abdi-Jalebi, Mojtaba; Andaji-Garmaroudi, Zahra; Cacovich, Stefania; Stavrakas, Camille; Philippe, Bertrand; Richter, Johannes M.; Alsari, Mejd; Booker, Edward P.; Hutter, Eline M.; Pearson, Andrew J.; Lilliu, Samuele; Savenije, Tom J.; Rensmo, Håkan; Divitini, Giorgio; Ducati, Caterina; Friend, Richard H.; Stranks, Samuel D.

    2018-03-01

    Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield—a quantity that must be maximized to obtain high efficiency—remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can

  11. Application of carbon nanotubes in perovskite solar cells: A review

    Science.gov (United States)

    Oo, Thet Tin; Debnath, Sujan

    2017-11-01

    Solar power, as alternative renewable energy source, has gained momentum in global energy generation in recent time. Solar photovoltaics (PV) systems now fulfill a significant portion of electricity demand and the capacity of solar PV capacity is growing every year. PV cells efficiency has improved significantly following decades of research, evolving into third generations of PV cells. These third generation PV cells are set out to provide low-cost and efficient PV systems, further improving the commercial competitiveness of solar energy generation. Among these latest generations of PV cells, perovskite solar cells have gained attraction due to the simple manufacturing process and the immense growth in PV efficiency in a short period of research and development. Despite these advantages, perovskite solar cells are known for the weak stability and decomposition in exposure to humidity and high temperature, hindering the possibility of commercialization. This paper will discuss the role of carbon nanotubes (CNTs) in improving the efficiency and stability of perovskite solar cells, in various components such as perovskite layer and hole transport layer, as well as the application of CNTs in unique aspects. These includes the use of CNTs fiber in making the perovskite solar cells flexible, as well as simplification of perovskite PV production by using CNT flash evaporation printing process. Despite these advances, challenges remain in incorporation CNTs into perovskite such as lower conversion efficiency compared to rare earth metals and improvements need to be made. Thus, the paper will be also highlighting the CNTs materials suggested for further research and improvement of perovskite solar cells.

  12. Perovskite classification: An Excel spreadsheet to determine and depict end-member proportions for the perovskite- and vapnikite-subgroups of the perovskite supergroup

    Science.gov (United States)

    Locock, Andrew J.; Mitchell, Roger H.

    2018-04-01

    Perovskite mineral oxides commonly exhibit extensive solid-solution, and are therefore classified on the basis of the proportions of their ideal end-members. A uniform sequence of calculation of the end-members is required if comparisons are to be made between different sets of analytical data. A Microsoft Excel spreadsheet has been programmed to assist with the classification and depiction of the minerals of the perovskite- and vapnikite-subgroups following the 2017 nomenclature of the perovskite supergroup recommended by the International Mineralogical Association (IMA). Compositional data for up to 36 elements are input into the spreadsheet as oxides in weight percent. For each analysis, the output includes the formula, the normalized proportions of 15 end-members, and the percentage of cations which cannot be assigned to those end-members. The data are automatically plotted onto the ternary and quaternary diagrams recommended by the IMA for depiction of perovskite compositions. Up to 200 analyses can be entered into the spreadsheet, which is accompanied by data calculated for 140 perovskite compositions compiled from the literature.

  13. The effect of strontium and barium doping on perovskite-structured energy materials for photovoltaic applications

    Science.gov (United States)

    Wu, Ming-Chung; Chen, Wei-Cheng; Chan, Shun-Hsiang; Su, Wei-Fang

    2018-01-01

    Perovskite solar cell is a novel photovoltaic technology with the superior progress in efficiency and the simple solution processes. Develop lead-free or lead-reduced perovskite materials is a significant concern for high-performance perovskite solar cell. Among the alkaline earth metals, the Sr2+ and Ba2+ are suitable for Pb2+ replacement in perovskite film due to fitting Goldschmidt's tolerance factor. In this study, we adopted Ba-doped and Sr-doped perovskite structured materials with different doping levels, including 1.0, 5.0, and 10.0 mol%, to prepare perovskite solar cells. Both Ba-doped and Sr-doped perovskite structured materials have a related tendency in absorption behavior and surface morphology. At 10.0 mol% doping level, the power conversion efficiency (PCE) of Sr-doped perovskite solar cells is only ∼0.5%, but the PCE of Ba-doped perovskite solar cells can be achieved to ∼9.7%. Ba-doped perovskite solar cells showed the acceptable photovoltaic characteristics than Sr-doped perovskite solar cells. Ba dopant can partially replace the amount of lead in the perovskite solar cells, and it could be a potential candidate in the field of lead-free or lead-reduced perovskite energy materials.

  14. Fabrication of Semiconducting Methylammonium Lead Halide Perovskite Particles by Spray Technology

    Science.gov (United States)

    Ahmadian-Yazdi, Mohammad-Reza; Eslamian, Morteza

    2018-01-01

    In this "nano idea" paper, three concepts for the preparation of methylammonium lead halide perovskite particles are proposed, discussed, and tested. The first idea is based on the wet chemistry preparation of the perovskite particles, through the addition of the perovskite precursor solution to an anti-solvent to facilitate the precipitation of the perovskite particles in the solution. The second idea is based on the milling of a blend of the perovskite precursors in the dry form, in order to allow for the conversion of the precursors to the perovskite particles. The third idea is based on the atomization of the perovskite solution by a spray nozzle, introducing the spray droplets into a hot wall reactor, so as to prepare perovskite particles, using the droplet-to-particle spray approach (spray pyrolysis). Preliminary results show that the spray technology is the most successful method for the preparation of impurity-free perovskite particles and perovskite paste to deposit perovskite thin films. As a proof of concept, a perovskite solar cell with the paste prepared by the sprayed perovskite powder was successfully fabricated.

  15. Fabrication of Semiconducting Methylammonium Lead Halide Perovskite Particles by Spray Technology.

    Science.gov (United States)

    Ahmadian-Yazdi, Mohammad-Reza; Eslamian, Morteza

    2018-01-10

    In this "nano idea" paper, three concepts for the preparation of methylammonium lead halide perovskite particles are proposed, discussed, and tested. The first idea is based on the wet chemistry preparation of the perovskite particles, through the addition of the perovskite precursor solution to an anti-solvent to facilitate the precipitation of the perovskite particles in the solution. The second idea is based on the milling of a blend of the perovskite precursors in the dry form, in order to allow for the conversion of the precursors to the perovskite particles. The third idea is based on the atomization of the perovskite solution by a spray nozzle, introducing the spray droplets into a hot wall reactor, so as to prepare perovskite particles, using the droplet-to-particle spray approach (spray pyrolysis). Preliminary results show that the spray technology is the most successful method for the preparation of impurity-free perovskite particles and perovskite paste to deposit perovskite thin films. As a proof of concept, a perovskite solar cell with the paste prepared by the sprayed perovskite powder was successfully fabricated.

  16. Two-Photon Absorption in Organometallic Bromide Perovskites

    KAUST Repository

    Walters, Grant

    2015-07-21

    Organometallic trihalide perovskites are solution processed semiconductors that have made great strides in third generation thin film light harvesting and light emitting optoelectronic devices. Recently it has been demonstrated that large, high purity single crystals of these perovskites can be synthesized from the solution phase. These crystals’ large dimensions, clean bandgap, and solid-state order, have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW-1 at 800 nm, comparable to epitaxial single crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

  17. Hybrid solar cells composed of perovskite and polymer photovoltaic structures

    Science.gov (United States)

    Phaometvarithorn, Apatsanan; Chuangchote, Surawut; Kumnorkaew, Pisist; Wootthikanokkhan, Jatuphorn

    2018-06-01

    Organic/inorganic lead halide perovskite solar cells have recently attracted much attention in photovoltaic research, due to the devices show promising ways to achieve high efficiencies. The perovskite devices with high efficiencies, however, are typically fabricated in tandem solar cell which is complicated. In this research work, we introduce a solar cell device with the combination of CH3NH3PbI3-xClx perovskite and bulk heterojunction PCDTBT:PC70BM polymer without any tandem structure. The new integrated perovskite/polymer hybrid structure of ITO/PEDOT:PSS/perovskite/PCDTBT:PC70BM/PC70BM/TiOx/Al provides higher power conversion efficiency (PCE) of devices compared with conventional perovskite cell structure. With the optimized PCDTBT:PC70BM thickness of ∼70 nm, the highest PCE of 11.67% is achieved. Variation of conducting donor polymers in this new structure is also preliminary demonstrated. This study provides an attractively innovative structure and a promising design for further development of the new-generation solar cells.

  18. Thermodynamic stability and kinetic dissolution of perovskite in natural waters

    International Nuclear Information System (INIS)

    Nesbitt, H.W.; Bancroft, G.M.; Fyfe, W.S.; Karkhanis, S.; Melling, P.; Nishijima, A.

    1981-01-01

    Ringwood and coworkers have recently proposed using titanates and zirconates as hosts for nuclear waste in the Synroc B process. Three minerals are used as hosts: perovskite (CaTiO 3 ), Ba-hollandite (BaAl 2 Ti 6 O 16 ), and zirconolite (CaZrTi 2 O 7 ). The Synroc philosophy relies heavily on geological and geochemical observations in selecting stable host minerals. Although it has been recognized that the Synroc minerals are not thermodynamically compatible with siliceous rocks, the minerals are considered to be thermodynamically stable in the presence of water, and it has been reported that these minerals are kinetically stable under high-temperature (up to 900 0 C) hydrothermal conditions. Detailed thermodynamic calculations and leach tests have been performed which demonstrate: first, that perovskite is thermodynamically unstable in all known natural waters; and second, that pervoskite leaches at a significant rate even at 100 0 C. Hydrothermal leach tests have been made on natural and synthetic perovskite and perovskite analogues between 100 0 C and 300 0 C. Weight losses and solution concentrations were monitored. The results reported previously in the literature also show that perovskite is kinetically unstable in the presence of common silicates. Our results show that perovskite may be no more stable than siliceous glasses, such as rhyolite, which have been studied previously. Geologic evidence from common alkaline rocks also indicates that hollandite and zirconolite probably will not survive in common rock matrices

  19. Two-Photon Absorption in Organometallic Bromide Perovskites

    KAUST Repository

    Walters, Grant; Sutherland, Brandon R; Hoogland, Sjoerd; Shi, Dong; Comin, Riccardo; Sellan, Daniel P.; Bakr, Osman; Sargent, Edward H.

    2015-01-01

    Organometallic trihalide perovskites are solution processed semiconductors that have made great strides in third generation thin film light harvesting and light emitting optoelectronic devices. Recently it has been demonstrated that large, high purity single crystals of these perovskites can be synthesized from the solution phase. These crystals’ large dimensions, clean bandgap, and solid-state order, have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW-1 at 800 nm, comparable to epitaxial single crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

  20. Tracking the formation of methylammonium lead triiodide perovskite

    International Nuclear Information System (INIS)

    Liu, Lijia; McLeod, John A.; Wang, Rongbin; Shen, Pengfei; Duhm, Steffen

    2015-01-01

    The formation mechanism of perovskite methylammonium lead triiodide (CH 3 NH 3 PbI 3 ) was studied with in situ X-ray photoelectron spectroscopy (XPS) on successive depositions of thermally evaporated methylammonium iodide (CH 3 NH 3 I) on a lead iodide (PbI 2 ) film. This deposition method mimics the “two-step” synthesis method commonly used in device fabrication. We find that several competing processes occur during the formation of perovskite CH 3 NH 3 PbI 3 . Our most important finding is that during vapour deposition of CH 3 NH 3 I onto PbI 2 , at least two carbon species are present in the resulting material, while only one nitrogen species is present. This suggests that CH 3 NH 3 I can dissociate during the transition to a perovskite phase, and some of the resulting molecules can be incorporated into the perovskite. The effect of partial CH 3 NH 3 substitution with CH 3 was evaluated, and electronic structure calculations show that CH 3 defects would impact the photovoltaic performance in perovskite solar cells. The possibility that not all A sites in the APbI 3 perovskite are occupied by CH 3 NH 3 is therefore an important consideration when evaluating the performance of organometallic trihalide solar cells synthesized using typical approaches

  1. Study of transport properties of bodies with a perovskite structure: application to the MgSiO3 perovskite

    International Nuclear Information System (INIS)

    Kapusta, Benedicte

    1990-01-01

    After some recalls on transport in ionic solids (Nernst-Einstein relationship, variation of ionic conductivity, hybrid conduction, fast ionic conduction), this research thesis presents the physical properties of perovskites and more particularly the structure and stability of the MgSiO 3 perovskite: structure and elastic properties, electric conductivity and transport properties in compounds with a perovskite structure. Then, the author reports the experimental study of the KZnF 3 perovskite (a structural analogous of MgSiO 3 ): measurements of electric conductivity under pressure, measurements under atmospheric pressure, result discussion. The next part addresses the numerical simulation of MgSiO 3 : simulation techniques (generalities on molecular dynamics, model description), investigation of structural, elastic and thermodynamic properties, diffusion properties in quadratic phase [fr

  2. Perovskite ThTaN3: A large-thermopower topological crystalline insulator

    Science.gov (United States)

    Jung, Myung-Chul; Lee, Kwan-Woo; Pickett, Warren E.

    2018-03-01

    ThTaN3, a rare cubic perovskite nitride semiconductor, has been studied using ab initio methods. Spin-orbit coupling (SOC) results in band inversion and a band gap of 150 meV at the zone center. Despite trivial Z2 indices, two pairs of spin-polarized surface bands cross the gap near the zone center, indicating that this system is a topological crystalline insulator with the mirror Chern number of | Cm|=2 protected by the mirror and C4 rotational symmetries. Additionally, SOC doubles the Seebeck coefficient, leading to a maximum of ˜400 μ V /K at 150 K for carrier-doping levels of several 1017/cm3.ThTaN3 combines excellent bulk thermopower with parallel conduction through topological surface states that may point toward new possibilities for platforms for engineering devices with larger figures of merit.

  3. Designing pseudocubic perovskites with enhanced nanoscale polarization

    Energy Technology Data Exchange (ETDEWEB)

    Levin, I. [Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA; Laws, W. J. [Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA; Wang, D. [Department of Materials Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom; Reaney, I. M. [Department of Materials Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom

    2017-11-20

    A crystal-chemical framework has been proposed for the design of pseudocubic perovskites with nanoscale ferroelectric order, and its applicability has been demonstrated using a series of representative solid solutions that combined ferroelectric (K0.5Bi0.5TiO3, BaTiO3, and PbTiO3) and antiferroelectric (Nd-substituted BiFeO3) end members. The pseudocubic structures obtained in these systems exhibited distortions that were coherent on a scale ranging from sub-nanometer to tens of nanometers, but, in all cases, the macroscopic distortion remained unresolvable even if using high-resolution X-ray powder diffraction. Different coherence lengths for the local atomic displacements account for the distinctly different dielectric, ferroelectric, and electromechanical properties exhibited by the samples. The guidelines identified provide a rationale for chemically tuning the coherence length to obtain the desired functional response.

  4. Ferroelastic Fingerprints in Methylammonium Lead Iodide Perovskite

    KAUST Repository

    Hermes, Ilka M.

    2016-02-12

    Methylammonium lead iodide (MAPbI3) perovskite materials show an outstanding performance in photovoltaic devices. However, certain material properties, especially the possible ferroic behavior, remain unclear. We observed distinct nanoscale periodic domains in the piezoresponse of MAPbI3(Cl) grains. The structure and the orientation of these striped domains indicate ferroelasticity as their origin. By correlating vertical and lateral piezoresponse force microscopy experiments performed at different sample orientations with x-ray diffraction, the preferred domain orientation was suggested to be the a1-a2-phase. The observation of these ferroelastic fingerprints appears to strongly depend on the film texture and thus the preparation route. The formation of the ferroelastic twin domains could be induced by internal strain during the cubic-tetragonal phase transition.

  5. Colour centre-free perovskite single crystals

    International Nuclear Information System (INIS)

    Petit, Pierre-Olivier; Petit, Johan; Goldner, Philippe; Viana, Bruno

    2009-01-01

    Yb 3+ :YAlO 3 (YAP) and Yb 3+ :GdAlO 3 (GAP) are interesting 1 μm high-power laser media thanks to their very good thermo-mechanical properties. However, as-grown perovskite single crystals exhibit colour centres. Parasitic thermal load generated by these centres is deleterious for high-power laser action and can lead to crystal damages. Moreover these defects decrease Yb 3+ lifetime. They are related to trapped holes on the oxygen network. In the present work, several schemes to remove colour centres are presented. Attention is focused on cerium codoping, thermal annealing under reducing atmosphere and growth of non-stoechiometric compounds.

  6. Properties and applications of perovskite proton conductors

    Directory of Open Access Journals (Sweden)

    Eduardo Caetano Camilo de Souza

    2010-09-01

    Full Text Available A brief overview is given of the main types and principles of solid-state proton conductors with perovskite structure. Their properties are summarized in terms of the defect chemistry, proton transport and chemical stability. A good understanding of these subjects allows the manufacturing of compounds with the desired electrical properties, for application in renewable and sustainable energy devices. A few trends and highlights of the scientific advances are given for some classes of protonic conductors. Recent results and future prospect about these compounds are also evaluated. The high proton conductivity of barium cerate and zirconate based electrolytes lately reported in the literature has taken these compounds to a highlight position among the most studied conductor ceramic materials.

  7. High annealing temperature induced rapid grain coarsening for efficient perovskite solar cells.

    Science.gov (United States)

    Cao, Xiaobing; Zhi, Lili; Jia, Yi; Li, Yahui; Cui, Xian; Zhao, Ke; Ci, Lijie; Ding, Kongxian; Wei, Jinquan

    2018-08-15

    Thermal annealing plays multiple roles in fabricating high quality perovskite films. Generally, it might result in large perovskite grains by elevating annealing temperature, but might also lead to decomposition of perovskite. Here, we study the effects of annealing temperature on the coarsening of perovskite grains in a temperature range from 100 to 250 °C, and find that the coarsening rate of the perovskite grain increase significantly with the annealing temperature. Compared with the perovskite films annealed at 100 °C, high quality perovskite films with large columnar grains are obtained by annealing perovskite precursor films at 250 °C for only 10 s. As a result, the power conversion efficiency of best solar cell increased from 12.35% to 16.35% due to its low recombination rate and high efficient charge transportation in solar cells. Copyright © 2018. Published by Elsevier Inc.

  8. Selective dissolution of halide perovskites as a step towards recycling solar cells.

    Science.gov (United States)

    Kim, Byeong Jo; Kim, Dong Hoe; Kwon, Seung Lee; Park, So Yeon; Li, Zhen; Zhu, Kai; Jung, Hyun Suk

    2016-05-23

    Most research on perovskite solar cells has focused on improving power-conversion efficiency and stability. However, if one could refurbish perovskite solar cells, their stability might not be a critical issue. From the perspective of cost effectiveness, if failed, perovskite solar cells could be collected and recycled; reuse of their gold electrodes and transparent conducting glasses could reduce the price per watt of perovskite photovoltaic modules. Herein, we present a simple and effective method for removing the perovskite layer and reusing the mesoporous TiO2-coated transparent conducting glass substrate via selective dissolution. We find that the perovskite layer can be easily decomposed in polar aprotic solvents because of the reaction between polar aprotic solvents and Pb(2+) cations. After 10 cycles of recycling, a mesoporous TiO2-coated transparent conducting glass substrate-based perovskite solar cell still shows a constant power-conversion efficiency, thereby demonstrating the possibility of recycling perovskite solar cells.

  9. New lithium-ion conducting perovskite oxides related to (Li, La)TiO3

    Indian Academy of Sciences (India)

    Unknown

    We describe the synthesis and lithium-ion conductivity of new perovskite-related oxides ... work on lithium-ion conducting perovskite oxides containing d0 cations. Keywords. ..... On the other hand, Nb/Ta compounds show a higher conductivity.

  10. Selective dissolution of halide perovskites as a step towards recycling solar cells

    Science.gov (United States)

    Kim, Byeong Jo; Kim, Dong Hoe; Kwon, Seung Lee; Park, So Yeon; Li, Zhen; Zhu, Kai; Jung, Hyun Suk

    2016-05-01

    Most research on perovskite solar cells has focused on improving power-conversion efficiency and stability. However, if one could refurbish perovskite solar cells, their stability might not be a critical issue. From the perspective of cost effectiveness, if failed, perovskite solar cells could be collected and recycled; reuse of their gold electrodes and transparent conducting glasses could reduce the price per watt of perovskite photovoltaic modules. Herein, we present a simple and effective method for removing the perovskite layer and reusing the mesoporous TiO2-coated transparent conducting glass substrate via selective dissolution. We find that the perovskite layer can be easily decomposed in polar aprotic solvents because of the reaction between polar aprotic solvents and Pb2+ cations. After 10 cycles of recycling, a mesoporous TiO2-coated transparent conducting glass substrate-based perovskite solar cell still shows a constant power-conversion efficiency, thereby demonstrating the possibility of recycling perovskite solar cells.

  11. Solar cells, structures including organometallic halide perovskite monocrystalline films, and methods of preparation thereof

    KAUST Repository

    Bakr, Osman; Peng, Wei; Wang, Lingfei

    2017-01-01

    Embodiments of the present disclosure provide for solar cells including an organometallic halide perovskite monocrystalline film (see fig. 1.1B), other devices including the organometallic halide perovskite monocrystalline film, methods of making

  12. Light-Responsive Ion-Redistribution-Induced Resistive Switching in Hybrid Perovskite Schottky Junctions

    KAUST Repository

    Guan, Xinwei; Hu, Weijin; Haque, Mohammed; Wei, Nini; Liu, Zhixiong; Chen, Aitian; Wu, Tao

    2017-01-01

    Hybrid Perovskites have emerged as a class of highly versatile functional materials with applications in solar cells, photodetectors, transistors, and lasers. Recently, there have also been reports on perovskite-based resistive switching (RS

  13. Growth and Characterization of PDMS-Stamped Halide Perovskite Single Microcrystals

    NARCIS (Netherlands)

    Khoram, P.; Brittman, S.; Dzik, W.I.; Reek, J.N.H.; Garneett, E.C.

    2016-01-01

    Recently, halide perovskites have attracted considerable attention for optoelectronic applications, but further progress in this field requires a thorough understanding of the fundamental properties of these materials. Studying perovskites in their single-crystalline form provides a model system for

  14. Phase transition in metastable perovskite Pb(AlNb)0,5O3

    International Nuclear Information System (INIS)

    Zhabko, T.E.; Olekhnovich, N.M.; Shilin, A.D.

    1987-01-01

    Dielectric properties of metastable perovskite Pb(AlNb) 0.5 O 3 and X-ray temperature investigations of both perovskite and pyrochlore modifications of the given compound are studied. Samples with the perovskite structure are prepared from the pyrochlorephase at 4-5 GPa pressure and 1170-1270 K. Ferroelectric phase transition is shown to occur in the metastable perovskite phase Pb(AlNb) 0.5 O 3 at 170 K

  15. Recent Advances in Interface Engineering for Planar Heterojunction Perovskite Solar Cells

    Directory of Open Access Journals (Sweden)

    Wei Yin

    2016-06-01

    Full Text Available Organic-inorganic hybrid perovskite solar cells are considered as one of the most promising next-generation solar cells due to their advantages of low-cost precursors, high power conversion efficiency (PCE and easy of processing. In the past few years, the PCEs have climbed from a few to over 20% for perovskite solar cells. Recent developments demonstrate that perovskite exhibits ambipolar semiconducting characteristics, which allows for the construction of planar heterojunction (PHJ perovskite solar cells. PHJ perovskite solar cells can avoid the use of high-temperature sintered mesoporous metal oxides, enabling simple processing and the fabrication of flexible and tandem perovskite solar cells. In planar heterojunction materials, hole/electron transport layers are introduced between a perovskite film and the anode/cathode. The hole and electron transporting layers are expected to enhance exciton separation, charge transportation and collection. Further, the supporting layer for the perovskite film not only plays an important role in energy-level alignment, but also affects perovskite film morphology, which have a great effect on device performance. In addition, interfacial layers also affect device stability. In this review, recent progress in interfacial engineering for PHJ perovskite solar cells will be reviewed, especially with the molecular interfacial materials. The supporting interfacial layers for the optimization of perovskite films will be systematically reviewed. Finally, the challenges remaining in perovskite solar cells research will be discussed.

  16. Solar cells, structures including organometallic halide perovskite monocrystalline films, and methods of preparation thereof

    KAUST Repository

    Bakr, Osman M.

    2017-03-02

    Embodiments of the present disclosure provide for solar cells including an organometallic halide perovskite monocrystalline film (see fig. 1.1B), other devices including the organometallic halide perovskite monocrystalline film, methods of making organometallic halide perovskite monocrystalline film, and the like.

  17. Computational study on oxynitride perovskites for CO_2 photoreduction

    International Nuclear Information System (INIS)

    Hafez, Ahmed M.; Zedan, Abdallah F.; AlQaradawi, Siham Y.; Salem, Noha M.; Allam, Nageh K.

    2016-01-01

    Highlights: • Oxynitride perovskites are investigated for photoelectrochemical CO_2 reduction. • They have small electron and hole effective masses, rendering higher mobility. • The effect of cation size on the band gap is investigated and discussed. • W-doping allowed the selection of specific CO_2 reduction products. - Abstract: The photocatalytic conversion of CO_2 into chemical fuels is an attractive route for recycling this greenhouse gas. However, the large scale application of such approach is limited by the low selectivity and activity of the currently used photocatalysts. Using first principles calculations, we report on the selection of optimum oxynitride perovskites as photocatalysts for photoelectrochemical CO_2 reduction. The results revealed six perovskites that perfectly straddle the carbon dioxide redox potential; namely, BaTaO_2N, SrTaO_2N, CaTaO_2N, LaTiO_2N, BaNbO_2N, and SrNbO_2N. The electronic structure and the effective mass of the selected candidates are discussed in details, the partial and total density of states illustrated the orbital hybridization and the contribution of each element in the valence and conduction band minima. The effect of cation size in the ABO_2N perovskites on the band gap is investigated and discussed. The optical properties of the selected perovskites are calculated to account for their photoactivity. Moreover, the effect of W doping on improving the selectivity of perovskites toward specific hydrocarbon product (methane) is discussed in details. This study reveals the promising optical and structural properties of oxynitride perovskite candidates for CO_2 photoreduction.

  18. Overcoming the Photovoltage Plateau in Large Bandgap Perovskite Photovoltaics.

    Science.gov (United States)

    Rajagopal, Adharsh; Stoddard, Ryan J; Jo, Sae Byeok; Hillhouse, Hugh W; Jen, Alex K-Y

    2018-05-09

    Development of large bandgap (1.80-1.85 eV E g ) perovskite is crucial for perovskite-perovskite tandem solar cells. However, the performance of 1.80-1.85 eV E g perovskite solar cells (PVKSCs) are significantly lagging their counterparts in the 1.60-1.75 eV E g range. This is because the photovoltage ( V oc ) does not proportionally increase with E g due to lower optoelectronic quality of conventional (MA,FA,Cs)Pb(I,Br) 3 and results in a photovoltage plateau ( V oc limited to 80% of the theoretical limit for ∼1.8 eV E g ). Here, we incorporate phenylethylammonium (PEA) in a mixed-halide perovskite composition to solve the inherent material-level challenges in 1.80-1.85 eV E g perovskites. The amount of PEA incorporation governs the topography and optoelectronic properties of resultant films. Detailed structural and spectroscopic characterization reveal the characteristic trends in crystalline size, orientation, and charge carrier recombination dynamics and rationalize the origin of improved material quality with higher luminescence. With careful interface optimization, the improved material characteristics were translated to devices and V oc values of 1.30-1.35 V were achieved, which correspond to 85-87% of the theoretical limit. Using an optimal amount of PEA incorporation to balance the increase in V oc and the decrease in charge collection, a highest power conversion efficiency of 12.2% was realized. Our results clearly overcome the photovoltage plateau in the 1.80-1.85 eV E g range and represent the highest V oc achieved for mixed-halide PVKSCs. This study provides widely translatable insights, an important breakthrough, and a promising platform for next-generation perovskite tandems.

  19. Co–Fe Prussian Blue Analogue Intercalated into Diamagnetic Mg–Al Layered Double Hydroxides

    Directory of Open Access Journals (Sweden)

    Cuijuan Zhang

    2016-04-01

    Full Text Available A heterostructure of diamagnetic magnesium‒aluminium layered double hydroxides (Mg‒Al LDHs and photomag‐ netic cobalt‒iron Prussian Blue analogue (Co‒Fe PBA was designed, synthesized and then designated as LDH‒PB. The cyanide-bridged Co‒Fe PBA was two-dimensionally intercalated into the Mg‒Al LDH template by the stepwise anion exchange method. LDH‒PB showed ferrimagnetic properties with in-plane antiferromagnetic exchange interactions, as well as small photo-induced magnetization by visible light illumination due to the low dimensional structures and the characteristic photo-induced electronic states of the mixed valence of FeIII(low spin, S = 1/2‒CN‒ CoII(high spin, S = 3/2‒NC‒FeII (low spin, S = 0.

  20. Planar-Structure Perovskite Solar Cells with Efficiency beyond 21.

    Science.gov (United States)

    Jiang, Qi; Chu, Zema; Wang, Pengyang; Yang, Xiaolei; Liu, Heng; Wang, Ye; Yin, Zhigang; Wu, Jinliang; Zhang, Xingwang; You, Jingbi

    2017-12-01

    Low temperature solution processed planar-structure perovskite solar cells gain great attention recently, while their power conversions are still lower than that of high temperature mesoporous counterpart. Previous reports are mainly focused on perovskite morphology control and interface engineering to improve performance. Here, this study systematically investigates the effect of precise stoichiometry, especially the PbI 2 contents on device performance including efficiency, hysteresis and stability. This study finds that a moderate residual of PbI 2 can deliver stable and high efficiency of solar cells without hysteresis, while too much residual PbI 2 will lead to serious hysteresis and poor transit stability. Solar cells with the efficiencies of 21.6% in small size (0.0737 cm 2 ) and 20.1% in large size (1 cm 2 ) with moderate residual PbI 2 in perovskite layer are obtained. The certificated efficiency for small size shows the efficiency of 20.9%, which is the highest efficiency ever recorded in planar-structure perovskite solar cells, showing the planar-structure perovskite solar cells are very promising. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.