Sample records for alloy-yundk 25ba

  1. Optical Properties of Ca0.25Ba0.75Nb2O6 Thin Films Prepared by Spinning Coating

    Institute of Scientific and Technical Information of China (English)

    Yuehua Wang; Min Zhang; Xinyin Zhao; Na Zhao


    Ca0.25Ba0.75Nb2O6 (CBN25) thin film was prepared on quartz substrate by spinning coating and the optical properties were investigated by a Hitachi U-3410 spectrophotometer and a Metricon 2010 prism coupler. The optical band gap, thickness and refractive index at 632.8 nm of the CBN25 thin film were determined to be 3.65 eV, 529 nm and 2.2258, respectively. The dispersion of the refractive index fitted to Sellmeier relation well and optical waves could be guided into the thin film, which implied that CBN25 thin films were promising for integrated optics and optically active devices.

  2. Enhanced ferroelectricity and magnetoelectricity in 0.75BaTiO3-0.25BaFe12O19 by spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Adiraj Srinivas


    Full Text Available Spark Plasma Sintering (SPS technique was employed to synthesize 0.75BaTiO3-0.25BaFe12O19 composite. X-ray diffraction studies revealed that the composite consisted of both BaTiO3 (ferroelectric phase andBaFe12O19 (ferrimagnetic phase, respectively. The SPS treated sample showed improved ferroelectric nature when compared to conventional sintered (CS sample. Transformation from hard to soft magnetic nature was envisaged by magnetization measurements for SPS sample. A slim hysteresis loop was recorded with a low coercivity values (390 Oe when compared to CS sample (3900 Oe. Mossbauer spectroscopy analysis indicated that the existence of a partial amount of γ-Fe2O3 phase in the lattice, giving rise to soft magnetic nature. The SPS sample showed slightly higher value of magnetoelectric output of 2.95 mV/cm at 3 kOe magnetic field when compared to the CS sample (1.45 mV/cm at 3 kOe. The present investigation compares the spark plasma sintered sample with the conventional sintered sample.

  3. Effect of cooling rate on phase transitions and ferroelectric properties in 0.75BiFeO3-0.25BaTiO3 ceramics (United States)

    Kim, Dae Su; Cheon, Chae Il; Lee, Seong Su; Kim, Jeong Seog


    The effect of the cooling rate on the electrical properties was investigated in the 0.75BiFeO3-0.25BaTiO3 ceramics. The air-quenched samples had superior ferroelectric and piezoelectric properties to the slowly cooled samples. The quenching effect weakened when the quenching temperature was less than 700 °C and eventually disappeared at 500 °C and below. The X-ray diffraction and transmission electron microscopy showed that the cooling rate had a significant effect on the crystal structure and domain structure. The slowly cooled sample showed a very small rhombohedral distortion and a poorly developed domain structure, which leads to weak ferroelectric and piezoelectric properties at room temperature. The quenched and slowly cooled samples had a ferroelectric rhombohedral structure (R3c) at room temperature and a paraelectric cubic structure (Pm-3m) at temperatures above 650 °C. On the other hand, the slowly cooled sample had a centro-symmetric orthorhombic (Pbnm) structure at intermediate temperatures, while the quenched sample had a noncentrosymmetric orthorhombic structure (Amm2). The diffusion of oxygen vacancies in the slowly cooled sample is believed to lead to a more symmetric orthorhombic structure at intermediate temperatures between 500 °C and 650 °C during the slow-cooling process and consequently very small rhombohedral distortion at room temperature.

  4. (La2/5Ba2/5Ca1/5)(Mn(2/5)–NiTi3/5)O3: Rietveld studies, dielectric and magnetic properties of new perovskite-related oxides

    Indian Academy of Sciences (India)

    Pika Jha; Saroj L Samal; Kandalam V Ramanujachary; Samuel E Lofland; Ashok K Ganguli


    Oxides of the type (La2/5Ba2/5Ca1/5)(Mn(2/5)–NiTi3/5)O3 (0 ≤ ≤ 0.4) have been synthesized by the ceramic route. All the above oxides have been found to crystallize in the cubic perovskite structure. Rietveld refinement of the Ni-based oxide, (La2/5Ba2/5Ca1/5)(Ni2/5Ti3/5)O3 gave rise to a composition (La0.44Ba0.38Ca0.18) (Ni0.42Ti0.58)O2.85(6) and the refined lattice parameter obtained was 3.9411(2) Å (space group $\\bar{3}$; (2) = 0.026, p = 0.074, p = 0.087). A shift from antiferromagnetic to paramagnetic behaviour is observed with increase in nickel concentration, the Mn-rich phases showing antiferromagnetism around 5 K. There is a systematic decrease in the dielectric constant, and loss tangent with increase in Ni concentration (from = 592 for = 0 to = 78 for = 0.4).

  5. Preparation and Characterization of LaNiO2.5-Ba(Zr0.1 Ce0.7Y0.2) O3-δ Composite Cathode for Intermediate Temperature Solid Oxide Fuel Cells%中温固体氧化物燃料电池LaNiO2.5-Ba(Zr0.1Ce0.7Y0.2)O3-δ阴极的制备和表征

    Institute of Scientific and Technical Information of China (English)

    吴春; 陈刚; 彭勃


    LaNiO3 is synthesized by the citric acid method, and LaNiO2.5 is prepared by hydride reduction reaction for the LaNiO3. Then a LaNiO2.5-Ba(Zr0.1Ce0.7 Y0.2) O3-δ composite cathode is manufactured with Ba(Zr0.1Ce0.7Y0.2) O3-δ as the electrolyte. The microstructure of the cathode is observed by scanning electron microscopy (SEM) and the electrochemical properties are characterized by both AC impedance and DC polarization measurements. The cathode polarization resistances get to 5. 27~0. 22 Ω· cm2 in a temperature range of 600~800℃. The rate-limiting of oxygen reduction reaction is governed by dissociation of oxygen molecules and charge transfer of oxygen atoms. The cathode overpotential reaches relatively high as 75 mV with current density of 0.05 A·cm-2 and at 750 ℃.%采用柠檬酸盐法合成了LaNiO3粉体,对其进行氢化物还原反应,制得具有单一结构的高氧缺位物相LaNiO2.5.以Ba(Zr0.1 Ce0.7 Y0.2)O3-δ (BZCY)为电解质制备了LaNiO2.5-BZCY复合阴极,利用扫描电镜对其微观结构进行了表征,并通过交流阻抗测试及直流极化测试对其电化学性能进行了研究.结果表明,LaNiO2.5-BZCY复合阴极在600~800℃范围内的极化面电阻为5.27~0.22 Ω·cm2,其氧还原反应速率控制步骤为氧分子的解离以及氧原子的电荷转移.另外,该阴极的极化过电势较高,在750℃及电流密度为0.05 A·cm-2时的极化过电势为75 mV.

  6. Transient inactivation of the infralimbic cortex induces antidepressant-like effects in the rat


    Slattery, David A.; Neumann, Inga D.; Cryan, John F.


    Affective disorders are among the main causes of disability worldwide, yet the underlying pathophysiology remains poorly understood. Recently, landmark neuroimaging studies have shown increased metabolic activity in Brodmann Area 25 (BA25) in depressed patients. Moreover, functional inactivation of this region using deep brain stimulation alleviated depressive symptoms in severely depressed patients. Thus, we examined the effect of a similar manipulation, pharmacological inactivation of the i...

  7. An influence of a Glass Braze Composition on the Properties of Li-Ti Ferrite Joints (United States)

    Lin, Panpan; Lin, Tiesong; He, Peng; Sekulic, Dusan P.; Zhao, Mengyuan; Wang, Shulei


    The influence of the chemical composition of Bi2O3-B2O3-SiO2-ZnO glass brazes on (i) the microstructure, (ii) the mechanical and (iii) the dielectric properties of Li-Ti ferrite joints was systematically investigated. The Bi5(Ti3Fe)O15 whisker and a white block phase consisting of Bi12SiO2 and Bi24B2O39 were observed in the joints of Li-Ti ferrite/Bi25-Ba and Li-Ti ferrite/glass brazes, respectively, containing a higher content of Bi2O3. No crystalline phase was detected in the Li-Ti ferrite/Bi25 and Li-Ti ferrite/Bi20 joints. The joint strength reached the maximum of 48 MPa in the Li-Ti ferrite/Bi25-Ba couples. It is assumed that this is mainly due to the strengthening effect of Bi5(Ti3Fe)O15 whiskers. The bonding temperature (700°C) had little effect on the dielectric properties of Li-Ti ferrite. Moreover, compared to the Bi25-Ba glass brazes, the Bi25 and Bi20 glass brazes had a less pronounced influence on the dielectric properties of joints. Different glass brazes can be tailored to different requirements depending on specific application and joint property requirements.

  8. US China Policy: Time for Robust Engagement (United States)


    Stimulus and Questions about Global Financial Governance.” (November 13, 2008): 1. Available at: 14 David Zweig and Bi...david- zweig -bi-jianhai/china-s-global-hunt-for-energy.html. 15 David Shambaugh, “China’s New Foray Into Latin America,” Yale Global, (November 17 2008...25BA81792E60 29 Derek Scissors, PhD, U.S. China Economic Dialogue, 6. 30 Paulson, A Strategic Economic Engagement, 4. 31 David Zweig and Bi Jiahai

  9. Provskite Structure Based Filler Impregnated Pvdf—Hfp Micro Composites For Lithium Ion Batteries (United States)

    Vickraman, P.; Pandiraj, A.


    Lithium BETI (Lithium bis (perfluoroethanesulfonyl) imide) (guest species) based PVDF-HFP(host matrix) Polymer NanoComposites (PNC) films by loading barium titanate (BaTiO3) as a filler, in ascending proportions with the plasticizer (mixture of EC+DMC) while keeping host and guest content as constants, has been investigated by employing AC impedance, Thermal, and XRD. The ionic conductivity measurements on these PNC show that 2.5% BaTiO3 loaded PNC showed mitigation in magnitude of the conductivity compared to that of 0 wt% loaded PNC but thereafter increase in conductivity is noted with increase in filler content upto 7.5 wt%. The higher conductivity is observed for 7.5 % filler loaded membrane. The XRD study identifies suppression of polymer phase associated with (200) plane. The thermal profile registers the endothermic changes associated with polymer host indicating varying heat of fusion ΔHm with filler increase.

  10. Evaluation of the FilmArray® system for detection of Bacillus anthracis, Francisella tularensis, and Yersinia pestis

    Energy Technology Data Exchange (ETDEWEB)

    Seiner, Derrick R.; Colburn, Heather A.; Baird, Cheryl L.; Bartholomew, Rachel A.; Straub, Tim M.; Victry, Kristin D.; Hutchison, Janine R.; Valentine, Nancy B.; Bruckner-Lea, Cindy J.


    To evaluate the sensitivity and specificity of the Idaho Technologies FilmArray® Biothreat Panel for the detection of Bacillus anthracis (Ba), Francisella tularensis (Ft), and Yersinia pestis (Yp) DNA, and demonstrate the detection of Ba spores. Methods and Results: DNA samples from Ba, Ft and Yp strains and near-neighbors, and live Ba spores were analyzed using the Biothreat Panel, a multiplexed PCR-based assay for 17 pathogens and toxins. Sensitivity studies with DNA suggest a limit of detection of 250 genome equivalents (GEs) per sample. Furthermore, the correct call of Ft, Yp or Bacillus species was made in 63 of 72 samples tested at 25 GE or less. With samples containing 25 Ba Sterne spores, at least one of the two possible Ba markers were identified in all samples tested. We observed no cross-reactivity with near-neighbor DNAs.

  11. Correlation between temperature-dependent permittivity dispersion and depolarization behaviours in Zr4+-modified BiFeO3–BaTiO3 piezoelectric ceramics

    Indian Academy of Sciences (India)

    Weidong Zeng; Changrong Zhou; Jianrong Xiao; Jiafeng Ma


    The correlation between permittivity frequency dispersion and depoling process upon heating was investigated in Zr4+-modified 0.75BiFeO3–0.25BaTiO3 (BF–BZT) ceramics. The temperature-dependent permittivity r() and the piezoelectric coefficient 33 for poled samples were measured under heating conditions to clarify the depolarization mechanism. The results indicate that the poling temperature plays a crucial role in the domains' alignment process, as expected. The temperature-dependent permittivity frequency dispersion and depolarization behaviours may have same origin. The aligned domains' break up into random state/nanodomains at depoling temperature ( d), which causes strong frequency dependence of the permittivity, simultaneously, induces the loss of piezoelectricity. It suggests that the temperature-dependent permittivity measurements method is a simple way to determine the depolarization temperature.

  12. Transient inactivation of the infralimbic cortex induces antidepressant-like effects in the rat. (United States)

    Slattery, David A; Neumann, Inga D; Cryan, John F


    Affective disorders are among the main causes of disability worldwide, yet the underlying pathophysiology remains poorly understood. Recently, landmark neuroimaging studies have shown increased metabolic activity in Brodmann Area 25 (BA25) in depressed patients. Moreover, functional inactivation of this region using deep brain stimulation alleviated depressive symptoms in severely depressed patients. Thus, we examined the effect of a similar manipulation, pharmacological inactivation of the infralimbic cortex, the rodent correlate of BA25, in an animal model of antidepressant activity: the modified rat forced swim test. Transient inactivation of the infralimbic cortex using muscimol reduced immobility, an antidepressant-like effect in the test. Importantly, this activity was not the result of a general increase in locomotor activity. Activation of the infralimbic cortex using bicuculline did not alter behaviour. Finally, we examined the effect of muscimol in animals bred for high anxiety-related behaviour, which also display elevated depression-related behaviour. Transient inactivation of the infralimbic cortex decreased the high inborn depression-like behaviour of these rats. These results show that it is possible to replicate findings from a clinical trial in a rodent model. Further, they support the use of the forced swim test to gain greater understanding of the neurocircuitry involved in depression and antidepressant-action.

  13. Formation and early hydration characteristics of C2.75B1.25A3$ in binary system of C2.75B1.25A3$-C2S

    Directory of Open Access Journals (Sweden)

    Wang, Shoude


    Full Text Available C2.75B1.25A3$ (2.75CaO•1.25BaO• 3Al2O3• SO3 is one of the important minerals and it govern-directly the early-strength of belite-barium calcium sulphoaluminate cement. In this paper a binary system C2.75B1.25A3$-C2S is selected to investigate the formation of C2.75B1.25A3$. In the range of 1100 °C–1200 °C, the earlier formed C2S hinders the formation of C2.75B1.25A3$. On the contrary, when the temperature is in the range of 1200 °C–1350 °C, the initially formed C2S could provide a surface for the nucleation of C2.75B1.25A3$ and cut down the potential barrier (?Gk* for the heterogeneous nucleation of C2.75B1.25A3$, which contributes to its formation. Moreover, at 1350 °C, the large amount of previously formed C2S benefits the extent of formation of C2.75B1.25A3$. The possible reason was that it could prevent sulfur evaporation. In early hydration age, AFm and AFt originating from C2.75B1.25A3$ hydration are found within 2 h and 12 h under 95% RH at 1 °C, respectively, whereas C2S is unhydrated at this moment.En el cemento de sulfoaluminato de calcio y bario, el C2.75B1.25A3$ (2.75CaO•1.25BaO• 3Al2 O3• SO3 es una de las principales fases, y regula directamente la resistencia inicial del cemento. En este trabajo, se ha seleccionado el sistema binario C2.75B1.25A3$-C2S para investigar la formación de C2.75B1.25A3$. En el rango de 1100 °C-1200 °C, el C2S formado anteriormente impide la formación de C2.75B1.25A3$, mientras que cuando la temperatura está entre 1200 °C-1350 °C, el C2S proporcionaría una superficie de nucleación de C2.75B1.25A3$ reduciendo la barrera de potencial (?Gk* para la nucleación heterogénea de C2.75B1.25A3$, lo que contribuye a su formación. Además, a 1350 °C, la gran cantidad de C2S formado beneficia la formación de C2.75B1.25A3$, ya que podía prevenir la evaporación del azufre. En las primeras etapas de la hidratación (entre 2 y 12h y 95% HR a 1 ºC se pueden encontrar AFM y AFt

  14. Meteorological variations of PM2.5/PM10 concentrations and particle-associated polycyclic aromatic hydrocarbons in the atmospheric environment of Zonguldak, Turkey. (United States)

    Akyüz, Mehmet; Cabuk, Hasan


    Airborne particulate matter (PM(2.5) and PM(10)) concentrations were measured in Zonguldak, Turkey from January to December 2007, using dichotomous Partisol 2025 sampler. Collected particulate matter was analyzed for 14 selected polycyclic aromatic hydrocarbons (PAHs) by high-performance liquid chromatography with fluorescence detection (HPLC-FL). The seasonal variations of PM(2.5) and PM(10) concentrations were investigated together with their relationships with meteorological parameters. The maximum daily concentrations of PM(2.5) and PM(10) reached 83.3 microg m(-3) and 116.7 microg m(-3) in winter, whereas in summer, they reached 32.4 microg m(-3) and 66.7 microg m(-3), respectively. Total concentration of PM(10)-associated PAHs reached 492.4 ng m(-3) in winter and 26.0 ng m(-3) in summer times. The multiple regression analysis was performed to predict total PM(2.5)- and PM(10)-associated PAHs and benzo(a)pyrene-equivalent (BaPE) concentrations with respect to meteorological parameters and particulate mass concentrations with the determination coefficients (R(2)) of 0.811, 0.805 and 0.778, respectively. The measured mean values of concentrations of total PM(2.5)- and PM(10)-associated PAHs were found to be 88.4 ng m(-3) and 93.7 ng m(-3) while their predicted mean values were found to be 92.5 ng m(-3) and 98.2 ng m(-3), respectively. In addition, observed and predicted mean concentration values of PM(2.5)-BaPE were found to be 14.1 ng m(-3) and 14.6 ng m(-3). The close annual mean concentrations of measured and predicted total particulate related PAHs imply that the models can be reliably used for future predictions of particulate related PAHs in urban atmospheres especially where fossil fuels are mainly used for heating.

  15. Dynamic Assessment of Incidental Vocabularies: A Case of Iranian ESP Learners

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    Sepideh Hanifi


    Full Text Available Dynamic assessment (DA, stemmed from both Vygotsky’s (1978 learning theory and Feuerstein’s (1979 theory of mediated learning experiences, is an alternative to static assessment. It focuses on both instruction and assessment aiming at promoting learning through mediation.  DA has been widely researched in different linguistic areas, but there is paucity of research on its practice in ESP contexts. Accordingly, this study investigated the effectiveness of DA on incidental vocabularies emerging in technical reading textbooks, written for electronic engineering students. The study employed a quasi-experimental research design. Due to sample selection problems, an intact group of 25 BA electronic students were selected from the University of Zanjan. A pre-test was administered to check whether they had previous knowledge of the target words, incidentally acquired during the reading activity. As for the instrument stage, DA procedures were utilized in order to individualize participants’ assessment. Following DA implementation, a post-test similar in content to pre-test, was administered to the same participants. The significance of DA for the enhancement of incidental vocabularies was to make participants aware of the strategies of identifying, evaluating and monitoring vocabularies (Nassaji, 2003 through mediation process.  The results indicated that participants' incidental vocabulary learning promoted dramatically using DA, which employed structured hints for the mediation process.  The results of this study can inform both teachers and learners to provide a step by step procedure to promote both teaching and assessment of ESP learners' vocabulary.Keywords: Dynamic Assessment, Incidental Vocabulary Learning, ESP Learners, ZPD, mediation 

  16. 硅酸三钙与硫铝酸钡钙共存的研究%Study on Mineral Formation and Coexistence of Tri-calcium Silicate and Ba-bearing Calcium Sulphoaluminate in Several Systems

    Institute of Scientific and Technical Information of China (English)



    以纯化学试剂配料,研究了微量元素氟化钙(CaF2)、温度以及液相(本文取铁铝酸四钙)等不同条件下对硅酸三钙(C3S)和硫铝酸钡钙(CBA(S),本文取化学计量为2.75CaO·1.25BaO·3Al2O3·SO3,简写为C2.75B1.25A3(S))矿物形成及共存的影响.运用了X射线衍射分析、扫描电子显微镜、能谱分析以及游离氧化钙的测定等多种分析测试手段进行测试,结果表明,适量CaF2的存在可以有效促进系统中游离氧化钙(f-CaO)的吸收,改善生料的易烧性,使硅酸三钙的形成较为充分;由X射线衍射分析及带能谱的扫描电子显微镜分析知,少量液相的存在可以改善配合料的易烧性,利于CBA(S)矿物的形成,拓宽水泥中两种主要强度矿物的温度共存范围;两种强度矿物适宜的共存温度范围应在1 360℃左右.

  17. Phase transition, piezoelectric, and multiferroic properties of La(Co{sub 0.5}Mn{sub 0.5})O{sub 3}-modified BiFeO{sub 3}-BaTiO{sub 3} lead-free ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Lingling; Jiang, Na; Zou, Xiao; Sun, Ting; Zheng, Qiaoji; Xu, Chenggang; Lin, Dunmin [College of Chemistry and Materials Science, Sichuan Normal University, Chengdu (China); Shi, Dongliang; Lam, Kwok Ho [Department of Electrical Engineering, The Hong Kong Polytechnic University, Kowloon (China)


    (0.75-x)BiFeO{sub 3}-0.25BaTiO{sub 3}-xLa(Co{sub 0.5}Mn{sub 0.5})O{sub 3} + 1 mol% MnO{sub 2} lead-free ceramics (x = 0-0.10) were synthesized by a conventional solid-state reaction route and the effects of La(Co{sub 0.5}Mn{sub 0.5})O{sub 3} on phase transition, piezoelectric, ferroelectric, and multiferroic properties of the ceramics were investigated. The ceramics can be well sintered at 960 C for 2 h. After the addition of La(Co{sub 0.5}Mn{sub 0.5})O{sub 3}, the crystal structure of the ceramics is transformed from rhombohedral (space group R3c) to orthorhombic symmetry (space group Amm2), and the morphotropic phase boundary (MPB) of rhombohedral and orthorhombic phases is formed at x = 0.01-0.03. The dielectric peak of the ceramics was found to become diffusive with increasing x. The ceramics with x = 0-0.03 possess strong piezoelectricity with d{sub 33} of 95-108 pC N{sup -1}, strong ferroelectricity with P{sub r} of 2.2-18.1 μC cm{sup -2}, considerable magnetoelectric coefficient of 372-672 mV/cmOe, and high Curie temperature of 523-659 C, showing potential applications in multiferroic devices. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Novel perovskite-related barium tungstate Ba 11W 4O 23 (United States)

    Hong, Seung-Tae


    Ba 11W 4O 23 was synthesized at 1300 °C, followed by quenching with liquid nitrogen. The crystal structure, which was known to be cryolite-related but has remained unclear, was initially determined by single-crystal X-ray diffraction for the isostructural Ru-substituted compound Ba 11(W 3.1Ru 0.9)O 22.5, which was discovered during exploratory synthesis in the Ba-Ru-O system. The structure of Ba 11W 4O 23 was refined by a combined powder X-ray and neutron Rietveld method ( Fd-3 m, a=17.1823(1) Å, Z=8, Rp=3.09%, Rwp=4.25%, χ2=2.8, 23 °C). The structure is an example of A-site vacancy-ordered 4×4×4 superstructure of a simple perovskite ABO 3, and it may be written as (Ba 1.75□ 0.25)BaWO 5.75□ 0.25, emphasizing vacancies on both metal and anion sites. The local structure of one of two asymmetric tungsten ions is the WO 6 octahedron, typical of perovskite. The other tungsten, however, is surrounded by oxygen and anionic vacancies statistically distributed over three divided sites to form 18 partially occupied oxygen atoms (˜30% on average), represented as WO 18/3. The A-site cation-vacancies are ordered at the 8a ( {1}/{8}, {1}/{8}, {1}/{8}) site in between adjoining WO 18/3 polyhedra which form 1-D arrangements along [110] and equivalent directions. In situ high-temperature XRD data have shown that the quenched Ba 11W 4O 23 at room temperature is isostructural to the high-temperature phase at 1100 °C.

  19. Structure-property relations in new fluorophosphate glasses singly- and co-doped with Er{sup 3+} and Yb{sup 3+}

    Energy Technology Data Exchange (ETDEWEB)

    Gonçalves, Tássia S.; Moreira Silva, Raphaell J.; Oliveira Junior, Marcos de; Ferrari, Cynthia R. [Physics Institute of São Carlos, University of São Paulo, São Carlos, SP 13566-590 (Brazil); Poirier, Gäel Y. [Science and Technology Institute, Federal University of Alfenas, Poços de Caldas, MG 37715-400 (Brazil); Eckert, Hellmut, E-mail: [Physics Institute of São Carlos, University of São Paulo, São Carlos, SP 13566-590 (Brazil); Physical Chemistry Institute, Westfälische Wilhelms Universität Münster, Münster D-48149 (Germany); Camargo, Andrea S.S. de, E-mail: [Physics Institute of São Carlos, University of São Paulo, São Carlos, SP 13566-590 (Brazil)


    Rare earth (RE{sup 3+})-doped fluorophosphate glasses are among the most promising candidates for high-efficiency laser generation in the near-infrared spectral region. By proper choice of composition, these materials can combine the advantages of fluorides (low phonon energies, low refractive indices, extensive optical window, low hygroscopicity) and of oxides (high chemical and mechanical stability and high dopant solubility), resulting in enhancement of the RE{sup 3+} emissive properties. In this work, we present the synthesis and structural/spectroscopic investigation of new glasses with composition 25BaF{sub 2}25SrF{sub 2}(30-x)Al(PO{sub 3}){sub 3}xAlF{sub 3}(20-z)YF{sub 3}:zREF{sub 3}, where x = 20 or 15, RE = Er{sup 3+} and/or Yb{sup 3+}, z = 0.25–5.0 mol%. Results indicate considerable improvement of the emissive properties of both ions when compared to phosphate or even other fluorophosphate host compositions. Long excited state lifetimes (τ = 10 ms for the Er{sup 3+} level {sup 4}I{sub 13/2}, and τ = 1.3 ms for the Yb{sup 3+} level {sup 2}F{sub 5/2}) imply high fluorescence quantum efficiencies η (up to 85% for both ions). Structural characterization by Raman and multinuclear solid state NMR spectroscopies indicate that the metaphosphate-type chain structure of the Al(PO{sub 3}){sub 3} vitreous framework is partially depolymerized and dominated by Q{sup (0)} and Q{sup (1)} units crosslinked by six-coordinate Al species. As revealed by {sup 27}Al{"3"1P} rotational echo double resonance (REDOR) NMR results the average local aluminum environment of the x = 20 sample comprises 1.6 phosphate and 4.4 fluoride species. These results indicate a clear bonding preference between aluminum and phosphorus, which is consistent with the desired dominance of fluoride species in the local environment of the rare earth and alkaline earth atoms in these glasses. - Highlights: • New fluorophosphate glass composition with excellent photophysical properties.