Filters for mobile radio from high Tc ceramic superconductors

International Nuclear Information System (INIS)

Peterson, G.E.; Wong, E.; Alford, N.McN.

1990-01-01

Mobile radio frequencies lie between 30 MHz and 1,000 MHz. This frequency range is ideal for ceramic high T c superconductors. We have designed Chebyshev, Butterworth and interdigital filters that can employ high T c superconductors in the form of rods, tubes and helices. In general, the performance of these filters at milliwatt power levels is excellent. We will describe fabrication of the superconductors and filter design

Investigation on the bisoliton mechanism of high-temperature superconductors

International Nuclear Information System (INIS)

Zhang Lingyun; Li Bozang; Pu Fucho; Lin Jiatih

1996-01-01

Microscopic parameters in the Davydov model are calculated on the basis of the bisoliton idea. The energy gap is obtained from combining the condition for the solution of Davydov's equation with the condensation energy of the superconductive state in zero field, and some characteristic parameters of high-temperature superconductors such as coherence length, penetration depth, and density of critical current for a thin film in weak magnetic field are given. It is also proved that lattice displacement in Davydov's equation satisfies the φ 4 field form. The critical temperature and the coefficient of linear specific heat of high-temperature superconductors are studied from the statistics of lattice kinks. The agreement between theoretical and experimental values for YBaCuO oxide ceramics suggests that the bisoliton model gives a reasonable explanation of high-temperature superconductivity. (orig.)

Electron microscopic observation at low temperature on superconductors

International Nuclear Information System (INIS)

Yokota, Yasuhiro; Hashimoto, Hatsujiro; Yoshida, Hiroyuki.

1991-01-01

The authors have observed superconducting materials with a high resolution electron microscope at liquid helium temperature. First, observation was carried out on Nb system intermetallic compounds such as Nb 3 Al and Nb 3 Sn of Al 5 type and Nb 3 Ge of 11 type at extremely low temperature. Next, the observation of high temperature superconductive ceramics in the state of superconductivity was attempted. In this paper, first the development of the liquid helium sample holder for a 400 kV electron microscope to realize the observation is reported. Besides, the sample holder of Gatan Co. and an extremely low temperature, high resolution electron microscope with a superconducting lens are described. The purpose of carrying out the electron microscope observation of superconductors at low temperature is the direct observation of the crystalline lattice image in the state of superconductivity. Also the structural transformation from tetragonal crystals to rhombic crystals in Al 5 type superconductors can be observed. The results of observation are reported. (K.I.)

Superconductors: The long road ahead

International Nuclear Information System (INIS)

Foner, S.; Orlando, T.P.

1988-01-01

Before the discovery of high-temperature superconductors, progress in superconductivity was measured by quite small increases in critical temperature, often of less than one degree. Today, there is no reason to believe that the dramatic leaps in critical temperature inaugurated by superconducting ceramics are over. Researchers may find new high-temperature superconducting materials with less severe technical limitations than the ceramics we know today. And if the day ever comes when a superconductor can be reliably manufactured to operate effectively at room temperature, then superconductors will be incorporated in a broad range of everyday household devices - motors, appliances, even children's toys - with a large consumer market. High-temperature superconductors may also cause us to extensively revise our traditional theories about how superconductivity works. Should it run out that superconductivity in ceramics involves new physical mechanisms, then these mechanisms could lead to applications never considered before. The recent discoveries have already reinvigorated superconductivity research. What was once largely the domain of a relatively small group of scientists has become a genuinely multidisciplinary realm. Now physicists, materials scientists, chemists, metallurgists, ceramists, and solid-state electronics engineers are all focusing on superconductivity. The cross-fertilization of these disciplines should contribute to further discoveries of importance to the practical application of superconductors

Studies of high temperature superconductors

International Nuclear Information System (INIS)

Narlikar, A.

1989-01-01

The high temperature superconductors (HTSCs) discovered are from the family of ceramic oxides. Their large scale utilization in electrical utilities and in microelectronic devices are the frontal challenges which can perhaps be effectively met only through consolidated efforts and expertise of a multidisciplinary nature. During the last two years the growth of the new field has occurred on an international scale and perhaps has been more rapid than in most other fields. There has been an extraordinary rush of data and results which are continually being published as short texts dispersed in many excellent journals, some of which were started to ensure rapid publication exclusively in this field. As a result, the literature on HTSCs has indeed become so massive and so diffuse that it is becoming increasingly difficult to keep abreast with the important and reliable facets of this fast-growing field. This provided the motivation to evolve a process whereby both professional investigators and students can have ready access to up-to- date in-depth accounts of major technical advances happening in this field. The present series Studies of High Temperature Superconductors has been launched to, at least in part, fulfill this need

Integration of semiconductor and ceramic superconductor devices for microwave applications

International Nuclear Information System (INIS)

Klopman, B.B.G.; Weijers, H.W.; Gao, J.; Gerritsma, G.J.; Rogalla, H.

1991-01-01

Due to the very low-loss properties of ceramic superconductors high-performance microwave resonators and filters can be realized. The fact that these devices may be operated at liquid nitrogen temperature, facilitates the integration with semiconductor devices. Examples are bandpass amplifiers, microwave-operated SQUIDs combined with GaAs preamplifiers, detectors, and MOSFET low-frequency amplifiers. This paper discusses the design of such circuits on a single one inch alumina substrate using surface mount techniques. Furthermore data on circuits that have been realized in our laboratory will be presented

Dense high temperature ceramic oxide superconductors

Science.gov (United States)

Landingham, Richard L.

1993-01-01

Dense superconducting ceramic oxide articles of manufacture and methods for producing these articles are described. Generally these articles are produced by first processing these superconducting oxides by ceramic processing techniques to optimize materials properties, followed by reestablishing the superconducting state in a desired portion of the ceramic oxide composite.

Magnetic properties of high temperature superconductors and their interaction with high energy permanent magnets

International Nuclear Information System (INIS)

Agarwala, A.K.

1990-01-01

Magnetic properties of sintered samples of YBCO ceramic superconductors at various temperatures were measured using a vibrating sample magnetometer (VSM). Also, measurements of forces experienced by a well characterized rare earth-transition metal (RE-TM) permanent magnet (PM) interacting with the superconducting YBCO sample cooled in liquid nitrogen, were performed. Based upon the observed hysteretic magnetization properties of these high temperature superconductors (HTS), the HTS-PM interaction force at liquid nitrogen temperature was calculated from first principle, and finally correlated to the force measurement results. With this analysis, magnetic forces between the same HTS and PM system including the levitation as well as suspension effects at liquid-helium temperature are predicted

Manufacturing of superconductive silver/ceramic composites

DEFF Research Database (Denmark)

Seifi, Behrouz; Bech, Jakob Ilsted; Eriksen, Morten

2000-01-01

Manufacturing of superconducting metal/ceramic composites is a rather new discipline within materials forming processes. High Temperature SuperConductors, HTSC, are manufactured applying the Oxide-Powder-In-Tube process, OPIT. A ceramic powder containing lead, calcium, bismuth, strontium, and cop......Manufacturing of superconducting metal/ceramic composites is a rather new discipline within materials forming processes. High Temperature SuperConductors, HTSC, are manufactured applying the Oxide-Powder-In-Tube process, OPIT. A ceramic powder containing lead, calcium, bismuth, strontium...

Oxide glass to high temperature ceramic superconductors - a novel route

International Nuclear Information System (INIS)

Chaudhuri, B.K.; Som, K.K.

1992-01-01

Recently it has been discovered that many of transition metal oxide (TMO) glasses like Bi-Sr-Ca-Cu-O, Y-Ba-Cu-O, Bi-Pb-Sr-Ca-Cu-O etc. can be directly converted to the corresponding high temperature superconducting phases by properly annealing the respective glasses. In this review recent developements in this field are summarised. The structural, electrical, dielectrical, magnetic, optical, and other properties of these new type of (TMO) glass systems have been elucidated comparing them with the corresponding results of already known (TMO) glasses which do not become superconductors on annealing above their glass transition temperatures (T g ). The electrical properties of this novel glass system have been analysed with reference to the various existing theoretical models based on polaron hopping conduction mechanism. The electrical, magnetic, and other properties of the respective superconductors obtained from their corresponding glass phases by annealing above (T g ) and the possibility of drawing wires, ribbons etc. from these glass matrices and then converting them to their high T c superconducting phases have also been discussed. (author). 107 refs., 32 figs., 5 tabs

Room temperature superconductors

International Nuclear Information System (INIS)

Sleight, A.W.

1995-01-01

If the Holy Grail of room temperature superconductivity could be achieved, the impact on could be enormous. However, a useful room temperature superconductor for most applications must possess a T c somewhat above room temperature and must be capable of sustaining superconductivity in the presence of magnetic fields while carrying a significant current load. The authors will return to the subject of just what characteristics one might seek for a compound to be a room temperature superconductor. 30 refs., 3 figs., 1 tab

Published assessments bearing on the future use of ceramic superconductors by the electric power sector

International Nuclear Information System (INIS)

Giese, R.F.; Wolsky, A.M.

1992-01-01

Much has been written about ceramic superconductors since their discovery in 1986. Most of this writing reports and describes scientific research. However, some authors have sought to put this research in context: to assess where the field stands, what might be technically feasible, what might be economically feasible, and what potential impacts ceramic superconductors will bring to the electric power sector. This report's purpose is to make the results of already published assessments readily available. To that end, this report lists and provides abstracts for various technical and economic assessments related to applications of High-Temperature Superconductors (HTS) to the electric power sector. Those studies deemed most important are identified and summarized. These assessments were identified by two means. First, members of the Executive Committee identified some reports as worthy of consideration and forwarded them to Argonne National Laboratory. Twelve assessments were selected. Each of these is listed and summarized in the following section. Second, a bibliographic search was performed on five databases: INSPEC, NTIS, COMPENDEX, Energy Science ampersand Technology, and Electric Power Database. The search consisted of first selecting all papers related to High Temperature Superconductors. Then papers related to SMES, cables, generators, motors, fault current limiters, or electric utilities were selected. When suitable variants of the above terms were included, this resulted in a selection of 493 citations. These citations were subjected to review by the authors. A number of citations were determined to be inappropriate (e.g. a number referred to digital transmission lines for electronics and communications applications). The reduced list consisted of 200 entries. Each of these citations, with an abstract, is presented in the following sections

Published assessments bearing on the future use of ceramic superconductors by the electric power sector

Energy Technology Data Exchange (ETDEWEB)

Giese, R.F.; Wolsky, A.M.

1992-08-25

Much has been written about ceramic superconductors since their discovery in 1986. Most of this writing reports and describes scientific research. However, some authors have sought to put this research in context: to assess where the field stands, what might be technically feasible, what might be economically feasible, and what potential impacts ceramic superconductors will bring to the electric power sector. This report's purpose is to make the results of already published assessments readily available. To that end, this report lists and provides abstracts for various technical and economic assessments related to applications of High-Temperature Superconductors (HTS) to the electric power sector. Those studies deemed most important are identified and summarized. These assessments were identified by two means. First, members of the Executive Committee identified some reports as worthy of consideration and forwarded them to Argonne National Laboratory. Twelve assessments were selected. Each of these is listed and summarized in the following section. Second, a bibliographic search was performed on five databases: INSPEC, NTIS, COMPENDEX, Energy Science Technology, and Electric Power Database. The search consisted of first selecting all papers related to High Temperature Superconductors. Then papers related to SMES, cables, generators, motors, fault current limiters, or electric utilities were selected. When suitable variants of the above terms were included, this resulted in a selection of 493 citations. These citations were subjected to review by the authors. A number of citations were determined to be inappropriate (e.g. a number referred to digital transmission lines for electronics and communications applications). The reduced list consisted of 200 entries. Each of these citations, with an abstract, is presented in the following sections.

Published assessments bearing on the future use of ceramic superconductors by the electric power sector

Energy Technology Data Exchange (ETDEWEB)

Giese, R.F.; Wolsky, A.M.

1992-08-25

Much has been written about ceramic superconductors since their discovery in 1986. Most of this writing reports and describes scientific research. However, some authors have sought to put this research in context: to assess where the field stands, what might be technically feasible, what might be economically feasible, and what potential impacts ceramic superconductors will bring to the electric power sector. This report`s purpose is to make the results of already published assessments readily available. To that end, this report lists and provides abstracts for various technical and economic assessments related to applications of High-Temperature Superconductors (HTS) to the electric power sector. Those studies deemed most important are identified and summarized. These assessments were identified by two means. First, members of the Executive Committee identified some reports as worthy of consideration and forwarded them to Argonne National Laboratory. Twelve assessments were selected. Each of these is listed and summarized in the following section. Second, a bibliographic search was performed on five databases: INSPEC, NTIS, COMPENDEX, Energy Science & Technology, and Electric Power Database. The search consisted of first selecting all papers related to High Temperature Superconductors. Then papers related to SMES, cables, generators, motors, fault current limiters, or electric utilities were selected. When suitable variants of the above terms were included, this resulted in a selection of 493 citations. These citations were subjected to review by the authors. A number of citations were determined to be inappropriate (e.g. a number referred to digital transmission lines for electronics and communications applications). The reduced list consisted of 200 entries. Each of these citations, with an abstract, is presented in the following sections.

Preparation of a ceramic superconductor from ultrafine particles by freeze-dry process in Ba-Y-Cu-O system

International Nuclear Information System (INIS)

Chen Zuyao; Qian Yitai; Wan Yanjian; Rong Jingfang; Zhang Han; Pan Guoqiang; Zhao Yong; Zhang Qirui

1989-01-01

Freeze-dry technique is first reported for preparing ceramic ultrafines. The single-phase complex oxide Ba 2 YCu 3 O/sub 9-δ/, a poly-crystallized compound, and ceramic superconductor have been synthesized successfully. The experimental results show that not only is the ceramic superconductor obtained uniform with fine particles and excellent superconductivity, but the conditions for solid reactions are relatively limited

The development of research on high temperature superconductors in Malaysia

International Nuclear Information System (INIS)

Shaari, A.H.; Hashim, M.; Dalimin, M.N.

1989-01-01

The background of the recent discovery of high-temperature oxide superconductor is given. This new discovery has driven scientists of different disciplines from many parts of the world into the race. Even those researchers from the developing countries are able to join the band wagon of the frontier research due to the convenience of working at temperatures well above that of liquid nitrogen. In Malaysia, some aspects of preparations and characterization of Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O ceramics are studied. The 90 K transition temperature is observed in Y-Ba-Cu-O. (Auth.). 10 figs.; 5 refs

Melt processed high-temperature superconductors

CERN Document Server

1993-01-01

The achievement of large critical currents is critical to the applications of high-temperature superconductors. Recent developments have shown that melt processing is suitable for producing high J c oxide superconductors. Using magnetic forces between such high J c oxide superconductors and magnets, a person could be levitated.This book has grown largely out of research works on melt processing of high-temperature superconductors conducted at ISTEC Superconductivity Research Laboratory. The chapters build on melt processing, microstructural characterization, fundamentals of flux pinning, criti

The defect structure of ceramic high Tc superconductors

International Nuclear Information System (INIS)

Van Tendeloo, G.; Amelinckx, S.; Zandbergen, H.W.; Verwerft, M.

1989-01-01

In this paper an overview is given of electron microscopy studies on the different ceramic superconductors: YBa 2 Cu 3 O 7 , Bi(Tl)-Sr(Ba)- Ca-Cu-O and Pb 2 Sr 2 Y 0.5 Ca 0.5 Cu 3 O x . Planar defects in these materials play an important role in the superconducting properties. Their structural characteristics are discussed

AC susceptibility response of bulk YBCO superconductors in the presence of a temperature gradient

International Nuclear Information System (INIS)

Bodi, A.C.; Kirschner, I.

1997-01-01

Low-frequency AC susceptibility measurements on ceramic YBCO superconductors carried out at the presence of a quasi-one-dimensional temperature gradient are compared with those made without the temperature gradient. The values of the different characteristic temperatures measured on samples without and with a temperature gradient are identical but in the second case its characteristic temperature is a medium value. When the temperature gradient is constant on the sample the arithmetic medium value of the local temperatures is the effective characteristic temperature different phenomena. (orig.)

High temperature superconductor accelerator magnets

NARCIS (Netherlands)

van Nugteren, J.

2016-01-01

For future particle accelerators bending dipoles are considered with magnetic fields exceeding 20T. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and

NSSEFF Designing New Higher Temperature Superconductors

Science.gov (United States)

2017-04-13

AFRL-AFOSR-VA-TR-2017-0083 NSSEFF - DESIGINING NEW HIGHER TEMPERATURE SUPERCONDUCTORS Meigan Aronson THE RESEARCH FOUNDATION OF STATE UNIVERSITY OF...2015 4. TITLE AND SUBTITLE NSSEFF - DESIGINING NEW HIGHER TEMPERATURE SUPERCONDUCTORS 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550-10-1-0191 5c...materials, identifying the most promising candidates. 15. SUBJECT TERMS TEMPERATURE, SUPERCONDUCTOR 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

Study of the glass formation of high temperature superconductors

Science.gov (United States)

Ethridge, Edwin C.; Kaukler, William F.; Rolin, Terry

1992-01-01

A number of compositions of ceramic oxide high T(sub c) superconductors were elevated for their glass formation ability by means of rapid thermal analysis during quenching, optical, and electron microscopy of the quenched samples, and with subsequent DSC measurements. Correlations between experimental measurements and the methodical composition changes identified the formulations of superconductors that can easily form glass. The superconducting material was first formed as a glass; then, with subsequent devitrification, it was formed into a bulk crystalline superconductor by a series of processing methods.

Use of the inverse temperature profile in microwave processing of advanced ceramics

International Nuclear Information System (INIS)

Binner, J.G.P.; Al-Dawery, I.A.; Aneziris, C.; Cross, T.E.

1992-01-01

Attempts are being made to exploit the inverse temperature profile which can be developed with microwave heating with respect to the processing of certain advanced ceramics. This paper discusses the results obtained to date during the microwave sintering of YBCO high-T c superconductors and the microwave reaction bonding of silicon nitride

High temperature superconductor current leads

International Nuclear Information System (INIS)

Zeimetz, B.; Liu, H.K.; Dou, S.X.

1996-01-01

Full text: The use of superconductors in high electrical current applications (magnets, transformers, generators etc.) usually requires cooling with liquid Helium, which is very expensive. The superconductor itself produces no heat, and the design of Helium dewars is very advanced. Therefore most of the heat loss, i.e. Helium consumption, comes from the current lead which connects the superconductor with its power source at room temperature. The current lead usually consists of a pair of thick copper wires. The discovery of the High Temperature Superconductors makes it possible to replace a part of the copper with superconducting material. This drastically reduces the heat losses because a) the superconductor generates no resistive heat and b) it is a very poor thermal conductor compared with the copper. In this work silver-sheathed superconducting tapes are used as current lead components. The work comprises both the production of the tapes and the overall design of the leads, in order to a) maximize the current capacity ('critical current') of the superconductor, b) minimize the thermal conductivity of the silver clad, and c) optimize the cooling conditions

An investigation of high-temperature irradiation test program of new ceramic materials

International Nuclear Information System (INIS)

Ishino, Shiori; Terai, Takayuki; Oku, Tatsuo

1999-08-01

The Japan Atomic Energy Research Institute entrusted the Atomic Energy Society of Japan with an investigation into the trend of irradiation processing/damage research on new ceramic materials. The present report describes the result of the investigation, which was aimed at effective execution of irradiation programs using the High Temperature Engineering Test Reactor (HTTR) by examining preferential research subjects and their concrete research methods. Objects of the investigation were currently on-going preliminary tests of functional materials (high-temperature oxide superconductor and high-temperature semiconductor) and structural materials (carbon/carbon and SiC/SiC composite materials), together with newly proposed subjects of, e.g., radiation effects on ceramics-coated materials and super-plastic ceramic materials as well as microscopic computer simulation of deformation and fracture of ceramics. These works have revealed 1) the background of each research subject, 2) its objective and significance from viewpoints of science and engineering, 3) research methodology in stages from preliminary tests to real HTTR irradiation, and 4) concrete HTTR-irradiation methods which include main specifications of test specimens, irradiation facilities and post-irradiation examination facilities and apparatuses. The present efforts have constructed the important fundamentals in the new ceramic materials field for further planning and execution of the innovative basic research on high-temperature engineering. (author)

Two decades on[Research into high-temperature superconductors

Energy Technology Data Exchange (ETDEWEB)

Durrani, M. [Physics World (United Kingdom)

2006-04-15

Research into high-temperature superconductors should focus on experiment, not theory. While the world looked on in horror at the events unfolding at the Chernobyl nuclear-power plant in the Soviet Union 20 years ago this month, another significant - but far less reported - development in the world of physics had just taken place. On 17 April 1986 a short paper by Georg Bednorz and Alexander Mueller arrived at the offices of Zeitschrift fuer Physik in Heidelberg, Germany. The two physicists, based at IBM's Zurich Research Laboratory in Switzerland, announced they had made a material from barium, lanthanum, copper and oxygen that could conduct electricity without resistance when cooled below a transition temperature, T{sub c}, of about 30 K. It was the world's first 'high-temperature' superconductor. Driven by the dream of materials that can superconduct at room temperature, experimentalists scurried back to their labs. Within a year, a T{sub c} of 90 K in another material had been reported and by October 1987 Bednorz and Mueller had been crowned with a Nobel prize. While papers on high-temperature superconductivity have continued to stream out since those heady days, progress has been slower than expected. Applications like levitating trains and resistance-free power cables are only now starting to come to market. Scientists have been unable to make superconducting wires that work much above 130 K, while a reliable theory of high-temperature superconductivity remains elusive. Even if we had such a theory, it is not clear that it would predict which materials might superconduct at room temperature. After all, the Bardeen-Cooper-Schrieffer theory, which explains the behaviour of low-temperature superconductors with admirable success, said nothing about the superconducting properties of Bednorz and Mueller's copper-oxide ceramics. What successes there have been over the last 20 years - such as the recent discoveries that iron, single crystals

Evaluation of oxygenation time in SmBa2Cu3O7-δ superconductors ceramics in air and ozone atmospheres

International Nuclear Information System (INIS)

Viana, P.R.P; Cunha, A.G.

2010-01-01

High temperature superconductors (HTSC) represent a major milestone in science. During the preparation of superconductors, oxygenation plays a key role, because oxygenation determines the distribution of charge carriers in these plans through the superconducting Cu-O and hence superconductivity. This paper proposes the preparation of polycrystalline superconductors using the ceramic method, and the step of oxygenation made with ozone gas (O 3 ). Ozone exerts chemical pressure on the compound, which has oxygen vacancies in its structure after the step of synthesis. The work was performed by varying the time between oxygenation 20, 40, 80 and 160 hours, with samples going through a process of oxygenation at 350 deg C after the step of synthesis. This study evaluates the time effect as oxygen can improve the superconducting properties such as resistivity and magnetic susceptibility. (author)

Deformation of high-temperature superconductors

International Nuclear Information System (INIS)

Goretta, K.C.; Routbort, J.L.; Miller, D.J.; Chen, N.; Dominguez-Rodriguez, A.; Jimenez-Melendo, M.; De Arellano-Lopez, A.R.

1994-08-01

Of the many families of high-temperature superconductors, only the properties of those discovered prior to 1989 - Y-Ba-Cu-O, Tl-Ba(Sr)-Ca-Cu-O, and Bi(Pb)-Sr-Ca-Cu-O - have been studied extensively. Deformation tests have been performed on YBa 2 Cu 3 O x (Y-123), YBa 2 Cu 4 O x (Y-124), TlBa 2 Ca 2 Cu 3 O x (Bi-2223). The tests have revealed that plasticity is generally limited in these compounds and that the rate-controlling diffusional kinetics for creep are very slow. Nevertheless, hot forming has proved to be quite successful for fabrication of bulk high-temperature superconductors, so long as deformation rates are low or large hydrostatic stresses are applied. Steady-state creep data have proved to be useful in designing optimal heat treatments for superconductors and in support of more-fundamental diffusion experiments. The high-temperature superconductors are highly complex oxides, and it is a challenge to understand their deformation responses. In this paper, results of interest and operant creep mechanisms will be reviewed

Passivation Of High-Temperature Superconductors

Science.gov (United States)

Vasquez, Richard P.

1991-01-01

Surfaces of high-temperature superconductors passivated with native iodides, sulfides, or sulfates formed by chemical treatments after superconductors grown. Passivating compounds nearly insoluble in and unreactive with water and protect underlying superconductors from effects of moisture. Layers of cuprous iodide and of barium sulfate grown. Other candidate passivating surface films: iodides and sulfides of bismuth, strontium, and thallium. Other proposed techniques for formation of passivating layers include deposition and gas-phase reaction.

Shape-forming and densification of ceramic superconductors

International Nuclear Information System (INIS)

Prakash, Om; Thomas, C.A.; Magadum, A.P.; Anklekar, R.M.; Khosla, N.K.; Kumar, Sunil; Chaudhuri, B.; Ramesh, M.; Rao, B.T.; Rama Mohan, T.R.

1991-01-01

Processing studies on varied shape-forming and densification of bulk ceramic superconductor, YBa 2 Cu 3 Osub(7-δ), are reported in this paper. Polyvinyl butyral-polyethylene glycol-trichloroethylene has been found to be the best binder-plasticizer-solvent system in plastic shape-forming. The effect of initial particle morphology on final densification has been the most sensitive single parameter as compared to compaction pressure and final sintering durations at ∼930degC. 1-2-3 powders of mean particle size ∼1.94μm have yielded sintered densities ∼92%T.D. albeit with lower oxygen intake Osub(6.7). (author). 8 refs., 8 figs

High temperature superconductor cable concepts for fusion magnets

CERN Document Server

AUTHOR|(CDS)2078397

2013-01-01

Three concepts of high temperature superconductor cables carrying kA currents (RACC, CORC and TSTC) are investigated, optimized and evaluated in the scope of their applicability as conductor in fusion magnets. The magnetic field and temperature dependence of the cables is measured; the thermal expansion and conductivity of structure, insulation and filling materials are investigated. High temperature superconductor winding packs for fusion magnets are calculated and compared with corresponding low temperature superconductor cases.

Slim-look superconductors lead the applications race

International Nuclear Information System (INIS)

Hellemans, A.

1996-01-01

When George Bednorz and Alex Mueller discovered high-temperature superconductivity (HTS) 10 years ago at IBM research labs near Zurich, newspapers, magazines, and TV news reports across the world were soon filled with forecasts of super-efficient power lines, trains floating along at unimaginable speeds levitated by superconducting magnets, and swift, silent ships powered by magnetohydro-dynamic drives. Chunks of these new ceramic materials, which can conduct electricity free form all resistance at temperatures high enough to require only cheap liquid nitrogen as a coolant rather than expensive liquid helium, would pave the way to the technological future. However, researchers are now thinking of thin films rather than chunks of HTS material. Superconductors do not always require long wires and coils or high currents. Electronic devices make from HTS ceramics have some remarkable properties, and all you need is a thin layer of film of the ceramic grown on a rigid substrate. This article discusses the possibilities of applications using new thin film superconductors

Reproducible, large-scale production of thallium-based high-temperature superconductors

International Nuclear Information System (INIS)

Gay, R.L.; Stelman, D.; Newcomb, J.C.; Grantham, L.F.; Schnittgrund, G.D.

1990-01-01

This paper reports on the development of a large scale spray-calcination technique generic to the preparation of ceramic high-temperature superconductor (HTSC) powders. Among the advantages of the technique is that of producing uniformly mixed metal oxides on a fine scale. Production of both yttrium and thallium-based HTSCs has been demonstrated using this technique. In the spray calciner, solutions of the desired composition are atomized as a fine mist into a hot gas. Evaporation and calcination are instantaneous, yielding an extremely fine, uniform oxide powder. The calciner is 76 cm in diameter and can produce metal oxide powder at relatively large rates (approximately 100 g/h) without contamination

Transport measurements in superconductors: critical current of granular high TC ceramic superconductor samples

International Nuclear Information System (INIS)

Passos, W.A.C.

2016-01-01

This work presents a method to obtain critical current of granular superconductors. We have carried out transport measurements (ρxT curves and VxI curves) in a YBa_2Cu_3O_7_-_δ sample to determine critical current density of it. Some specimens reveal a 'semiconductor-like' behavior (electrical resistivity decreases with increasing temperatures above critical temperature T_c of material) competing with superconductor behavior. Due to high granular fraction of the sample, these competition is clearly noted in ρxT curves. Measurements carried out from 0 to 8500 Oe of applied field show the same behavior, and the critical current density of the samples is shown. (author)

High temperature superconductors and other superfluids

CERN Document Server

Alexandrov, A S

2017-01-01

Written by eminent researchers in the field, this text describes the theory of superconductivity and superfluidity starting from liquid helium and a charged Bose-gas. It also discusses the modern bipolaron theory of strongly coupled superconductors, which explains the basic physical properties of high-temperature superconductors. This book will be of interest to fourth year graduate and postgraduate students, specialist libraries, information centres and chemists working in high-temperature superconductivity.

Resistive current limiter with high-temperature superconductors. Final report

International Nuclear Information System (INIS)

Schubert, M.

1995-12-01

Fundamental results of the possibility of using high temperature superconductors (HTSC) in resistive fault current limiters are discussed. Measurement of the homogeneity of BSCCO-powder-in-tube materials were made. In addition, investigations of the transition from superconducting to normalconducting state under AC-current conditions were carried out. Based on these results, simulations of HTSC-materials on ceramic substrate were made and recent results are presented. Important results of the investigations are: 1. Current-limiting without external trigger only possible when the critical current density of HTSC exceeds 10 4 A/cm 2 . 2. Inhomogeneities sometimes cause problems with local destruction. This can be solved by parallel-elements or external trigger. 3. Fast current-limiting causes overvoltages which can be reduced by using parallel-elements. (orig.) [de

Temperature dependence of the phonon structure in the high-temperature superconductor Bi2Sr2CaCu2O8 studied by infrared reflectance spectroscopy

International Nuclear Information System (INIS)

Kamaras, K.; Herr, S.L.; Porter, C.D.; Tanner, D.B.; Etemad, S.; Tarascon, J.

1991-01-01

We have investigated a ceramic sample of the high-temperature superconductor Bi 2 Sr 2 CaCu 2 O 8 (T c =85 K) by infrared and visible reflectance spectroscopy at several temperatures both below and above the superconducting transition. We find that the temperature variation in the vibrational region is associated with minima or antiresonance features of the optical conductivity, instead of maxima, indicating strong Fano-type electron-phonon interaction and implying that the phonon structure in the infrared is strongly affected by the ab-plane response

High Temperature Superconductor Machine Prototype

DEFF Research Database (Denmark)

Mijatovic, Nenad; Jensen, Bogi Bech; Træholt, Chresten

2011-01-01

A versatile testing platform for a High Temperature Superconductor (HTS) machine has been constructed. The stationary HTS field winding can carry up to 10 coils and it is operated at a temperature of 77K. The rotating armature is at room temperature. Test results and performance for the HTS field...

Potentialities in electronics of new high critical temperature superconductors

International Nuclear Information System (INIS)

Hartemann, P.

1989-01-01

The main electronic applications of superconductors involve the signal processing, the electromagnetic wave detection and the magnetometry. Characteristics of devices based on conventional superconductors cooled by liquid helium are given and the changes induced by incorporating high-temperature superconductors are estimated. After a survey of new superconductor properties, the superconducting devices for analog or digital signal processing are reviewed. The gains predicted for high-temperature superconducting analog devices are considered in greater detail. Different sections deal with the infrared or (sub)millimeter wave detection. The most sensitive apparatuses for magnetic measurements are based on SQUIDs. Features of SQUIDs made of granular high-temperature superconducting material samples (grain boundaries behave as barriers of intrinsic junctions) are discussed [fr

Searching for superconductors with high critical temperature

Energy Technology Data Exchange (ETDEWEB)

Chao, C

1977-08-18

Critical temperature of superconductors can be and must be raised so that their range of application can be broadened. It was estimated that, in 3 to 5 years, superconductor electric generators might be used in nuclear submarines and/or other applications where the requirements of small volume and light weight are critical. The BCS theory was recapitulated. Possible methods of achieving higher critical temperature were proposed and discussed.

High Temperature Superconductor Resonator Detectors

Data.gov (United States)

National Aeronautics and Space Administration — High Temperature Superconductor (HTS) infrared detectors were studied for years but never matured sufficiently for infusion into instruments. Several recent...

Technique of Critical Current Density Measurement of Bulk Superconductor with Linear Extrapolation Method

International Nuclear Information System (INIS)

Adi, Wisnu Ari; Sukirman, Engkir; Winatapura, Didin S.

2000-01-01

Technique of critical current density measurement (Jc) of HTc bulk ceramic superconductor has been performed by using linear extrapolation with four-point probes method. The measurement of critical current density HTc bulk ceramic superconductor usually causes damage in contact resistance. In order to decrease this damage factor, we introduce extrapolation method. The extrapolating data show that the critical current density Jc for YBCO (123) and BSCCO (2212) at 77 K are 10,85(6) Amp.cm - 2 and 14,46(6) Amp.cm - 2, respectively. This technique is easier, simpler, and the use of the current flow is low, so it will not damage the contact resistance of the sample. We expect that the method can give a better solution for bulk superconductor application. Key words. : superconductor, critical temperature, and critical current density

Epitaxial heterojunctions of oxide semiconductors and metals on high temperature superconductors

Science.gov (United States)

Vasquez, Richard P. (Inventor); Hunt, Brian D. (Inventor); Foote, Marc C. (Inventor)

1994-01-01

Epitaxial heterojunctions formed between high temperature superconductors and metallic or semiconducting oxide barrier layers are provided. Metallic perovskites such as LaTiO3, CaVO3, and SrVO3 are grown on electron-type high temperature superconductors such as Nd(1.85)Ce(0.15)CuO(4-x). Alternatively, transition metal bronzes of the form A(x)MO(3) are epitaxially grown on electron-type high temperature superconductors. Also, semiconducting oxides of perovskite-related crystal structures such as WO3 are grown on either hole-type or electron-type high temperature superconductors.

Low-Temperature Synthesis Routes to Intermetallic Superconductors

Energy Technology Data Exchange (ETDEWEB)

Schaak, Raymond E

2008-01-08

Over the past few years, our group has gained expertise at developing low-temperature solution-based synthetic pathways to complex nanoscale solids, with particular emphasis on nanocrystalline intermetallic compounds. Our synthetic capabilities are providing tools to reproducibly generate intermetallic nanostructures with simultaneous control over crystal structure, composition, and morphology. This DOE-funded project aims to expand these capabilities to intermetallic superconductors. This could represent an important addition to the tools that are available for the synthesis and processing of intermetallic superconductors, which traditionally utilize high-temperature, high-pressure, thin film, or gas-phase vacuum deposition methods. Our current knowledge of intermetallic superconductors suggests that significant enhancements could result from the inherent benefits of low-temperature solution synthesis, e.g. metastable phase formation, control over nanoscale morphology to facilitate size-dependent property studies, robust and inexpensive processability, low-temperature annealing and consolidation, and impurity incorporation (for doping, stoichiometry control, flux pinning, and improving the critical fields). Our focus is on understanding the superconducting properties as a function of synthetic route, crystal structure, crystallite size, and morphology, and developing the synthetic tools necessary to accomplish this. This research program can currently be divided into two classes of superconducting materials: intermetallics (transition metal/post transition metal) and metal carbides/borides. Both involve the development and exploitation of low-temperature synthesis routes followed by detailed characterization of structures and properties, with the goal of understanding how the synthetic pathways influence key superconducting properties of selected target materials. Because of the low-temperature methods used to synthesize them and the nanocrystalline morphologies

High temperature superconductors applications in telecommunications

Energy Technology Data Exchange (ETDEWEB)

Kumar, A.A.; Li, J.; Zhang, M.F. [Prairie View A& M Univ., Texas (United States)

1994-12-31

The purpose of this paper is twofold: to discuss high temperature superconductors with specific reference to their employment in telecommunications applications; and to discuss a few of the limitations of the normally employed two-fluid model. While the debate on the actual usage of high temperature superconductors in the design of electronic and telecommunications devices-obvious advantages versus practical difficulties-needs to be settled in the near future, it is of great interest to investigate the parameters and the assumptions that will be employed in such designs. This paper deals with the issue of providing the microwave design engineer with performance data for such superconducting waveguides. The values of conductivity and surface resistance, which are the primary determining factors of a waveguide performance, are computed based on the two-fluid model. A comparison between two models-a theoretical one in terms of microscopic parameters (termed Model A) and an experimental fit in terms of macroscopic parameters (termed Model B)-shows the limitations and the resulting ambiguities of the two-fluid model at high frequencies and at temperatures close to the transition temperature. The validity of the two-fluid model is then discussed. Our preliminary results show that the electrical transport description in the normal and superconducting phases as they are formulated in the two-fluid model needs to be modified to incorporate the new and special features of high temperature superconductors. Parameters describing the waveguide performance-conductivity, surface resistance and attenuation constant-will be computed. Potential applications in communications networks and large scale integrated circuits will be discussed. Some of the ongoing work will be reported. In particular, a brief proposal is made to investigate of the effects of electromagnetic interference and the concomitant notion of electromagnetic compatibility (EMI/EMC) of high T{sub c} superconductors.

High temperature superconductors applications in telecommunications

International Nuclear Information System (INIS)

Kumar, A.A.; Li, J.; Zhang, M.F.

1994-01-01

The purpose of this paper is twofold: to discuss high temperature superconductors with specific reference to their employment in telecommunications applications; and to discuss a few of the limitations of the normally employed two-fluid model. While the debate on the actual usage of high temperature superconductors in the design of electronic and telecommunications devices-obvious advantages versus practical difficulties-needs to be settled in the near future, it is of great interest to investigate the parameters and the assumptions that will be employed in such designs. This paper deals with the issue of providing the microwave design engineer with performance data for such superconducting waveguides. The values of conductivity and surface resistance, which are the primary determining factors of a waveguide performance, are computed based on the two-fluid model. A comparison between two models-a theoretical one in terms of microscopic parameters (termed Model A) and an experimental fit in terms of macroscopic parameters (termed Model B)-shows the limitations and the resulting ambiguities of the two-fluid model at high frequencies and at temperatures close to the transition temperature. The validity of the two-fluid model is then discussed. Our preliminary results show that the electrical transport description in the normal and superconducting phases as they are formulated in the two-fluid model needs to be modified to incorporate the new and special features of high temperature superconductors. Parameters describing the waveguide performance-conductivity, surface resistance and attenuation constant-will be computed. Potential applications in communications networks and large scale integrated circuits will be discussed. Some of the ongoing work will be reported. In particular, a brief proposal is made to investigate of the effects of electromagnetic interference and the concomitant notion of electromagnetic compatibility (EMI/EMC) of high T c superconductors

Targets on the basis of ferrites and high-temperature superconductors for ion-plasma sputtering

International Nuclear Information System (INIS)

Lepeshev, A.A.; Saunin, V.N.; Telegin, S.V.; Polyakova, K.P.; Seredkin, V.A.; Pol'skij, A.I.

2000-01-01

Paper describes a method to produce targets for ion-plasma sputtering using plasma splaying of the appropriate powders on a cooled metal basis. Application of the plasma process was demonstrated to enable to produce complex shaped targets under the controlled atmosphere on the basis of ceramic materials ensuring their high composition homogeneity, as well as, reliable mechanical and thermal contact of the resultant coating with the base. One carried out experiments in ion-plasma sputtering of targets to prepare ferrite polycrystalline films to be used in magnetooptics and to prepare high-temperature superconductor epitaxial films [ru

Theoretical modeling of critical temperature increase in metamaterial superconductors

Science.gov (United States)

Smolyaninov, Igor; Smolyaninova, Vera

Recent experiments have demonstrated that the metamaterial approach is capable of drastic increase of the critical temperature Tc of epsilon near zero (ENZ) metamaterial superconductors. For example, tripling of the critical temperature has been observed in Al-Al2O3 ENZ core-shell metamaterials. Here, we perform theoretical modelling of Tc increase in metamaterial superconductors based on the Maxwell-Garnett approximation of their dielectric response function. Good agreement is demonstrated between theoretical modelling and experimental results in both aluminum and tin-based metamaterials. Taking advantage of the demonstrated success of this model, the critical temperature of hypothetic niobium, MgB2 and H2S-based metamaterial superconductors is evaluated. The MgB2-based metamaterial superconductors are projected to reach the liquid nitrogen temperature range. In the case of an H2S-based metamaterial Tc appears to reach 250 K. This work was supported in part by NSF Grant DMR-1104676 and the School of Emerging Technologies at Towson University.

High point for CERN and high-temperature superconductors

CERN Multimedia

2007-01-01

Amalia Ballarino is named the Superconductor Industry Person of the year 2006. Amalia Ballarino showing a tape of high-superconducting material used for the LHC current leads.The CERN project leader for the high-temperature superconducting current leads for the LHC, Amalia Ballarino, has received the award for "Superconductor Industry Person of the Year". This award, the most prestigious international award in the development and commercialization of superconductors, is presented by the leading industry newsletter "Superconductor Week". Amalia Ballarino was selected from dozens of nominations from around the world by a panel of recognized leading experts in superconductivity. "It is a great honour for me," says Amalia Ballarino. "It has been many years of hard work, and it’s a great satisfaction to see that the work has been completed successfully." Amalia Ballarino has been working on high-temperature superconducting materials sin...

Plastic deformation of YBa2Cu3O7-x superconductor compound

International Nuclear Information System (INIS)

Torres V, G.; Moreno, J.E.

1988-01-01

The high temperature superconductor YBa 2 Cu 3 O 7-x shown a brittle behavior when deformed under ambient conditions. If a hydrostatic state of stress is imposed with a metal matrix, it is possible to induce exttended plastic deformations as a great as 200% were achieved using this method without loosing the superconductivity in the ceramic. The observed deformations mechanisms are similar to those observed in the superplastic metals and the boundary ceramic metal matrix was found to be highly coherent. This method opens a new technique that can be apllied in the manufacture of superconductor wire. (author) [pt

Advanced technologies related to a high temperature superconductor for small laboratory experiments

International Nuclear Information System (INIS)

Ogawa, Yuichi; Mito, Toshiyuki; Yanagi, Nagato

2006-01-01

Advanced technologies related to a high temperature superconductor materials and small refrigerator are reviewed. Mini-RT/RT-1 is designed and constructed as a plasma examination device. The element technology of low temperature apparatus, the results of performance tests and application examples are explained. The superconductors such as Bi 2 Sr 2 CaCu 2 O 8 (Bi-2212) for the low temperature phase, Bi 2 Sr 2 Ca 2 Cu 3 O 10 (Bi-2223) for the high temperature phase, and YBa 2 Cu 3 O y (YBCO or Y123) are described. Advanced 4K-Giford-Mcmahon (GM) refrigerator on the market put superconductor coil made of low temperature superconductor metals to practical use and extends its application field. Small laboratory is able to experiment on the high temperature superconductor materials. (S.Y.)

High-Temperature Cuprate Superconductors Experiment, Theory, and Applications

CERN Document Server

Plakida, Nikolay Maksimilianovich

2010-01-01

High-Temperature Cuprate Superconductors provides an up-to-date and comprehensive review of the properties of these fascinating materials. The essential properties of high-temperature cuprate superconductors are reviewed on the background of their theoretical interpretation. The experimental results for structural, magnetic, thermal, electric, optical and lattice properties of various cuprate superconductors are presented with respect to relevant theoretical models. A critical comparison of various theoretical models involving strong electron correlations, antiferromagnetic spin fluctuations, phonons and excitons provides a background for understanding of the mechanism of high-temperature superconductivity. Recent achievements in their applications are also reviewed. A large number of illustrations and tables gives valuable information for specialists. A text-book level presentation with formulation of a general theory of strong-coupling superconductivity will help students and researches to consolidate their...

Manufacturing of Superconductors

DEFF Research Database (Denmark)

Bech, Jakob Ilsted; Bay, Niels

Superconducting tapes based on the ceramic high temperature superconductor (HTS) is a new promising product for high current applications such as electro-magnets and current transmission cables. The tapes are made by the oxide powder in tube (OPIT) method implying drawing and rolling of silver...... tubes containing ceramic powder. The final product is a composite tape, where ceramic superconducting fibres are embedded in a silver matrix. The critical current density Je [kA/cm 2 ] is the primary quality parameter of the product. The quality of the superconducting tape depends very much...... in the individual fibres. · The stresses and strains in the deformation zone are analysed. It is concluded that more detailed mechanical tests and a more detailed constitutive plasticity model is desirable in order to improve the precision of the numerical modelling. New test equipment is designed implying the new...

Ceramic high temperature superconductors for high current applications

Energy Technology Data Exchange (ETDEWEB)

Christiansen, J.

1996-12-31

Composite Reaction Texturing (CRT) is a technique which uses a fine distribution of pre-aligned seeds as nucleating sites for texturing oxide superconductors. It has successfully been applied to the texturing of Bi-2212 compounds. A furhter application of CRT is reported in which Y-123 is biaxially textured using seeds of other Rare Earth-123 compounds with higher melting points as nucleating sites. The resultant textured microstructure exhibits mainly low angle grain boundaries (up to 5 deg. misorientation). Results will be presented on the seed alignment techniques, the development of microstructure during reaction of the composite preform and preliminary measurements of electromagnetic properties. (au). 111 refs.

Ceramic high temperature superconductors for high current applications

Energy Technology Data Exchange (ETDEWEB)

Christiansen, J

1997-12-31

Composite Reaction Texturing (CRT) is a technique which uses a fine distribution of pre-aligned seeds as nucleating sites for texturing oxide superconductors. It has successfully been applied to the texturing of Bi-2212 compounds. A furhter application of CRT is reported in which Y-123 is biaxially textured using seeds of other Rare Earth-123 compounds with higher melting points as nucleating sites. The resultant textured microstructure exhibits mainly low angle grain boundaries (up to 5 deg. misorientation). Results will be presented on the seed alignment techniques, the development of microstructure during reaction of the composite preform and preliminary measurements of electromagnetic properties. (au). 111 refs.

Ceramic high temperature superconductors for high current applications

International Nuclear Information System (INIS)

Christiansen, J.

1996-01-01

Composite Reaction Texturing (CRT) is a technique which uses a fine distribution of pre-aligned seeds as nucleating sites for texturing oxide superconductors. It has successfully been applied to the texturing of Bi-2212 compounds. A furhter application of CRT is reported in which Y-123 is biaxially textured using seeds of other Rare Earth-123 compounds with higher melting points as nucleating sites. The resultant textured microstructure exhibits mainly low angle grain boundaries (up to 5 deg. misorientation). Results will be presented on the seed alignment techniques, the development of microstructure during reaction of the composite preform and preliminary measurements of electromagnetic properties. (au)

Stress analysis in high-temperature superconductors under pulsed field magnetization

Science.gov (United States)

Wu, Haowei; Yong, Huadong; Zhou, Youhe

2018-04-01

Bulk high-temperature superconductors (HTSs) have a high critical current density and can trap a large magnetic field. When bulk superconductors are magnetized by the pulsed field magnetization (PFM) technique, they are also subjected to a large electromagnetic stress, and the resulting thermal stress may cause cracking of the superconductor due to the brittle nature of the sample. In this paper, based on the H-formulation and the law of heat transfer, we can obtain the distributions of electromagnetic field and temperature, which are in qualitative agreement with experiment. After that, based on the dynamic equilibrium equations, the mechanical response of the bulk superconductor is determined. During the PFM process, the change in temperature has a dramatic effect on the radial and hoop stresses, and the maximum radial and hoop stress are 24.2 {{MPa}} and 22.6 {{MPa}}, respectively. The mechanical responses of a superconductor for different cases are also studied, such as the peak value of the applied field and the size of bulk superconductors. Finally, the stresses are also presented for different magnetization methods.

Electro-physical properties of superconducting ceramic thick film prepared by partial melting method.

Science.gov (United States)

Lee, Sang Heon

2013-05-01

BiSrCaCuO superconductor thick films were prepared at several curing temperatures, and their electro-physical properties were determined to find an optimum fabrication conditions. Critical temperatures of the superconductors were decreased with increasing melting temperature, which was related to the amount of equilibrium phases of the superconducting materials with temperature. The critical temperature of BiSrCaCuO bulk and thick film superconductors were 107 K and 96 K, respectively. The variation of susceptibility of the superconductor thick film formed at 950 degrees C had multi-step-type curve for 70 G externally applied field, whereas, a superconductor thick film formed at 885 degrees C had a single step-type curve like a bulk BiSrCaCuO ceramic superconductor in the temperature-susceptibility curves. A partial melting at 865 degrees C is one of optimum conditions for making a superconductor thick film with a relatively homogeneous phase.

Proceedings, phenomenology and applications of high temperature superconductors

International Nuclear Information System (INIS)

Bedell, K.S.

1991-01-01

Phenomenology and Applications of High Temperature Superconductors, The Los Alamos Symposium: 1991, was sponsored by the Los Alamos National Laboratory, Center for Materials Science, the Advanced Studies Program on High Temperature Superconductivity Theory (ASP) and the Exploratory Research and Development Center. This is the second symposium in the series. High Temperature Superconductivity, The Los Alamos Symposium: 1989, also published by Addison Wesley, focused on the cutting-edge theoretical and experimental issues in high temperature superconductors. This symposium, with its focus on the phenomenology and applications of high temperature superconductors, gives a complementary review of the aspects of the field closely related to the impact of high temperature superconductors on technology. The objective of ASP is to advance the field on a broad front with no specific point of view by bringing a team of leading academic theorists into a joint effort with the theoretical and experimental scientists of a major DOE national laboratory. The ASP consisted of fellows led by Robert Schrieffer (UCSB and now FSU) joined by David Pines (University of illinois), Elihu Abrahams (Rutgers), Sebastian Doniach (Stanford), and Maurice Rice (ETH, Zurich) and theoretical and experimental staff of Los Alamos National Laboratory. This synergism of academic, laboratory, theoretical and experimental research produced a level of interaction and excitement that would not be possible otherwise. This publication and the previous one in the series are just examples of how this approach to advancing science can achieve significant contributions

High-temperature cuprate superconductors. Experiment, theory, and applications

International Nuclear Information System (INIS)

Plakida, Nikolay

2010-01-01

High-Temperature Cuprate Superconductors provides an up-to-date and comprehensive review of the properties of these fascinating materials. The essential properties of high-temperature cuprate superconductors are reviewed on the background of their theoretical interpretation. The experimental results for structural, magnetic, thermal, electric, optical and lattice properties of various cuprate superconductors are presented with respect to relevant theoretical models. A critical comparison of various theoretical models involving strong electron correlations, antiferromagnetic spin fluctuations, phonons and excitons provides a background for understanding of the mechanism of high-temperature superconductivity. Recent achievements in their applications are also reviewed. A large number of illustrations and tables gives valuable information for specialists. A text-book level presentation with formulation of a general theory of strong-coupling superconductivity will help students and researches to consolidate their knowledge of this remarkable class of materials. (orig.)

Properties of Y Ba2 Cu3 O7-δ-Ag superconductors prepared by the citrate method

International Nuclear Information System (INIS)

Fonseca, F.C.; Muccillo, R.

1996-01-01

Y Ba 2 Cu 3 O 7-δ (123) ceramic superconductor and YBa 2 Cu 3 O 7-δ - Ag composite superconductors have been prepared by the citrate method. Microstructural analysis has been done by X-ray diffractometry and optical ceramography. The superconducting behaviour has been studied by 4-probe dc resistivity in the 77 K - 140 K temperature range. Silver percolation in the ceramic matrix was studied by electrical resistivity measurements at room temperature; the percolation threshold was found to be approximately 25 vol% (35.5 wt%) Ag. Specimens with silver addition showed improvement in the flexural strength of the 123 compound. The main results show that the critical temperature does not depend on the silver content in the composite specimens, and that approximately 3 wt% (1.8 vol%) Ag doping yields an optimized composite superconductor from the microstructural point of view, with platelet-like grain shapes. (author)

Enhancement of critical temperature in fractal metamaterial superconductors

Energy Technology Data Exchange (ETDEWEB)

Smolyaninov, Igor I., E-mail: smoly@umd.edu [Department of Electrical and Computer Engineering, University of Maryland, College Park, MD 20742 (United States); Smolyaninova, Vera N. [Department of Physics Astronomy and Geosciences, Towson University, 8000 York Road, Towson, MD 21252 (United States)

2017-04-15

Fractal metamaterial superconductor geometry has been suggested and analyzed based on the recently developed theoretical description of critical temperature increase in epsilon near zero (ENZ) metamaterial superconductors. Considerable enhancement of critical temperature has been predicted in such materials due to appearance of large number of additional poles in the inverse dielectric response function of the fractal. Our results agree with the recent observation (Fratini et al. Nature 466, 841 (2010)) that fractal defect structure promotes superconductivity.

Comparative study of irreversibility effects in Nb foil and high temperature superconducting ceramics by μSR

International Nuclear Information System (INIS)

Grebinnik, V.G.; Duginov, V.N.; Zhukov, V.A.

1990-01-01

We present the results of investigation of superconducting niobium and high temperature ceramical superconductor La 1.9 Sr 0.1 CuO 4 by the μSR technique. The experiments with the niobium sample have confirmed high reliability of the μSR-technique in determining such characteristics of type II superconductors as T c , H c1 , H c2 , the magnetic field penetration depth λ, and the critical current density J c . The analysis of the field dependences of the distribution width and mean value of the magnetic fields on the muon when the samples are magnetized was carried out. One has revealed qualitative difference in the behaviour of the magnetic dield distribution width in Nb and LaSrCuO. While the niobium data are well described in the frame of the critical state model, application of the similar approach to the high-T c superconductor did not give satisfactory description of our experimental results. 10 refs.; 4 figs

Application of High Temperature Superconductors to Accelerators

CERN Document Server

Ballarino, A

2000-01-01

Since the discovery of high temperature superconductivity, a large effort has been made by the scientific community to investigate this field towards a possible application of the new oxide superconductors to different devices like SMES, magnetic bearings, flywheels energy storage, magnetic shielding, transmission cables, fault current limiters, etc. However, all present day large scale applications using superconductivity in accelerator technology are based on conventional materials operating at liquid helium temperatures. Poor mechanical properties, low critical current density and sensitivity to the magnetic field at high temperature are the key parameters whose improvement is essential for a large scale application of high temperature superconductors to such devices. Current leads, used for transferring currents from the power converters, working at room temperature, into the liquid helium environment, where the magnets are operating, represent an immediate application of the emerging technology of high t...

Signature of electron-phonon interaction in high temperature superconductors

Directory of Open Access Journals (Sweden)

Vinod Ashokan

2011-09-01

Full Text Available The theory of thermal conductivity of high temperature superconductors (HTS based on electron and phonon line width (life times formulation is developed with Quantum dynamical approach of Green's function. The frequency line width is observed as an extremely sensitive quantity in the transport phenomena of HTS as a collection of large number of scattering processes. The role of resonance scattering and electron-phonon interaction processes is found to be most prominent near critical temperature. The theory successfully explains the spectacular behaviour of high Tc superconductors in the vicinity of transition temperature. A successful agreement between theory and experiment has been obtained by analyzing the thermal conductivity data for the sample La1.8Sr0.2CuO4 in the temperature range 0 − 200K. The theory is equally and successfully applicable to all other high Tc superconductors.

Temperature measurement of RE123 bulk superconductors on magnetizing process

International Nuclear Information System (INIS)

Yokoyama, K.; Kaneyama, M.; Oka, T.; Fujishiro, H.; Noto, K.

2004-01-01

We study on the magnetization behavior of to magnetize RE123 bulk superconductors to apply it as strong magnets. Through magnetizing process, the temperature of bulk superconductors is raised by pinning loss caused by the magnetic fluxes motion (e.g. flux jump of flux flow), and the trapped field is decreased. This paper presents the measurement of temperature changes of Sm123 bulk superconductors during the exciting process by iteratively magnetizing pulsed-field operation with reducing amplitudes (IMRA) method. Five thermocouples are put on the surface of Sm123 bulk superconductor of 46 mm in diameter. The temperatures at the center, on the growth sector boundary (GSB) line and in the sector region surrounded by GSB's line (inter-GSB region) are monitored. The temperature at a cold stage is also measured. A Hall sensor is attached near the center thermocouple to measure the trapped field. After a bulk superconductor is cooled by the GM type refrigerator until 40 K, iterative pulsed-fields of 2.32-5.42 T are applied by a magnetizing coil. When high magnetic field of 5.42 T is applied, a temperature of bulk superconductor reaches to 72.4 K and the magnetic field distribution has C form with which a part of circle is dented, and then, a trapped field is 2.28 T. When a lower magnetic field of 4.64 T is applied, a maximum temperature is 68.3 K and a trapped field is raised to 2.70 T, and moreover, the distribution becomes round shape like field-cooling method (FC). We showed clearly that heat generation by pinning loss was related to the mechanism of magnetic field capture

Weak links in high critical temperature superconductors

Science.gov (United States)

Tafuri, Francesco; Kirtley, John R.

2005-11-01

The traditional distinction between tunnel and highly transmissive barriers does not currently hold for high critical temperature superconducting Josephson junctions, both because of complicated materials issues and the intrinsic properties of high temperature superconductors (HTS). An intermediate regime, typical of both artificial superconductor-barrier-superconductor structures and of grain boundaries, spans several orders of magnitude in the critical current density and specific resistivity. The physics taking place at HTS surfaces and interfaces is rich, primarily because of phenomena associated with d-wave order parameter (OP) symmetry. These phenomena include Andreev bound states, the presence of the second harmonic in the critical current versus phase relation, a doubly degenerate state, time reversal symmetry breaking and the possible presence of an imaginary component of the OP. All these effects are regulated by a series of transport mechanisms, whose rules of interplay and relative activation are unknown. Some transport mechanisms probably have common roots, which are not completely clear and possibly related to the intrinsic nature of high-TC superconductivity. The d-wave OP symmetry gives unique properties to HTS weak links, which do not have any analogy with systems based on other superconductors. Even if the HTS structures are not optimal, compared with low critical temperature superconductor Josephson junctions, the state of the art allows the realization of weak links with unexpectedly high quality quantum properties, which open interesting perspectives for the future. The observation of macroscopic quantum tunnelling and the qubit proposals represent significant achievements in this direction. In this review we attempt to encompass all the above aspects, attached to a solid experimental basis of junction concepts and basic properties, along with a flexible phenomenological background, which collects ideas on the Josephson effect in the presence

Weak links in high critical temperature superconductors

International Nuclear Information System (INIS)

Tafuri, Francesco; Kirtley, John R

2005-01-01

The traditional distinction between tunnel and highly transmissive barriers does not currently hold for high critical temperature superconducting Josephson junctions, both because of complicated materials issues and the intrinsic properties of high temperature superconductors (HTS). An intermediate regime, typical of both artificial superconductor-barrier-superconductor structures and of grain boundaries, spans several orders of magnitude in the critical current density and specific resistivity. The physics taking place at HTS surfaces and interfaces is rich, primarily because of phenomena associated with d-wave order parameter (OP) symmetry. These phenomena include Andreev bound states, the presence of the second harmonic in the critical current versus phase relation, a doubly degenerate state, time reversal symmetry breaking and the possible presence of an imaginary component of the OP. All these effects are regulated by a series of transport mechanisms, whose rules of interplay and relative activation are unknown. Some transport mechanisms probably have common roots, which are not completely clear and possibly related to the intrinsic nature of high-T C superconductivity. The d-wave OP symmetry gives unique properties to HTS weak links, which do not have any analogy with systems based on other superconductors. Even if the HTS structures are not optimal, compared with low critical temperature superconductor Josephson junctions, the state of the art allows the realization of weak links with unexpectedly high quality quantum properties, which open interesting perspectives for the future. The observation of macroscopic quantum tunnelling and the qubit proposals represent significant achievements in this direction. In this review we attempt to encompass all the above aspects, attached to a solid experimental basis of junction concepts and basic properties, along with a flexible phenomenological background, which collects ideas on the Josephson effect in the presence

The Born-Mayer-Huggins potential in high temperature superconductors

Science.gov (United States)

Singh, Hempal; Singh, Anu; Indu, B. D.

2016-07-01

The Born-Mayer-Huggins potential which has been found the best suitable potential to study the YBa2Cu3O7-δ type high temperature superconductors is revisited in a new framework. A deeper insight in it reveals that the Born-Mayer parameters for different interactions in high temperature superconductor are not simple quantities but several thermodynamic and spatial functions enter the problem. Based on the new theory, the expressions for pressure, bulk modulus and Born-Mayer parameters have been derived and it is established that these quantities depend upon Gruneisen parameter which is the measure of the strength of anharmonic effects in high temperature superconductors. This theory has been applied to a specific model YBa2Cu3O7-δ crystal for the purpose of numerical estimates to justify the new results.

High Temperature Superconductor Accelerator Magnets

CERN Document Server

AUTHOR|(CDS)2079328; de Rijk, Gijs; Dhalle, Marc

2016-11-10

For future particle accelerators bending dipoles are considered with magnetic fields exceeding $20T$. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and development before they can be applied in a practical accelerator magnet. In order to study HTS in detail, a five tesla demonstrator magnet named Feather-M2 is designed and constructed. The magnet is based on ReBCO coated conductor, which is assembled into a $10kA$ class Roebel cable. A new and optimized Aligned Block layout is used, which takes advantage of the anisotropy of the conductor. This is achieved by providing local alignment of the Roebel cable in the coil windings with the magnetic field lines. A new Network Model capable of analyzing transient electro-magnetic and thermal phenomena in coated conductor cables and coils is developed. This model is necessary to solve critical issues in coated conductor ac...

Open questions in the magnetic behaviour of high-temperature superconductors

International Nuclear Information System (INIS)

Cohen, L.F.; Jensen, Henrik Jeldtoft

1997-01-01

A principally experimental review of vortex behaviour in high-temperature superconductors is presented. The reader is first introduced to the basic concepts needed to understand the magnetic properties of type II superconductors. The concepts of vortex melting, the vortex glass, vortex creep, etc are also discussed briefly. The bulk part of the review relates the theoretical predictions proposed for the vortex system in high temperature superconductors to experimental findings. The review ends with an attempt to direct the reader to those areas which still require further clarification. (author)

TECHNICAL TRAINING SEMINAR: High Temperature Superconductors: Progress and Issues

CERN Multimedia

Davide Vitè

2002-01-01

Monday 24 June from 14:30 to 15:30 - Training Centre Auditorium - bldg. 593-11 High Temperature Superconductors: Progress and Issues Prof. Jan Evetts / UNIVERSITY OF CAMBRIDGE, Department of Materials Science and Metallurgy, UK Grappling with grain boundaries: Current transport processes in granular High Temperature Superconductors (HTS) The development of High Temperature Superconductors, seen from a materials scientist's point of view, is relevant to the superconductivity community at CERN: their possible high current applications can include high performance magnets for future accelerators. There is an urgent need to develop a quantitative description of HTS conductors in terms of their complex anisotropy, inhomogeneity and dimensionality. This is essential both for the practical specification of a conductor and for charting routes to conductor optimisation. The critical current, the n-value, dissipation and quenching characteristics are amongst most important parameters that make up an engineering specifi...

Studies on ceramic superconductors

International Nuclear Information System (INIS)

Chaklader, A.C.D.; Roemer, G.; Hardy, W.N.; Brewer, J.H.; Carolan, J.F.; Parsons, R.R.

1987-01-01

The superconducting properties of both bulk specimens and sputtered thin films of the YBa 2 Cu 3 O x compound have been studied. The bulk specimens were fabricated by cold pressing and sintering, and also by hot-pressing (subsequent reheating). The dc resistivity measurements showed a sharp drop in the temperature range 92-87K in this material. Muon spin relaxation (μSR) measurements of sintered discs in 3.4 kOe revealed the formation of a mixed state with an effective magnetic penetration depth λ ∼ 1365 angstrom at 6K, implying an effective charge carrier density of 6 x 10 21 cm -3 . The temperature dependence λ(T) is that of an ordinary s-wave superconductor. The resistivity of the thin film prepared from the compound by dc planar magnetron sputtering, showed a sharp drop to a very low value near 80K. The compound YBa 2 Cu 3 O x loses its superconducting properties, when either hot-pressed (in air) or oxidized at 500 degree C in high O 2 pressure, but this property can be restored when reheated in one atmosphere of O 2 above 900 degree C

Contact spectroscopy of high-temperature superconductors. Review

International Nuclear Information System (INIS)

Yanson, I.K.

1991-01-01

We have attempted to systematize the research of high temperature superconductors by means of tunneling and point-contact spectroscopy. The theoretical grounds of the methods are briefly described. The deviations of current-voltage characteristics from ordinary superconductors are considered. The properties of point contacts with direct energy gap measurfements and the fine structure of derivatives of i(v) curves at the overlap energies are reviewed for the high-T c La 2-x Sr x CuO 4 materials

Probing High Temperature Superconductors with Magnetometry in Ultrahigh Magnetic Fields

Energy Technology Data Exchange (ETDEWEB)

Li, Lu [Univ. of Michigan, Ann Arbor, MI (United States)

2017-07-26

The objective of this research is to investigate the high-field magnetic properties of high temperature superconductors, materials that conduct electricity without loss. A technique known as high-resolution torque magnetometry that was developed to directly measure the magnetization of high temperature superconductors. This technique was implemented using the 65 Tesla pulsed magnetic field facility that is part of the National High Magnetic Field Laboratory at Los Alamos National Laboratory. This research addressed unanswered questions about the interplay between magnetism and superconductivity, determine the electronic structure of high temperature superconductors, and shed light on the mechanism of high temperature superconductivity and on potential applications of these materials in areas such as energy generation and power transmission. Further applications of the technology resolve the novel physical phenomena such as correlated topological insulators, and spin liquid state in quantum magnets.

An investigation of texturing by magnetic and mechanical techniques in high critical temperature superconducting ceramics

International Nuclear Information System (INIS)

Deschanels, X.

1992-11-01

The principal goal of this work is to quantify the influence of texture of ceramic superconductors ReBaCuO (Re=Dy, Y) on their critical current density (Jc). The magnetic alignment of particles at ambient temperature is the first technique who has allowed us to produce superconducting (Meissner effect) and textured ceramics. However, these materials are very brittle because of their porosity and this makes it impossible to measure their Jc. Press-forging (or creep sintering) is the second technique who has allowed us to prepare highly textured ceramics materials which are also dense. We have studied the influence of various conditions of thermomechanical treatment (sintering time and temperature, applied load, rate of deformation, density of the material at the beginning) on the texture quality. We have shown that at 900 deg, the eutectic liquid formed by BaCuO 2 , CuO and YBa 2 Cu 3 0 7-Y various mechanisms that help explain the formation of observed texture. After the oxidation stage which requires heat treatment under controlled atmospheres, we obtain superconducting ceramics (Tc=85 K). Moreover, this study also shows that the texture can improve the Jc by 400%, to 750 A/cm 2 at 77 K in the best specimens. This low value is explained by the presence of non-superconducting secondary phases and amorphous phases at the grain boundaries. (Author). 120 refs., figs., tabs

High-temperature superconductors in application - fight for the top

International Nuclear Information System (INIS)

Anon.

1990-01-01

For the superconductor market two-digit growth rates are predicted until after the year 2000. The decrosslinking of the high temperature superconductors initiated a worldwide race for first applications. The report considers the situation of raw materials and the application potentials in the USA, Japan and Western Europe. (orig.) [de

High Temperature Superconductor Bolometers for Planetary Science

Data.gov (United States)

National Aeronautics and Space Administration — This work is a design study of an instrument optimized for JPL's novel high temperature superconductor bolometers. The work involves designing an imaging...

Superconductor come on the market. Pt. 2

International Nuclear Information System (INIS)

Heinzelmann, E.

1995-01-01

Switzerland has the leading position in the field of high-temperature superconductors (HTS). The research group of Professor Ott at the ETH Zurich holds the international high-temperature record with 140 C. The company ABB with its powerful current limiter is one of the world's leading enterprises in this field. The ceramic bands developed by professor Fluekiger of the University of Geneve conduct electric current free of loss with such an efficiency that can only by reached by Japan and the USA. In order to use the applications of the HTS-technology for series production, special types of ceramic are required as they are being developed by professor Ludwig J. Gaukler and his team at the ETH Zurich. (orig.) [de

Chemical stability of high-temperature superconductors

Science.gov (United States)

Bansal, Narottam P.

1992-01-01

A review of the available studies on the chemical stability of the high temperature superconductors (HTS) in various environments was made. The La(1.8)Ba(0.2)CuO4 HTS is unstable in the presence of H2O, CO2, and CO. The YBa2Cu3O(7-x) superconductor is highly susceptible to degradation in different environments, especially water. The La(2-x)Ba(x)CuO4 and Bi-Sr-Ca-Cu-O HTS are relatively less reactive than the YBa2Cu3O(7-x). Processing of YBa2Cu3O(7-x) HTS in purified oxygen, rather than in air, using high purity noncarbon containing starting materials is recommended. Exposure of this HTS to the ambient atmosphere should also be avoided at all stages during processing and storage. Devices and components made out of these oxide superconductors would have to be protected with an impermeable coating of a polymer, glass, or metal to avoid deterioration during use.

Fabrication of high temperature superconductors

Science.gov (United States)

Balachandran, Uthamalingam; Dorris, Stephen E.; Ma, Beihai; Li, Meiya

2003-06-17

A method of forming a biaxially aligned superconductor on a non-biaxially aligned substrate substantially chemically inert to the biaxially aligned superconductor comprising is disclosed. A non-biaxially aligned substrate chemically inert to the superconductor is provided and a biaxially aligned superconductor material is deposited directly on the non-biaxially aligned substrate. A method forming a plume of superconductor material and contacting the plume and the non-biaxially aligned substrate at an angle greater than 0.degree. and less than 90.degree. to deposit a biaxially aligned superconductor on the non-biaxially aligned substrate is also disclosed. Various superconductors and substrates are illustrated.

Low temperature X-ray imaging of magnetic flux patterns in high temperature superconductors

Science.gov (United States)

Stahl, Claudia; Ruoß, Stephen; Weigand, Markus; Bechtel, Michael; Schütz, Gisela; Albrecht, Joachim

2015-05-01

We present X-ray magnetic circular dichroism (XMCD) microscopy results obtained at liquid nitrogen temperatures on the high-Tc superconductor YBCO (YBa2Cu3O7-δ). The magnetic flux distribution arising from electric currents in the superconductor is detected and visualized using soft-magnetic Co40Fe40B20 (CoFeB) as sensor layer and XMCD as contrast mechanism. It has been shown that the XMCD contrast in the sensor layer directly corresponds to magnetic flux distribution of the superconductor and hence can be used to image magnetic structures in superconductors [Stahl et al., Phys. Rev. B 90, 104515 (2014)]. The existing scanning UHV X-ray microscopy setup MAXYMUS at the synchrotron BESSY II in Berlin has been upgraded for that purpose: we use a nitrogen based MMR Micro Miniature Joule-Thompson Cryostat with temperature range from 75 K to 580 K. The capability of the method is demonstrated on two different superconducting samples, an optimally doped thin film and a melt-textured block.

ASM Inaugural Lecture 2009: High temperature superconductors: Materials, mechanisms and applications

International Nuclear Information System (INIS)

Roslan Abdul Shukor

2009-01-01

A surprising variety of new superconducting materials has been discovered in recent years. Many compounds with light elements such as fullerenes, oxides, borides, nitrides, some organic materials and also heavy fermions have been found to superconductor at various temperatures. Hitherto, superconductors have proven to be highly varied in composition but elusive and mysterious. The juxtaposition of superconductivity and magnetism at the nano scale in some of these new materials has paved the way to a rich and exciting new field in condensed matter and materials research. An overview of superconductor research in Malaysian institutions is presented in this paper. Some of the new superconducting materials and their possible mechanisms, conventional and exotic, are presented. The possible role of lattice vibrations in the mechanisms of high temperature superconductivity and the study of this via acoustic methods are discussed. Frozen flux superconductors in a nano magnet-superconductor hybrid system are also discussed. (author)

High temperature superconductors

CERN Document Server

Paranthaman, Parans

2010-01-01

This essential reference provides the most comprehensive presentation of the state of the art in the field of high temperature superconductors. This growing field of research and applications is currently being supported by numerous governmental and industrial initiatives in the United States, Asia and Europe to overcome grid energy distribution issues. The technology is particularly intended for densely populated areas. It is now being commercialized for power-delivery devices, such as power transmission lines and cables, motors and generators. Applications in electric utilities include current limiters, long transmission lines and energy-storage devices that will help industries avoid dips in electric power.

Impact of high temperature superconductors on the possibility of radio-frequency confinement

International Nuclear Information System (INIS)

Dean, S.O.

1989-01-01

Recent discoveries of superconducting materials that operate at high temperatures may have both technical and economic consequences for magnetic confinement fusion. In addition, they could also open up the possibility of plasma confinement by radio-frequency fields. The new, high temperature superconductors may impact the feasibility of rf confinement in two important ways: (1) higher temperature superconductors should have higher critical B fields and consequently may allow higher critical electric fields to be sustained in the cavity, thus allowing the necessary confining pressure to be achieved; and (2) the higher temperature superconductors lower the refrigeration power necessary to maintain the superconducting cavity, thus allowing a favorable energy balance

Processing of Mixed Oxide Superconductors

Science.gov (United States)

1990-07-01

rapid changes world wide a major research centre on high Tc superconductors was awarded to Cambridge which involved moving the work and people to a...reports and paper is in the appendices. Separation Ceramic superconductors tend to be mixtures of phases, especially when first discovered. It would...properties of the superconducting state will in principle allow superconducting material to be levitated from the non superconductor and several designs

High-temperature superconductors make major progress

CERN Multimedia

CERN Bulletin

2014-01-01

This month's Nature Materials featured an important breakthrough for high-temperature superconductors. A new method has been found for processing Bi-2212 high-temperature superconducting round wire in order to drastically increase its critical current density. The result confirms that this conductor is a serious candidate for future very-high-field magnets.   This image shows the cross-section of two Bi-2212 wires. The bottom wire has less leakage and void porosity due to a heat treatment done at an overpressure of 100 bar - about 100 times the pressure used to produce the top wire (image from [Nature Materials, Vol. 13 (2014), 10.1038/nmat3887]). The workhorse for building superconducting accelerator magnets has been, so far, the Niobium-Titanium (Nb-Ti) alloy superconductor. But with Nb-Ti having reached its full potential, other conductors must be used to operate in higher magnetic fields beyond those reached with the LHC magnets. Today, the intermetallic Niobium-Tin (Nb3Sn) is th...

The DC Electrical Resistivity Curves of Bismuth-2212 Ceramic Superconductors: Evaluation of the Hole-Carrier Concentrations per-Cu Ion

Directory of Open Access Journals (Sweden)

nurmalita .

2016-04-01

Full Text Available In this study the samples of Bismuth ceramic superconductors were synthesized by the melt textured growth methods from a 2212 stoichiometric composition in order to obtain a large amount of pure Bi-2212. The effects of Pb substitution on the properties of Bi-based Bi2−xPbxSr2CaCu2Oy superconductor with x = 0, 0.2, and 0.4 were investigated by means of DC electrical resistivity measurements. It has been found that the hole-carrier concentrations per-Cu ion of the samples change independently of Pb content.

Spins in the vortices of a high-temperature superconductor

DEFF Research Database (Denmark)

Lake, B.; Aeppli, G.; Clausen, K.N.

2001-01-01

Neutron scattering is used to characterize the magnetism of the vortices for the optimally doped high-temperature superconductor La2-xSrxCuO4 (x = 0.163) in an applied magnetic field. As temperature is reduced, Low-frequency spin fluctuations first disappear with the loss of vortex mobility......, but then reappear. We find that the vortex state can be regarded as an inhomogeneous mixture of a superconducting spin fluid and a material containing a nearly ordered antiferromagnet. These experiments show that as for many other properties of cuprate superconductors, the important underlying microscopic forces...

Positron annihilation studies on high temperature superconductors

International Nuclear Information System (INIS)

Sundar, C.S.; Bharathi, A.

1996-01-01

A survey of the positron annihilation studies on high temperature superconductors (HTSC), with results drawn mainly from our work, is presented. These include results of the studies on the temperature dependence of positron lifetime across T c , which have been carried out in the whole gamut of oxide superconductors. These experimental results are discussed in conjunction with the results of theoretically calculated positron density distribution, and it is shown that the observed temperature dependence of lifetime is intimately linked to the probing of the Cu-O network by the positrons. Results on the investigation of oxygen defects, which play a crucial role in HTSC, are presented. The most significant contribution of positrons to HTSC relates to the investigation of Fermi surface and the results of these studies, drawn from literature, are indicated. Some of our recent results in other novel superconducting materials, viz., the fullerenes and borocarbides are also presented. (author). 69 refs., 15 figs

Transport phenomena in high Tc superconductors. Resume of Ph.D thesis

International Nuclear Information System (INIS)

Crisan, I.A.

1994-01-01

This is an extended abstract of the Ph. D. thesis devoted to the transport phenomena in high-Tc superconductors. There are three chapters. The first chapter presents an overview of the essential theoretical aspects concerning the vortex dynamics particularly in ceramic superconductors. The chapter two gives a description of the preparation methods of superconductor samples used by the author as well as the measurement devices for volt-ampere characteristics and the associated electronic circuitry. In the third chapter there are presented the experimental data obtained from different samples prepared in different temperature and magnetic field conditions. The obtained results are finally interpreted in the frame of existent or original models. (M.I.C.). 31 Refs

Research On Bi-Based High-Temperature Superconductors

Science.gov (United States)

Banks, Curtis; Doane, George B., III; Golben, John

1993-01-01

Brief report describes effects of melt sintering on Bi-based high-temperature superconductor system, as well as use of vibrating-sample magnetometer to determine hysteresis curves at 77 K for partially melt-sintered samples. Also discussed is production of high-temperature superconducting thin films by laser ablation: such films potentially useful in detection of signals of very low power.

Electronic Structure of the Bismuth Family of High Temperature Superconductors

Energy Technology Data Exchange (ETDEWEB)

Dunn, Lisa

2002-03-07

High temperature superconductivity remains the central intellectual problem in condensed matter physics fifteen years after its discovery. Angle resolved photoemission spectroscopy (ARPES) directly probes the electronic structure, and has played an important role in the field of high temperature superconductors. With the recent advances in sample growth and the photoemission technique, we are able to study the electronic structure in great detail, and address regimes that were previously inaccessible. This thesis work contains systematic photoemission studies of the electronic structure of the Bi-family of high temperature superconductors, which include the single-layer system (Bi2201), the bi-layer system (Bi2212), and the tri-layer system (Bi2223). We show that, unlike conventional BCS superconductors, phase coherence information emerges in the single particle excitation spectrum of high temperature superconductors as the superconducting peak in Bi2212. The universality and various properties of this superconducting peak are studied in various systems. We argue that the origin of the superconducting peak may provide the key to understanding the mechanism of High-Tc superconductors. In addition, we identified a new experimental energy scale in the bilayer material, the anisotropic intra-bilayer coupling energy. For a long time, it was predicted that this energy scale would cause bilayer band splitting. We observe this phenomenon, for the first time, in heavily overdoped Bi2212. This new observation requires the revision of the previous picture of the electronic excitation in the Brillouin zone boundary. As the first ARPES study of a trilayer system, various detailed electronic proper- ties of Bi2223 are examined. We show that, comparing with Bi2212, both superconducting gap and relative superconducting peak intensity become larger in Bi2223, however, the strength of the interlayer coupling within each unit cell is possibly weaker. These results suggest that the

Identifying the genes of unconventional high temperature superconductors.

Science.gov (United States)

Hu, Jiangping

We elucidate a recently emergent framework in unifying the two families of high temperature (high [Formula: see text]) superconductors, cuprates and iron-based superconductors. The unification suggests that the latter is simply the counterpart of the former to realize robust extended s-wave pairing symmetries in a square lattice. The unification identifies that the key ingredients (gene) of high [Formula: see text] superconductors is a quasi two dimensional electronic environment in which the d -orbitals of cations that participate in strong in-plane couplings to the p -orbitals of anions are isolated near Fermi energy. With this gene, the superexchange magnetic interactions mediated by anions could maximize their contributions to superconductivity. Creating the gene requires special arrangements between local electronic structures and crystal lattice structures. The speciality explains why high [Formula: see text] superconductors are so rare. An explicit prediction is made to realize high [Formula: see text] superconductivity in Co/Ni-based materials with a quasi two dimensional hexagonal lattice structure formed by trigonal bipyramidal complexes.

Potentialities in electronics of new high critical temperature superconductors. Potentialites en electronique des nouveaux supraconducteurs a haute temperature critique

Energy Technology Data Exchange (ETDEWEB)

Hartemann, P [Thomson-CSF, 75 - Paris (FR)

1989-09-01

The main electronic applications of superconductors involve the signal processing, the electromagnetic wave detection and the magnetometry. Characteristics of devices based on conventional superconductors cooled by liquid helium are given and the changes induced by incorporating high-temperature superconductors are estimated. After a survey of new superconductor properties, the superconducting devices for analog or digital signal processing are reviewed. The gains predicted for high-temperature superconducting analog devices are considered in greater detail. Different sections deal with the infrared or (sub)millimeter wave detection. The most sensitive apparatuses for magnetic measurements are based on SQUIDs. Features of SQUIDs made of granular high-temperature superconducting material samples (grain boundaries behave as barriers of intrinsic junctions) are discussed.

Microstructural analysis of high-temperature superconductors

International Nuclear Information System (INIS)

Passing, H.

1987-01-01

At present, research concentrates on the composition YBa 2 Cu 3 O 7-δ , which, in the appropriate synthesis, shows a transition from the state of normal conductivity to superconductivity at a temperature of 91 K. An exact control of the oxygen content of the composition is necessary so that the super-conducting orthorhombic structure develops. Depending on the composition and the sintering temperature, it is possible to produce fine-grained and coarse-grained ceramics with a directed crystal structure. Under the light-optical microscope in polarized light, coarse-grained ceramics show twinning, which occurs during cooling down from the sintering temperature because of a phase change combined with a variation in volume. (orig./MM) [de

Low-energy physics of high-temperature superconductors

International Nuclear Information System (INIS)

Emery, V.J.; Kivelson, S.A.

1992-01-01

It is argued that the low-energy properties of high temperature superconductors are dominated by the interaction between the mobile holes and a particular class of collective modes, corresponding to local large-amplitude low-energy fluctuations in the hole density. The latter are a consequence of the competition between the effects of long-range Coulomb interactions and the tendency of a low concentration of holes in an antiferromagnet to phase separate. The low-energy behavior of the system is governed by the same fixed point as the two-channel Kondo problem, which accounts for the ''universality'' of the properties of the cuprate superconductors. Predictions of the optical properties and the spin dynamics are compared with experiment. The pairing resonance of the two Kondo problem gives a mechanism of high temperature superconductivity with an unconventional symmetry of the order parameter

Hall viscosity of a chiral two-orbital superconductor at finite temperatures

Science.gov (United States)

Yazdani-Hamid, Meghdad; Shahzamanian, Mohammad Ali

2018-06-01

The Hall viscosity known as the anti-symmetric part of the viscosity fourth-rank tensor. Such dissipationless response which appears for systems with broken time reversal symmetry. We calculate this non-dissipative quantity for a chiral two-orbital superconductor placed in a viscoelastic magnetic field using the linear response theory and apply our calculations to the putative multiband chiral superconductor Sr2RuO4. The chirality origin of a multiband superconductor arises from the interorbital coupling of the superconducting state. This feature leads to the robustness of the Hall viscosity against temperature and impurity effects. We study the temperature effect on the Hall viscosity at the one-loop approximation.

Universal linear-temperature resistivity: possible quantum diffusion transport in strongly correlated superconductors.

Science.gov (United States)

Hu, Tao; Liu, Yinshang; Xiao, Hong; Mu, Gang; Yang, Yi-Feng

2017-08-25

The strongly correlated electron fluids in high temperature cuprate superconductors demonstrate an anomalous linear temperature (T) dependent resistivity behavior, which persists to a wide temperature range without exhibiting saturation. As cooling down, those electron fluids lose the resistivity and condense into the superfluid. However, the origin of the linear-T resistivity behavior and its relationship to the strongly correlated superconductivity remain a mystery. Here we report a universal relation [Formula: see text], which bridges the slope of the linear-T-dependent resistivity (dρ/dT) to the London penetration depth λ L at zero temperature among cuprate superconductor Bi 2 Sr 2 CaCu 2 O 8+δ and heavy fermion superconductors CeCoIn 5 , where μ 0 is vacuum permeability, k B is the Boltzmann constant and ħ is the reduced Planck constant. We extend this scaling relation to different systems and found that it holds for other cuprate, pnictide and heavy fermion superconductors as well, regardless of the significant differences in the strength of electronic correlations, transport directions, and doping levels. Our analysis suggests that the scaling relation in strongly correlated superconductors could be described as a hydrodynamic diffusive transport, with the diffusion coefficient (D) approaching the quantum limit D ~ ħ/m*, where m* is the quasi-particle effective mass.

Electron Sources of the Diode Type with Cathode and Anode of High Temperature Superconductors

International Nuclear Information System (INIS)

Korenev, S.A.

1994-01-01

The planar electron sources of the diode type with cathode and anode of high temperature superconductors (HTSC) are considered. Explosive emission cathode on the basis of bismuth ceramics (Bi-Ca-Sr-Cu-O) allows forming microsecond pulse (duration > 1 μs) and low energy electron beams (10-25 keV). Tube anode of HTSC in superconducting phase compresses the pulsed electron beam (K = 2-8). It leads to an increase of the beam power density. The high voltage of the generator of Arkad'ev-Marx type (U = 100-600 kV) and the generator with double L C-line are used for experiments. The pulsed method of measuring of the HTSC critical current with the help of pulsed high current electron beam is described. (author). 16 refs., 13 figs

High temperature alloys and ceramic heat exchanger

International Nuclear Information System (INIS)

Okamoto, Masaharu

1984-04-01

From the standpoint of energy saving, the future operating temperatures of process heat and gas turbine plants will become higher. For this purpose, ceramics is the most promissing candidate material in strength for application to high-temperature heat exchangers. This report deals with a servey of characteristics of several high-temperature metallic materials and ceramics as temperature-resistant materials; including a servey of the state-of-the-art of ceramic heat exchanger technologies developed outside of Japan, and a study of their application to the intermediate heat exchanger of VHTR (a very-high-temperature gas-cooled reactor). (author)

MHD oxidant intermediate temperature ceramic heater study

Science.gov (United States)

Carlson, A. W.; Chait, I. L.; Saari, D. P.; Marksberry, C. L.

1981-09-01

The use of three types of directly fired ceramic heaters for preheating oxygen enriched air to an intermediate temperature of 1144K was investigated. The three types of ceramic heaters are: (1) a fixed bed, periodic flow ceramic brick regenerative heater; (2) a ceramic pebble regenerative heater. The heater design, performance and operating characteristics under conditions in which the particulate matter is not solidified are evaluated. A comparison and overall evaluation of the three types of ceramic heaters and temperature range determination at which the particulate matter in the MHD exhaust gas is estimated to be a dry powder are presented.

High temperature superconductors for fusion magnets -influence of neutron irradiation

International Nuclear Information System (INIS)

Chudy, M.; Eisterer, M.; Weber, H. W.

2010-01-01

In this work authors present the results of study of influence of neutron irradiation of high temperature superconductors for fusion magnets. High temperature superconductors (type of YBCO (Yttrium-Barium-Copper-Oxygen)) are strong candidates to be applied in the next step of fusion devices. Defects induced by fast neutrons are effective pinning centres, which can significantly improve critical current densities and reduce J c anisotropy. Due to induced lattice disorder, T c is reduced. Requirements for ITER (DEMO) are partially achieved at 64 K.

The critical current of granular superconductor

International Nuclear Information System (INIS)

Ignat'ev, V.K.

1998-01-01

A mechanism of hyper vortex pinning in granular superconductors is proposed to describe the field dependence of the critical current density and pinning potential. The results are in a good agreement with the experiment. The model represents the peak effect and the percolation mechanism of conductivity in ceramic superconductors

Positron annihilation studies on high temperature superconductors

International Nuclear Information System (INIS)

Sundar, C.S.; Bharathi, A.

1991-01-01

The results of positron annihilation measurements as a function of temperature, across Tc, in a variety of high temperature superconductors such as Y-Ba-Cu-O (Y1237), Y-Ba-Cu-O (Y1248), Bi-Sr-Ca-Cu-O, Tl-Ba-Ca-Cu-O, Ba-K-Bi-O and Nd-Ce-Cu-O are presented. It is shown that the variation of annihilation parameters in the superconducting state is correlated with the diposition of the positron density distribution with respect to the superconducting CuO planes. An increase in positron lifetime is observed below Tc when the positrons probe the CuO planes whereas a decrease in lifetime is observed when the positron density overlaps predominantly with the apical oxygen atom. With this correlation, the different temperature variation of annihilation parameters, seen in the various high temperature superconductors, is understood in terms of a local charge transfer from the planar oxygen atom to the apical oxygen atom. The significance of these results in the context of various theoretical models of high temperature superconductivity is discussed. In addition, the application of positron annihilation spectroscopy to the study of oxygen defects in the Y-Ba-Cu-O, Bi-Sr-Ca-Cu-O and Nd-Ce-Cu-O is presented. (author). 53 refs., 17 figs., 2 tabs

The local structure of high-temperature superconductors

International Nuclear Information System (INIS)

Mustre de Leon, J.; Conradson, S.D.; Bishop, A.R.; Raistrick, I.D.

1992-01-01

We show how x-ray absorption fine structure (XAFS) has been successfully used in the determination of the local crystal structure of high-temperature superconductors, with advantages over traditional diffraction techniques. We review the experimental results that yielded the first evidence for an axial-oxygen-centered lattice instability connected with the superconductivity transition. The interpretation of this instability in terms of a dynamical tunneling model suggests the presence of polarons in these materials. XAFS on Tl 2 Ba 2 CuO 6 and other Tl-based superconductors indicate the presence of local instabilities in the CuO 2 planes of these materials, in addition to axial-oxygen instabilities

Macroscopic phase separation in high-temperature superconductors

Science.gov (United States)

Wen, Hai-Hu

2000-01-01

High-temperature superconductivity is recovered by introducing extra holes to the Cu-O planes, which initially are insulating with antiferromagnetism. In this paper I present data to show the macroscopic electronic phase separation that is caused by either mobile doping or electronic instability in the overdoped region. My results clearly demonstrate that the electronic inhomogeneity is probably a general feature of high-temperature superconductors. PMID:11027323

Temperature dependence of the upper critical field of type II superconductors with fluctuation effects

International Nuclear Information System (INIS)

Mikitik, G.P.

1992-01-01

Fluctuations of the order parameter are taken into consideration in an analysis of the temperature dependence of the upper critical field of a type II superconductor with a three-dimensional superconductivity. This temperature dependence is of universal applicability, to all type II superconductors, if the magnetic fields and temperatures are expressed in appropriate units. This dependence is derived explicitly for the regions of strong and weak magnetic fields. The results are applied to high T c superconductors, for which fluctuation effects are important. For these superconductors, the H c2 (T) dependence is quite different from the linear dependence characteristic of the mean-field theory, over a broad range of magnetic fields

Alloy model for high temperature superconductors

International Nuclear Information System (INIS)

Weissmann, M.; Saul, A.

1991-07-01

An alloy model is proposed for the electronic structure of high temperature superconductors. It is based on the assumption that holes and extra electrons are localized in small copper oxygen clusters, that would be the components of such alloy. This model, when used together with quantum chemical calculations on small clusters, can explain the structure observed in the experimental densities of states of both hole and electron superconductors close to the Fermi energy. The main point is the strong dependence of the energy level distribution and composition on the number of electrons in a cluster. The alloy model also suggests a way to correlate Tc with the number of holes, or extra electrons, and the number of adequate clusters to locate them. (author). 21 refs, 4 figs, 1 tab

Processing of bulk Bi-2223 high-temperature superconductor

Directory of Open Access Journals (Sweden)

Alexander Polasek

2005-12-01

Full Text Available The Bi2Sr2Ca2Cu3 O10+x (Bi-2223 is one of the main high temperature superconductors for applications. One of these applications is the Superconductor Fault Current Limiter (SCFCL, which is a very promising high temperature superconducting device. SCFCL's can be improved by using bulk superconductors with high critical currents, which requires a sufficiently dense and textured material. In the present work, a process for improving the microstructure of Bi-2223 bulk samples is investigated. Pressed precursor blocks are processed by sintering with a further partial melting step, in order to enhance the Bi-2223 grain texture and to healing cracks induced by pressing. In order to improve the microstructure, the precursor is mixed with silver powder before pressing. Samples with and without silver powder have been studied, with the aim of investigating the influence of silver on the microstructure evolution. The phase contents and the microstructure obtained have been analyzed through XRD and SEM/EDS. The electromagnetic characterization has been performed by Magnetic Susceptibility Analysis. We present and discuss the process and the properties of the superconducting blocks. High fractions of textured Bi-2223 grains have been obtained.

The design of high-Tc superconductors - Room-temperature superconductivity?

International Nuclear Information System (INIS)

Tallon, J.L.; Storey, J.G.; Mallett, B.

2012-01-01

This year is the centennial of the discovery of superconductivity and the 25th anniversary of the discovery of high-T c superconductors (HTS). Though we still do not fully understand how HTS work, the basic rules of design can be determined from studying their systematics. We know what to do to increase T c and, more importantly, what to do to increase critical current density J c . This in turn lays down a challenge for the chemist. Can the ideal design be synthesized? More importantly, what are the limits? Can one make a room-temperature superconductor? In fact fluctuations place strict constraints on this objective and provide important guidelines for the design of the ideal superconductor.

Boundary conditions in Ginsburg Landau theory and critical temperature of high-T superconductors

Science.gov (United States)

Lykov, A. N.

2008-06-01

New mixed boundary conditions to the Ginsburg-Landau equations are found to limit the critical temperature ( T) of high- T superconductors. Moreover, the value of the pseudogap in these superconductors can be explained by using the method. As a result, the macroscopic approach is proposed to increase T of cuprate superconductors.

An explanation of the irreversibility behavior in the highly- anisotropic high-temperature superconductors

International Nuclear Information System (INIS)

Gray, K.E.; Kim, D.H.

1991-01-01

The wide temperature range of the reversible, lossy state of the new high-temperature superconductors in a magnetic field was recognized soon after their discovery. This behavior, which had gone virtually undetected in conventional superconductors, has generated considerable interest, both for a fundamental understanding of the HTS and because it degrades the performance of HTS for finite-field applications. We show that recently proposed explanation of this behavior for the highly-anisotropic high-temperature superconductors, as a dimensional crossover of the magnetic vortices, is strongly supported by recent experiments on a Bi 2 Sr 2 CaCu 2 O x single crystal using the high-Q mechanical oscillator techniques

On the stability of critical state in hard superconductors with nonhomogeneous temperature profile

CERN Document Server

Tajlanov, N A

2002-01-01

One studied the problem on thermal and magnetic breaking of critical state in hard superconductors. One assumes that initial distribution of temperature and of electrical field is very nonhomogeneous one. In quasi-stationary approximation one determined the limit of occurrence of thermal and magnetic instability in a superconductor. The derived integral criterion is shown to take account of the effect of each segment of a superconductor on the threshold of occurrence of critical state instability on contrast to similar criterion for homogeneous temperature profile

Preparation of silver doped high temperature superconductors

International Nuclear Information System (INIS)

Stavek, Jiri; Zapletal, Vladimir

1989-01-01

High temperature superconductors were prepared by the controlled double-jet precipitation to manipulate the chemical composition, composition gradients, average grain size, grain size distribution, and other factors which contribute to the actual properties and performance of HTSC. The cations (Y-Ba-Cu or Bi-Pb-Ca-Sr-Cu) and oxalic anions solutions were simultaneously separately introduced to the crystallizer with a stirred solution of gelatin under conditions where the temperature, excess of oxalic anions in solution, pH, reactant addition rate, and other reaction conditions were tightly controlled to prepare the high sinterability powder. To increase the sinterability of submicron particles of produced precursor, the silver ions were introduced at the end of the controlled double-jet precipitation. This approach improves the electrical and mechanical properties of produced HTSC specimens. The controlled double jet precipitation provides a viable technique for preparation of oxide superconductors and the process is amenable for scaling up

High temperature strengthening of zirconium-toughened ceramics

International Nuclear Information System (INIS)

Claussen, N.

1986-01-01

Transformation-toughened (i.e. ZrO/sub 2/-toughened) ceramics represent a new class of high performance ceramics with spectacular strength properties at low and intermediate temperatures. However, at temperatures above about 700 0 C, most of these tough oxide-base ceramics can no longer be used as load-bearing engineering parts because of characteristic deficiencies. The aim of the present paper is to provide and discuss microstructural design strategies which may enable ZrO/sub 2/-toughened ceramics to be applied at higher temperatures. From the various strategies suggested, three appear to show good prospects, namely (a) the prevention of glassy intergranular films, (b) the addition of hard high modulus particles and (c) whikser or fibre reinforcement. Experimental approaches are presented from some ZrO/sub 2/-toughened ceramics, elg. tetragonal ZrO/sub 2/ polycrystals and ZrO/sub 2/-toughened cordierite, spinel and mullite

Panel report on high temperature ceramics

Energy Technology Data Exchange (ETDEWEB)

Nolet, T C [ed.

1979-01-01

Fundamental research is reported concerning high temperature ceramics for application in turbines, engines, batteries, gasifiers, MHD, fuel cells, heat exchangers, and hot wall combustors. Ceramics microstructure and behavior are included. (FS)

Transport properties of Pb-doped Bi4Sr3Ca3Cu4Ox semiconducting glasses and glass-ceramic superconductors

International Nuclear Information System (INIS)

Chatterjee, S.; Banerjee, S.; Mollah, S.; Chaudhuri, B.K.

1996-01-01

Electrical conductivity and thermoelectric power (TEP) of the as-quenched and annealed (at 500 degree C for 10 h and 840 degree C for 24 h) Bi 4-n Pb n Sr 3 Ca 3 Cu 4 O x (x = 0 endash 1.0) glasses have been measured. The dc conductivity data of the as-quenched and the partially annealed (at 500 degree C) glasses can be explained by considering the small-polaron hopping conduction mechanism which is found to change from the nonadiabatic to the adiabatic regime with annealing the glasses at 500 degree C. This change over is due to the presence of microcrystals in the partially annealed glasses as observed from x-ray-diffraction and scanning electron microscopic studies. This adiabatic behavior is also visualized even for some as-quenched glasses having a very small amount of the more conducting microcrystalline phase. All the 840 degree C annealed glasses are superconductors with T c between 110 and 115 K. The Seebeck coefficient (S) of the partially annealed glass system is found to be positive and increases linearly with temperature. The S values of the corresponding glass-ceramic superconductors showing broad peaks around T c . A change over in the values of S from positive (below ∼290 K) to negative (above ∼290 K) indicates the coexistence of both electrons and holes in these superconductors. The TEP data can be fitted with both the two-band model of Forro et al. [Solid State Commun. 73, 501 (1990)] and the Nagaosa-Lee model [Phys. Rev. Lett. 64, 2450 (1990)]. Therefore, the bosonic contribution in the transport properties of these superconductors, as suggested by the Nagaosa-Lee model, is supported. copyright 1996 The American Physical Society

Boundary conditions in Ginsburg-Landau theory and critical temperature of high-Tc superconductors

International Nuclear Information System (INIS)

Lykov, A.N.

2008-01-01

New mixed boundary conditions to the Ginsburg-Landau equations are found to limit the critical temperature (T c ) of high-T c superconductors. Moreover, the value of the pseudogap in these superconductors can be explained by using the method. As a result, the macroscopic approach is proposed to increase T c of cuprate superconductors

Nonmonotonic critical temperature in superconductor ferromagnet bilayers

NARCIS (Netherlands)

Fominov, Ya. V.; Fominov, I.V.; Chtchelkatchev, N.M.; Golubov, Alexandre Avraamovitch

2002-01-01

The critical temperature Tc of a superconductor/ferromagnet (SF) bilayer can exhibit nonmonotonic dependence on the thickness df of the F layer. SF systems have been studied for a long time; according to the experimental situation, a ¿dirty¿ limit is often considered which implies that the mean free

Application of high temperature superconductors for fusion

International Nuclear Information System (INIS)

Fietz, W.H.; Heller, R.; Schlachter, S.I.; Goldacker, W.

2011-01-01

The use of High Temperature Superconductor (HTS) materials in future fusion machines can increase the efficiency drastically. For ITER, W7-X and JT-60SA the economic benefit of HTS current leads was recognized after a 70 kA HTS current lead demonstrator was designed, fabricated and successfully tested by Karlsruhe Institute of Technology (KIT, which is a merge of former Forschungszentrum Karlsruhe and University of Karlsruhe). For ITER, the Chinese Domestic Agency will provide the current leads as a part of the superconducting feeder system. KIT is in charge of design, construction and test of HTS current leads for W7-X and JT-60SA. For W7-X 14 current leads with a maximum current of 18.2 kA are required that are oriented with the room temperature end at the bottom. JT60-SA will need 26 current leads (20 leads - 20 kA and 6 leads - 25.7 kA) which are mounted in vertical, normal position. These current leads are based on BiSCCO HTS superconductors, demonstrating that HTS material is now state of the art for highly efficient current leads. With respect to future fusion reactors, it would be very promising to use HTS material not only in current leads but also in coils. This would allow a large increase of efficiency if the coils could be operated at temperatures ≥65 K. With such a high temperature it would be possible to omit the radiation shield of the coils, resulting in a less complex cryostat and a size reduction of the machine. In addition less refrigeration power is needed saving investment and operating costs. However, to come to an HTS fusion coil it is necessary to develop low ac loss HTS cables for currents well above 20 kA at high fields well above 10 T. The high field rules BiSCCO superconductors out at temperatures above 50 K, but RE-123 superconductors are promising. The development of a high current, high field RE-123 HTS fusion cable will not be targeted outside fusion community and has to be in the frame of a long term development programme for

Superconductor-ferromagnet-superconductor nanojunctions from perovskite materials

International Nuclear Information System (INIS)

Štrbík, V.; Beňačka, Š.; Gaži, Š.; Španková, M.; Šmatko, V.; Knoška, J.; Gál, N.; Chromik, Š.; Sojková, M.; Pisarčík, M.

2017-01-01

Highlights: • Superconductor-ferromagnet-superconductor nanojunction. • Nanojunctions prepared by Ga"3"+ focused ion beam patterning. • Indication of triplet Cooper pair component in junction superconducting current. • Qualitative agreement with theoretical model. - Abstract: The lateral superconductor-ferromagnet–superconductor (SFS) nanojunctions based on high critical temperature superconductor YBa_2Cu_3O_x (YBCO) and half-metallic ferromagnet La_0_._6_7Sr_0_._3_3MnO_3 (LSMO) thin films were prepared to investigate a possible presence of long range triplet component (LRTC) of Cooper pairs in the LSMO. We applied Ga"3"+ focused ion beam patterning to create YBCO/LSMO/YBCO lateral type nanojunctions with LSMO length as small as 40 nm. The resistivity vs. temperature, critical current density vs. temperature and resistance vs. magnetic field dependence were studied to recognize the LRTC of Cooper pairs in the LSMO. A non-monotonic temperature dependence of junction critical current density and a decrease of the SFS nanojunction resistance in increased magnetic field were observed. Only weak manifestations of LRTC and some qualitative agreement with theory were found out in SFS nanojunctions realized from the perovskite materials. The presence of equal-spin triplet component of Cooper pairs in half-metallic LSMO ferromagnet is not such apparent as in SFS junctions prepared from low temperature superconductors NbTiN and half-metallic ferromagnet CrO_2.

High temperature resistive phase transition in A15 high temperature superconductors

International Nuclear Information System (INIS)

Chu, C.W.; Huang, C.Y.; Schmidt, P.H.; Sugawara, K.

1976-01-01

Resistive measurements were made on A15 high temperature superconductors. Anomalies indicative of a phase transition were observed at 433 0 K in a single crystal Nb 3 Sn and at 485 0 K in an unbacked Nb 3 Ge sputtered thin film. Results are compared with the high temperature transmission electron diffraction studies of Nb 3 Ge films by Schmidt et al. A possible instability in the electron energy spectrum is discussed

Time dependence of magnetization of high temperature superconductors

International Nuclear Information System (INIS)

Larkin, A.I.; Geshkenbein, V.B.

1988-10-01

Magnetization of high T c superconductors logarithmically decreases with time. There is a maximum in the temperature dependence of the coefficient at this logarithm. If one assumes that there do exist two kinds of pinning centers, then this dependence can be described in the Anderson theory of thermal creeps of Abrikosov's vortices. The temperature dependence of the critical current is also discussed. (author). 23 refs

High temperature superconductivity: Concept, preparation and testing of high Tc superconductor compounds, and applications

International Nuclear Information System (INIS)

Harara, Wafik

1992-06-01

Many studies have been carried out on high temperature superconductors with transition temperature above that of the liquid nitrogen. In this scientific study the concept and the mechanism of this phenomena are discussed, in addition the examples of preparation and testing of high temperature superconductors compounds are shown. Also the most important applications in industry are explained. (author). 15 refs., 2 tabs., 18 figs

Critical fields in high temperature superconductors

International Nuclear Information System (INIS)

Finnemore, D.K.

1991-01-01

An analysis of various methods to obtain the critical fields of the high temperature superconductors from experimental data is undertaken in order to find definitions of these variables that are consistent with the models used to define them. Characteristic critical fields of H c1 , H c2 and H c that occur in the Ginsburg-Landau theory are difficult to determine experimentally in the high temperature superconductors because there are additional physical phenomena that obscure the results. The lower critical field is difficult to measure because there are flux pinning and surface barrier effects to flux entry; the upper critical field is difficult because fluctuation effects are large at this phase boundary; the thermodynamic critical field is difficult because fluctuations make it difficult to know the field where the magnetization integral should be terminated. In addition to these critical fields there are at least two other cross-over fields. There is the so called irreversibility line where the vortices transform from a rigid flux line lattice to a fluid lattice and there is a second cross-over field associated with the transition from the fluctuation to the Abrikosov vortex regime. The presence of these new physical effects may require new vocabulary

High density high-TC ceramic superconductors by hot pressing

International Nuclear Information System (INIS)

Mak, S.; Chaklader, A.C.D.

1989-01-01

High density and high T C superconductor specimens, YBa 2 Cu 3 O x , have been produced by hot-pressing. The factors studied are the effect of hot pressing on the density, the oxygen stoichiometry, the crystal structure, and the critical temperature. Hot pressing followed by heat treatment increased the density of the specimen to 93%. The hot pressing itself did not significantly affect the oxygen content in the specimen, and although the crystal structure appeared to be orthorhombic, the specimens were not superconducting above liquid nitrogen temperature. The superconductivity was restored after head treatment in oxygen. The highest critical temperature (T C ) of the hot pressed pellets was 82K, which was slightly lower than the T C that could be obtained with the cold pressed/sintered pellets. (6 refs., 5 figs., tab.)

Passivation of high temperature superconductors

Science.gov (United States)

Vasquez, Richard P. (Inventor)

1991-01-01

The surface of high temperature superconductors such as YBa2Cu3O(7-x) are passivated by reacting the native Y, Ba and Cu metal ions with an anion such as sulfate or oxalate to form a surface film that is impervious to water and has a solubility in water of no more than 10(exp -3) M. The passivating treatment is preferably conducted by immersing the surface in dilute aqueous acid solution since more soluble species dissolve into the solution. The treatment does not degrade the superconducting properties of the bulk material.

Theory of tunneling in metal--superconductor devices: Supercurrents in the superconductor gap at zero temperature

International Nuclear Information System (INIS)

Garcia, N.; Flores, F.; Guinea, F.

1988-01-01

Tunneling experiments in metal-oxide superconductor have shown the existence of ''leakage'' currents for applied voltages V smaller than one-half of the superconductor gap Δ. These currents are independent of temperature T. Recently experiments with scanning tunneling microscopy (STM) and squeezable tunnel junctions have shown that the observation of the superconductor gap depends strongly on the resistance in the junction. In fact only for resistances larger than ∼10 6 Ω the gap is clearly observable. These experiments have been explained in terms of the perturbative Hamiltonian formalism of Bardeen. However, it may happen that this theory while applicable for very large resistances may not be so for small tunnel resistances. We present here a nonperturbative theory in all orders of the transmitivity chemical bondTochemical bond 2 and show the existence of supercurrents for values of V 2 . We believe that experiments in STM and other junctions should be interpreted in the frame of this theory

Method of manufacture of single phase ceramic superconductors

Science.gov (United States)

Singh, Jitrenda P.; Poeppel, Roger B.; Goretta, Kenneth C.; Chen, Nan

1995-01-01

A ceramic superconductor is produced by close control of oxygen partial pressure during sintering of the material. The resulting microstructure of YBa.sub.2 Cu.sub.3 O.sub.x indicates that sintering kinetics are enhanced at reduced p(O.sub.2) and that because of second phase precipitates, grain growth is prevented. The density of specimens sintered at 910.degree. C. increased from 79 to 94% theoretical when p(O.sub.2) was decreased from 0.1 to 0.0001 MPa. The increase in density with decrease in p(O.sub.2) derives from enhanced sintering kinetics, due to increased defect concentration and decreased activation energy of the rate-controlling species undergoing diffusion. Sintering at 910.degree. C resulted in a fine-grain microstructure, with an average grain size of about 4 .mu.m. Post sintering annealing in a region of stability for the desired phase converts the second phases and limits grain growth. The method of pinning grain boundaries by small scale decompositive products and then annealing to convert its product to the desired phase can be used for other complex asides. Such a microstructure results in reduced microcracking, strengths as high as 230 MPa and high critical current density capacity.

Superconductor-ferromagnet-superconductor nanojunctions from perovskite materials

Energy Technology Data Exchange (ETDEWEB)

Štrbík, V., E-mail: vladimir.strbik@savba.sk [Institute of Electrical Engineering, SAS, Dúbravská Cesta 9, Bratislava (Slovakia); Beňačka, Š.; Gaži, Š.; Španková, M.; Šmatko, V. [Institute of Electrical Engineering, SAS, Dúbravská Cesta 9, Bratislava (Slovakia); Knoška, J. [Center for Free-Electron Laser Science, DESY, Notkestraße 85, 22607, Hamburg (Germany); Department of Physics, University of Hamburg, Luruper Chaussee 149, 22607, Hamburg (Germany); Gál, N.; Chromik, Š.; Sojková, M.; Pisarčík, M. [Institute of Electrical Engineering, SAS, Dúbravská Cesta 9, Bratislava (Slovakia)

2017-02-15

Highlights: • Superconductor-ferromagnet-superconductor nanojunction. • Nanojunctions prepared by Ga{sup 3+} focused ion beam patterning. • Indication of triplet Cooper pair component in junction superconducting current. • Qualitative agreement with theoretical model. - Abstract: The lateral superconductor-ferromagnet–superconductor (SFS) nanojunctions based on high critical temperature superconductor YBa{sub 2}Cu{sub 3}O{sub x} (YBCO) and half-metallic ferromagnet La{sub 0.67}Sr{sub 0.33}MnO{sub 3} (LSMO) thin films were prepared to investigate a possible presence of long range triplet component (LRTC) of Cooper pairs in the LSMO. We applied Ga{sup 3+} focused ion beam patterning to create YBCO/LSMO/YBCO lateral type nanojunctions with LSMO length as small as 40 nm. The resistivity vs. temperature, critical current density vs. temperature and resistance vs. magnetic field dependence were studied to recognize the LRTC of Cooper pairs in the LSMO. A non-monotonic temperature dependence of junction critical current density and a decrease of the SFS nanojunction resistance in increased magnetic field were observed. Only weak manifestations of LRTC and some qualitative agreement with theory were found out in SFS nanojunctions realized from the perovskite materials. The presence of equal-spin triplet component of Cooper pairs in half-metallic LSMO ferromagnet is not such apparent as in SFS junctions prepared from low temperature superconductors NbTiN and half-metallic ferromagnet CrO{sub 2}.

Local antiferromagnetic exchange and collaborative Fermi surface as key ingredients of high temperature superconductors

Science.gov (United States)

Hu, Jiangping; Ding, Hong

2012-01-01

Cuprates, ferropnictides and ferrochalcogenides are three classes of unconventional high temperature superconductors, who share similar phase diagrams in which superconductivity develops after a magnetic order is suppressed, suggesting a strong interplay between superconductivity and magnetism, although the exact picture of this interplay remains elusive. Here we show that there is a direct bridge connecting antiferromagnetic exchange interactions determined in the parent compounds of these materials to the superconducting gap functions observed in the corresponding superconducting materials: in all high temperature superconductors, the Fermi surface topology matches the form factor of the pairing symmetry favored by local magnetic exchange interactions. We suggest that this match offers a principle guide to search for new high temperature superconductors. PMID:22536479

Filtering properties of Thue-Morse nano-photonic crystals containing high-temperature superconductor

Science.gov (United States)

Talebzadeh, Robabeh; Bavaghar, Mehrdad

2018-05-01

In this paper, we introduced new design of quasi-periodic layered structures by choosing order two of ternary Thue-Morse structure. We considered Superconductor-dielectric photonic crystal with mirror symmetric as (ABSSAB)N(BASSBA)N composed of two kinds of nano-scale dielectric layers (A and B) and high-temperature superconductor layers where N is the number of period. This structure is assumed to be the free space. By using the transfer matrix method and the two fluid model, we theoretically study the transmission spectrum of ternary Thue-Morse superconducting photonic crystals with mirror symmetry and introduce this structure as a narrow optical filter. We showed that transmission peak so-called defect mode appears itself inside the transmission spectrum of suggested structure as same as defective layered structure. Also, we analyzed the influence of various related parameters such as the operating temperature of superconductor layer on position of defect mode. The redshift of defect mode with increasing the operating temperature was observed.

High temperature fracture of ceramic materials

International Nuclear Information System (INIS)

Wiederhorn, S.M.

1979-01-01

A review is presented of fracture mechanisms and methods of lifetime prediction in ceramic materials. Techniques of lifetime prediction are based on the science of fracture mechanics. Application of these techniques to structural ceramics is limited by our incomplete understanding of fracture mechanisms in these materials, and by the occurrence of flaw generation in these materials at elevated temperatures. Research on flaw generation and fracture mechanisms is recommended as a way of improving the reliability of structural ceramics

Temperature dependence of piezoelectric properties for textured SBN ceramics.

Science.gov (United States)

Kimura, Masahiko; Ogawa, Hirozumi; Kuroda, Daisuke; Sawada, Takuya; Higuchi, Yukio; Takagi, Hiroshi; Sakabe, Yukio

2007-12-01

Temperature dependences of piezoelectric properties were studied for h001i textured ceramics of bismuth layer-structured ferroelectrics, SrBi(2)Nb(2)O(9) (SBN). The textured ceramics with varied orientation degrees were fabricated by templated, grain-growth method, and the temperature dependences of resonance frequency were estimated. Excellent temperature stability of resonance frequency was obtained for the 76% textured ceramics. The resonance frequency of the 76% textured specimens varied almost linearly over a wide temperature range. Therefore, the variation was slight, even in a high temperature region above 150 degrees C. Temperature stability of a quartz crystal oscillator is generally higher than that of a ceramic resonator around room temperature. The variation of resonance frequency for the 76% textured SrBi(2)Nb(2)O(9) was larger than that of oscillation frequency for a typical quartz oscillator below 150 degrees C also in this study. However, the variation of the textured SrBi(2)Nb(2)O(9) was smaller than that of the quartz oscillator over a wide temperature range from -50 to 250 degrees C. Therefore, textured SrBi(2)Nb(2)O(9) ceramics is a major candidate material for the resonators used within a wide temperature range.

Current sharing effect on the current instability and allowable temperature rise of composite high-TC superconductors

International Nuclear Information System (INIS)

Romanovskii, V.R.; Watanabe, K.; Awaji, S.; Nishijima, G.; Takahashi, Ken-ichiro

2004-01-01

To understand the basic mechanisms of the thermal runaway phenomenon, the limiting margin of the current instability, which may spontaneously occur in composite high-T C superconductors like multifilament Bi-based wire or tape, is derived under DC magnetic field. The current sharing and allowable temperature rise effects were considered. A static zero-dimensional model was utilized to describe the basic formulae dealing with the peculiarities of the non-isothermal change of superconducting composite voltage-current characteristic. The boundary of allowable stable values of the temperature, electric field and current are derived analytically. It was shown that permissible values of the current and electric field might be higher than those determined by use of the standard critical current criterion. In consequence of this feature, the noticeable allowable temperature rise of the composite superconductor before its transition to the normal state may be seen. The criterion for complete thermal stability condition is written describing the state when temperature of the composite equals critical temperature of a superconductor and the transport current flows stably only in matrix. The performed analysis also proves the existence of value of the volume fraction of a superconductor in composite at which its current-carrying capacity has minimum. These peculiarities are due to the stable current redistribution between superconductor and stabilizing matrix. Therefore, the current sharing not only leads to the matrix/superconductor ratio effect on the stable operating characteristics of the composite high-T C superconductors but also becomes important in the adequate description of quench process in the high-T C superconducting magnets

Magnetization hysteresis and history effects in conventional and high temperature superconductors

International Nuclear Information System (INIS)

Chaddah, P.

1990-01-01

The magnetization in hard superconductors is irreversible and history-dependent, and cannot be a priori compared with the equilibrium magnetization. These features have gained prominence in the high T c superconductors (HTSC) where the short coherence length presumably leads to intrinsic pinning. Various experimental features, first noticed in the HTSC, are explained by an extension of Bean's macroscopic model to include temperature variations and the field dependence of J c . This paper discusses recent measurements of history effects in niobium and show their similarities with other published data on HTSC. The authors also present our calculations of magnetization behaviour in hard superconductors of sample-shapes having a non-zero demagnetization factor

Cryocooler applications for high-temperature superconductor magnetic bearings

International Nuclear Information System (INIS)

Niemann, R. C.

1998-01-01

The efficiency and stability of rotational magnetic suspension systems are enhanced by the use of high-temperature superconductor (HTS) magnetic bearings. Fundamental aspects of the HTS magnetic bearings and rotational magnetic suspension are presented. HTS cooling can be by liquid cryogen bath immersion or by direct conduction, and thus there are various applications and integration issues for cryocoolers. Among the numerous cryocooler aspects to be considered are installation; operating temperature; losses; and vacuum pumping

Second-Generation High-Temperature Superconductor Wires for the Electric Power Grid

Science.gov (United States)

Malozemoff, A. P.

2012-08-01

Superconductors offer major advantages for the electric power grid, including high current and power capacity, high efficiency arising from the lossless current flow, and a unique current-limiting functionality arising from a superconductor-to-resistive transition. These advantages can be brought to bear on equipment such as underground power cables, fault current limiters, rotating machinery, transformers, and energy storage. The first round of significant commercial-scale superconductor power-equipment demonstrations, carried out during the past decade, relied on a first-generation high-temperature superconductor (HTS) wire. However, during the past few years, with the recent commercial availability of high-performance second-generation HTS wires, power-equipment demonstrations have increasingly been carried out with these new wires, which bring important advantages. The foundation is being laid for commercial expansion of this important technology into the power grid.

High critical temperature superconductors: Progress achieved after two years

International Nuclear Information System (INIS)

Maillard, J.M.; Rammal, R.; Vittorge, M.C.

1989-01-01

Progress concerning the theory of high temperature superconductors and activity of laboratories of the CNRS (France) are reviewed and news on strategy, budgets, theoretical research, materials characterization, fabrication process technology transfers, commercialisation, uses and data bases are given [fr

Computer modelling of high-temperature superconductors using an A-V formulation

Energy Technology Data Exchange (ETDEWEB)

Ruiz-Alonso, D; Coombs, T; Campbell, A M [Cambridge University Engineering Department, Trumpington Street, Cambridge, CB2 1PZ (United Kingdom)

2004-05-01

Numerical methods for calculating the current and field distribution in high-temperature superconductors under non-uniform time-varying fields are being investigated. The highly non-linear behaviour of superconductors makes them difficult to analyse and computationally expensive. This non-linear behaviour is often accounted for through a non-linear E-J constitutive law. This paper proposes a fast method based on the finite element method to solve 2D and axially symmetric problems that contain superconducting materials. An E-J power law together with an A-V formulation is used to calculate the induction of currents in the superconductor due to time-varying external magnetic fields or forced transport current. Experimental data of a magnet-above-superconductor system is obtained in order to validate the model. In the experimental set-up a magnet is brought towards a superconducting puck at different speed rates and is also vibrated on top of it. The force between the magnet and the superconductor is measured and is found to vary with both time and frequency of excitation.

Computer modelling of high-temperature superconductors using an A-V formulation

International Nuclear Information System (INIS)

Ruiz-Alonso, D; Coombs, T; Campbell, A M

2004-01-01

Numerical methods for calculating the current and field distribution in high-temperature superconductors under non-uniform time-varying fields are being investigated. The highly non-linear behaviour of superconductors makes them difficult to analyse and computationally expensive. This non-linear behaviour is often accounted for through a non-linear E-J constitutive law. This paper proposes a fast method based on the finite element method to solve 2D and axially symmetric problems that contain superconducting materials. An E-J power law together with an A-V formulation is used to calculate the induction of currents in the superconductor due to time-varying external magnetic fields or forced transport current. Experimental data of a magnet-above-superconductor system is obtained in order to validate the model. In the experimental set-up a magnet is brought towards a superconducting puck at different speed rates and is also vibrated on top of it. The force between the magnet and the superconductor is measured and is found to vary with both time and frequency of excitation

Advanced magneto-optical Kerr effect measurements of superconductors at low temperatures

Directory of Open Access Journals (Sweden)

Claudia Stahl

2017-10-01

Full Text Available Magneto-optical Kerr-effect (MOKE measurements of superconducting films with soft-magnetic coatings are performed at low temperatures using a laser-based MOKE set-up. An elaborate measurement scheme with internal reference allows the quantitative comparison of the temperature dependent Kerr-amplitude with the magnetic field generated by supercurrents. For this purpose, an amorphous CoFeB thin film exhibiting a large Kerr-signal is deposited directly on top of the YBCO superconductor acting as field sensing layer. It is shown that the resulting magnetic hysteresis loops of the soft-magnetic film can be used to reconstruct the electric properties of the superconductor.

Influence of oxygen disordering on static magnetic susceptibility of YBa2Cu3O7-x ceramics

International Nuclear Information System (INIS)

Sokolov, B.Yu.; Vil'danov, R.R.

2008-01-01

Influence of disordering of the populated oxygen positions in YBa 2 Cu 3 O 7-x ceramic's structure on its static magnetic susceptibility in the range of temperatures T>Tc is investigated. For occurrence of disordering the initial ceramics YBa 2 Cu 3 O 6,9 was annealed at T=520 C with the subsequent quenching in liquid nitrogen. Evolutions of a magnetic susceptibility and resistance of annealed ceramics during its air storage at a room temperature were studied. It is revealed that, unlike the initial optimum doped ceramics, annealed samples have appreciable temperature dependence of a magnetic susceptibility. Interpretation of results is executed on the basis of model of electronic phase separation and occurrence of a pseudo gap in a energy spectrum of free carriers of a superconductor. (authors)

American superconductor technology to help CERN to explore the mysteries of matter company's high temperature superconductor wire to be used in CERN's Large Hadron Collider

CERN Multimedia

2003-01-01

American Superconductor Corporation has been selected by CERN, to provide 14,000 meters of high temperature superconductor (HTS) wire for current lead devices that will be used in CERN's Large Hadron Collider (1 page).

Survey of potential electronic applications of high temperature superconductors

International Nuclear Information System (INIS)

Hammond, R.B.; Bourne, L.C.

1991-01-01

In this paper the authors present a survey of the potential electronic applications of high temperature superconductor (HTSC) thin films. During the past four years there has been substantial speculation on this topic. The authors will cover only a small fraction of the potential electronic applications that have been identified. Their treatment is influenced by the developments over the past few years in materials and device development and in market analysis. They present their view of the most promising potential applications. Superconductors have two important properties that make them attractive for electronic applications. These are (a) low surface resistance at high frequencies, and (b) the Josephson effect

Potential aerospace applications of high temperature superconductors

Science.gov (United States)

Selim, Raouf

1994-01-01

The recent discovery of High Temperature Superconductors (HTS) with superconducting transition temperature, T(sub c), above the boiling point of liquid nitrogen has opened the door for using these materials in new and practical applications. These materials have zero resistance to electric current, have the capability of carrying large currents and as such have the potential to be used in high magnetic field applications. One of the space applications that can use superconductors is electromagnetic launch of payloads to low-earth-orbit. An electromagnetic gun-type launcher can be used in small payload systems that are launched at very high velocity, while sled-type magnetically levitated launcher can be used to launch larger payloads at smaller velocities. Both types of launchers are being studied by NASA and the aerospace industry. The use of superconductors will be essential in any of these types of launchers in order to produce the large magnetic fields required to obtain large thrust forces. Low Temperature Superconductor (LTS) technology is mature enough and can be easily integrated in such systems. As for the HTS, many leading companies are currently producing HTS coils and magnets that potentially can be mass-produced for these launchers. It seems that designing and building a small-scale electromagnetic launcher is the next logical step toward seriously considering this method for launching payloads into low-earth-orbit. A second potential application is the use of HTS to build sensitive portable devices for the use in Non Destructive Evaluation (NDE). Superconducting Quantum Interference Devices (SQUID's) are the most sensitive instruments for measuring changes in magnetic flux. By using HTS in SQUID's, one will be able to design a portable unit that uses liquid nitrogen or a cryocooler pump to explore the use of gradiometers or magnetometers to detect deep cracks or corrosion in structures. A third use is the replacement of Infra-Red (IR) sensor leads on

Transport properties of high-temperature superconductors: Surface vs bulk effect

International Nuclear Information System (INIS)

Burlachkov, L.; Koshelev, A.E.; Vinokur, V.M.

1996-01-01

We investigate surface-related transport properties of high-temperature superconductors. We find the mean vortex velocity under applied transport current determined by the activation energies for vortex penetration and exit through the Bean-Livingston barrier. We determine the current distribution between the surfaces of superconductor and the field and current dependencies of the transport activation energies. For a three-dimensional superconductor the transport activation energy, U s 3D , is found to decrease with the external field, H, and transport current, J, as U s 3D ∝H -1/2 and U s 3D ∝J -1/2 , respectively. In the quasi-two-dimensional compounds, U s 2D decays logarithmically with field and current. The interplay between the surface and the bulk contributions to the transport properties, such as current-voltage characteristics, is discussed. copyright 1996 The American Physical Society

A high temperature testing system for ceramic composites

Science.gov (United States)

Hemann, John

1994-01-01

Ceramic composites are presently being developed for high temperature use in heat engine and space power system applications. The operating temperature range is expected to be 1090 to 1650 C (2000 F to 3000 F). Very little material data is available at these temperatures and, therefore, it is desirable to thoroughly characterize the basic unidirectional fiber reinforced ceramic composite. This includes testing mainly for mechanical material properties at high temperatures. The proper conduct of such characterization tests requires the development of a tensile testing system includes unique gripping, heating, and strain measuring devices which require special considerations. The system also requires an optimized specimen shape. The purpose of this paper is to review various techniques for measuring displacements or strains, preferably at elevated temperatures. Due to current equipment limitations it is assumed that the specimen is to be tested at a temperature of 1430 C (2600F) in an oxidizing atmosphere. For the most part, previous high temperature material characterization tests, such as flexure and tensile tests, have been performed in inert atmospheres. Due to the harsh environment in which the ceramic specimen is to be tested, many conventional strain measuring techniques can not be applied. Initially a brief description of the more commonly used mechanical strain measuring techniques is given. Major advantages and disadvantages with their application to high temperature tensile testing of ceramic composites are discussed. Next, a general overview is given for various optical techniques. Advantages and disadvantages which are common to these techniques are noted. The optical methods for measuring strain or displacement are categorized into two sections. These include real-time techniques. Finally, an optical technique which offers optimum performance with the high temperature tensile testing of ceramic composites is recommended.

Electronic phase separation and high temperature superconductors

International Nuclear Information System (INIS)

Kivelson, S.A.

1994-01-01

The authors review the extensive evidence from model calculations that neutral holes in an antiferromagnet separate into hole-rich and hole-poor phases. All known solvable limits of models of holes in a Heisenberg antiferromagnet exhibit this behavior. The authors show that when the phase separation is frustrated by the introduction of long-range Coulomb interactions, the typical consequence is either a modulated (charge density wave) state or a superconducting phase. The authors then review some of the strong experimental evidence supporting an electronically-driven phase separation of the holes in the cuprate superconductors and the related Ni oxides. Finally, the authors argue that frustrated phase separation in these materials can account for many of the anomalous normal state properties of the high temperature superconductors and provide the mechanism of superconductivity. In particular, it is shown that the T-linear resistivity of the normal state is a paraconductivity associated with a novel composite pairing, although the ordered superconducting state is more conventional

The superconductor

International Nuclear Information System (INIS)

Lad, J.K.

1979-01-01

Techniques for fabrication of a few important superconductors like Nb, Ti and Nb 3 Sn are described. Copper or bronze or both can be used as a matrix in the superconductor. Current densities obtained for different ratios of copper to superconductor are studied. The specifications of multi-filament Nb 3 Sn superconductors are given. The relative merits of the two superconductors are discussed. The temperature range obtained is approximately 3 0 K and a magnetic field of 9T(tesla) can be achieved. (A.K.)

Levitation Experiment Using a High-Temperature Superconductor Coil for a Plasma Confinement Device

Science.gov (United States)

Morikawa, Junji; Ozawa, Daisaku; Ogawa, Yuichi; Yanagi, Nagato; Hamaguchi, Sinji; Mito, Toshiyuki

2001-10-01

Levitation experiments using a high-temperature superconductor coil have been carried out. A coil with a minor radius of 42 mm was fabricated with a Bi-2223 tape conductor, and immersed in the liquid nitrogen. The coil current was induced by the field-cooling method up to the critical current value. The current decay of the coil can be accounted for by the flux flow resistance and the normal resistance at the lap joint. The high-temperature superconductor coil can be levitated for 4 min or more within an accuracy of 25-30 μm.

High-temperature superconductors learn from heavy fermions

International Nuclear Information System (INIS)

Varma, C.

1998-01-01

Physicists have been intrigued by the nature of high-temperature superconductors since they were discovered 12 years ago. Superconducting materials lose their electrical resistance below a transition temperature, T c , and certain copper-oxide compounds remain superconducting at temperatures up to 160 K. Research into these materials has been driven by fundamental, yet intractable, questions about the basic concepts of condensed-matter physics and the mechanisms of superconductivity. A key question is how the electrons come together to form the Cooper pairs responsible for superconductivity. Physicists at Cambridge University have now studied two heavy-fermion compounds experimentally, and have found that the electron pairing is caused by magnetic effects (N Mathur et al. 1998 Nature 394 39). In this article the author describes their research. (UK)

4TH International Conference on High-Temperature Ceramic Matrix Composites

National Research Council Canada - National Science Library

2001-01-01

.... Topic to be covered include fibers, interfaces, interphases, non-oxide ceramic matrix composites, oxide/oxide ceramic matrix composites, coatings, and applications of high-temperature ceramic matrix...

Finding high-temperature superconductors by metallizing the σ-bonding electrons

International Nuclear Information System (INIS)

Gao Miao; Lu Zhongyi; Xiang Tao

2015-01-01

Raising superconducting transition temperature (T_c) is an important task of fundamental research on superconductivity. It is also a prerequisite for the large scale application of superconductors. Since the microscopic mechanism of high-T_c superconductivity is unknown, the conventional approach for increasing T_c is either to apply high pressure to a material which has the potential to become superconducting, or to push it close to an antiferromagnetic or some other quantum instability point by chemical doping. In this article, the authors point out that another general approach for raising T_c is to lift the σ-bonding bands to the Fermi level, or to metallize the σ-bonding elections. This approach can increase the probability of finding a novel high-T_c superconductor because the coupling of σ-bonding electrons with phonons is generally strong and the superconducting transition induced by this interaction can occur at relatively high temperatures. After elucidating the underlying mechanism, the authors discuss a number of schemes to metallize σ-bonding electrons, and present their recent prediction for the crystalline and electronic structures of two potential high-T_c superconductors, Li_2B_3C and Li_3B_4C_2, with T_c higher than 50 K. (authors)

The refrigeration of high temperature superconductors between 25K and 65K

International Nuclear Information System (INIS)

Richardson, R.N.; Scurlock, R.G.; Tavner, A.C.R.

1996-01-01

The present state of the art indicates that acceptable j - H characteristics for power applications of the new high Tc superconductors will only be achieved using materials at temperatures below liquid nitrogen temperature. A boiling point of 27.1K and high specific cooling capacity make neon an eminently suitable choice of refrigerant at these temperatures. A cryostat has been constructed which employs a two stage Gifford-McMahon cooler to liquefy neon gas. The cryostat contains up to 5 litres of liquid neon which can be used for open-quote in-situ close-quote experiments or transfer to another cryostat. Another set of cryostats are being used with liquid nitrogen/oxygen mixtures at reduced pressure for temperatures down to 50K. All these cryostats provide a core facility for characterising and operating high T c superconductors at Southampton

Leaders in high temperature superconductivity commercialization win superconductor industry award

CERN Multimedia

2007-01-01

CERN's Large Hadron Collider curretn leads project head Amalia Ballarino named superconductor industry person of the year 2006. Former high temperature superconductivity program manager at the US Department of energy James Daley wins lifetime achievement award. (1,5 page)

Maglev system concept using 20-K high-temperature superconductors and hyperconductors

Science.gov (United States)

Hull, J. R.; He, Jianliang

A magnetically levitated high-speed ground transportation concept is proposed that uses high-temperature superconductors or hyperconductors, cooled by liquid hydrogen at 20 K, to provide levitation. An on-board hydrogen-powered turbine/generator provides electricity for propulsion by linear induction motors. The liquid hydrogen is used to cool the superconductors and the windings of the generator and motors before combusting in the turbine. The principal advantage of this system is the potential to greatly reduce the cost of the guideway, which is completely passive.

Plastic superconductor bearings any size-any shape: 77 K and up

Science.gov (United States)

Reick, Franklin G.

1991-01-01

'Friction free' bearings at 77 K or higher are possible using the high T(sub c) copper oxide ceramic superconductors. The conventional method for making such bearings is to use a sintered ceramic monolith. This puts great restraints on size, shape, and postforming machining. The material is hard and abrasive. It is possible to grind up ceramic superconductors and suspend the granules in a suitable matrix. Mechanical properties improve and are largely dependent on the binder. The Meissner effect is confined to individual grains containing electron vortices. Tracks, rails, levitation areas, and bearings can be made this way with conventional plastic molding and extruding machines or by painting. The parts are easily machined. The sacrifice is in bulk electrical conductivity. A percolating wick feed for LN2 is used to cool remote superconductors and large areas quite effectively. A hollow spheroid or cylinder of superconductor material is molded with the internal surfaces shielded by the Meissner effect. It can be thought of as the DC magnetic analog of the Faraday cage and the inside is the 'Meissner space'. It is selective. The AC fields are transmitted with minor attenuation. Particle size and distribution have a profound effect on final magnetic and electrical characteristics.

Plastic superconductor bearings any size-any shape: 77 K and up

International Nuclear Information System (INIS)

Reick, F.G.

1991-01-01

'Friction free' bearings at 77 K or higher are possible using the high T(sub c) copper oxide ceramic superconductors. The conventional method for making such bearings is to use a sintered ceramic monolith. This puts great restraints on size, shape, and postforming machining. The material is hard and abrasive. It is possible to grind up ceramic superconductors and suspend the granules in a suitable matrix. Mechanical properties improve and are largely dependent on the binder. The Meissner effect is confined to individual grains containing electron vortices. Tracks, rails, levitation areas, and bearings can be made this way with conventional plastic molding and extruding machines or by painting. The parts are easily machined. The sacrifice is in bulk electrical conductivity. A percolating wick feed for LN2 is used to cool remote superconductors and large areas quite effectively. A hollow spheroid or cylinder of superconductor material is molded with the internal surfaces shielded by the Meissner effect. It can be thought of as the DC magnetic analog of the Faraday cage and the inside is the 'Meissner space'. It is selective. The AC fields are transmitted with minor attenuation. Particle size and distribution have a profound effect on final magnetic and electrical characteristics

Ceramic Integration Technologies for Advanced Energy Systems: Critical Needs, Technical Challenges, and Opportunities

Science.gov (United States)

Singh, Mrityunjay

2010-01-01

Advanced ceramic integration technologies dramatically impact the energy landscape due to wide scale application of ceramics in all aspects of alternative energy production, storage, distribution, conservation, and efficiency. Examples include fuel cells, thermoelectrics, photovoltaics, gas turbine propulsion systems, distribution and transmission systems based on superconductors, nuclear power generation and waste disposal. Ceramic integration technologies play a key role in fabrication and manufacturing of large and complex shaped parts with multifunctional properties. However, the development of robust and reliable integrated systems with optimum performance requires the understanding of many thermochemical and thermomechanical factors, particularly for high temperature applications. In this presentation, various needs, challenges, and opportunities in design, fabrication, and testing of integrated similar (ceramic ceramic) and dissimilar (ceramic metal) material www.nasa.gov 45 ceramic-ceramic-systems have been discussed. Experimental results for bonding and integration of SiC based Micro-Electro-Mechanical-Systems (MEMS) LDI fuel injector and advanced ceramics and composites for gas turbine applications are presented.

Eight-fold quantum states blossom in a high-temperature superconductor

CERN Multimedia

2003-01-01

"Researchers based at Lawrence Berkeley National Laboratory and the University of California at Berkeley have used a scanning tunneling microscope (STM) to reveal eight-fold patterns of quasiparticle interference in the high-temperature superconductor Bi-2212 (bismuth strontium calcium copper oxide)" (2 pages).

Electronic ceramics in high-temperature environments

International Nuclear Information System (INIS)

Searcy, A.W.; Meschi, D.J.

1982-01-01

Simple thermodynamic means are described for understanding and predicting the influence of temperature changes, in various environments, on electronic properties of ceramics. Thermal gradients, thermal cycling, and vacuum annealing are discussed, as well as the variations of ctivities and solubilities with temperature. 7 refs

Modeling forces in high-temperature superconductors

International Nuclear Information System (INIS)

Turner, L. R.; Foster, M. W.

1997-01-01

We have developed a simple model that uses computed shielding currents to determine the forces acting on a high-temperature superconductor (HTS). The model has been applied to measurements of the force between HTS and permanent magnets (PM). Results show the expected hysteretic variation of force as the HTS moves first toward and then away from a permanent magnet, including the reversal of the sign of the force. Optimization of the shielding currents is carried out through a simulated annealing algorithm in a C++ program that repeatedly calls a commercial electromagnetic software code. Agreement with measured forces is encouraging

Temperature Measurement of Ceramic Materials Using a Multiwavelength Pyrometer

Science.gov (United States)

Ng, Daniel; Fralick, Gustave

1999-01-01

The surface temperatures of several pure ceramic materials (alumina, beryllia, magnesia, yittria and spinel) in the shape of pellets were measured using a multiwavelength pyrometer. In one of the measurements, radiation signal collection is provided simply by an optical fiber. In the other experiments, a 4.75 inch (12 cm) parabolic mirror collects the signal for the spectrometer. Temperature measurement using the traditional one- and two-color pyrometer for these ceramic materials is difficult because of their complex optical properties, such as low emissivity which varies with both temperature and wavelength. In at least one of the materials, yittria, the detected optical emission increased as the temperature was decreased due to such emissivity variation. The reasons for such changes are not known. The multiwavelength pyrometer has demonstrated its ability to measure surface temperatures under such conditions. Platinum electrodes were embedded in the ceramic pellets for resistance measurements as the temperature changed.

Levitation experiment using a high-temperature superconductor coil for a plasma confinement device

Energy Technology Data Exchange (ETDEWEB)

Morikawa, Junji; Ogawa, Yuichi [Tokyo Univ., High Temperature Plasma Center, Tokyo (Japan); Ozawa, Daisaku [Tokyo Univ., School of Engineering, Tokyo (Japan); Yanagi, Nagato; Hamaguchi, Sinji; Mito, Toshiyuki [National Institute for Fusion Science, Toki, Gifu (Japan)

2001-10-01

Levitation experiments using a high-temperature superconductor coil have been carried out. A coil with a minor radius of 42 mm was fabricated with a Bi-2223 tape conductor, and immersed in the liquid nitrogen. The coil current was induced by the field-cooling method up to the critical current value. The current decay of the coil can be accounted for by the flux flow resistance and the normal resistance at the lap joint. The high-temperature superconductor coil can be levitated for 4 min or more within an accuracy of 25-30 {mu}m. (author)

Levitation experiment using a high-temperature superconductor coil for a plasma confinement device

International Nuclear Information System (INIS)

Morikawa, Junji; Ogawa, Yuichi; Ozawa, Daisaku; Yanagi, Nagato; Hamaguchi, Sinji; Mito, Toshiyuki

2001-01-01

Levitation experiments using a high-temperature superconductor coil have been carried out. A coil with a minor radius of 42 mm was fabricated with a Bi-2223 tape conductor, and immersed in the liquid nitrogen. The coil current was induced by the field-cooling method up to the critical current value. The current decay of the coil can be accounted for by the flux flow resistance and the normal resistance at the lap joint. The high-temperature superconductor coil can be levitated for 4 min or more within an accuracy of 25-30 μm. (author)

Superconductors

International Nuclear Information System (INIS)

1988-01-01

The chapter 6.3 p. 143 to 153 of this book deals with superconductors 19 items are briefly presented with address of manufacturer or laboratory to contact, mainly in the USA or Japan. In particular magnets, films, high temperature superconductors and various applications are presented [fr

Magnetic irreversibility in granular superconductors: ac susceptibility study

International Nuclear Information System (INIS)

Perez, F.; Obradors, X.; Fontcuberta, J.; Vallet, M.; Gonzalez-Calbet, J.

1991-01-01

Ac susceptibility measurements of a ceramic weak-coupled superconductor in very low ac fields (2mG, 111Hz) are reported. We present evidence for the observation of the magnetic irreversibility following a ZFC-FC thermal cycling by means of ac susceptibilty measurements. It is shown that this technique also reflect local magnetic field effects in granular superconductors, as previously suggested in microwave surface resistance and I-V characteristics. (orig.)

Synthesis and Microstructure Properties of (Bi,Pb2Sr2Ca1Cu2Oy Ceramic Superconductor

Directory of Open Access Journals (Sweden)

nurmalita .

2015-11-01

Full Text Available Properties of (Bi, Pb2Sr2Ca1Cu2Oy ceramic superconductors were prepared by the melt textured growth methods in order to investigate the effects of the slow cooling time on the microstructur.  Phase analyses of the samples by X-ray diffraction (XRD has been carried out to assess the effects of the slow cooling time. From XRD analyses, the addition to the sample of  the slow cooling time degrades formation of the high-Tc Bi-2212 phase. The possible reasons for the observed degradation in the microstructure properties due to the slow cooling time addition were discussed.

Measurement of relative permittivity of LTCC ceramic at different temperatures

Directory of Open Access Journals (Sweden)

Qiulin Tan

2014-02-01

Full Text Available Devices based on LTCC (low-temperature co-fired ceramic technology are more widely applied in high temperature environments, and the temperature-dependent properties of the LTCC material play an important role in measurements of the characteristics of these devices at high temperature. In this paper, the temperature-dependence of the relative permittivity of DuPont 951 LTCC ceramic is studied from room temperature to 500 °C. An expression for relative permittivity is obtained, which relates the relative permittivity to the resonant frequency, inductance, parasitic capacitance and electrode capacitance of the LTCC sample. Of these properties, the electrode capacitance is the most strongly temperature-dependent. The LTCC sample resonant frequency, inductance and parasitic capacitance were measured (from room temperature to 500 °C with a high temperature measurement system comprising a muffle furnace and network analyzer. We found that the resonant frequency reduced and the inductance and parasitic capacitance increased slightly as the temperature increases. The relative permittivity can be calculated from experimental frequency, inductance and parasitic capacitance measurements. Calculating results show that the relative permittivity of DuPont 951 LTCC ceramic ceramic increases to 8.21 from room temperature to 500 °C.

Design and manufacture of ceramic heat pipes for high temperature applications

International Nuclear Information System (INIS)

Meisel, Peter; Jobst, Matthias; Lippmann, Wolfgang; Hurtado, Antonio

2015-01-01

Heat exchangers based on ceramic heat pipes were designed for use under highly abrasive and corrosive atmospheres at temperatures in the range of 800–1200 °C for high-temperature power-engineering applications. The presented heat pipes are gravity assisted and based on a multi-layer concept comprising a ceramic cladding and an inner metal tube that contains sodium as the working fluid. Hermetical encapsulation of the working fluid was achieved by electron-beam welding of the inner metal tube. Subsequently, closure of the surrounding ceramic tube was performed by laser brazing technology using a glass solder. Temperature resistance and functionality of the manufactured ceramic thermosyphons could be confirmed experimentally in a hot combustion gas atmosphere at temperatures up to 1100 °C. The ceramic tubes used had an outer diameter of 22 mm and a total length of 770 mm. The measured axial heat transfer of the ceramic gravity assisted heat pipes at the stationary operating point with cold/hot gas temperature of 100 °C/900 °C was 400 W. The result of the calculation using the created mathematical model amounted to 459 W. - Highlights: • Heat-pipe design consists of a ceramic shell and an inner metallic tube. • Laser brazing technology is suitable to seal ceramic heat-pipes. • Thermal characteristic of double wall thermosyphon was modelled using FEM code. • Experimental investigations demonstrated functionality of double wall thermosyphons

Low temperature sintering of fluorapatite glass-ceramics

Science.gov (United States)

Denry, Isabelle; Holloway, Julie A.

2014-01-01

Fluorapatite glass-ceramics have been shown to be excellent candidates as scaffold materials for bone grafts, however, scaffold production by sintering is hindered by concurrent crystallization of the glass. Our goal was to investigate the effect of Ca/Al ratio on the sintering behavior of Nb-doped fluorapatite-based glasses in the SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2 system. Glass compositions with Ca/Al ratio of 1 (A), 2 (B), 4 (C) and 19 (D) were prepared by twice melting at 1525°C for 3h. Glasses were either cast as cylindrical ingots or ground into powders. Disc-shaped specimens were prepared by either sectioning from the ingots or powder-compacting in a mold, followed by heat treatment at temperatures ranging between 700 and 1050°C for 1h. The density was measured on both sintered specimens and heat treated discs as controls. The degree of sintering was determined from these measurements. XRD showed that fluorapatite crystallized in all glass-ceramics. A high degree of sintering was achieved at 775°C for glass-ceramic D (98.99±0.04%), and 900°C for glass-ceramic C (91.31±0.10). Glass-ceramics A or B were only partially sintered at 1000°C (63.6±0.8% and 74.1±1.5%, respectively). SEM revealed a unique microstructure of micron-sized spherulitic fluorapatite crystals in glass-ceramics C and D. Increasing the Ca/Al ratio promoted low temperature sintering of fluorapatite glass-ceramics, which are traditionally difficult to sinter. PMID:24252652

High pressure study of high-temperature superconductors

Energy Technology Data Exchange (ETDEWEB)

Souliou, Sofia-Michaela

2014-09-29

The current thesis studies experimentally the effect of high external pressure on high-T{sub c} superconductors. The structure and lattice dynamics of several members of the high-T{sub c} cuprate and Fe-based superconductors families were investigated by means of Raman spectroscopy and X-ray diffraction under well-controlled, hydrostatic high pressure and low temperature conditions. The lattice dynamics of the high-T{sub c} superconductor YBa{sub 2}Cu{sub 3}O{sub 6+x} have been investigated systematically by Raman spectroscopy as a function of doping (x = 0.95, 0.75, 0.60, 0.55, and 0.45) and external pressure. Under ambient pressure conditions, in addition to the Raman modes expected from group theory, we observe new Raman active phonons upon cooling the underdoped samples, at temperatures well above the superconducting transition temperature. The doping dependence and the onset temperatures of the new Raman features suggest that they are associated with the incommensurate charge density wave (CDW) state recently discovered in underdoped cuprates using synchrotron X-ray scattering techniques. Under high pressure conditions (from 2 to 12 GPa), our Raman measurements on highly ordered underdoped YBa{sub 2}Cu{sub 3}O{sub 6.55} samples do not show any of the new Raman phonons seen at ambient pressure. High pressure and low temperature Raman measurements have been performed on the underdoped superconductor YBa{sub 2}Cu{sub 4}O{sub 8}. A clear renormalization of some of the Raman phonons is seen below T{sub c} as a result of the changes in the phonon self-energy upon the opening of the superconducting gap, with the most prominent one being that of the B{sub 1g}-like buckling phonon mode. The amplitude of this renormalization strongly increases with pressure, resembling the effect of hole doping in YBa{sub 2}Cu{sub 3}O{sub 6+x}. At ∝ 10 GPa, the system undergoes a reversible pressure-induced structural phase transition to a non-centrosymmmetric structure (space group

High pressure study of high-temperature superconductors

International Nuclear Information System (INIS)

Souliou, Sofia-Michaela

2014-01-01

The current thesis studies experimentally the effect of high external pressure on high-T c superconductors. The structure and lattice dynamics of several members of the high-T c cuprate and Fe-based superconductors families were investigated by means of Raman spectroscopy and X-ray diffraction under well-controlled, hydrostatic high pressure and low temperature conditions. The lattice dynamics of the high-T c superconductor YBa 2 Cu 3 O 6+x have been investigated systematically by Raman spectroscopy as a function of doping (x = 0.95, 0.75, 0.60, 0.55, and 0.45) and external pressure. Under ambient pressure conditions, in addition to the Raman modes expected from group theory, we observe new Raman active phonons upon cooling the underdoped samples, at temperatures well above the superconducting transition temperature. The doping dependence and the onset temperatures of the new Raman features suggest that they are associated with the incommensurate charge density wave (CDW) state recently discovered in underdoped cuprates using synchrotron X-ray scattering techniques. Under high pressure conditions (from 2 to 12 GPa), our Raman measurements on highly ordered underdoped YBa 2 Cu 3 O 6.55 samples do not show any of the new Raman phonons seen at ambient pressure. High pressure and low temperature Raman measurements have been performed on the underdoped superconductor YBa 2 Cu 4 O 8 . A clear renormalization of some of the Raman phonons is seen below T c as a result of the changes in the phonon self-energy upon the opening of the superconducting gap, with the most prominent one being that of the B 1g -like buckling phonon mode. The amplitude of this renormalization strongly increases with pressure, resembling the effect of hole doping in YBa 2 Cu 3 O 6+x . At ∝ 10 GPa, the system undergoes a reversible pressure-induced structural phase transition to a non-centrosymmmetric structure (space group Imm2). The structural transition is clearly reflected in the high pressure

Flux motion and dissipation in high-temperature superconductors

International Nuclear Information System (INIS)

Gray, K.E.; Kim, D.H.

1991-01-01

The effects on flux motion and dissipation of interlayer coupling of the Cu-O planes along the c-axis are considered for the high-temperature superconductors (HTS). It is argued that for the highly-anisotropic HTS, the weak interlayer coupling plays a dominant role that can be described by incoherent Josephson tunneling between superconducting Cu-O bi- or tri-layers. In YBa 2 Cu 3 O 7 , the layers are strongly coupled, presumably because the conducting Cu-O chains short circuit the Josephson tunneling, so that these effects are weak or missing. Recently, the effects of anisotropy and fluctuations on critical current densities, J c (T,H) and the field-induced broadening of resistivity transitions, ρ(T,H), have been studied in high-temperature superconductors (HTS). Although the broadening looks similar for the applied field, H, oriented either parallel to the superconducting Cu-O layers (H parallel ab) or parallel to the c-axis (H parallel c), its width and the detailed shape of ρ(T,H) are different. The explanations given in this paper for the highly anisotropic HTS differ in detail for the two cases, but have a crucial feature in common: they result from fluctuations affecting the Josephson coupling across the interlayer junctions

Temperature variation in metal ceramic technology analyzed using time domain optical coherence tomography

Science.gov (United States)

Sinescu, Cosmin; Topala, Florin I.; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian G.

2014-01-01

The quality of dental prostheses is essential in providing good quality medical services. The metal ceramic technology applied in dentistry implies ceramic sintering inside the dental oven. Every ceramic material requires a special sintering chart which is recommended by the producer. For a regular dental technician it is very difficult to evaluate if the temperature inside the oven remains the same as it is programmed on the sintering chart. Also, maintaining the calibration in time is an issue for the practitioners. Metal ceramic crowns develop a very accurate pattern for the ceramic layers depending on the temperature variation inside the oven where they are processed. Different patterns were identified in the present study for the samples processed with a variation in temperature of +30 °C to +50 °C, respectively - 30 0°C to -50 °C. The OCT imagistic evaluations performed for the normal samples present a uniform spread of the ceramic granulation inside the ceramic materials. For the samples sintered at a higher temperature an alternation between white and darker areas between the enamel and opaque layers appear. For the samples sintered at a lower temperature a decrease in the ceramic granulation from the enamel towards the opaque layer is concluded. The TD-OCT methods can therefore be used efficiently for the detection of the temperature variation due to the ceramic sintering inside the ceramic oven.

Low-temperature rapid synthesis and superconductivity of Fe-based oxypnictide superconductors.

Science.gov (United States)

Fang, Ai-Hua; Huang, Fu-Qiang; Xie, Xiao-Ming; Jiang, Mian-Heng

2010-03-17

Fe-based oxypnictide superconductors were successfully synthesized at lower reaction temperatures and with shorter reaction times made possible by starting with less stable compounds, which provide a larger driving force for reactions. Using ball-milled powders of intermediate compounds, phase-pure superconductors with T(c) above 50 K were synthesized at 1173 K in 20 min. This method is particularly advantageous for retaining F, a volatile dopant that enhances superconductivity. Bulk superconductivity and high upper critical fields up to 392 T in Sm(0.85)Nd(0.15)FeAsO(0.85)F(0.15) were demonstrated.

High temperature superconducting compounds II; Proceedings of the Second Symposium, Anaheim, CA, Feb. 20, 21, 1990

International Nuclear Information System (INIS)

Whang, S.H.; Dasgupta, A.; Laibowitz, R.

1990-01-01

Various topics relevant to the production and implementation of high-temperature superconducting compounds are highlighted including critical current; texturing; ceramics and novel processing; composites; deformation and consolidation; thin films; microstructures; tapes, filaments, and ribbons; and thermodynamics. The thermally activated flux creep, critical current density and current enhancement in high-temperature superconductors are addressed. Also discussed are the phase stability and microstructure of doped superconductors, mechanical considerations in the processing of high-Tc superconductors, fabrication and application of high current density, high RTc superconducting thin films and devices, the effect of substrate temperature and RF biasing on the composition of sputtered Bi-based superconducting thin films, and optical electron microanalysis of cuprate superconductors. The microstructure dependence of critical current density and fabrication of double-layered ribbons from cuprate are also discussed

Ceramic superconductivity research at Alfred Univ

International Nuclear Information System (INIS)

Snyder, R.L.

1990-01-01

A survey of the science and technology advances made by the research groups at Alfred will be presented. These ranges on the technology side from the first melt-textured and glass ceramic superconductors to recently demonstrating that 123 thin films can be deposited below the superconducting transition at atmospheric pressure using an aerosol plasma deposition technique. On the science side advances in understanding have come from looking at the crystal structures, high and low temperature reactions, phase equilibria, effects of doping and XRD standards. Recent advances will be summarized

Transport measurements in superconductors: critical current of granular high TC ceramic superconductor samples; Medidas de transporte em supercondutores: corrente critica de supercondutores granulares de alta temperatura critica

Energy Technology Data Exchange (ETDEWEB)

Passos, W.A.C., E-mail: wagner.passos@univasf.edu.br [Universidade Federal do Vale do Sao Francisco (IPCM/UNIVASF), Juazeiro do Norte, BA (Brazil). Instituto de Pesquisas em Ciencia dos Materiais; Silva, E.B. [Companhia Energetica do Sao Francisco (CHESF), Recife, PE (Brazil)

2016-07-01

This work presents a method to obtain critical current of granular superconductors. We have carried out transport measurements (ρxT curves and VxI curves) in a YBa{sub 2}Cu{sub 3}O{sub 7-δ} sample to determine critical current density of it. Some specimens reveal a 'semiconductor-like' behavior (electrical resistivity decreases with increasing temperatures above critical temperature T{sub c} of material) competing with superconductor behavior. Due to high granular fraction of the sample, these competition is clearly noted in ρxT curves. Measurements carried out from 0 to 8500 Oe of applied field show the same behavior, and the critical current density of the samples is shown. (author)

Chapter 27. Superconductors

International Nuclear Information System (INIS)

Vavra, O.

2007-01-01

In this chapter author deals with superconductors and superconductivity. Different chemical materials used as high-temperature superconductors are presented. Some applications of superconductivity are presented.

Experimental Consequences of Mottness in High-Temperature Copper-Oxide Superconductors

Science.gov (United States)

Chakraborty, Shiladitya

2009-01-01

It has been more than two decades since the copper-oxide high temperature superconductors were discovered. However, building a satisfactory theoretical framework to study these compounds still remains one of the major challenges in condensed matter physics. In addition to the mechanism of superconductivity, understanding the properties of the…

Studies of superconductors using a low-temperature, high-field scanning tunneling microscope

International Nuclear Information System (INIS)

Kirtley, J.R.; Feenstra, R.M.; Fein, A.P.

1988-01-01

We have developed a scanning tunneling microscope (STM) capable of operating at temperatures as low as 0.4 K and fields as high as 8 T. We have used this STM to study the energy gap of the high-T/sub c/ superconductors La--Sr--Cu--O and Y--Ba--Cu--O. We find that the reduced gap for these oxide superconductors falls in the range 3<2Δ/k/sub B/T/sub c/<7, for polycrystalline, single-crystal, and thin-film samples. We have also simultaneously imaged the surface topography and superconducting energy gap for thin films of the granular superconductor NbN. We occasionally see regions with smaller best-fit gaps that correlate with surface topographical features, but have been unable so far to image flux vortices

Theoretical upper critical field Hc2 for inhomogeneous high temperature superconductors

International Nuclear Information System (INIS)

Caixeiro, E.S.; Gonzalez, J.L.; Mello, E.V.L. de

2004-01-01

We present the theoretical upper critical field H c2 (T) of the high temperature superconductors (HTSC), calculated through a linearized Ginzburg-Landau equation modified to consider the intrinsic inhomogeneity of the HTSC. The unusual behavior of H c2 (T) for these compounds, and other properties like the Meissner and Nernst effects detected at temperatures much higher than the critical temperature T c of the sample, are explained by the approach

Low temperature sintering of fluorapatite glass-ceramics.

Science.gov (United States)

Denry, Isabelle; Holloway, Julie A

2014-02-01

Fluorapatite glass-ceramics have been shown to be excellent candidates as scaffold materials for bone grafts, however, scaffold production by sintering is hindered by concurrent crystallization of the glass. Objective, our goal was to investigate the effect of Ca/Al ratio on the sintering behavior of Nb-doped fluorapatite-based glasses in the SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2 system. Methods, glass compositions with Ca/Al ratio of 1 (A), 2 (B), 4 (C) and 19 (D) were prepared by twice melting at 1525°C for 3h. Glasses were either cast as cylindrical ingots or ground into powders. Disk-shaped specimens were prepared by either sectioning from the ingots or powder-compacting in a mold, followed by heat treatment at temperatures ranging between 700 and 1050°C for 1h. The density was measured on both sintered specimens and heat treated discs as controls. The degree of sintering was determined from these measurements. Results and Significance XRD showed that fluorapatite crystallized in all glass-ceramics. A high degree of sintering was achieved at 775°C for glass-ceramic D (98.99±0.04%), and 900°C for glass-ceramic C (91.31±0.10). Glass-ceramics A or B were only partially sintered at 1000°C (63.6±0.8% and 74.1±1.5%, respectively). SEM revealed a unique microstructure of micron-sized spherulitic fluorapatite crystals in glass-ceramics C and D. Increasing the Ca/Al ratio promoted low temperature sintering of fluorapatite glass-ceramics, which are traditionally difficult to sinter. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Fundamental studies of ceramic/metal interfacial reactions at elevated temperatures.

Energy Technology Data Exchange (ETDEWEB)

McDeavitt, S. M.; Billings, G. W.; Indacochea, J. E.

2000-12-14

This work characterizes the interfaces resulting from exposing oxide and non-oxide ceramic substrates to zirconium metal and stainless steel-zirconium containing alloys. The ceramic/metal systems together were preheated at about 600 C and then the temperatures were increased to the test maximum temperature, which exceeded 1800 C, in an atmosphere of high purity argon. Metal samples were placed onto ceramic substrates, and the system was heated to elevated temperatures past the melting point of the metallic specimen. After a short stay at the peak temperature, the system was cooled to room temperature and examined. The chemical changes across the interface and other microstructural developments were analyzed with energy dispersive spectroscopy (EDS). This paper reports on the condition of the interfaces in the different systems studied and describes possible mechanisms influencing the microstructure.

The influence of electric discharge on the properties of high-temperature superconductors

International Nuclear Information System (INIS)

Parashchuk, V.V.

1990-01-01

The influence is studied of pulse voltage with amplitude 100 kV and duration 100 to 200 ns on the temperature dependence of diamagnetic susceptibility of yttrium ceramics. As a result of the action of spark discharge on the ceramics, the superconducting transition parameters change. As the number of voltage pulses is increased, the diamagnetic susceptibility and the critical temperature determined by it first increase rapidly, then drop slowly. At the same time the transition in the optimum becomes more sharp. In the case of treatment in the air, Tc increases by 15 K and at discharge in liquid nitrogen by 25 K. It is found that the atmospheric air under certain conditions affects the temperature dependence of the diamagnetic susceptibility of HTSC ceramics. Treatment by a high-voltage spark decreases the susceptibility of the ceramics due to atmospheric effects. The highest efficiency of spark treatment is achieved at discharge in liquid nitrogen. (orig.)

Abrasive wear of ceramic wear protection at ambient and high temperatures

Science.gov (United States)

Varga, M.; Adam, K.; Tumma, M.; Alessio, K. O.

2017-05-01

Ceramic wear protection is often applied in abrasive conditions due to their excellent wear resistance. This is especially necessary in heavy industries conveying large amounts of raw materials, e.g. in steel industry. Some plants also require material transport at high temperatures and velocities, making the need of temperature stable and abrasion resistant wear protection necessary. Various types and wear behaviour of ceramic protection are known. Hence, the goal of this study is to identify the best suitable ceramic materials for abrasive conditions in harsh environments at temperatures up to 950°C and severe thermal gradients. Chamottes, known for their excellent thermal shock resistance are compared to high abrasion resistant ceramic wear tiles and a cost efficient cement-bounded hard compound. Testing was done under high-stress three-body abrasion regime with a modified ASTM G65 apparatus enabling for investigations up to ~950°C. Thereto heated abrasive is introduced into the wear track and also preheated ceramic samples were used and compared to ambient temperature experiments. Results indicate a significant temperature influence on chamottes and the hard compound. While the chamottes benefit from temperature increase, the cement-bounded hard compound showed its limitation at abrasive temperatures of 950°C. The high abrasion resistant wear tiles represented the materials with the best wear resistance and less temperature influence in the investigated range.

Two classes of superconductors discovered in our material research: Iron-based high temperature superconductor and electride superconductor

International Nuclear Information System (INIS)

Hosono, Hideo

2009-01-01

We discovered two new classes of superconductors in the course of material exploration for electronic-active oxides. One is 12CaO . 7Al 2 O 3 crystal in which electrons accomodate in the crystallographic sub-nanometer-sized cavities. This material exhibiting metal-superconductor transition at 0.2 K is the first electride superconductor. The other is iron oxypnicitides with a layered structure. This superconductor is rather different from high T c cuprates in several respects. The high T c is emerged by doping carriers to the metallic parent phases which undergo crystallographic transition (tetra to ortho) and Pauli para to antiferromagnetic transition at ∼150 K. The T c is robust to impurity doping to the Fe sites or is induced by partial substitution of the Fe 2+ sites with Co 2+ or Ni 2+ . This article gives a brief summary of these discoveries and recent advances.

Josephson plasma resonance in vortex filament state of high temperature superconductors

International Nuclear Information System (INIS)

Matsuda, Yuji; Gaifullin, M.B.

1996-01-01

High temperature superconductors have the crystalline structure in which two-dimensional CuO 2 planes are piled in layers, consequently, the anisotropy of electroconductivity arises, and this brings about stable and low energy Josephson plasma in superconducting state. Also as to the vortex filament state of high temperature superconductors, the effect of thermal fluctuation due to low dimensionality, short coherence length and high transition temperature becomes conspicuous. In reality, these plasma and vortex filament state are related closely. Light reflection and plasma edge in superconducting state, Josephson plasma resonance in the vortex filament state of BiO 2 Sr 2 CaCu 2 O 8+δ , the plasma vibration in Josephson junction, Josephson plasma in magnetic field, Josephson plasma in the liquid state of vortex filament, Josephson plasma in the solid state of vortex filament, and Josephson plasma in parallel magnetic field are reported. The Josephson plasma resonance is the experimental means for exploring vortex filament state from microscopic standpoint, and its development hereafter is expected. (K.I.)

Surface electrostatic waves in bounded high temperature superconductors

International Nuclear Information System (INIS)

Averkov, Yu.O.; Yakovenko, V.M.

2008-01-01

The dispersion relations of surface electrostatic waves propagating along the surface of semi bounded layered superconductor and in the slab of layered superconductor are theoretically investigated. An arbitrary inclination of superconductor layers to the interface of a vacuum - crystal and an arbitrary direction of propagation of surface waves in the plane of the interface are taking into account. The possibility of initiation of an absolute instability during the propagation of a non-relativistic plasma stream above the surface of the layered superconductor is shown

Design of High Field Solenoids made of High Temperature Superconductors

Energy Technology Data Exchange (ETDEWEB)

Bartalesi, Antonio; /Pisa U.

2010-12-01

This thesis starts from the analytical mechanical analysis of a superconducting solenoid, loaded by self generated Lorentz forces. Also, a finite element model is proposed and verified with the analytical results. To study the anisotropic behavior of a coil made by layers of superconductor and insulation, a finite element meso-mechanic model is proposed and designed. The resulting material properties are then used in the main solenoid analysis. In parallel, design work is performed as well: an existing Insert Test Facility (ITF) is adapted and structurally verified to support a coil made of YBa{sub 2}Cu{sub 3}O{sub 7}, a High Temperature Superconductor (HTS). Finally, a technological winding process was proposed and the required tooling is designed.

Novel low-temperature sintering ceramic substrate based on indialite/cordierite glass ceramics

Science.gov (United States)

Varghese, Jobin; Vahera, Timo; Ohsato, Hitoshi; Iwata, Makoto; Jantunen, Heli

2017-10-01

In this paper, a novel low-temperature sintering substrate for low temperature co-fired ceramic applications based on indialite/cordierite glass ceramics with Bi2O3 as a sintering aid showing low permittivity (εr) and ultralow dielectric loss (tan δ) is described. The fine powder of indialite was prepared by the crystallization of cordierite glass at 1000 °C/1 h. The optimized sintering temperature was 900 °C with 10 wt % Bi2O3 addition. The relative density achieved was 97%, and εr and tan δ were 6.10 and 0.0001 at 1 MHz, respectively. The composition also showed a moderately low temperature coefficient of relative permittivity of 118 ppm/°C at 1 MHz. The obtained linear coefficient of thermal expansion was 3.5 ppm/°C in the measured temperature range of 100 to 600 °C. The decreasing trend in dielectric loss, the low relative permittivity at 1 MHz, and the low thermal expansion of the newly developed composition make it an ideal choice for radio frequency applications.

Pairing theory of high and low temperature superconductors

International Nuclear Information System (INIS)

Nam, Sang Boo

1997-01-01

A scenario which can account for all observed features of both high-Tc superconductors (HTS) and low-Tc superconductors (LTS) is discussed. This scenario is based on the fact that a finite pairing interaction energy range Td is required to have a finite value of Tc and that not all carriers participate in pairings, yielding multiconnected superconductors (MS). A new density of states, derived by keeping the order parameter zero outside of Td, is shown to account for the observed low energy states in HTS and for the temperature dependences in the specific heat, the penetration depth, the optical conductivity, and the tunneling conductance data. I argue that the notion of MS can account for the tunneling data along the a(or b)-, ab-, and c-axis, and the 1/2 flux quantum observed in HTS. The region occupied by unpaired carriers can be considered as a vortex with a fluxoid quantum number equal to 1 (VF), 0 (VZF), or -1 (VAF) when the magnetic flux around the vortex is greater than, equal to, or less than the effective flux produced by the supercurrent, respectively. The Hall anomaly depends on the relative strengths of the contributions via VF and VAF. The fact that the present scenario can account for all observed features of HTS and LTS suggests that the symmetry of the order parameter in HTS may not be different from one in LTS. (author)

Stability of magnets levitated above superconductors

International Nuclear Information System (INIS)

Davis, L.C.; Logothetis, E.M.; Soltis, R.E.

1988-01-01

The stability of a permanent magnet levitated above a slab of hard superconductor is considered. The force on a dipole magnet over a perfectly diamagnetic disk is calculated. It is found that the radial component of the force is directed outward and is 10%--20% of the image (vertical) force near the edge. Estimates of the magnetic friction force due to flux motion in a hard superconductor are made using Bean's model. The magnitude of the magnetic friction is large enough to stabilize the magnet over most of the disk for typical values of the critical current in ceramic superconductors (∼10 3 A/cm 2 ), but too small for the highest values reported (>10 6 A/cm 2 ). It is conjectured that flux trapping due to inhomogeneities gives rise to transient restoring forces

Electron-beam damaged high-temperature superconductor Josephson junctions

International Nuclear Information System (INIS)

Pauza, A.J.; Booij, W.E.; Herrmann, K.; Moore, D.F.; Blamire, M.G.; Rudman, D.A.; Vale, L.R.

1997-01-01

Results are presented on the fabrication and characterization of high critical temperature Josephson junctions in thin films of YBa 2 Cu 3 O 7-δ produced by the process of focused electron-beam irradiation using 350 keV electrons. The junctions so produced have uniform spatial current densities, can be described in terms of the resistive shunted junction model, and their current densities can be tailored for a given operating temperature. The physical properties of the damaged barrier can be described as a superconducting material of either reduced or zero critical temperature (T c ), which has a length of ∼15nm. The T c reduction is caused primarily by oxygen Frenkel defects in the Cu - O planes. The large beam currents used in the fabrication of the junctions mean that the extent of the barrier is limited by the incident electron-beam diameter, rather than by scattering within the film. The properties of the barrier can be calculated using a superconductor/normal/superconductor (SNS) junction model with no boundary resistance. From the SNS model, we can predict the scaling of the critical current resistance (I c R n ) product and gain insight into the factors controlling the junction properties, T c , and reproducibility. From the measured I c R n scaling data, we can predict the I c R n product of a junction at a given operating temperature with a given current density. I c R n products of ∼2mV can be achieved at 4.2 K. The reproducibility of several junctions in a number of samples can be characterized by the ratio of the maximum-to-minimum critical currents on the same substrate of less than 1.4. Stability over several months has been demonstrated at room and refrigerator temperatures (297 and 281 K) for junctions that have been initially over damaged and then annealed at temperatures ∼380K. (Abstract Truncated)

High-performance ceramics - state of the art and trends of development

International Nuclear Information System (INIS)

Gadow, R.; Keizer, K; Burggraaf, A.J.; Boch, P.; Chartier, T.; Thomann, H.

1989-01-01

This paper contains 4 lectures on the following topics: 1. fiber and whisker reinforced ceramics (R. Gadow), 2. ceramic membranes (K. Keizer, A.J. Burggraf), 3. ceramic processing techniques: The case of tape casting (P. Bach, T. Chartier), 4. ceramic superconductors (H. Thomann). Three contributions are separately analyzed for the ENERGIE database. (MM) [de

Design and application consideration of high temperature superconducting current leads

International Nuclear Information System (INIS)

Wu, J.L.

1994-01-01

As a potential major source of heat leak and the resultant cryogen boiloff, cryogenic current leads can significantly affect the refrigeration power requirement of cryogenic power equipment. Reduction of the heat leak associated with current leads can therefore contribute to the development and application of this equipment. Recent studies and tests have demonstrated that, due to their superconducting and low thermal conductivity properties, ceramic high temperature superconductor (HTSC) can be employed in current leads to significantly reduce the heat leak. However, realization of this benefit requires special design considerations pertaining to the properties and the fabrication technology of the relatively new ceramic superconductor materials. Since processing and fabrication technology are continuously being developed in the laboratories, data on material properties unrelated to critical states are quite limited. Therefore, design analysis and experiments have to be conducted in tandem to achieve a successful development. Due to the rather unique combination of superconducting and thermal conductivities which are orders of magnitude lower than copper, ceramic superconductors allow expansion of the operating scenarios of current leads. In addition to the conventional vapor-cooled lead type application, low heat leak conduction-cooled type current leads may be practical and are being developed. Furthermore, a current lead with an intermediate heat leak intercept has been successfully demonstrated in a multiple current lead assembly employing HTSC. These design and application considerations of high temperature superconducting current leads are addressed here

The influence of measurement and relaxation time on flux jumps in high temperature superconductors

International Nuclear Information System (INIS)

Yang Xiaobin; Zhou Youhe; Tu Shandong

2010-01-01

The influence of the magnetization and relaxation time on flux jumps in high temperature superconductors (HTSC) under varying magnetic field is studied using the fundamental electromagnetic field equations and the thermal diffusion equation; temperature variety corresponding to flux jump is also discussed. We find that for a low sweep rate of the applied magnetic field, the measurement and relaxation times can reduce flux jump and to constrain the number of flux jumps, even stabilizing the HTSC, since much heat produced by the motion of magnetic flux can transfer into coolant during the measurement and relaxation times. As high temperature superconductors are subjected to a high sweep rate or a strong pulsed magnetic field, magnetization undergoes from stability or oscillation to jump for different pause times. And the period of temperature oscillation is equal to the measurement and relaxation time.

Electrical properties and temperature stability of a new kind of lead-free piezoelectric ceramics

International Nuclear Information System (INIS)

Wang Yuanyu; Wu Jiagang; Xiao Dingquan; Zhang Bin; Wu Wenjuan; Shi Wei; Zhu Jianguo

2008-01-01

0.995[(K 0.50 Na 0.50 ) 0.94 Li 0.06 ]NbO 3 -0.005AETiO 3 (AE=Ca, Sr, Mg, Ba) lead-free piezoelectric ceramics were prepared by normal sintering. The effects of the AETiO 3 and poling temperature on the electrical properties of the ceramics were carefully studied, and the temperature stability of the electrical properties of the ceramics was also investigated. The experimental results show that the ceramics with Li and CaTiO 3 possess the pure phase, Li and AETiO 3 improves the electrical properties of the pure (K 0.50 Na 0.50 )NbO 3 ceramics, the poling temperature near tetragonal and orthorhombic phase transition will enhance the piezoelectric properties of the ceramics and the KNLN-CT ceramics exhibit good temperature stability of electrical properties for tetragonal and orthorhombic phase transition below room temperature. The KNLN-CT ceramics exhibit relatively good properties: d 33 = 172 pC N -1 , k p = 0.43, tan δ = 0.032, ε r = 771 and T c = 465 deg. C. As a result, the KNLN-CT ceramic is promising candidate material for piezoelectric devices.

Three-dimensionality of field-induced magnetism in a high-temperature superconductor

DEFF Research Database (Denmark)

Lake, B.; Lefmann, K.; Christensen, N.B.

2005-01-01

Many physical properties of high-temperature superconductors are two-dimensional phenomena derived from their square-planar CuO(2) building blocks. This is especially true of the magnetism from the copper ions. As mobile charge carriers enter the CuO(2) layers, the antiferromagnetism of the parent...

A formulation for the critical temperature T/sub c/ of Ll2-type superconductors

International Nuclear Information System (INIS)

Wang Rong-Yao; Zhang Xiao

1985-01-01

From the examination of Ll 2 type superconductors, the superconducting critical temperature T/sub b/ of Ll 2 -type superconductors is obtained by: T/sub c/ = 15.9T/sub B/V(B)G/sub A//(√M/sub m/) V(Ll 2 )/sub m/ G/sub B/ where T/sub B/ is the superconducting critical temperature of pure B, V(B) the atomic volume in pure B, V(Ll 2 )/sub m/ the average atomic volume in the Ll 2 type compound, M/sub m/ the average atomic weight of the compound, and G/sub A/, G/sub B/ are the Gordy electronegative values. (author)

X-ray photoelectron spectroscopy of high-temperature superconductor clean surfaces and interfaces

International Nuclear Information System (INIS)

Hill, D.M.

1989-01-01

X-ray photoelectron spectroscopy was used to determine the characteristic spectra for the high temperature superconductors La 1.85 Sr 0.15 CuO 4 , YBa 2 Cu 3 O 7-x , and Bi 2 Sr 2-x Ca 1+x Cu 2 O 8+y and their impurity phases. The oxidation state of Cu in all of these materials was predominantly Cu 2+ . The O 1s emission for clean surfaces was a single broad peak near 529 eV derived from emission from inequivalent O sites in the superconductors. The valence bands were a -6 eV wide manifold of Cu 3d-O 2p hybrid bands in the ∼ 1-7 eV binding energy range, with very low emission at E F arising from antibonding Cu 3d-O 2p orbitals. Emission from grain boundary and other impurity phases appeared at 531 eV for the O 1s core level, and in general ∼ 1-2 eV higher energy than the superconductor peak for other core levels except for Cu 2p. Impurity phases appeared in the valence bands as a shoulder at ∼ 5 eV. The amount of impurities detected was shown to be dependent on the fracture properties of the superconductors. All of the materials were shown to be stable under vacuum. The products and spatial extent of chemical reactions with Ag, Al, Al oxide, Au, Bi, Bi oxide, CaF 2 , Cu, Fe, Si, and Si oxide overlayers on these materials also were examined. Au, CaF 2 , and metal oxides deposited by activated oxidation during evaporation were non-reactive and non-disruptive of the superconductor surfaces. Ag overlayers were unique in that they disrupted the superconductor during deposition, but exhibited no evidence of any chemical reactions. Overlayers with an affinity for oxygen withdrew O from the superconductor. The O loss occurred preferentially from Cu atoms in the superconductor and disrupted the planar bonding structure

Magneto-optical Kerr-effect at low temperatures. Investigation of superconductor/ferromagnet heterostructures

Energy Technology Data Exchange (ETDEWEB)

Zahn, Patrick; Bayer, Jonas [Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart (Germany); Institute for Innovative Surfaces FINO, Aalen University, Beethovenstrasse 1, 73430 Aalen (Germany); Stahl, Claudia; Ruoss, Stephen; Graefe, Joachim; Schuetz, Gisela [Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart (Germany); Albrecht, Joachim [Institute for Innovative Surfaces FINO, Aalen University, Beethovenstrasse 1, 73430 Aalen (Germany)

2016-07-01

With XMCD microscopy it is possible to visualize the critical current density of the superconductor YBCO with high spatial resolution. Therefore, soft magnetic CoFeB is introduced as sensor layer. The magnetic stray fields of the supercurrents lead to a local reorientation of the magnetic moments in the ferromagnet, which are then imaged via X-ray microscopy. These experiments have to be carried out at the scanning X-ray microscope MAXYMUS at the synchrotron Bessy II in Berlin. For that purpose pre-characterization of the sensor is highly desirable: Magnetic interactions between the superconductor and the ferromagnetic sensor layer have been investigated at low temperatures using Kerr-effect measurements. Therefore hysteresis loops are obtained by a sophisticated magnet and field ramping setup within the NanoMOKE3 system. The results are used to optimize the ferromagnetic sensor layer for XMCD microscopy of superconductors.

Possibility of the vortex-antivortex transition temperature of a thin-film superconductor being renormalized by disorder

International Nuclear Information System (INIS)

Hebard, A.F.; Kotliar, G.

1989-01-01

The universal relation between the Kosterlitz-Thouless transition temperature T/sub c/ and the superfluid sheet density of thin-film superconductors with mean-field transition temperature T/sub c/ 0 results in a monotonically decreasing dependence of the ratio T/sub c//T/sub c0/ on the normal-state sheet resistance R/sub n/. Ambiguity in the experimental definition of R/sub n/ in highly disordered thin-film superconductors is addressed by reexamining previously published data on amorphous composite In/InO/sub x/ films. Arguments are presented in favor of using the zero-temperature value of R/sub n/, a quantity obtained by extrapolation. The dependence of T/sub c//T/sub c0/ on R/sub n/ that results from such a choice is in agreement with theory for dirty superconductors and thus suggests that additional corrections to T/sub c/ in the presence of extreme disorder are not required

The temperature dependences of electromechanical properties of PLZT ceramics

Science.gov (United States)

Czerwiec, M.; Zachariasz, R.; Ilczuk, J.

2008-02-01

The mechanical and electrical properties in lanthanum modified lead zirconate-titanate ceramics of 5/50/50 and 10/50/50 were studied by mechanical loss Q - 1, Young's modulus E, electric permittivity ɛ and tangent of dielectric loss of angle tgδ measurements. The internal friction Q - 1 and Young modulus E measured from 290 K to 600 K shows that Curie temperature TC is located at 574 K and 435 K (1st cycle of heating) respectively for ceramic samples 5/50/50 and 10/50/50. The movement of TC in second cycle of heating to lower temperature (561 K for 5/50/50 and 420 K for 10/50/50) has been observed. Together with Q - 1 and E measurements, temperature dependences of ɛ=f(T) and tgδ=f(T) were determinated in temperature range from 300 K to 730 K. The values of TC obtained during ɛ and tgδ measurements were respectively: 560 K for 5/50/50 and 419 K for 10/50/50. These temperatures are almost as high as the temperatures obtained by internal friction Q - 1 measurements in second cycle of heating. In ceramic sample 10/50/50 the additional maximum on internal friction Q - 1 curve at the temperature 316 K was observed.

Olson sees how they conduct (High Tc superconductors)

International Nuclear Information System (INIS)

Olson, C.

1989-01-01

Thanks to Cliff Olson's synchrotron radiation measurements of the surface of several of the new high-temperature superconducting materials, these ceramic-like crystals can now be classified as metals. This means their electronic band structure meets the criteria for a metal or conductor, rather than those of an insulator, or of a semiconductor. Working with graduate assistant Liu, Olson has now measured the energy gap in crystals of a bismuth-strontium-calcium-copper oxide with a 100K or 300K transition temperature. They determined that the superconductivity gap is isotropic, or independent of direction within the layer. This is significant, because the high temperature materials are all anisotropic, layered in flat sheets, a fact that had led to speculations about a very different kind of superconducting coupling in these materials. The superconducting mechanism now turns out to be the same as that in classical superconductors

High density microelectronics package using low temperature cofirable ceramics

International Nuclear Information System (INIS)

Fu, S.-L.; Hsi, C.-S.; Chen, L.-S.; Lin, W. K.

1997-01-01

Low Temperature Cofired Ceramics (LTCC) is a relative new thick film process and has many engineering and manufacturing advantages over both the sequential thick film process and high temperature cofired ceramic modules. Because of low firing temperature, low sheet resistance metal conductors, commercial thick film resistors, and thick film capacitors can be buried in or printed on the substrates. A 3-D multilayer ceramic substrate can be prepared via laminating and co-firing process. The packing density of the LTCC substrates can be increased by this 3-D packing technology. At Kaohsiung Polytechnic Institute (KPI), a LTCC substrate system has been developed for high density packaging applications, which had buried surface capacitors and resistors. The developed cordierite-glass ceramic substrate, which has similar thermal expansion as silicon chip, is a promising material for microelectronic packaging. When the substrates were sintered at temperatures between 850-900 degree centigrade, a relative density higher than 96 % can be obtained. The substrate had a dielectric constant between 5.5 and 6.5. Ruthenium-based resistor pastes were used for resistors purposes. The resistors fabricated in/on the LTCC substrates were strongly depended on the microstructures developed in the resistor films. Surface resistors were laser trimmed in order to obtain specific values for the resistors. Material with composition Pb(Fe 2/3 W 1/3 ) x (Fe l/2 Nb l/2 ) y Ti 2 O 3 was used as dielectric material of the capacitor in the substrate. The material can be sintered at temperatures between 850-930 degree centigrade, and has dielectric constant as high as 26000. After cofiring, good adhesion between dielectric and substrate layers was obtained. Combing the buried resistors and capacitors together with the lamination of LTCC layer, a 3-dimensional multilayered ceramic package was fabricated. (author)

High density microelectronics package using low temperature cofirable ceramics

Energy Technology Data Exchange (ETDEWEB)

Fu, S -L; Hsi, C -S; Chen, L -S; Lin, W K [Kaoshiung Polytechnic Institute Ta-Hsu, Kaoshiung (China)

1998-12-31

Low Temperature Cofired Ceramics (LTCC) is a relative new thick film process and has many engineering and manufacturing advantages over both the sequential thick film process and high temperature cofired ceramic modules. Because of low firing temperature, low sheet resistance metal conductors, commercial thick film resistors, and thick film capacitors can be buried in or printed on the substrates. A 3-D multilayer ceramic substrate can be prepared via laminating and co-firing process. The packing density of the LTCC substrates can be increased by this 3-D packing technology. At Kaohsiung Polytechnic Institute (KPI), a LTCC substrate system has been developed for high density packaging applications, which had buried surface capacitors and resistors. The developed cordierite-glass ceramic substrate, which has similar thermal expansion as silicon chip, is a promising material for microelectronic packaging. When the substrates were sintered at temperatures between 850-900 degree centigrade, a relative density higher than 96 % can be obtained. The substrate had a dielectric constant between 5.5 and 6.5. Ruthenium-based resistor pastes were used for resistors purposes. The resistors fabricated in/on the LTCC substrates were strongly depended on the microstructures developed in the resistor films. Surface resistors were laser trimmed in order to obtain specific values for the resistors. Material with composition Pb(Fe{sub 2/3}W{sub 1/3}){sub x}(Fe{sub l/2}Nb{sub l/2}){sub y}Ti{sub 2}O{sub 3} was used as dielectric material of the capacitor in the substrate. The material can be sintered at temperatures between 850-930 degree centigrade, and has dielectric constant as high as 26000. After cofiring, good adhesion between dielectric and substrate layers was obtained. Combing the buried resistors and capacitors together with the lamination of LTCC layer, a 3-dimensional multilayered ceramic package was fabricated. (author)

Finding new superconductors: the spin-fluctuation gateway to high Tc and possible room temperature superconductivity.

Science.gov (United States)

Pines, David

2013-10-24

We propose an experiment-based strategy for finding new high transition temperature superconductors that is based on the well-established spin fluctuation magnetic gateway to superconductivity in which the attractive quasiparticle interaction needed for superconductivity comes from their coupling to dynamical spin fluctuations originating in the proximity of the material to an antiferromagnetic state. We show how lessons learned by combining the results of almost three decades of intensive experimental and theoretical study of the cuprates with those found in the decade-long study of a strikingly similar family of unconventional heavy electron superconductors, the 115 materials, can prove helpful in carrying out that search. We conclude that, since Tc in these materials scales approximately with the strength of the interaction, J, between the nearest neighbor local moments in their parent antiferromagnetic state, there may not be a magnetic ceiling that would prevent one from discovering a room temperature superconductor.

High Temperature Characterization of Ceramic Pressure Sensors

National Research Council Canada - National Science Library

Fonseca, Michael A; English, Jennifer M; Von Arx, Martin; Allen, Mark G

2001-01-01

This work reports functional wireless ceramic micromachined pressure sensors operating at 450 C, with demonstrated materials and readout capability indicating potential extension to temperatures in excess of 600 C...

Low critical temperature superconductors for electromagnets

International Nuclear Information System (INIS)

Devred, A.

2002-01-01

After a brief history of the main discoveries in applied superconductivity (section 1), we discuss the structure and properties of NbTi and Nb3 Sn (section 2). Then, we explain why low critical-temperature superconductors are produced under the form of multifilamentary composites (section 3), and we review the manufacturing processes of NbTi and Nb3Sn wires (section 4). We follow by a description of the transition from the superconducting to the normal resistive state of multifilamentary composite wires (section 5) and we detail their magnetization properties section 6). Last, we present the most commonly used cable configurations (section 7) and we provide simple formulae illustrating on a few examples the computation of losses generated under time-varying magnetic fields (section 8). (author)

High temperature tribological properties of plasma-sprayed metallic coatings containing ceramic particles

International Nuclear Information System (INIS)

Dallaire, S.; Legoux, J.G.

1995-01-01

For sealing a moving metal component with a dense silica-based ceramic pre-heated at 800 C, coatings with a low coefficient of friction and moderate wear loss are required. As reported previously, plasma-sprayed coatings containing solid lubricants could reduce sliding wear in high-temperature applications. Plasma-sprayed metal-based coatings containing ceramic particles have been considered for high temperature sealing. Selected metal powders (NiCoCrAlY, CuNi, CuNiIn, Ag, Cu) and ceramic particles (boron nitride, Zeta-B ceramic) were agglomerated to form suitable spray powders. Plasma-sprayed composite coatings and reference materials were tested in a modified pin-on-disc apparatus in which the stationary disc consisted of a dense silica-based ceramic piece initially heated at 800 C and allowed to cool down during tests. The influence of single exposure and repeated contacts with a dense silica-based ceramic material pre-heated to 800 C on the coefficient of friction, wear loss and damage to the ceramic piece was evaluated. Being submitted to a single exposure at high temperature, coatings containing malleable metals such as indium, silver and copper performed well. The outstanding tribological characteristics of the copper-Zeta-B ceramic coating was attributed to the formation of a glazed layer on the surface of this coating which lasted over exposures to high temperature. This glazed layer, composed of fine oxidation products, provided a smooth and polished surface and helped maintaining the coefficient of friction low

Tribology of selected ceramics at temperatures to 900 C

Science.gov (United States)

Sliney, H. E.; Jacobson, T. P.; Deadmore, D.; Miyoshi, K.

1986-01-01

Results of fundamental and focused research on the tribological properties of ceramics are discussed. The basic friction and wear characteristics are given for ceramics of interest for use in gas turbine, adiabatic diesel, and Stirling engine applications. The importance of metal oxides in ceramic/metal sliding combinations is illustrated. The formulation and tribological additives are described. Friction and wear data are given for carbide and oxide-based composite coatings for temperatures to at least 900 C.

XES studies of density of states of high temperature superconductors

Science.gov (United States)

Jasiolek, Gabriel

1991-01-01

X-ray emission spectroscopic studies concerning the superconducting crystals, thin films, and ceramics of the Y-Ba-Cu-O, Tm-Ba-Cu-O, Bi-Sr-Ca-Cu-O, Bi-Pb-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O types are presented. The contributions of the 13d(9)L, 13d(10)L, 13d(10)LL, and 13d(10)L(2) configurations, where L denotes a ligand hole at the oxygen orbitals in the spectroscopic pattern of these superconductors are discussed. An attempt to connect the x-ray 'as registered' Cu L(alpha) emission spectra with the density of states close to the Fermi level, considering an influence of the CuL3 absorption edge, is presented. The corrected intensity distributions below the Fermi level are found to correspond to the theoretical density of states. Furthermore, an approach to the average valence of copper basing on the account of the self-absorption and fluorescence effects and on the configurations listed above is shown. The average valence of copper in the materials investigated is estimated to lie in the range of +2.10 to 2.32 when the formal trivalent copper is considered as that characterized by the 13d(9)L configuration. The density of states at the Fermi level was estimated to be 2.4 states/eV-cell for a Bi-Sr-Ca-Cu-O crystal and 3.6 states/eV-cell for a Tl-Ba-Ca-CU-O ceramic.

Design study of SMES system using high temperature superconductors

International Nuclear Information System (INIS)

Yoshihara, T.; Masuda, M.; Shintomi, T.; Hasegawa, J.

1988-01-01

Various studies of high Tc superconductors are being energetically pursued all over the world, since IBM Zurich Research Laboratory reported on the superconducting oxide. A new design using a high Tc superconductor is under study for 5000 MWh, on the assumption that it is available like conventional superconductors. Problems related to the Tc SMES system, mainly thermal insulation, refrigeration system, stability of superconductors, etc., are considered. Some design examples of high Tc SMES system are proposed

Non-contact temperature Raman measurement in YSZ and alumina ceramics

Science.gov (United States)

Thapa, Juddha; Chorpening, Benjamin T.; Buric, Michael P.

2018-02-01

Yttria-stabilized zirconia (YSZ: ZrO2 + Y2O3) and alumina (Al2O3) are widely used in high-temperature applications due to their high-temperature stability, low thermal conductivity, and chemical inertness. Alumina is used extensively in engineered ceramic applications such as furnace tubes and thermocouple protection tubes, while YSZ is commonly used in thermal barrier coatings on turbine blades. Because they are already often found in high temperature and combustion applications, these two substances have been compared as candidates for Raman thermometry in high-temperature energy-related applications. Both ceramics were used with as-received rough surfaces, i.e., without polishing or modification. This closely approximates surface conditions in practical high-temperature situations. A single-line argon ion laser at 488nm was used to excite the materials inside a cylindrical furnace while measuring Raman spectra with a fixed-grating spectrometer. The shift in the peak positions of the most intense A1g peak at 418cm-1 (room temperature position) of alumina ceramic and relatively more symmetric Eg peak at 470cm-1 (room temperature position) of YSZ were measured and reported along with a thermocouple-derived reference temperature up to about 1000°C. This study showed that alumina and YSZ ceramics can be used in high-temperature Raman thermometry with an accuracy of 4.54°C and 10.5°C average standard deviations respectively over the range of about 1000°C. We hope that this result will guide future researchers in selecting materials and utilizing Raman non-contact temperature measurements in harsh environments.

Quantum oscillations and key theoretical issues in high temperature superconductors from the perspective of density waves

International Nuclear Information System (INIS)

Chakravarty, Sudip

2011-01-01

High temperature superconductivity in cuprate superconductors remains an unsolved problem in theoretical physics. The same statement can also be made about a number of other superconductors that have been dubbed novel. What makes these superconductors so elusive is an interesting question in itself. This paper focuses on the recent magnetic oscillation experiments and how they fit into the broader picture. Many aspects of these experiments can be explained by Fermi liquid theory; the key issue is the extent to which this is true. If true, the entire paradigm developed over the past three decades must be reexamined. A critical analysis of this issue has necessitated a broader analysis of questions about distinct ground states of matter, which may be useful in understanding other novel superconductors.

Flux motion and dissipation in high-temperature superconductors

International Nuclear Information System (INIS)

Gray, K.E.; Kim, D.H.

1991-08-01

The effects on flux motion and dissipation of interlayer coupling of the Cu-O planes along the c-axis are considered for the high- temperature superconductors (HTS). It is argued that for the highly-anisotropic HTS, the weak interlayer coupling plays a dominant role that can be described by incoherent Josephson tunneling between superconducting Cu-O bi- or tri-layers. In YBa 2 Cu 3 O 7 , the layers are strongly coupled, presumably because the conducting Cu-O chains short circuit the Josephson tunneling, so that these effects are weak or missing

An unusual isotope effect in a high-transition-temperature superconductor

International Nuclear Information System (INIS)

Gweon, G.-H.; Sasagawa, T.; Zhou, S.Y.; Graf, J.; Takagi, H.; Lee, D.-H.; Lanzara, A.

2004-01-01

In conventional superconductors, the electron pairing that allows superconductivity is caused by exchange of virtual phonons, which are quanta of lattice vibration. For high-transition-temperature (high-Tc) superconductors, it is far from clear that phonons are involved in the pairing at all. For example, the negligible change in Tc of optimally doped Bi2Sr2CaCu2O8 (Bi2212) upon oxygen isotope substitution (16O to 18O leads to Tc decreasing from 92 to 91 K) has often been taken to mean that phonons play an insignificant role in this material. Here we provide a detailed comparison of the electron dynamics of Bi2212 samples containing different oxygen isotopes, using angle-resolved photoemission spectroscopy. Our data show definite and strong isotope effects. Surprisingly, the effects mainly appear in broad high-energy humps, commonly referred to as ''incoherent peaks''. As a function of temperature and electron momentum, the magnitude of the isotope effect closely correlates with the superconducting gap--that is, the pair binding energy. We suggest that these results can be explained in a dynamic spin-Peierls picture, where the singlet pairing of electrons and the electron-lattice coupling mutually enhance each other

Temperature factor for magnetic instability conditions of type – II superconductors

International Nuclear Information System (INIS)

Romanovskii, V.

2014-01-01

Highlights: • Electrodynamics and thermal diffusion phenomena in superconductors have the fission-chain-reaction nature. • There exist nontrivial relations between stability conditions, allowable losses and stable superconductor’s overheating. • The magnetic stability conditions are direct consequence of the states when the heat releases exceeds the critical energy. • The critical energy of magnetic instability depends on the nature of an external disturbance. • The non-isothermal magnetic instability conditions of the critical state are formulated. - Abstract: The macroscopic development of interrelated electrodynamics and thermal states taking place both before and after instability onset in type-II superconductors are studied using the critical state and the flux creep concepts. The physical mechanisms of the non-isothermal formation of the critical state are discussed solving the set of unsteady thermo-electrodynamics equations taking into consideration the unknown moving penetration boundary of the magnetic flux. To make it, the numerical method, which allows to study diffusion phenomena with unknown moving phase-two boundary, is developed. The corresponding non-isothermal flux jump criteria are written. It is proved for the first time that, first, the diffusion phenomena in superconductors have the fission-chain-reaction nature, second, the stability conditions, losses in superconductor and its stable overheating before instability onset are mutually dependent. The results are compared with those following from the existing magnetic instability theory, which does not take into consideration the stable temperature increase of superconductor before the instability onset. It is shown that errors of isothermal approximation are significant for modes closed to adiabatic ones. Therefore, the well-known adiabatic flux jump criterion limits the range of possible stable superconducting states since a correct determination of their stability states must

Raman studies of lanthanum cuprate superconductors

International Nuclear Information System (INIS)

Weber, W.H.; Peters, C.R.; Logothetis, E.M.

1989-01-01

Raman-scattering studies of the high-T/sub c/ superconductor La/sub 2-//sub x/(Sr, Ba)/sub x/CuO 4 are briefly reviewed. A detailed analysis of the phonon-mode symmetries is given along with a discussion of the effects expected from the orthorhombic-to-tetragonal phase transition, which is known to occur in these materials. Survey spectra are given for powders, ceramics, and single crystals, and an oxide of Cu is identified as the primary impurity phase. Extensive spectra are given from oriented single crystals of La 2 CuO 4 and La/sub 1.85/Sr/sub 0.15/CuO 4 , and several mode assignments are made. Spectra for the high-temperature tetragonal phase and the low-temperature orthorhombic phase are given for each material. The soft phonon associated with the phase transition is seen in La 2 CuO 4 as is a broad peak arising from two-magnon scattering. Neither of these features is seen in the Sr-doped sample

Application of high temperature superconductors for optimization of regime of the electroenergetic system

International Nuclear Information System (INIS)

Manusov, V.Z.; Mikheev, P.A.

2005-01-01

Application of the phenomenon of superconductivity in the energetic systems, as in the form of longitudinal engine, also in the transverse appearance (changing of the regime of neutral) is considerate in this article. In the normal regimes of the work of net it is profitable to have less resistance for contraction loss of the capability in the network and decrease of the tension, in emergency state ground return, on the contrary, from the security and safety point of view the work of such resistance will not arrange. Major properties of superconductors are their ability to change electrical parameters (in particular electric resistance) in dependence of the size of current crossing over them, notably nonlinearity of their volt-ampere characteristics. A high temperature superconductor, on the score of economical appropriateness of cooling of superconductor with liquid nitrogen instead of liquid gel is considered

Ceramic matrix composites -- Advanced high-temperature structural materials

International Nuclear Information System (INIS)

Lowden, R.A.; Ferber, M.K.; DiPietro, S.G.

1995-01-01

This symposium on Ceramic Matrix Composites: Advanced High-Temperature Structural Materials was held at the 1994 MRS Fall Meeting in Boston, Massachusetts on November 28--December 2. The symposium was sponsored by the Department of Energy's Office of Industrial Technology's Continuous Fiber Ceramic Composites Program, the Air Force Office of Scientific Research, and NASA Lewis Research Center. Among the competing materials for advanced, high-temperature applications, ceramic matrix composites are leading candidates. The symposium was organized such that papers concerning constituents--fibers and matrices--were presented first, followed by composite processing, modeling of mechanical behavior, and thermomechanical testing. More stable reinforcements are necessary to enhance the performance and life of fiber-reinforced ceramic composites, and to ensure final acceptance of these materials for high-temperature applications. Encouraging results in the areas of polymer-derived SiC fibers and single crystal oxide filaments were given, suggesting composites with improved thermomechanical properties and stability will be realized in the near future. The significance of the fiber-matrix interface in the design and performance of these materials is evident. Numerous mechanical models to relate interface properties to composite behavior, and interpret test methods and data, were enthusiastically discussed. One issue of great concern for any advanced material for use in extreme environments is stability. This theme arose frequently throughout the symposium and was the topic of focus on the final day. Fifty nine papers have been processed separately for inclusion on the data base

Temperature controlled infrared broadband cloaking with the bilayer coatings of semiconductor and superconductor

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiaohua [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); College of Physics and Electronics, Yancheng Teachers University, Yancheng 224051 (China); Liu, Youwen, E-mail: ywliu@nuaa.edu.cn [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Feng, Yuncai [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)

2015-06-15

Highlights: • We first propose that the cloak is composed of the bilayer of semiconductor and superconductor. • We realize the infrared broadband cloaking based on the scattering cancellation method. • The cloaking frequency can be tuned by external temperature. - Abstract: The infrared broadband tunable cloaking have been proposed and investigated with the bilayer coating materials of semiconductor (n-Ge) and high-temperature superconductor (YBa{sub 2}Cu{sub 3}O{sub 7}), whose cloaking frequency can be controlled by external temperature. The analytical solution is derived based on the scattering cancellation cloaking technique from the Mie scattering theory, and the full-wave numerical simulation is performed by the finite element method. The calculated and simulated results have demonstrated that this invisibility cloak may reduce the total scattering cross section of the composite structure of 90% over a broad frequency band of nearly 20 THz, and the infrared cloaking frequency can be tuned by the external temperature. It can provide a feasible way to design a broadband tunable cloak.

Electron spectroscopy on high-temperature superconductors and related compounds

International Nuclear Information System (INIS)

Knupfer, M.

1994-01-01

In the last two classes of materials have been discovered which distinguish themselves due to a transition into the superconducting state at relatively high temperatures. These are the cuprate superconductors and the alkali metal doped fullerenes. In this work the electronic structure of representatives of these materials, undoped and Ca-doped YBa 2 Cu 4 O 8 and A 3 C 60 (A=K, Rb), has been investigated using electron energy-loss spectroscopy and photoemission spectroscopy. (orig.) [de

Powder processing of high Tc oxide superconductors and their properties

International Nuclear Information System (INIS)

Vajpei, A.C.; Upadhyaya, G.S.

1992-01-01

Powder processing of ceramics is an established technology and in the area of high T c superconductors, its importance is felt even more significantly. The present monograph is an attempt in this direction to explore the perspectives and practice of powder processing routes towards control and optimization of the microstructure and pertinent properties of high T c oxide superconductors. The monograph consists of 6 chapters. After a very brief introduction (Chapter 1), Chapter 2 describes various classes of high T c oxide superconductors and their phase equilibria. Chapter 3 highlights the preparation of oxide superconductor powders through various routes and details their subtle distinctions. Chapter 4 briefly covers characterisation of the oxide superconductors, laying emphasis on the process-analysis and microstructure. Chapter 5 describes in detail various fabrication techniques for bulk superconductors through the powder routes. The last Chapter (Chapter 6) describing properties of bulk oxide superconductors, discusses the role of subtituents, compositional variations and processing methods on such properties. References are given at the end of each chapter. (orig.)

The interaction between the permanent magnet and ceramic superconductor with organic filler

International Nuclear Information System (INIS)

Woźny, L; Kisiel, A; Garbera, A

2016-01-01

The aim of the study was to examine the phenomenon of magnetic levitation for YBaCuO superconducting samples in pure form and with epoxy resin content of 40%. Samples of superconductors were prepared by the standard reaction in the solid state. The forces of interaction between the superconductor and neodymium permanent magnet were measured. Samples with epoxy resin fillers had significantly smaller levitation force than the sample of the sintered superconductors. This is due to a much lower content of pure superconducting material in the sample volume (about 60% of the YBaCuO). However, the obvious advantage of such samples is the possibility of preparation superconductors with complicated shapes, eg. for use in a superconducting bearings or other devices. (paper)

Spatially resolved electronic structure inside and outside the vortex cores of a high-temperature superconductor

Science.gov (United States)

Mitrović, V. F.; Sigmund, E. E.; Eschrig, M.; Bachman, H. N.; Halperin, W. P.; Reyes, A. P.; Kuhns, P.; Moulton, W. G.

2001-10-01

Puzzling aspects of high-transition-temperature (high-Tc) superconductors include the prevalence of magnetism in the normal state and the persistence of superconductivity in high magnetic fields. Superconductivity and magnetism generally are thought to be incompatible, based on what is known about conventional superconductors. Recent results, however, indicate that antiferromagnetism can appear in the superconducting state of a high-Tc superconductor in the presence of an applied magnetic field. Magnetic fields penetrate a superconductor in the form of quantized flux lines, each of which represents a vortex of supercurrents. Superconductivity is suppressed in the core of the vortex and it has been suggested that antiferromagnetism might develop there. Here we report the results of a high-field nuclear-magnetic-resonance (NMR) imaging experiment in which we spatially resolve the electronic structure of near-optimally doped YBa2Cu3O7-δ inside and outside vortex cores. Outside the cores, we find strong antiferromagnetic fluctuations, whereas inside we detect electronic states that are rather different from those found in conventional superconductors.

System and method for quench and over-current protection of superconductor

Science.gov (United States)

Huang, Xianrui; Laskaris, Evangelos Trifon; Sivasubramaniam, Kiruba Haran; Bray, James William; Ryan, David Thomas; Fogarty, James Michael; Steinbach, Albert Eugene

2005-05-31

A system and method for protecting a superconductor. The system may comprise a current sensor operable to detect a current flowing through the superconductor. The system may comprise a coolant temperature sensor operable to detect the temperature of a cryogenic coolant used to cool the superconductor to a superconductive state. The control circuit is operable to estimate the superconductor temperature based on the current flow and the coolant temperature. The system may also be operable to compare the estimated superconductor temperature to at least one threshold temperature and to initiate a corrective action when the superconductor temperature exceeds the at least one threshold temperature.

Future applications of superconductors for industrial use

International Nuclear Information System (INIS)

Reddy, S.P.

1988-01-01

Superconductors have been in existence for many years. Recent developments in superconductivity at higher temperatures are directed towards the potential use of superconductors at ambient temperatures. The diligent efforts of the scientific, engineering, and political agencies in researching and developing superconducting materials have resulted in encouraging accomplishments. Although superconductors could be used in every branch of electrical engineering, the authors focuses on a few areas in this paper. The power distribution and utilization in a typical industry is compared to that of a system using superconductors. Brief discussions of various machines with superconductors at ambient temperatures, based on developments made so far on large superconducting machines, for potential industrial applications are included in this paper

Stiffness Evaluation of High Temperature Superconductor Bearing Stiffness for 10 kWh Superconductor Flywheel Energy Storage System

International Nuclear Information System (INIS)

Park, B. J.; Jung, S. Y.; Lee, J. P.; Park, B. C.; Kim, C. H.; Han, S. C.; Du, S. G.; Han, Y. H.; Sung, T. H.

2009-01-01

A superconductor flywheel energy storage(SFES) system is mainly act an electro-mechanical battery which transfers mechanical energy into electrical form and vice versa. SFES system consists of a pair of non-contacting High Temperature Superconductor (HTS) bearings with a very low frictional loss. But it is essential to design an efficient HTS bearing considering with rotor dynamic properties through correct calculation of stiffness in order to support a huge composite flywheel rotor with high energy storage density. Static properties of HTS bearings provide data to solve problems which may occur easily in a running system. Since stiffness to counter vibration is the main parameter in designing an HTS bearing system, we investigate HTS bearing magnetic force through static properties between the Permanent Magnet(PM) and HTS. We measured axial / radial stiffness and found bearing stiffness can be easily changed by activated vibration direction between PM and HTS bulk. These results are used to determine the optimal design for a 10 kWh SFES.

Optimization of superconductor--normal-metal--superconductor Josephson junctions for high critical-current density

International Nuclear Information System (INIS)

Golub, A.; Horovitz, B.

1994-01-01

The application of superconducting Bi 2 Sr 2 CaCu 2 O 8 and YBa 2 Cu 3 O 7 wires or tapes to electronic devices requires the optimization of the transport properties in Ohmic contacts between the superconductor and the normal metal in the circuit. This paper presents results of tunneling theory in superconductor--normal-metal--superconductor (SNS) junctions, in both pure and dirty limits. We derive expressions for the critical-current density as a function of the normal-metal resistivity in the dirty limit or of the ratio of Fermi velocities and effective masses in the clean limit. In the latter case the critical current increases when the ratio γ of the Fermi velocity in the superconductor to that of the weak link becomes much less than 1 and it also has a local maximum if γ is close to 1. This local maximum is more pronounced if the ratio of effective masses is large. For temperatures well below the critical temperature of the superconductors the model with abrupt pair potential on the SN interfaces is considered and its applicability near the critical temperature is examined

Improving Erosion Resistance of Plasma-Sprayed Ceramic Coatings by Elevating the Deposition Temperature Based on the Critical Bonding Temperature

Science.gov (United States)

Yao, Shu-Wei; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu

2018-01-01

Interlamellar bonding within plasma-sprayed coatings is one of the most important factors dominating the properties and performance of coatings. The interface bonding between lamellae significantly influences the erosion behavior of plasma-sprayed ceramic coatings. In this study, TiO2 and Al2O3 coatings with different microstructures were deposited at different deposition temperatures based on the critical bonding temperature concept. The erosion behavior of ceramic coatings was investigated. It was revealed that the coatings prepared at room temperature exhibit a typical lamellar structure with numerous unbonded interfaces, whereas the coatings deposited at the temperature above the critical bonding temperature present a dense structure with well-bonded interfaces. The erosion rate decreases sharply with the improvement of interlamellar bonding when the deposition temperature increases to the critical bonding temperature. In addition, the erosion mechanisms of ceramic coatings were examined. The unbonded interfaces in the conventional coatings act as pre-cracks accelerating the erosion of coatings. Thus, controlling interlamellar bonding formation based on the critical bonding temperature is an effective approach to improve the erosion resistance of plasma-sprayed ceramic coatings.

Effect of texture on grain boundary misorientation distributions in polycrystalline high temperature superconductors

International Nuclear Information System (INIS)

Goyal, A.; Specht, E.D.; Kroeger, D.M.; Mason, T.A.

1996-01-01

Computer simulations were performed to determine the most probable grain boundary misorientation distribution (GBMD) in model polycrystalline superconductors. GBMDs in polycrystalline superconductors can be expected to dictate the macroscopic transport critical current density, J c . Calculations were performed by simulating model polycrystals and then determining the GBMD. Such distributions were calculated for random materials having cubic, tetragonal, and orthorhombic crystal symmetry. In addition, since most high temperature superconductors are tetragonal or pseudotetragonal, the effect of macroscopic uniaxial and biaxial grain orientation texture on the GBMD was determined for tetragonal materials. It is found that macroscopic texture drastically alters the grain boundary misorientation distribution. The fraction of low angle boundaries increases significantly with uniaxial and biaxial texture. The results of this study are important in correlating the macroscopic transport J c with the measured grain orientation texture as determined by x-ray diffraction copyright 1996 American Institute of Physics

Glass formability of high T(sub c) Bi-Sr-Ca-Cu-O superconductors

Science.gov (United States)

Kaukler, William F.

1992-01-01

A number of compositions of ceramic oxide high T(sub c) superconductors were evaluated for their glass formation ability by means of rapid thermal analysis during quenching, optical and electron microscopy of the quenched samples, and with subsequent DSC measurements. Correlations between experimental measurements and the methodical composition changes identified the formulations of superconductors that can easily form glass. The superconducting material was first formed as a glass, then with subsequent devitrification it was formed into bulk crystalline superconductor by a series of processing methods.

Ceramic/metal and A15/metal superconducting composite materials exploiting the superconducting proximity effect and method of making the same

International Nuclear Information System (INIS)

Holcomb, M.J.

1999-01-01

A composite superconducting material made of coated particles of ceramic superconducting material and a metal matrix material is disclosed. The metal matrix material fills the regions between the coated particles. The coating material is a material that is chemically nonreactive with the ceramic. Preferably, it is silver. The coating serves to chemically insulate the ceramic from the metal matrix material. The metal matrix material is a metal that is susceptible to the superconducting proximity effect. Preferably, it is a NbTi alloy. The metal matrix material is induced to become superconducting by the superconducting proximity effect when the temperature of the material goes below the critical temperature of the ceramic. The material has the improved mechanical properties of the metal matrix material. Preferably, the material consists of approximately 10% NbTi, 90% coated ceramic particles (by volume). Certain aspects of the material and method will depend upon the particular ceramic superconductor employed. An alternative embodiment of the invention utilizes A15 compound superconducting particles in a metal matrix material which is preferably a NbTi alloy

Ceramic/metal and A15/metal superconducting composite materials exploiting the superconducting proximity effect and method of making the same

Science.gov (United States)

Holcomb, Matthew J.

1999-01-01

A composite superconducting material made of coated particles of ceramic superconducting material and a metal matrix material. The metal matrix material fills the regions between the coated particles. The coating material is a material that is chemically nonreactive with the ceramic. Preferably, it is silver. The coating serves to chemically insulate the ceramic from the metal matrix material. The metal matrix material is a metal that is susceptible to the superconducting proximity effect. Preferably, it is a NbTi alloy. The metal matrix material is induced to become superconducting by the superconducting proximity effect when the temperature of the material goes below the critical temperature of the ceramic. The material has the improved mechanical properties of the metal matrix material. Preferably, the material consists of approximately 10% NbTi, 90% coated ceramic particles (by volume). Certain aspects of the material and method will depend upon the particular ceramic superconductor employed. An alternative embodiment of the invention utilizes A15 compound superconducting particles in a metal matrix material which is preferably a NbTi alloy.

Charge redistribution and properties of high-temperature superconductors

International Nuclear Information System (INIS)

Khomskii, D.I.; Kusmartsev, F.V.

1992-01-01

We show that in high-T c superconductors (HTSC) with two groups of electrons (e.g., holes in CuO 2 planes and in a ''reservoir'') there should exist a charge redistribution with the temperature: the hole concentration N h in ''active'' superconducting CuO 2 planes increases below T c . This effect may explain structural changes such as the shift of the apical oxygen atom, anomalous thermal expansion, the shift of nuclear quadrupole resonance lines, the change of the positron lifetime, and the modification of the ion channeling below T c . Some other possible consequences of the charge redistribution (the modification of the temperature dependence of a gap Δ and of the ratio 2Δ 0 /T c , the phenomena at a contact of HTSC with normal metals and semiconductors) are discussed

Relationship of electrical, magnetic, and mechanical properties to processing in high-temperature superconductors

International Nuclear Information System (INIS)

Blendell, J.E.; Chiang, C.K.; Cranmer, D.C.

1987-01-01

The interrelation between processing, microstructure, and properties is an important factor in understanding the behavior of ceramic materials. This type of understanding will be particularly important in the development of the new high T/sub c/ superconducting ceramic oxides of the type Ba/sub 2/YCu/sub 3/O/sub 7-x/. As an initial effort in understanding these relations, a number of properties have been measured for these superconducting ceramics and related to their microstructure and processing sequence. The Ba/sub 2/YCu/sub 3/O/sub 7-x/ ceramics were prepared by powder processing techniques, followed by dry pressing and sintering in both air and flowing oxygen at various temperatures. The sintered bodies were annealed at various temperatures and environments. Superconducting properties, such as the transition temperature and the width of the transition, were measured by both electrical conductivity and AC magnetic susceptibility; both of these properties show a strong sensitivity to annealing temperature and atmosphere. The microstructure and density were also strongly dependent on processing conditions. In this regard, compositional mapping proved to be an important technique for quantifying microstructural variations. Mechanical properties, such as elastic modulus, hardness, and fracture toughness, which will be important for the reliable use of these materials in large scale structures, were also determined

Irradiation effects of high temperature superconductor of lanthanoid oxides

Energy Technology Data Exchange (ETDEWEB)

Ueda, Koh-ichi; Kohara, Takao [Himeji Inst. of Tech., Hyogo (Japan)

1996-04-01

Neutron irradiation effects on excess oxygen were studied by neutron irradiation on La{sub 2}CuO{sub 4} treated with high pressure oxygen. La{sub 2}CuO{sub 4} was prepared by the usual method and annealed for 10 h under the oxygen pressure of 800-2000 atm. at 600degC. The superconducting transition temperature (Tc) is 27-32K before irradiation (La{sub 2}CuO{sub 4+d}, amount of excess oxygen d=0.03-0.12). Neutron irradiation was carried out by two kinds of experiments. Low irradiation dose test at low temperature (LTL: {approx}20-200K, storage in LN{sub 2}) showed Tc decreased more slowly than that of high temperature range. Experiment at high temperature (Hyd:{approx}80deg{yields}, storage at room temperature) showed -10K/10{sup 18}n/cm{sup 2}, the decrease of Tc was three times larger than that of YBCO type superconductor. (S.Y.)

Analysis of flux-flow curves in superconductors as a function of temperature

International Nuclear Information System (INIS)

Boboshko, N.

1978-01-01

A phenomenological method to analyse the experimental data of flux-flow resistivity in superconductors as a function of temperature is proposed and successfully applied to existing data for t = kappa >= 0.07. An empirical curve relating the flux-flow resistivity with the Ginsburg-Landau parameter kappa was obtained. (author)

Formation of hot spots in a superconductor observed by low-temperature scanning electron microscopy

International Nuclear Information System (INIS)

Eichele, R.; Seifert, H.; Huebener, R.P.

1981-01-01

Low-temperature scanning electron microscopy can be used for the direct observation of hot spots in a superconductor. Experiments performed at 2.10 K with tim films demonstrating the method are reported

Effect of silver content on mechanical and electric properties of HTSC YBaCuO/Ag ceramics

International Nuclear Information System (INIS)

Markov, L.K.; Orlova, T.S.; Peschanskaya, N.N.; Smirnov, B.I.; Stepanov, Yu.P.; Shpejzman, V.V.

2003-01-01

It is shown that addition of 3-5 wt. % silver to YBaCuO superconducting ceramics leads to noticeable increase on its microplasticity and strength. Temperature spectra of microplastic deformation rates for YbaCuO/Ag ceramics with 0, 1.6, 2.9, 4.2 and 7.6 wt. % silver are obtained. Spectra structure as well as a bond of one of the peaks with superconducting transition is discussed. Peculiarities of the volt-ampere characteristics (VAC) of samples cooled in the magnetic field are considered. It is shown that the position of VAC ascending branch depends on VAC start point which may be used for fixing two or more stable positions of the memory cell on the basis of high-temperature superconductors [ru

Nickel W14 substrates for high-temperature superconductors

International Nuclear Information System (INIS)

Kolb-Telieps, Angelika; Gehrmann, Bodo

2008-01-01

High-temperature superconductivity is on the threshold of market launch. Starting from the results of a research project, ThyssenKrupp VDM has successfully developed an industrial-scale production process for nickel W14, which is used as substrate strip in superconductors destined for applications such as generators for wind turbines. The deoxidation of the melt presented a particular challenge. On the one hand, this is required in order to avoid fractures during the hot forming, on the other, the usual deoxidation elements have negative effects on the nanoscale texture and surface roughness needed for the substrate strip. (orig.)

Thermoelectric and thermomagnetic effects in high-temperature superconductors

International Nuclear Information System (INIS)

Huebener, R.P.; Ri, H.C.; Gross, R.; Kober, F.

1992-01-01

In the mixed state of high-temperature superconductors the dominant part of the Seebeck and Nernst effect is due to the thermal diffusion of quasiparticles and vortices, respectively. The authors' understanding of the Seebeck effect is based on the two-fluid counterflow model of Ginzburg and its extension to the mixed state with the presence of vortices. From the Nernst effect the transport entropy of the vortices is obtained. In this paper summarize the recent thermoelectric and thermomagnetic experiments, paying also attention to the role of the Magnus force (Hall effect) and to the thermal fluctuation effects near T c

"Ultra"-Fast Fracture Strength of Advanced Structural Ceramic Materials Studied at Elevated Temperatures

Science.gov (United States)

Choi, Sung R.; Gyekenyesi, John P.

1999-01-01

The accurate determination of inert strength is important in reliable life prediction of structural ceramic components. At ambient temperature, the inert strength of a brittle material is typically regarded as free of the effects of slow crack growth due to stress corrosion. Therefore, the inert strength can be determined either by eliminating active species, especially moisture, with an appropriate inert medium, or by using a very high test rate. However, at elevated temperatures, the concept or definition of the inert strength of brittle ceramic materials is not clear, since temperature itself is a degrading environment, resulting in strength degradation through slow crack growth and/or creep. Since the mechanism to control strength is rate-dependent viscous flow, the only conceivable way to determine the inert strength at elevated temperatures is to utilize a very fast test rate that either minimizes the time for or eliminates slow crack growth. Few experimental studies have measured the elevated-temperature, inert (or "ultra"-fast fracture) strength of advanced ceramics. At the NASA Lewis Research Center, an experimental study was initiated to better understand the "ultra"-fast fracture strength behavior of advanced ceramics at elevated temperatures. Fourteen advanced ceramics - one alumina, eleven silicon nitrides, and two silicon carbides - have been tested using constant stress-rate (dynamic fatigue) testing in flexure with a series of stress rates including the "ultra"-fast stress rate of 33 000 MPa/sec with digitally controlled test frames. The results for these 14 advanced ceramics indicate that, notwithstanding possible changes in flaw populations as well as flaw configurations because of elevated temperatures, the strength at 33 000 MPa/sec approached the room-temperature strength or reached a higher value than that determined at the conventional test rate of 30 MPa/sec. On the basis of the experimental data, it can be stated that the elevated-temperature

Applications of superconductors to electric motors

International Nuclear Information System (INIS)

McConnell, B.W.

1988-01-01

This paper reviews previous experience in applying superconductors to electric motors and examines the difficulties encountered. While motors and generators have a common basis, several significant differences exist. The application of high temperature superconductors to the major electric motor types is discussed and expected difficulties are presented. The limitations imposed by various motor designs are reflected in a statement of the desired material properties for high temperature superconductor electric motor applications

Effect of exciton pairing on the stationary Josephson current in superconductor-semimetal-superconductor junctions

International Nuclear Information System (INIS)

Itskovich, I.F.; Shekhter, R.I.

1983-01-01

The effect of exciton pairing of charge carriers in a semimetal on the stationary Josephson current in superconductor-semimetal-superconductor junctions is considered. It is shown that the phase transition of the semimetal interlayer into an exciton dielectric state for T/sub γ/< T/sub c/ (T/sub γ/, T/sub c/ are the superconducting and exciton transition temperatures, respectively) is accompanied by a kink on the critical current j/sub c/ versus temperature curve at the point T = T/sub γ/. A sharp nonmonotonic temperature dependence of the reduced current j/sub c//j/sub c/0 (j/sub c/0 is the critical current at T/sub γ/ = 0) is also possible in the range T< T/sub γ/. At low temperatures T<< v/sub 1,2//d<< T/sub γ/ (v/sub 1,2/ are the Fermi velocities of the carriers in the semimetal, d is the thickness of the interlayer) the critical current of the superconductor-semimetal-superconductor junction is exponentially smaller than the current in the absence of exciton pairing

Critical currents and thermally activated flux motion in high-temperature superconductors

NARCIS (Netherlands)

Palstra, T.T.M.; Batlogg, B.; Dover, R.B. van; Schneemeyer, L.F.; Waszczak, J.V.

1989-01-01

We have measured the resistance below Tc of single crystals of the high-temperature superconductors Ba2YCu3O7 and Bi2.2Sr2Ca0.8Cu2O8+δ in magnetic fields up to 12 T. The resistive transition of both compounds is dominated by intrinsic dissipation which is thermally activated, resulting in an

Fracture Mechanisms of Zirconium Diboride Ultra-High Temperature Ceramics under Pulse Loading

Science.gov (United States)

Skripnyak, Vladimir V.; Bragov, Anatolii M.; Skripnyak, Vladimir A.; Lomunov, Andrei K.; Skripnyak, Evgeniya G.; Vaganova, Irina K.

2015-06-01

Mechanisms of failure in ultra-high temperature ceramics (UHTC) based on zirconium diboride under pulse loading were studied experimentally by the method of SHPB and theoretically using the multiscale simulation method. The obtained experimental and numerical data are evidence of the quasi-brittle fracture character of nanostructured zirconium diboride ceramics under compression and tension at high strain rates and the room temperatures. Damage of nanostructured porous zirconium diboride -based UHTC can be formed under stress pulse amplitude below the Hugoniot elastic limit. Fracture of nanostructured ultra-high temperature ceramics under pulse and shock-wave loadings is provided by fast processes of intercrystalline brittle fracture and relatively slow processes of quasi-brittle failure via growth and coalescence of microcracks. A decrease of the shear strength can be caused by nano-voids clusters in vicinity of triple junctions between ceramic matrix grains and ultrafine-grained ceramics. This research was supported by grants from ``The Tomsk State University Academic D.I. Mendeleev Fund Program'' and also N. I. Lobachevski State University of Nizhny Novgorod (Grant of post graduate mobility).

Theory of tunneling and photoemission spectroscopy for high-temperature superconductors

International Nuclear Information System (INIS)

Kouznetsov, K.; Coffey, L.

1996-01-01

A comprehensive analysis is presented of the tunneling conductance and angle-resolved photoemission spectra in high-temperature superconductors. It is shown that unexplained features of the tunneling and photoemission spectra such as broad backgrounds, dips, and asymmetry of the tunneling conductance can arise in a model of spin-fluctuation mediated inelastic tunneling. Effects of directionality in tunneling play an important role in determining the behavior of the tunneling conductance. copyright 1996 The American Physical Society

High output power reluctance electric motors with bulk high-temperature superconductor elements

Energy Technology Data Exchange (ETDEWEB)

Kovalev, L.K. [Moscow State Aviation Institute (Technical University) (MAI), Moscow (Russian Federation)]. E-mail: kovalev@mail.sitek.net; Ilushin, K.V.; Penkin, V.T. [Moscow State Aviation Institute (Technical University) (MAI), Moscow (RU)] [and others

2002-05-01

We present new types of electric machines with the rotors containing bulk high-temperature superconductor (HTS)-YBCO and Bi-Ag-elements. We discuss different schematics of hysteresis, reluctance, 'trapped field' and composed synchronous HTS machines. The two-dimensional mathematical models describing the processes in such types of HTS machines were developed on the basis of the theoretical analysis of the electrodynamic and hysteresis processes in the single-domain and polycrystal YBCO ceramic samples and plate shape Bi-Ag elements. We give the test results of the series of hysteresis, reluctance, 'trapped field' and composed with permanent magnets HTS motors with an output power rating of 0.1-18 kW and current frequencies 50 Hz and 400 Hz. These results show that in the media of liquid nitrogen the specific output power per one unit weight of the HTS motor is four to seven times better than for conventional electric machines. A comparison of the theoretical and experimental characteristics of the developed HTS motors show that they are in good agreement. We discuss the test results for a liquid nitrogen cryogenic pump system with a hysteresis 500 W HTS motor. We describe several designs of new HTS motors operating in the media of liquid nitrogen with an output power 125 kW (and more) and a power factor of more than 0.8. We discuss future applications of new types of HTS motors for aerospace technology, on-land industry and transport systems. (author)

Multilayer ceramic capacitors for pulsed power, high temperature applications

International Nuclear Information System (INIS)

Cygan, S.; McLarney, J.; Prymak, J.; Bohn, P.

1991-01-01

The performance of the multilayer ceramic capacitors (MLC) in high frequency power applications has improved significantly over the last years. One of the possible applications of MLC capacitors is the automotive industry where repetitive discharging of capacitors is required. A 0.25-μF capacitor using NPO dielectric subjected to repetitive discharging with the rate of 700 pulses per second, magnitude of 600-V and 195-A peak currents showed no degradation in performance at 298 K or 398 K even after 1 billion discharge cycles. Less than a 5-K temperature rise was observed under these conditions. The most exciting, newly emerging utilization for MLC capacitors, however, might be the high temperature application (up to 473 K for underhood utilization), where ceramic capacitors with higher volumetric efficiency as compared to glass or polymer type capacitors prove very superior. Moreover ceramic capacitors, which next to glass capacitors exhibit the greatest radiation resistance among all insulating materials (Hanks and Hamman 1971), might also be best suited in the future for high temperature operation in space environment. The pulsed power performance of the 0.25-μF NPO capacitor was evaluated under repetitive discharge conditions (200 V, 700 pps) at high temperature, 473 K, and the results are presented in this paper

Quenched disorder and thermopower fluctuations in high temperature superconductors

International Nuclear Information System (INIS)

Khalil, A.E.

1997-01-01

Thermopower behavior in high temperature superconductors YBa 2 Cu 3 O 7-δ single crystals near the transition temperature was examined. An expression for the thermoelectric power containing the divergent term (1-T/T c ) -s , where s is a scaling exponent that does not appear in Maki's calculations, was derived. This divergent term is the result of contributions due to the flow of currents across disordered conduction paths in the sample. These currents are driven by the density gradients of the conductivity fluctuations as a result of the increased disorder due to the existence of amorphous regions in the two-dimensional lattice. The present calculations include the most divergent effects to the thermopower due to the conductivity fluctuations near the transition temperature. The model predictions are in good agreement with recent experimental measurements reported in the literature. (orig.)

Method for preparing high transition temperature Nb.sub.3 Ge superconductors

Science.gov (United States)

Newkirk, Lawrence R.; Valencia, Flavio A.

1977-01-01

Bulk coatings of Nb.sub.3 Ge superconductors having transition temperatures in excess of 20 K are readily formed by a chemical vapor deposition technique involving the coreduction of NbCl.sub.5 and GeCl.sub.4 in the presence of hydrogen. The NbCl.sub.5 vapor may advantageously be formed quantitatively in the temperature range of about 250.degree. to 260.degree. C by the chlorination of Nb metal provided the partial pressure of the product NbCl.sub.5 vapor is maintained at or below about 0.1 atm.

Fermionic spectral functions in backreacting p-wave superconductors at finite temperature

Energy Technology Data Exchange (ETDEWEB)

Giordano, G.L.; Grandi, N.E.; Lugo, A.R. [Instituto de Física de La Plata - CONICET & Departamento de Física - UNLP,C.C. 67, 1900 La Plata (Argentina)

2017-04-14

We investigate the spectral function of fermions in a p-wave superconducting state, at finite both temperature and gravitational coupling, using the AdS/CFT correspondence and extending previous research. We found that, for any coupling below a critical value, the system behaves as its zero temperature limit. By increasing the coupling, the “peak-dip-hump” structure that characterizes the spectral function at fixed momenta disappears. In the region where the normal/superconductor phase transition is first order, the presence of a non-zero order parameter is reflected in the absence of rotational symmetry in the fermionic spectral function at the critical temperature.

Characterization of high-current, high-temperature superconductor current lead elements

International Nuclear Information System (INIS)

Niemann, R.C.; Evans, D.J.; Fisher, B.L.; Brockenborough, W.E.; Roberts, P.R.; Rodenbush, A.J.

1996-08-01

The refrigeration loads of current leads for superconducting magnets can be significantly reduced by using high-temperature superconductor (HTS) leads. An HTS conductor type that is well suited for this application is a laminated sintered stack of HTS powder-in-tube (PIT) tapes. The superconducting elements are normally characterized by their manufacturer by measuring critical currents at 77 K in self field. Additional characterization, which correlates electrical performance at 77 K and at lower temperatures with applied magnetic fields, provides the current lead designer and conductor element manufacturer with critical information. For HTS conductor elements comprising a laminated and sintered stack of Bi-2223 PIT tapes having an alloyed Ag sheath, this characterization uses variable applied fields and operating temperatures

Common phase diagram for low-dimensional superconductors

International Nuclear Information System (INIS)

Michalak, Rudi

2003-01-01

A phenomenological phase diagram which has been derived for high-temperature superconductors from NMR Knight-shift measurements of the pseudogap is compared to the phase diagram that is obtained for organic superconductors and spin-ladder superconductors, both low-dimensional systems. This is contrasted to the phase diagram of some Heavy Fermion superconductors, i.e. superconductors not constrained to a low dimensionality

Magnetization studies in high temperature and conventional superconductors

International Nuclear Information System (INIS)

Grover, A.K.; Chaddah, P.

1991-01-01

In this paper, the authors state the contemporary view of the physical basis of a celebrated phenomenological model for hard superconductors. The authors highlight the qualitative and general predictions of this model relevant to various magnetic measurements. The authors give prescriptions to correlate data of different experiments with the predictions of the model with the intention of extracting information on material parameters, like J c (H), pinning potential, etc. These prescriptions will be illustrated with the data on both conventional and HTSC superconductors. The correlation of these data with the predictions of the model underscores the similarity in behaviour between the two classes of hard superconductors

Origin of photovoltaic effect in superconducting YBa2Cu3O6.96 ceramics

Science.gov (United States)

Yang, F.; Han, M. Y.; Chang, F. G.

2015-01-01

We report remarkable photovoltaic effect in YBa2Cu3O6.96 (YBCO) ceramic between 50 and 300 K induced by blue-laser illumination, which is directly related to the superconductivity of YBCO and the YBCO-metallic electrode interface. There is a polarity reversal for the open circuit voltage Voc and short circuit current Isc when YBCO undergoes a transition from superconducting to resistive state. We show that there exists an electrical potential across the superconductor-normal metal interface, which provides the separation force for the photo-induced electron-hole pairs. This interface potential directs from YBCO to the metal electrode when YBCO is superconducting and switches to the opposite direction when YBCO becomes nonsuperconducting. The origin of the potential may be readily associated with the proximity effect at metal-superconductor interface when YBCO is superconducting and its value is estimated to be ~10–8 mV at 50 K with a laser intensity of 502 mW/cm2. Combination of a p-type material YBCO at normal state with an n-type material Ag-paste forms a quasi-pn junction which is responsible for the photovoltaic behavior of YBCO ceramics at high temperatures. Our findings may pave the way to new applications of photon-electronic devices and shed further light on the proximity effect at the superconductor-metal interface. PMID:26099727

Temperature dependence of high field electromechanical coupling in ferroelectric ceramics

Energy Technology Data Exchange (ETDEWEB)

Weaver, P M; Cain, M G; Stewart, M, E-mail: paul.weaver@npl.co.u [National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW (United Kingdom)

2010-04-28

A study of the temperature dependence of the electromechanical response of ferroelectric lead zirconate titanate (PZT) ceramics at high electric fields (up to 1.3 kV mm{sup -1}) is reported. Simultaneous measurements were performed of strain, electric field and polarization to form a complete response map from room temperature up to 200 {sup 0}C. An electrostrictive model is shown to provide an accurate description of the electromechanical response to high levels of induced polarization and electric field. This provides a method for decoupling strain contributions from thermal expansion and polarization changes. Direct measurements of electrostriction and thermal expansion, above and below the Curie temperature, are reported. Electrostriction coefficients are shown to be temperature dependent in these ceramic materials, with different values above and below the Curie temperature.

Contact spectroscopy of high-temperature superconductors (Review). I - Physical and methodological principles of the contact spectroscopy of high-temperature superconductors. Experimental results for La(2-x)Sr(x)CuO4 and their discussion

Science.gov (United States)

Ianson, I. K.

1991-03-01

Research in the field of high-temperature superconductors based on methods of tunneling and microcontact spectroscopy is reviewed in a systematic manner. The theoretical principles of the methods are presented, and various types of contacts are described and classified. Attention is given to deviations of the measured volt-ampere characteristics from those predicted by simple theoretical models and those observed for conventional superconductors. Results of measurements of the energy gap and fine structure of volt ampere characteristic derivatives are presented for La(2-x)Sr(x)CuO4.

Kohn anomalies in superconductors

International Nuclear Information System (INIS)

Flatte, M.E.

1994-01-01

The detailed behavior of phonon dispersion curves near momenta which span the electronic Fermi sea in a superconductor is presented. An anomaly, similar to the metallic Kohn anomaly, exists in a superconductor's dispersion curves when the frequency of the photon spanning the Fermi sea exceeds twice the superconducting energy gap. This anomaly occurs at approximately the same momentum but is stronger than the normal-state Kohn anomaly. It also survives at finite temperature, unlike the metallic anomaly. Determination of Fermi-surface diameters from the location of these anomalies, therefore, may be more successful in the superconducting phase than in the normal state. However, the superconductor's anomaly fades rapidly with increased phonon frequency and becomes unobservable when the phonon frequency greatly exceeds the gap. This constraint makes these anomalies useful only in high-temperature superconductors such as La 1.85 Sr 0.15 CuO 4

Development of high temperature superconductors having high critical current density

International Nuclear Information System (INIS)

Hong, Gye Wong; Kim, C. J.; Lee, H.G.; Kwon, S. C.; Lee, H. J.; Kim, K. B.; Park, J. Y.; Jung, C. H.

2000-08-01

Fabrication of high T c superconductors and its applications for electric power device were carried out for developing superconductor application technologies. High quality YBCO superconductors was fabricated by melt texture growth, top-seeded melt growth process and multi-seeded melt growth process and the properties was compared. The critical current density of the melt processed YBCO superconductors was about few 10,000 A/cm 2 and the levitation force was 50 N. The processing time needed for the growth of the 123 single grain was greatly reduced by applying multi-seeding without no significant degradation of the levitation force. The multi-seeded melt growth process was confirmed as a time-saving and cost-effective method for the fabrication of bulk superconductors with controlled crystallographic orientation

Development of high temperature superconductors having high critical current density

Energy Technology Data Exchange (ETDEWEB)

Hong, Gye Wong; Kim, C. J.; Lee, H.G.; Kwon, S. C.; Lee, H. J.; Kim, K. B.; Park, J. Y.; Jung, C. H

2000-08-01

Fabrication of high T{sub c} superconductors and its applications for electric power device were carried out for developing superconductor application technologies. High quality YBCO superconductors was fabricated by melt texture growth, top-seeded melt growth process and multi-seeded melt growth process and the properties was compared. The critical current density of the melt processed YBCO superconductors was about few 10,000 A/cm{sup 2} and the levitation force was 50 N. The processing time needed for the growth of the 123 single grain was greatly reduced by applying multi-seeding without no significant degradation of the levitation force. The multi-seeded melt growth process was confirmed as a time-saving and cost-effective method for the fabrication of bulk superconductors with controlled crystallographic orientation.

The evidence of unconventional pairing in heavy fermion superconductors and high-Tc superconductors

International Nuclear Information System (INIS)

Tien, C.; Wur, C.S.; Jiang, I.M.

1989-01-01

Recently there has been a great deal of interest in two classes of superconductors, heavy fermion superconductors and high T c copper oxide superconductors. The behavior and nature of superconductivity in these two classes of materials are very similar. The temperature dependences of spin-lattice relaxation time (T 1 ) and spin-spin relaxation time (T 2 ) of 9 Be in UBe 13 are quite similar to those of 63 Cu and 89 Y in YBa 2 Cu 3 O 7-δ . The Knight shift of UBe 13 is unchanged during the superconducting phase transition. The Knight shift of YBa 2 Cu 3 O 7-δ changes from the value in the normal state K n /K s = 1 at T ≥ T c to K n /K s = 0.5 at T = 6 K. Both do not approach zero as expected in BCS theory. The acoustic attenuation is enhanced just below T c instead of rapid drop near T c for these two superconducting system. Neither the enhancement, the temperature variation, nor any other anomalous behaviors appear to be mirrored in EPR data for heavy Fermion superconductors and high T c superconductors. This strongly suggests that the unconventional pairing mechanism which induces superconductivity in heavy fermion materials might also involve in high T c superconductors

Modeling high-temperature superconductors and metallic alloys on the Intel iPSC/860

International Nuclear Information System (INIS)

Geist, G.A.; Peyton, B.W.; Shelton, W.A.; Stocks, G.M.

1990-01-01

Oak Ridge National Laboratory has embarked on several computational grand Challenges, which require the close cooperation of physicists, mathematicians, and computer scientists. One of these projects is the determination of the material properties of alloys form first principles and, in particular, the electronic structure of high-temperature superconductors. The physical basis for high Tc superconductivity is not well understood. The design of materials with higher critical temperatures and the ability to carry higher current densities can be greatly facilitated by the modeling and detailed study of the electronic structure of existing superconductors. This paper describes the progress to data on this project. We include a description of a self-consistent KKR-CPA method, parallelization of the model, and the incorporation of a dynamic load balancing scheme into the algorithm. We also describe the development and performance of a consolidated KKR-CPA code capable of running on CRAYs, workstations, and several parallel computers without source code modification

Method for producing ceramic composition having low friction coefficient at high operating temperatures

Science.gov (United States)

Lankford, Jr., James

1988-01-01

A method for producing a stable ceramic composition having a surface with a low friction coefficient and high wear resistance at high operating temperatures. A first deposition of a thin film of a metal ion is made upon the surface of the ceramic composition and then a first ion implantation of at least a portion of the metal ion is made into the near surface region of the composition. The implantation mixes the metal ion and the ceramic composition to form a near surface composite. The near surface composite is then oxidized sufficiently at high oxidizing temperatures to form an oxide gradient layer in the surface of the ceramic composition.

Physical characterization and study of the electrical magnetic and thermal properties of the ceramic high Tc superconductor Y1Ba2Cu3O7-x

International Nuclear Information System (INIS)

Azeredo Orlando, M.T. de.

1991-01-01

It was built four systems for physical characterization of high Tc superconductors, with data acquisition by computer, and recent results on AC susceptibility, AC resistivity, specific heat and thermal diffusivity of the YBa 2 Cu 3 O 7-x (x ≅ 0.15) compound, in a ceramic form, could be reproduced. Our study pointed that those ceramics exhibit a preferential orientation of the grains, being the c axis of the compound parallel to the compression direction. The study of this material in the four different technics, for samples with same density and oxygen stoichiometry, has pointed also that its magnetic behavior is strongly influenced by the intergrain region. This influence can be described by the clem model for the intergrain region and by the Malozemoff proposition for the fluxoids collective behavior. (author)

Proceedings of the national symposium on materials and processing: functional glass/glass-ceramics, advanced ceramics and high temperature materials

International Nuclear Information System (INIS)

Ghosh, A.; Sahu, A.K.; Viswanadham, C.S.; Ramanathan, S.; Hubli, R.C.; Kothiyal, G.P.

2012-10-01

With the development of materials science it is becoming increasingly important to process some novel materials in the area of glass, advanced ceramics and high temperature metals/alloys, which play an important role in the realization of many new technologies. Such applications demand materials with tailored specifications. Glasses and glass-ceramics find exotic applications in areas like radioactive waste storage, optical communication, zero thermal expansion coefficient telescopic mirrors, human safety gadgets (radiation resistance windows, bullet proof apparels, heat resistance components etc), biomedical (implants, hyperthermia treatment, bone cement, bone grafting etc). Advanced ceramic materials have been beneficial in biomedical applications due to their strength, biocompatibility and wear resistance. Non-oxide ceramics such as carbides, borides, silicides, their composites, refractory metals and alloys are useful as structural and control rod components in high temperature fission/ fusion reactors. Over the years a number of novel processing techniques like selective laser melting, microwave heating, nano-ceramic processing etc have emerged. A detailed understanding of the various aspects of synthesis, processing and characterization of these materials provides the base for development of novel technologies for different applications. Keeping this in mind and realizing the need for taking stock of such developments a National Symposium on Materials and Processing -2012 (MAP-2012) was planned. The topics covered in the symposium are ceramics, glass/glass-ceramics and metals and materials. Papers relevant to INIS are indexed separately

Applications of high-temperature superconductors in power technology

International Nuclear Information System (INIS)

Hull, John R

2003-01-01

Since the discovery of the first high-temperature superconductors (HTSs) in the late 1980s, many materials and families of materials have been discovered that exhibit superconductivity at temperatures well above 20 K. Of these, several families of HTSs have been developed for use in electrical power applications. Demonstration of devices such as motors, generators, transmission lines, transformers, fault-current limiters, and flywheels in which HTSs and bulk HTSs have been used has proceeded to ever larger scales. First-generation wire, made from bismuth-based copper oxides, was used in many demonstrations. The rapid development of second-generation wire, made by depositing thin films of yttrium-based copper oxide on metallic substrates, is expected to further accelerate commercial applications. Bulk HTSs, in which large single-grain crystals are used as basic magnetic components, have also been developed and have potential for electrical power applications

Power-law temperature dependence of the inelastic-scattering rate in disordered superconductors

International Nuclear Information System (INIS)

Devereaux, T.P.; Belitz, D.

1991-01-01

We present a theory of the quasiparticle inelastic lifetime τ in in disordered superconducting films. We find that both the Coulomb and the electron-phonon contribution to τ in -1 are enhanced by disorder, and that for reasonably strong electron-phonon coupling the latter is dominant. In contrast to clean superconductors, the scattering rate is larger than the recombination rate at all temperatures. This leads to a power-law temperature dependence of τ in -1 , in agreement with experimental observations. The theory quantitatively accounts for the magnitude, disorder dependence, and temperature dependence of τ in measured in recent experiments

Micro-machinable polymer-derived ceramic sensors for high-temperature applications

Science.gov (United States)

Liu, Jian; Xu, Chengying; An, Linan

2010-04-01

Micro-sensors are highly desired for on-line temperature/pressure monitoring in turbine engines to improve their efficiency and reduce pollution. The biggest challenge for developing this type of sensors is that the sensors have to sustain at extreme environments in turbine engine environments, such as high-temperatures (>800 °C), fluctuated pressure and oxidation/corrosion surroundings. In this paper, we describe a class of sensors made of polymer-derived ceramics (PDCs) for such applications. PDCs have the following advantages over conventional ceramics, making them particularly suitable for these applications: (i) micromachining capability, (ii) tunable electric properties, and (iii) hightemperature capability. Here, we will discuss the materials and their properties in terms of their applications for hightemperature micro-sensors, and microfabrication technologies. In addition, we will also discuss the design of a heat-flux sensor based on polymer-derived ceramics.

High temperature properties and processes in ceramics: thermomigration

International Nuclear Information System (INIS)

1978-01-01

The focus of this program is on the effects of large temperature gradients on the transport processes, the defect structure and resulting physical properties of ceramics. In particular, the transport of ions due to thermal gradients is one of the least understood phenomenon in materials science and is presumably based on fundamental understanding of thermodynamics, atomistic kinetic processes, and structure-property relationships. The purpose of this research is to systematically consider each of the elements of atomic transport due to driving forces other than composition gradients in a model ceramic system

First principles simulation on the K0.8Fe2Se2 high-temperature structural superconductor

International Nuclear Information System (INIS)

Guo, Rui; Yang, Shizhong; Khosravi, Ebrahim; Zhao, Guang-Lin; Bagayoko, Diola

2013-01-01

Highlights: • The superconductor K 0.8 Fe 2 Se 2 super cell size, shape, and atomic positions are fully optimized using first principles density functional theory method. • Each K atom donates 0.8 |e| with K vacancies in the supercell, each Fe atom donates 0.4 |e|, while each Se atom gains 0.7 |e| ∼ 0.8 |e|. • Fe atoms show magnetic moment fluctuation and possible strong spin-orbital coupling. -- Abstract: Since the synthesis of the first ones in 2008, iron-based high temperature superconductors have been the subject of many studies. This great interest is partly due to their higher, upper magnetic field, smaller Fermi surface around the Γ point, and a larger coherence length. This work is focused on A x Fe 2 Se 2 structural superconductor (FeSe, 11 hierarchy; A = K, Cs) as recently observed. ARPES data show novel, electronic structure and a hole-free Fermi surface which is different from previously observed Fermi surface images. We use ab initio density functional theory method to simulate the electronic structure of the novel superconductor A x Fe 2 Se 2 . We compare this electronic structure with those of other Fe-based superconductors

Recent advances in high-temperature superconductor wire fabrication and applications development

International Nuclear Information System (INIS)

Hull, J.R.; Uherka, K.L.

1992-01-01

In this paper, recent advances in fabrication of high-temperature superconductor wires are summarized and detailed discussion is provided on developments in near- and intermediate-term applications. Near-term applications, using presently obtainable current densities, include liquid-nitrogen depth sensors, cryostat current leads, and magnetic bearings. Intermediate-term applications, using current densities expected to be available in the near future, include fault-current limiters and short transmission lines

Temperature stability and electrical properties in La-doped KNN-based ceramics

KAUST Repository

Lv, Xiang; Wu, Jiagang; Zhu, Jianguo; Xiao, Dingquan; Zhang, Xixiang

2018-01-01

To improve the temperature stability and electrical properties of KNN‐based ceramics, we simultaneously consider the phase boundary and the addition of rare earth element (La), 0.96K0.5Na0.5Nb0.96Sb0.04O3‐0.04(Bi1‐xLax)0.5Na0.5ZrO3 (0 ≤ x ≤ 1.0) ceramics. More specifically, we investigate how the phase boundary and the addition of La3+ affect the phase structure, electrical properties, and temperature stability of the ceramic. We show that increasing the La3+ content leads to a change in phase structure, from a rhombohedral‐tetragonal (R‐T) phase coexistence to a cubic phase. More importantly, we show that the appropriate addition of La3+ (x = 0.2) can simultaneously improve the unipolar strain (from 0.127% to 0.147%) and the temperature stability (i.e., the unipolar strain of 0.147% remains unchanged when T is increased from 25 to 80°C). In addition, we find that the ceramics with x = 0.2 exhibit a large piezoelectric constant (d33) of ~430 pC/N, a high Curie temperature (TC) of ~240°C and a fatigue‐free behavior (after 106 electric cycles). The enhanced electrical properties mostly originate from the easy domain switching, whereas the improved temperature stability can be attributed to the R‐T phase boundary and the appropriate addition of La3+.

Temperature stability and electrical properties in La-doped KNN-based ceramics

KAUST Repository

Lv, Xiang

2018-04-16

To improve the temperature stability and electrical properties of KNN‐based ceramics, we simultaneously consider the phase boundary and the addition of rare earth element (La), 0.96K0.5Na0.5Nb0.96Sb0.04O3‐0.04(Bi1‐xLax)0.5Na0.5ZrO3 (0 ≤ x ≤ 1.0) ceramics. More specifically, we investigate how the phase boundary and the addition of La3+ affect the phase structure, electrical properties, and temperature stability of the ceramic. We show that increasing the La3+ content leads to a change in phase structure, from a rhombohedral‐tetragonal (R‐T) phase coexistence to a cubic phase. More importantly, we show that the appropriate addition of La3+ (x = 0.2) can simultaneously improve the unipolar strain (from 0.127% to 0.147%) and the temperature stability (i.e., the unipolar strain of 0.147% remains unchanged when T is increased from 25 to 80°C). In addition, we find that the ceramics with x = 0.2 exhibit a large piezoelectric constant (d33) of ~430 pC/N, a high Curie temperature (TC) of ~240°C and a fatigue‐free behavior (after 106 electric cycles). The enhanced electrical properties mostly originate from the easy domain switching, whereas the improved temperature stability can be attributed to the R‐T phase boundary and the appropriate addition of La3+.

Dynamic phases of low-temperature low-current driven vortex matter in superconductors

International Nuclear Information System (INIS)

Benkraouda, M; Obaidat, I M; Khawaja, U Al; Mulaa, N M J

2006-01-01

Using molecular dynamics simulations of vortices in a high-temperature superconductor with square periodic arrays of pinning sites, dynamic phases of the low-current driven vortices are studied at low temperatures. A rough vortex phase diagram of three distinct regimes of vortex flow is proposed. At zero temperature, we obtain a coupled-channel regime where rows of vortices flow coherently in the direction of the driving force. As the temperature is increased, a smooth crossover into an uncoupled-channel regime occurs where the coherence between the flowing rows of vortices becomes weaker. Increasing the temperature further leads to a plastic vortex regime, where the channels of flowing vortices completely disappear. The temperatures of the crossovers between these regimes were found to decrease with the driving force

Behavior of high Tc-superconductors and irradiated defects under reactor irradiation

International Nuclear Information System (INIS)

Atobe, Kozo; Honda, Makoto; Fukuoka, Noboru; Yoshida, Hiroyuki.

1991-01-01

It has been well known that the lattice defects of various types are introduced in ceramics without exception, and exert large effect to the function of these materials. Among oxides, the electronic materials positively using oxygen defect control have been already put in practical use. Also in the oxide high temperature superconductors which are Perovskite type composite oxides, the superconductive characteristics are affected largely by the concentration of the oxygen composing them. This is regarded as an important factor for causing superconductivity, related with the oxygen cavities arising at this time and the carriers bearing superconductivity. In this study, the irradiation effect with relatively low dose, the measurement under irradiation, the effect of irradiation temperature, and the effect of radiation quality were evaluated by the irradiation of YBCO, EBCO and LBCO. The experimental method, and the irradiation effect at low temperature and normal temperature, the effect of Co-60 gamma ray irradiation instead of reactor irradiation are reported. (K.I.)

Dynamics of superconductor bearings in a cryogenic failure

Energy Technology Data Exchange (ETDEWEB)

Rastogi, Amit [Department of Engineering, Cambridge University, Cambridge CB2 1PZ (United Kingdom)]. E-mail: Amit.Rastogi@avizatechnology.com; Campbell, A.M. [Department of Engineering, Cambridge University, Cambridge CB2 1PZ (United Kingdom); Coombs, T.A. [Department of Engineering, Cambridge University, Cambridge CB2 1PZ (United Kingdom)

2006-08-01

The dynamics of superconductor bearings in a cryogenic failure scenario have been analyzed. As the superconductor warms up, the rotor goes through multiple resonance frequencies, begins to slow down and finally touches down when the superconductor goes through its transition temperature. The bearing can be modelled as a system of springs with axial, radial and cross stiffness. These springs go through various resonant modes as the temperature of the superconductor begins to rise. We have presented possible explanations for such behaviour.

The influence of the statistical distributed parameters of the shape of the magneto-resistive transition of a HTc superconductor

International Nuclear Information System (INIS)

Grobnic, D.; Popescu, I.M.

1993-01-01

As a result of their granular structure the conductance of ceramic high temperature superconductors depends strongly on the characteristics of the parameter distribution. To study the influence of these distributions of the magneto-resistive transition from normal to superconductive state, a mathematical model was used. This model simulates the superconductor sample, considered as large three-dimensional collection of Josephson tunnel junctions. Each individual junction, according to the values of the parameters that define it, in a given environment (temperature, magnetic field and current density) allows or not the supercurrent to flow with a given probability. The bond percolation problem was solved using a Monte Carlo procedure. To solve the random resistor network formed, a sparse matrix package was used. As parameters that defined Josephson junction which choose the resistance of the normal junction state and the critical temperature of the grain. We considered the normal junction resistance as obeying a log normal distribution and the critical temperature, a Gaussian one. The influences of the relative dispersion of the first distribution and the dispersion of the critical temperature distribution on the shape of the resistivity versus magnetic field was studied. (Author)

Influence of radiant heating treatments on fusion of high-temperature superconducting yttrium ceramics

International Nuclear Information System (INIS)

Bitenbaev, M.I.; Polyakov, A.I.

1999-01-01

Regardless of the fact that the materials made of HTSC-ceramics are promising, there is no any information about their successful practical application in publications. To our opinion, it is explained by the fact, first of all, that the conservative technologies of the powder metallurgy do not allow producing HTSC systems with excellent operating performance (structure homogeneity, long-term stability of Sc properties and etc.). This report presents outcomes of experiments on fusion of yttrium ceramics containing raw components irradiated by g-rays 60 Co under the temperature exceeding 500 degrees C. HTSC properties of ceramics were studied according to their differential spectra of radio-frequency (RF) field absorption. The RF absorption spectrum of yttrium ceramics samples produced according to conservative technology is sufficiently permitted triplet with the Sc transition temperatures range of 80 K, 90 K, 95 K. Irradiation under the increased temperatures and mechanical limitation allow producing samples of yttrium HTSC-ceramics with sufficient homogeneous structure and superconducting properties that are stable to air conditions for not less than one year

Dynamics of the vortex state in high temperature superconductors

International Nuclear Information System (INIS)

Kapitulnik, A.

1991-01-01

The large thermal energy available, the strong anisotropy, and short coherence lengths of high temperature superconductors give rise to new phenomena in the mixed state. The author discusses transport and thermodynamic measurements of high-Tc materials and of model systems. In particular, he uses experiments on two dimensional films to compare and isolate two dimensional effects in the cuprates. By using multilayer systems with similar parameters, he identifies decoupling of the superconducting planes in magnetic fields at temperatures much above the irreversibility line. He shows that if the irreversibility line is to be considered a melting transition line, it implies melting of the solid state into a liquid of three dimensional flux lines. He further uses Monte Carlo simulations to study the structure of the vortex state as well as melting

Processing of high-temperature simulated waste glass in a continuous ceramic melter

International Nuclear Information System (INIS)

Barnes, S.M.; Brouns, R.A.; Hanson, M.S.

1980-01-01

Recent operations have demonstrated that high-melting-point glasses and glass-ceramics can be successfully processed in joule-heated, ceramic-lined melters with minor modifications to the existing technology. Over 500 kg of simulated waste glasses have been processed at temperatures up to 1410 0 C. The processability of the two high-temperature waste forms tested is similar to existing borosilicate waste glasses. High-temperature waste glass formulations produced in the bench-scale melter exhibit quality comparing favorably to standard waste glass formulations

Risk Mitigaion for HTS Motors: Intermediate Temperature (27 K) Strain Effects in Reinforced Bi-Sr-Ca-Cu-O Superconductors

National Research Council Canada - National Science Library

Schwartz, Justin

2004-01-01

High temperature superconductors , known for their high critical temperatures, also have very high upper critical fields and thus have received significant attention for superconducting magnets (SCMs...

Superconductor stability 90: A review

International Nuclear Information System (INIS)

Dresner, L.

1990-01-01

This paper reviews some recent developments in the field of stability of superconductors. The main topics dealt with are hydrodynamic phenomena in cable-in-conduit superconductors, namely, multiple stability, quench pressure, thermal expulsion, and thermal hydraulic quenchback, traveling normal zones in large, composite conductors, such as those intended for SMES, and the stability of vapor-cooled leads made of high-temperature superconductors. 31 refs., 5 figs

Fabrication of Nb_3Al superconductor by the optimized mechanical alloying method with low temperature

International Nuclear Information System (INIS)

Zhang, Y.; Lin, W.J.; Xu, L.Y.; Yang, D.W.; Chen, Y.L.; Li, P.Y.; Pan, X.F.; Yan, G.; Zhao, Y.

2016-01-01

Highlights: • Due to a much better strain tolerance than Nb_3Sn, Nb_3Al has been considered as an excellent candidate for making high field magnets. At present, the Nb_3Al superconducting wires were prepared mainly by the Jelly-roll method combined with a rapid heating and quenching (RHQ) heat treatment at around 2000 °C. In this study, Nb_3Al superconductor with T_c of 15.6 K is directly prepared with a mechanical alloying method followed by a low temperature annealing at 800 to 900 °C. Our results hint the possibility that Nb_3Al superconducting wire with high performance can be prepared below the melting point of Cu (1080 °C) by a conventional powder in tube (PIT) method, thus effectively avoiding high temperature heat treatment and RHQ device. - Abstract: Mechanical alloying was used to synthesize Nb_3Al superconductor successfully, and the process was optimization under various preparation conditions. In the current study, Nb_3Al superconductor with T_c of 15.6 K was directly prepared from high quality Nb (Al) solid solution by mechanical alloying method and heat treatment at a low temperature of 800 to 900 °C. The results showed that Nb_3Al superconducting wire with high performance could be prepared after heat treatment below the melting point of Cu (1080°C) and using Nb (Al) solid solution and conventional powder in tube (PIT) method, thus effectively avoiding ultra-high temperature heat treatment and special rapid heating and quenching(RHQ) device.

Glass precursor approach to high-temperature superconductors

Science.gov (United States)

Bansal, Narottam P.

1992-01-01

The available studies on the synthesis of high T sub c superconductors (HTS) via the glass precursor approach were reviewed. Melts of the Bi-Sr-Ca-Cu-O system as well as those doped with oxides of some other elements (Pb, Al, V, Te, Nb, etc.) could be quenched into glasses which, on further heat treatments under appropriate conditions, crystallized into the superconducting phase(s). The nature of the HTS phase(s) formed depends on the annealing temperature, time, atmosphere, and the cooling rate and also on the glass composition. Long term annealing was needed to obtain a large fraction of the 110 K phase. The high T sub c phase did not crystallize out directly from the glass matrix, but was preceded by the precipitation of other phases. The 110 K HTS was produced at high temperatures by reaction between the phases formed at lower temperatures resulting in multiphase material. The presence of a glass former such as B2O3 was necessary for the Y-Ba-Cu-O melt to form a glass on fast cooling. A discontinuous YBa2Cu3O(7-delta) HTS phase crystallized out on heat treatment of this glass. Attempts to prepare Tl-Ba-Ca-Cu-O system in the glassy state were not successful.

Prospects of High Temperature Superconductors for fusion magnets and power applications

International Nuclear Information System (INIS)

Fietz, Walter H.; Barth, Christian; Drotziger, Sandra; Goldacker, Wilfried; Heller, Reinhard; Schlachter, Sonja I.; Weiss, Klaus-Peter

2013-01-01

Highlights: • An overview of HTS application in fusion is given. • BSCCO application for current leads is discussed. • Several approaches to come to a high current HTS cable are shown. • Open issues and benefits of REBCO high current HTS cables are discussed. -- Abstract: During the last few years, progress in the field of second-generation High Temperature Superconductors (HTS) was breathtaking. Industry has taken up production of long length coated REBCO conductors with reduced angular dependency on external magnetic field and excellent critical current density jc. Consequently these REBCO tapes are used more and more in power application. For fusion magnets, high current conductors in the kA range are needed to limit the voltage during fast discharge. Several designs for high current cables using High Temperature Superconductors have been proposed. With the REBCO tape performance at hand, the prospects of fusion magnets based on such high current cables are promising. An operation at 4.5 K offers a comfortable temperature margin, more mechanical stability and the possibility to reach even higher fields compared to existing solutions with Nb 3 Sn which could be interesting with respect to DEMO. After a brief overview of HTS use in power application the paper will give an overview of possible use of HTS material for fusion application. Present high current HTS cable designs are reviewed and the potential using such concepts for future fusion magnets is discussed

Engineered flux-pinning centers in BSCCO TBCCO and YBCO superconductors

Science.gov (United States)

Goretta, K.C.; Lanagan, M.T.; Miller, D.J.; Sengupta, S.; Parker, J.C.; Hu, J.; Balachandran, U.; Siegel, R.W.; Shi, D.

1999-07-27

A method of preparing a high temperature superconductor is disclosed. A method of preparing a superconductor includes providing a powdered high temperature superconductor and a nanophase material. These components are combined to form a solid compacted mass with the material disposed in the polycrystalline high temperature superconductor. This combined mixture is rapidly heated, forming a dispersion of nanophase size particles without a eutectic reaction. These nanophase particles can have a flat plate or columnar type morphology. 4 figs.

Influence of sintering temperature in red ceramic with addition of mill scale

International Nuclear Information System (INIS)

Arnt, A.B.C.; Rocha, M.R.; Bernardin, A.M.; Meller, J.G.

2010-01-01

This study aimed to evaluate the influence of sintering temperature in a red ceramic body with the addition of mill scale. This residue consists of oxides of iron had to replace the function of pigments used in ceramic materials. After chemical characterization, by X-ray diffraction, X-ray fluorescence and scanning electron microscopy, this residue was added at a rate of 5% in commercial ceramic past. The formulations were subjected to different burn temperatures of around 950 deg C, 1000 deg C and 1200 deg C. The formulations were evaluated for physical loss to fire, linear firing shrinkage, water absorption and flexural strength by 3 and intensity of tone. The results indicate that the different firing temperatures influence the strength and stability of tone in the formulations tested. (author)

High-temperature superconductors induced by ion implantation. Final report

International Nuclear Information System (INIS)

Greenwald, A.C.; Johnson, E.

1988-08-01

High dose oxygen ion implantation (10 to the 17th power ions per sq. cm.) at elevated temperatures (300 C) has been shown to adjust the critical temperature of gamma-Y-Ba-Cu-O and Bi-Ca-Sr-Cu-O materials. These results are in marked contrast to earlier work which showed complete destruction of superconducting properties for similar radiation doses, and marked reduction in superconducting properties at one-tenth this dose in the 1-2-3- compound only. Experiments also showed that the superconducting materials can be patterned into conducting and nonconducting areas without etching by ion implantation, allowing maintenance of planar geometries required for microcircuit fabrication. Experiments on deposition of thin films of high temperature superconductors for use with the ion implantation experiments showed that ion beam sputtering from a single target could achieve the correct stoichiometry. Variations of composition with ion beam energy and angle of sputtered ions were studied

Critical transport current in granular high temperature superconductors

International Nuclear Information System (INIS)

Bogolyubov, N.A.

1999-01-01

The temperature and size dependence of the critical current in a zero magnetic field of three bismuth-based ceramic samples with round cross section and one sample with rectangular triangle cross section have been studied by a contactless technique. It is shown that the critical current can be presented as a product of the temperature and size dependent factors. The temperature-dependent multiplier reflects the individual peculiarities of the Josephson net of each sample, while the size factor is a homogeneous function of the cross-section sizes. The index of this function is independent of the cross-section form, the temperature and individual properties of HTSC samples. The radial distribution of critical current density in round samples and dependence of the critical current density on the magnetic conduction in granular HTSC have been found from the analysis of experimental data

The study on a new superconductor (oxide Ba-Y-Cu) with high critical temperature Tc by positron annihilation

International Nuclear Information System (INIS)

Zhang Caigu; Yu Zhuxing; Wang Zhu; Huang Zhe; Zhou Jun

1987-01-01

The study on a new superconductor oxide Ba-Y-Cu with high critical temperature Tc is described. The experimental results show that positron lifetime reducing reflects variable curve of resistance with temperature. A peak of positron lifetime is appeared at critical temperature

"Fluctuoscopy" of Superconductors

Science.gov (United States)

Varlamov, A. A.

Study of fluctuation phenomena in superconductors (SCs) is the subject of great fundamental and practical importance. Understanding of their physics allowed to clear up the fundamental properties of SC state. Being predicted in 1968, one of the fluctuation effects, namely paraconductivity, was experimentally observed almost simultaneously. Since this time, fluctuations became a noticeable part of research in the field of superconductivity, and a variety of fluctuation effects have been discovered. The new wave of interest to fluctuations (FL) in superconductors was generated by the discovery of cuprate oxide superconductors (high-temperature superconductors, HTS), where, due to extremely short coherence length and low effective dimensionality of the electron system, superconductive fluctuations manifest themselves in a wide range of temperatures. Moreover, anomalous properties of the normal state of HTS were attributed by many theorists to strong FL in these systems. Being studied in the framework of the phenomenological Ginzburg-Landau theory and, more extensively, in diagrammatic microscopic approach, SC FLs side by side with other quantum corrections (weak localization, etc.) became a new tool for investigation and characterization of such new systems as HTS, disordered electron systems, granular metals, Josephson structures, artificial super-lattices, etc. The characteristic feature of SC FL is their strong dependence on temperature and magnetic fields in the vicinity of phase transition. This allows one to definitely separate the fluctuation effects from other contributions and to use them as the source of information about the microscopic parameters of a material. By their origin, SC FLs are very sensitive to relaxation processes, which break phase coherence. This allows using them for versatile characterization of SC. Today, one can speak about the " fluctuoscopy" of superconductive systems. In review, we present the qualitative picture both of thermodynamic

High-frequency applications of high-temperature superconductor thin films

Science.gov (United States)

Klein, N.

2002-10-01

High-temperature superconducting thin films offer unique properties which can be utilized for a variety of high-frequency device applications in many areas related to the strongly progressing market of information technology. One important property is an exceptionally low level of microwave absorption at temperatures attainable with low power cryocoolers. This unique property has initiated the development of various novel type of microwave devices and commercialized subsystems with special emphasis on application in advanced microwave communication systems. The second important achievement related to efforts in oxide thin and multilayer technology was the reproducible fabrication of low-noise Josephson junctions in high-temperature superconducting thin films. As a consequence of this achievement, several novel nonlinear high-frequency devices, most of them exploiting the unique features of the ac Josephson effect, have been developed and found to exhibit challenging properties to be utilized in basic metrology and Terahertz technology. On the longer timescale, the achievements in integrated high-temperature superconductor circuit technology may offer a strong potential for the development of digital devices with possible clock frequencies in the range of 100 GHz.

High-frequency applications of high-temperature superconductor thin films

International Nuclear Information System (INIS)

Klein, N.

2002-01-01

High-temperature superconducting thin films offer unique properties which can be utilized for a variety of high-frequency device applications in many areas related to the strongly progressing market of information technology. One important property is an exceptionally low level of microwave absorption at temperatures attainable with low power cryocoolers. This unique property has initiated the development of various novel type of microwave devices and commercialized subsystems with special emphasis on application in advanced microwave communication systems. The second important achievement related to efforts in oxide thin and multilayer technology was the reproducible fabrication of low-noise Josephson junctions in high-temperature superconducting thin films. As a consequence of this achievement, several novel nonlinear high-frequency devices, most of them exploiting the unique features of the ac Josephson effect, have been developed and found to exhibit challenging properties to be utilized in basic metrology and Terahertz technology. On the longer timescale, the achievements in integrated high-temperature superconductor circuit technology may offer a strong potential for the development of digital devices with possible clock frequencies in the range of 100 GHz. (author)

Charge transport in junctions between d-wave superconductors

International Nuclear Information System (INIS)

Barash, Y.S.; Galaktionov, A.V.; Zaikin, A.D.

1995-01-01

We develop a microscopic analysis of superconducting and dissipative currents in junctions between superconductors with d-wave symmetry of the order parameter. We study the proximity effect in such superconductors and show that for certain crystal orientations the superconducting order parameter can be essentially suppressed in the vicinity of a nontransparent specularly reflecting boundary. This effect strongly influences the value and the angular dependence of the dc Josephson current j S . At T∼T c it leads to a crossover between j S ∝T c -T and j S ∝(T c -T) 2 respectively for homogeneous and nonhomogeneous distribution of the order parameter in the vicinity of a tunnel junction. We show that at low temperatures the current-phase relation j S (cphi) for superconductor--normal-metal--superconductor junctions and short weak links between d-wave superconductors is essentially nonharmonic and contains a discontinuity at cphi=0. This leads to further interesting features of such systems which can be used for pairing symmetry tests in high-temperature superconductors (HTSC). We also investigated the low-temperature I-V curves of normal-metal--superconductor and superconductor-superconductor tunnel junctions and demonstrated that depending on the junction type and crystal orientation these curves show zero-bias anomalies I∝V 2 , I∝V 2 ln(1/V), and I∝V 3 caused by the gapless behavior of the order parameter in d-wave superconductors. Many of our results agree well with recent experimental findings for HTSC compounds

High temperature superconductor bulk materials. Fundamentals - processing - properties control - application aspects

International Nuclear Information System (INIS)

Krabbes, G.; Fuchs, G.; Canders, W.R.; May, H.; Palka, R.

2006-01-01

This book presents all the features of bulk high temperature superconducting materials. Starting from physical and chemical fundamentals, the authors move on to portray methods and problems of materials processing, thoroughly working out the characteristic properties of bulk superconductors in contrast to long conductors and films. The authors provide a wide range of specific materials characteristics with respect to the latest developments and future applications guiding from fundamentals to practical engineering examples. This book contains the following chapters: 1. Fundamentals 2. Growth and melt processing of YBCO 3. Pinning-relevant defects in bulk YBCO 4. Properties of bulk YBCO 5. Trapped fields 6. Improved YBCO based bulk superconductors and functional elements 7. Alternative systems 8. Peak effect 9. Very high trapped fields in YBCO permanent magnets 10. Engineering aspects: Field distribution in bulk HTSC 11. Inherently stable superconducting magnetic bearings 12. Application of bulk HTSCs in electromagnetic energy converters 13. Applications in magnet technologies and power supplies

High critical temperature superconductors: Progress achieved after two years. Les supraconducteurs haute temperature critique: L'etat des lieux deux ans apres

Energy Technology Data Exchange (ETDEWEB)

Maillard, J M; Rammal, R; Vittorge, M C

1989-01-01

Progress concerning the theory of high temperature superconductors and activity of laboratories of the CNRS (France) are reviewed and news on strategy, budgets, theoretical research, materials characterization, fabrication process technology transfers, commercialisation, uses and data bases are given.

Thermally activated flux creep in strongly layered high-temperature superconductors

International Nuclear Information System (INIS)

Chakravarty, S.; Ivlev, B.I.; Ovchinnikov, Y.N.

1990-01-01

Thermal activation energies for single vortices and vortex bundles in the presence of a magnetic field parallel to the layers are calculated. The pinning considered is intrinsic and is due to the strongly layered structure of high-temperature superconductors. The magnetic field and the current dependence of the activation energy are studied in detail. The calculation of the activation energy is used to determine the current-voltage characteristic. It may be possible to observe the effects discussed in this paper in a pure enough sample

Effect of impurity scattering on the low temperature magnetic penetration depth of a nonlocal and nonlinear d-wave superconductor

International Nuclear Information System (INIS)

Yavary, H.

2006-01-01

The magnetic penetration depth of a quasi-two dimensional d-wave superconductor in the presence of nonlineary, nonlocality, and impurity effects is investigated by using Green's function method. It is shown that a d-wave superconductor would inevitably avoid the violation of the Nernst theorem by creating a T 2 term in its penetration depth through a competition of nonlinear, nonlocal, and impurity effects and this system may be stable at low temperatures. I also show that in the impure sample at low temperatures, T < T * ∝ γ the impurity effect determines the temperature dependence of the penetration depth, i.e., nonlocal and nonlinear effects are completely masked by impurities

Survey report on high temperature irradiation experiment programs for new ceramic materials in the HTTR (High Temperature Engineering Test Reactor). 2

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-02-01

A survey research on status of research activities on new ceramic materials in Japan was carried out under contract between Japan Atomic Energy Research Institute and Atomic Energy Society of Japan. The purpose of the survey is to provide information to prioritize prospective experiments and tests in the HTTR. The HTTR as a high temperature gas cooled reactor has a unique and superior capability to irradiate large-volumed specimen at high temperature up to approximately 800degC. The survey was focused on mainly the activities of functional ceramics and heat resisting ceramics as a kind of structural ceramics. As the result, the report recommends that the irradiation experiment of functional ceramics is feasible to date. (K. Itami)

Hybrid molecule/superconductor assemblies

International Nuclear Information System (INIS)

McDevitt, J.T.; Haupt, S.G.; Riley, D.R.; Zhao, J.; Zhou, J.P., Jones, C.

1993-01-01

The fabrication of electronic devices from molecular materials has attracted much attention recently. Schottky diodes, molecular transistors, metal-insulator-semiconductor diodes, MIS field effect transistors and light emitting diodes have all been prepared utilizing such substances. The active elements in these devices have been constructed by depositing the molecular phase onto the surface of a metal, semiconductor or insulating substrate. With the recent discovery of high temperature superconductivity, new opportunities now exist for the study of molecule/superconductor interactions as well as for the construction of novel hybrid molecule/superconductor devices. In this paper, methods for preparing the initial two composite molecule/semiconductor devices will be reported. Consequently, light sensors based on dye-coated superconductor junctions as well as molecular switches fashioned from conductive polymer coated superconductor junctions as well as molecular switches fashioned from conductive polymer coated superconductor microbridges will be discussed. Moreover, molecule/superconductor energy and electron transfer phenomena will be illustrated also for the first time

Relationship between Magnetic Anisotropy below Pseudogap Temperature and Short-Range Antiferromagnetic Order in High-Temperature Cuprate Superconductor

Science.gov (United States)

Morinari, Takao

2018-06-01

The central issue in high-temperature cuprate superconductors is the pseudogap state appearing below the pseudogap temperature T*, which is well above the superconducting transition temperature. In this study, we theoretically investigate the rapid increase of the magnetic anisotropy below the pseudogap temperature detected by the recent torque-magnetometry measurements on YBa2Cu3Oy [Y. Sato et al., 10.1038/nphys4205" xlink:type="simple">Nat. Phys. 13, 1074 (2017)]. Applying the spin Green's function formalism including the Dzyaloshinskii-Moriya interaction arising from the buckling of the CuO2 plane, we obtain results that are in good agreement with the experiment and find a scaling relationship. Our analysis suggests that the characteristic temperature associated with the magnetic anisotropy, which coincides with T*, is not a phase transition temperature but a crossover temperature associated with the short-range antiferromagnetic order.

Electronic structure of the Y Ba2 Cu3 O7-x high temperature superconductor ceramic

International Nuclear Information System (INIS)

Lima, G.A.R.

1990-01-01

We investigate the electronic structure of superconductor Y Ba 2 Cu 3 O 7-x through a molecular cluster approach. The calculations are performed self consistently through a semi empirical L.C.A.O. technique, where different charge states are considered. The correlation effects are taken into account by configuration interaction procedure (INDO/CI). The results for the larger cluster yield a density of states showing a strong p-d covalency resulting in a width of around 8,0 eV for the valence band. The optical excitations is analyzed in detail and compared with the experimental data. (author)

Ceramic membranes for high temperature hydrogen separation

Energy Technology Data Exchange (ETDEWEB)

Fain, D.E.; Roettger, G.E. [Oak Ridge K-25 Site, TN (United States)

1996-08-01

Ceramic gas separation membranes can provide very high separation factors if the pore size is sufficiently small to separate gas molecules by molecular sieving and if oversized pores are adequately limited. Ceramic membranes typically have some pores that are substantially larger than the mean pore size and that should be regarded as defects. To assess the effects of such defects on the performance of ceramic membranes, a simple mathematical model has been developed to describe flow through a gas separation membrane that has a primary mode of flow through very small pores but that has a secondary mode of flow through undesirably large pores. This model permits separation factors to be calculated for a specified gas pair as a function of the molecular weights and molecular diameters of the gases, the membrane pore diameter, and the diameter and number of defects. This model will be described, and key results from the model will be presented. The separation factors of the authors membranes continue to be determined using a permeance test system that measures flows of pure gases through a membrane at temperatures up to 275{degrees}C. A primary goal of this project for FY 1996 is to develop a mixed gas separation system for measuring the separation efficiency of membranes at higher temperatures. Performance criteria have been established for the planned mixed gas separation system and design of the system has been completed. The test system is designed to measure the separation efficiency of membranes at temperatures up to 600{degrees}C and pressures up to 100 psi by separating the constituents of a gas mixture containing hydrogen. The system will accommodate the authors typical experimental membrane that is tubular and has a diameter of about 9 mm and a length of about 23 cm. The design of the new test system and its expected performance will be discussed.

Preparation and electromagnetic properties of low-temperature sintered ferroelectric-ferrite composite ceramics

International Nuclear Information System (INIS)

Yue Zhenxing; Chen Shaofeng; Qi Xiwei; Gui Zhilun; Li Longtu

2004-01-01

For the purpose of multilayer chip EMI filters, the new ferroelectric-ferrite composite ceramics were prepared by mixing PMZNT relaxor ferroelectric powder with composition of 0.85Pb(Mg 1/3 Nb 2/3 )O 3 -0.1Pb(Ni 1/3 Nb 2/3 )O 3 -0.05PbTiO 3 and NiCuZn ferrite powder with composition of (Ni 0.20 Cu 0.20 Zn 0.60 )O(Fe 2 O 3 ) 0.97 at low sintering temperatures. A small amount of Bi 2 O 3 was added to low sintering temperature. Consequently, the dense composite ceramics were obtained at relative low sintering temperatures, which were lower than 940 deg. C. The X-ray diffractometer (XRD) identifications showed that the sintered ceramics retained the presence of distinct ferroelectric and ferrite phases. The sintering studies and scanning electron microscope (SEM) observations revealed that the co-existed two phases affect the sintering behavior and grain growth of components. The electromagnetic properties, such as dielectric constant and initial permeability, change continuously between those of two components. Thus, the low-temperature sintered ferroelectric-ferrite composite ceramics with tunable electromagnetic properties were prepared by adjusting the relative content of two components. These materials can be used for multilayer chip EMI filters with various properties

Microstructure and Properties of High-Temperature Superconductors

CERN Document Server

Parinov, Ivan A

2007-01-01

The main features of high-temperature superconductors (HTSC) that define their properties are intrinsic brittleness of oxide cuprates, the layered anisotropic structure and the supershort coherence length. Taking into account these features, this treatise presents research into HTSC microstructure and properties, and also explores the possibilities of optimization of the preparation techniques and superconducting compositions. The "composition-technique-experiment-theory-model," employed here, assumes considerable HTSC defectiveness and structure heterogeneity and helps to draw a comprehensive picture of modern representations of the microstructure, strength and the related structure-sensitive properties of the materials considered. Special attention is devoted to the Bi-Sr-Ca-Cu-O and Y-Ba-Cu-O families, which currently offer the most promising applications. Including a great number of illustrations and references, this monograph addresses students, post-graduate students and specialists, taking part in the ...

Microstructure and Properties of High-Temperature Superconductors

CERN Document Server

Parinov, I A

2012-01-01

The main features of high-temperature superconductors (HTSC) that define their properties are intrinsic brittleness of oxide cuprates, the layered anisotropic structure and the supershort coherence length. Taking into account these features, this treatise presents research into HTSC microstructure and properties, and also explores the possibilities of optimization of the preparation techniques and superconducting compositions. The "composition-technique-experiment-theory-model," employed here, assumes considerable HTSC defectiveness and structure heterogeneity and helps to draw a comprehensive picture of modern representations of the microstructure, strength and the related structure-sensitive properties of the materials considered. Special attention is devoted to the Bi-Sr-Ca-Cu-O and Y-Ba-Cu-O families, which currently offer the most promising applications. Including a great number of illustrations and references, this monograph addresses students, post-graduate students and specialists, taking part in the ...

High temperature microplasticity of fine-grained ceramics

International Nuclear Information System (INIS)

Lakki, A.; Schaller, R.

1996-01-01

Several fine-grained ceramics exhibit enhanced ductility or even structural superplasticity at high temperature. Grain boundaries play a dominant role in the deformation process of these materials which usually involves diffusion-accommodated grain boundary sliding. Sliding is either lubricated by an amorphous intergranular phase or takes place by glide and climb of grain boundary dislocations. At high temperature, anelastic deformation precedes plastic deformation and stems from the short range motion of lattice defects, such as dislocations and grain boundaries. The energy loss (''mechanical loss'') associated with such motion can be measured by using the technique of mechanical spectroscopy. Moreover, at the onset of plasticity (''microplasticity''), long range irrecoverable motion of defects contributes to additional mechanical loss. Mechanical loss spectra may then give an insight into mechanisms operating at the transition between anelastic and plastic deformation. As an illustration, the spectra of three fine-grained ceramics (Si 3 N 4 , ZrO 2 , Al 2 O 3 ) are presented. In all cases, anelastic relaxation phenomena (peak and background) have been observed at high temperature (> 1200 K), bearing a close relation with creep behaviour. Their analysis permits to distinguish between different types of microstructrual elements: bulk regions of amorphous intergranular phase at triple points, grain boundaries separated by a thin glassy film and ''clean'' grain boundaries. (orig.)

Nanoscale strain-induced pair suppression as a vortex-pinning mechanism in high-temperature superconductors

International Nuclear Information System (INIS)

Llordes, Anna; Palau, A.; Gazquez, J.; Coll, M.; Vlad, R.; Pomar, A.; Arbiol, Jordi; Guzman, Roger; Ye, S.; Rouco, V.; Sandiumenge, Felip; Ricart, Susagna; Puig, Teresa; Varela del Arco, Maria; Chataigner, D.; Vanacken, J.; Gutierrez, J.; Moschalkov, V.; Deutscher, G.; Magen Dominguez, Cesar; Obradors, Xavier

2012-01-01

Boosting large-scale superconductor applications require nanostructured conductors with artificial pinning centres immobilizing quantized vortices at high temperature and magnetic fields. Here we demonstrate a highly effective mechanism of artificial pinning centers in solution-derived high-temperature superconductor nanocomposites through generation of nanostrained regions where Cooper pair formation is suppressed. The nanostrained regions identified from transmission electron microscopy devise a very high concentration of partial dislocations associated with intergrowths generated between the randomly oriented nanodots and the epitaxial YBa 2 Cu 3 O 7 matrix. Consequently, an outstanding vortex-pinning enhancement correlated to the nanostrain is demonstrated for four types of randomly oriented nanodot, and a unique evolution towards an isotropic vortex-pinning behaviour, even in the effective anisotropy, is achieved as the nanostrain turns isotropic. We suggest a new vortex-pinning mechanism based on the bond-contraction pairing model, where pair formation is quenched under tensile strain, forming new and effective core-pinning regions.

Mechanical Properties of Ceramics for High Temperature Applications

Science.gov (United States)

1976-12-01

meets another aim of gas turbine ceramics. Temperature measuring by optical pyrometer gives here a reproducibility of approximately 150 C. The...with a similar acoustic impedence to the host material (e.g., certain inclusions, large grains) will be minimal, signal averaging instrumentation

Generation of charge imbalance in a superconductor by a temperature gradient

International Nuclear Information System (INIS)

Entin-Wohlman, O.; Orbach, R.

1980-01-01

The charge-imbalance voltage in a superconductor carrying a current in the presence of a temperature gradient is calculated from the Boltzmann equation in the clean limit. We demonstrate why the Green's-function approach in the dirty limit, first performed by Schmid and Schoem, generates the same Boltzmann-like equation for the distribution function. In addition, the charge-imbalance voltage in the absence of an impressed current is calculated. It is shown to depend on del 2 T+(delT) 2 /T, and not solely on (delT) 2 . The calculations are limited to the temperature regime near T/sub c/, such that Δ<< T

Measuring condensate fraction in superconductors

International Nuclear Information System (INIS)

Chakravarty, Sudip; Kee, Hae-Young

2000-01-01

An analysis of off-diagonal long-range order in superconductors shows that the spin-spin correlation function is significantly influenced by the order if the order parameter is anisotropic on a microscopic scale. Thus, magnetic neutron scattering can provide a direct measurement of the condensate fraction of a superconductor. It is also argued that recent measurements in high-temperature superconductors come very close to achieving this goal. (c) 2000 The American Physical Society

High temperature bismuth cuprate superconductors synthesis and characterization

International Nuclear Information System (INIS)

Mansori, M.; Satre, P.; Breandon, C.; Roubin, M.; Sebaoun, A.

1993-01-01

High temperature superconductor phases synthesis by coprecipitation in alkaline solution is reported. (Bi 1.6 Pb 0.4 )Sr 2 Ca 1 Cu 2 O 8+x and (Bi 1.6 Pb 0.4 )Sr 2 Ca 2 Cu 3 O 10+y noted (2212) and (2223) have been prepared and studied. From aqueous nitrate solutions of Bi, Pb, Sr, Ca and Cu and oxalic acid aqueous solution as well as ethylene glycol, using an organic base (the triethylamine), the pH was increased up to the path of the precipitation zone (pH = 10.5-11.2). This method assures a good granulometric homogeneity of powders. Thermal analysis and characterization of the different components produced during the synthesis have been studied by DTA (differential thermal analysis)- TGA (thermogravimetric analysis), X-ray diffraction at different temperatures and by Infrared spectroscopy with a Fourier transformation. The measurements of magnetic susceptibility for the 2212 (with and without lead) and 2223 (with lead) phases have permitted us to observe the critical temperatures of 84 K, 87 K and 114 K. (author). 29 refs., 2 figs., 4 tabs

Transmission formalism for supercurrent flow in multiprobe superconductor-semiconductor-superconductor devices

International Nuclear Information System (INIS)

van Wees, B.J.; Lenssen, K.H.; Harmans, C.J.P.M.

1991-01-01

A theoretical study is given of supercurrent flow in a one-dimensional semiconductor channel coupled to superconductors at both ends. In addition, the channel is coupled to a semiconductor reservoir by means of a junction with variable coupling strength var-epsilon. The supercurrent I(cphi) is calculated from the phase-coherent propagation of electronlike and holelike excitations emitted by the superconductor reservoirs, together with electron and hole excitations from the semiconductor reservoir. The effect of temperature and var-epsilon on I(cphi) is studied. It is shown that a voltage applied between the semiconductor reservoir and the superconductors modifies the I(cphi) relation, even in the limit var-epsilon →0

Pinning and creep in superconductors

International Nuclear Information System (INIS)

Ovchinnikov, Yu.N.

1994-01-01

All superconductors can be separated into two large groups: type I and type II. The behaviour of these two groups in a magnetic field is quite different. The superconductors of type I, in a strong magnetic field, enter the intermediate state. Phenomenological picture of this state was given by Landau. The type II superconductors, in strong magnetic fields, form the mixed state (or Shubnikov phase). The microscopic picture of the mixed state was given by Abrikosov on the basis of Ginzburg-Landau equations. In ideal homogeneous superconductors the free energy is not changed if all the vortex structure is shifted on some distance u. The transport current will be proportional, therefore, to the electric field E. All the real superconductors, however, are inhomogeneous. Inhomogeneities interact with vortex lattice and pin it. In this new state the transport current below some critical value does not lead to the motion of the flux lattice and to the energy dissipation. The value of critical current strongly depends on the type of inhomogeneities, on the value of magnetic field and on temperature. In new layered superconductors, the critical current depends also on the orientation of the magnetic field B with respect to the layer planes. Temperature and quantum fluctuations lead to the transition between different metastable states in superconductors with current. As a result, the vortex lattice slowly moves (creep phenomenon). Below we will briefly discuss all these phenomena. (orig.)

Studies of nonlinear electrodynamics of high-temperature superconductors

International Nuclear Information System (INIS)

Lam, Q.H.

1991-01-01

Nonlinear electrodynamics of high-Tc superconductors are studied theoretically and experimentally. For powdered samples, a novel model is presented in which the metallographically observed superconducting grains in the powder are modeled as superconducting current loops of various areas with weak links. Surprising harmonic generation behavior in an ac field, H 1 cos(ωt), is predicted by the model; the power at high harmonics show sharp dips almost periodic in a super-posing dc magnetic field, revealing flux quantization in the prototype loops in the model. Such oscillation of the harmonic power in dc magnetic field, P nf (H dc ), is experimentally observed in powdered YBa 2 Cu 3 O 7 . For bulk sintered cylindrical samples, a generalized critical state model is presented. The nonlinear electrodynamics are due to flux-pinning. Experiments in ac and dc magnetic fields on a sintered cylindrical rod of YBa 2 Cu 3 O 7 yield unambiguous evidence of independent inter- and intragranular contributions to the complex harmonic permeability μ n = μ' n - iμ double-prime n . These data, together with P nf (H dc ), are explained quantitatively by the generalized critical state model, yielding a dependence on magnetic field of J c (H) ∼ H 02 local for the intergranular component, a steeper field dependence than for conventional type-II superconductors. Temperature-dependence measurements reveal that, while the intragranular supercurrents disappear at T c ≥ 91.2 K, the intergranular supercurrents disappear at T ≥ 86.6 K

Flux motion and dissipation in high temperature superconductors

International Nuclear Information System (INIS)

Tinkham, M.

1991-01-01

Two quite different motivations spark the study of flux motion and resistance in the new high-temperature superconductors. Achievement of usefully low resistance at usefully large current densities is the key to most practical applications, but conceptual understanding of the idealized resistive behavior in the O current limit motivates much theoretical work. Some analyses emphasize the pinning of individual flux lines to inhomogeneities in the underlying material; others emphasize the collective aspects of the interacting flux lines, whether liquid, solid, crystalline, or glassy; still others emphasize the concept of percolative Josephson coupling between grains. In this paper an overview is given of these various approaches, their interrelation, and the experiment evidence, including some new results on flux motion in large SNS arrays, treated as a model system

Behaviour of magnetic superconductors in a magnetic field

International Nuclear Information System (INIS)

Buzdin, A.I.

1984-01-01

The behaviour of magnetic superconductors with close ferromagnetic and superconducting transition temperatures in a magnetic field is considered. It is shown that on lowering of the temperature the superconducting transition changes from a second to first order transition. The respective critical fields and dependence of the magnetization on the magnetic field and temperature are found. The magnetization discontinuity in the vortex core in magnetic superconductors is noted. Due to this property and the relatively large scattering cross section, magnetic superconductors are convenient for studying the superconducting vortex lattice by neutron diffraction techniques

High temperature measurements of the microwave dielectric properties of ceramics

International Nuclear Information System (INIS)

Baeraky, T.A.

1999-06-01

Equipment has been developed for the measurement of dielectric properties at high temperature from 25 to 1700 deg. C in the microwave frequency range 614.97 to 3620.66 MHz using the cavity perturbation technique, to measure the permittivity of a range of ceramic materials. The complex permittivities of the standard materials, water and methanol, were measured at low temperature and compared with the other published data. A statistical analysis was made for the permittivity measurements of water and methanol using sample holders of different diameter. Also the measurements of these materials were used to compare the simple perturbation equation with its modifications and alternation correction methods for sample shape and the holes at the two endplates of the cavity. The dielectric properties of solid materials were investigated from the permittivity measurements on powder materials, shown in table 4.7, using the dielectric mixture equations. Two kinds of ceramics, oxide and nitrides, were selected for the high temperature dielectric measurements in microwave frequency ranges. Pure zirconia, yttria-stabilised zirconia, and Magnesia-stabilised zirconia are the oxide ceramics while aluminium nitride and silicon nitride are the nitride ceramics. A phase transformation from monoclinic to tetragonal was observed in pure zirconia in terms of the complex permittivity measurements, and the conduction mechanism in three regions of temperature was suggested to be ionic in the first region and a mixture of ionic and electronic in the second. The phase transition disappeared with yttria-stabilised zirconia but it was observed with magnesia-stabilised zirconia. Yttria doped zirconia was fully stabilised while magnesia stabilised was partially stabilised zirconia. The dielectric property measurements of aluminium nitride indicated that there is a transition from AIN to AlON, which suggested that the external layer of the AIN which was exposed to the air, contains alumina. It was

Soluble and meltable hyperbranched polyborosilazanes toward high-temperature stable SiBCN ceramics.

Science.gov (United States)

Kong, Jie; Wang, Minjun; Zou, Jianhua; An, Linan

2015-04-01

High-temperature stable siliconborocarbonitride (SiBCN) ceramics produced from single-source preceramic polymers have received increased attention in the last two decades. In this contribution, soluble and meltable polyborosilazanes with hyperbranched topology (hb-PBSZ) were synthesized via a convenient solvent-free, catalyst-free and one-pot A2 + B6 strategy, an aminolysis reaction of the A2 monomer of dichloromethylsilane and the B6 monomer of tris(dichloromethylsilylethyl)borane in the presence of hexamethyldisilazane. The amine transition reaction between the intermediates of dichlorotetramethyldisilazane and tri(trimethylsilylmethylchlorosilylethyl)borane led to the formation of dendritic units of aminedialkylborons rather than trialkylborons. The cross-linked hb-PBSZ precursors exhibited a ceramic yield higher 80%. The resultant SiBCN ceramics with a boron atomic composition of 6.0-8.5% and a representative formula of Si1B(0.19)C(1.21)N(0.39)O(0.08) showed high-temperature stability and retained their amorphous structure up to 1600 °C. These hyperbranched polyborosilazanes with soluble and meltable characteristics provide a new perspective for the design of preceramic polymers possessing advantages for high-temperature stable polymer-derived ceramics with complex structures/shapes.

High temperature ceramic-tubed reformer

Science.gov (United States)

Williams, Joseph J.; Rosenberg, Robert A.; McDonough, Lane J.

1990-03-01

The overall objective of the HiPHES project is to develop an advanced high-pressure heat exchanger for a convective steam/methane reformer. The HiPHES steam/methane reformer is a convective, shell and tube type, catalytic reactor. The use of ceramic tubes will allow reaction temperature higher than the current state-of-the-art outlet temperatures of about 1600 F using metal tubes. Higher reaction temperatures increase feedstock conversion to synthesis gas and reduce energy requirements compared to currently available radiant-box type reformers using metal tubes. Reforming of natural gas is the principal method used to produce synthesis gas (primarily hydrogen and carbon monoxide, H2 and CO) which is used to produce hydrogen (for refinery upgrading), methanol, as well as several other important materials. The HiPHES reformer development is an extension of Stone and Webster's efforts to develop a metal-tubed convective reformer integrated with a gas turbine cycle.

Investigation of the thermophysical properties of oxide ceramic materials at liquid-helium temperatures

International Nuclear Information System (INIS)

Taranov, A. V.; Khazanov, E. N.

2008-01-01

The main regularities in the transport of thermal phonons in oxide ceramic materials are investigated at liquid-helium temperatures. The dependences of the thermophysical characteristics of ceramic materials on their structural parameters (such as the grain size R, the grain boundary thickness d, and the structure of grain boundaries) are analyzed. It is demonstrated that, in dense coarse-grained ceramic materials with qR>>1 (where q is the phonon wave vector), the grain boundaries and the grain size are the main factors responsible for the thermophysical characteristics of the material at liquid-helium temperatures. A comparative analysis of the thermophysical characteristics of optically transparent ceramic materials based on the Y 3 Al 5 O 12 (YAG) and Y 2 O 3 cubic oxides synthesized under different technological conditions is performed using the proposed criterion

High temperature resistant cermet and ceramic compositions

Science.gov (United States)

Phillips, W. M. (Inventor)

1978-01-01

Cermet compositions having high temperature oxidation resistance, high hardness and high abrasion and wear resistance, and particularly adapted for production of high temperature resistant cermet insulator bodies are presented. The compositions are comprised of a sintered body of particles of a high temperature resistant metal or metal alloy, preferably molybdenum or tungsten particles, dispersed in and bonded to a solid solution formed of aluminum oxide and silicon nitride, and particularly a ternary solid solution formed of a mixture of aluminum oxide, silicon nitride and aluminum nitride. Also disclosed are novel ceramic compositions comprising a sintered solid solution of aluminum oxide, silicon nitride and aluminum nitride.

Microstructural factors influencing critical-current densities of high-temperature superconductors

International Nuclear Information System (INIS)

Suenaga, M.

1992-01-01

Microstructural defects are the primary determining factors for the values of critical current densities in superconductors. A review is made to assess, (1) what would be the maximum achievable critical-current density in the oxide superconductors if nearly ideal pinning sites were introduced? and (2) what types of pinning defects are currently introduced in these superconductors and how effective are these in pinning the vortices? Only the case where the applied field is parallel to the c-axis is considered here

Enhanced green upconversion by controlled ceramization of Er3+–Yb3+ co-doped sodium niobium tellurite glass–ceramics for low temperature sensors

International Nuclear Information System (INIS)

Suresh Kumar, J.; Pavani, K.; Graça, M.P.F.; Soares, M.J.

2014-01-01

Highlights: • Upconversion luminescence improved in glass–ceramics compared to host glass. • Judd–Ofelt and radiative parameters calculated. • NIR decay curve results concur the results of improved luminescence. • Temperature dependent upconversion support the use of materials for sensors. - Abstract: Tellurite based glasses are well-known for their upconversion properties besides having a disadvantage of low mechanical strength dragging them away from practical applications. The present work deals with preparation of sodium niobium tellurite (SNT) glasses using melt quenching method, in which small quantities of boron and silicon in the form of oxides are added to improve their mechanical properties. Controlled heat treatment is performed to ceramize the prepared glasses based on the thermal data given by DTA. XRD and SEM profiles of the glass–ceramics which confirmed the formation of crystalline monoclinic Sodium Tellurium Niobium Oxide (Na 1.4 Nb 3 Te 4.9 O 18 ) phase (JCPDS card No. 04–011-7556). Upconversion measurements in the visible region were made for the prepared Er 3+ –Yb 3+ co-doped glasses and glass–ceramics with 980 nm laser excitation varying the laser power and concentration of Er 3+ ions. Results showed that the upconversion luminescence intensity was enhanced by ten times in SNT glass–ceramics compared to that in the SNT glasses. Decay curves give evidence of high performance of glass–ceramics compared to glasses due to ceramization and structural changes. Temperature dependent visible upconversion was performed to test the ability of efficient SNT glass–ceramic at low temperatures and variation of upconversion intensities was studied

Proceedings of the workshop on 'anomalous electronic states and physical properties in high-temperature superconductors'

International Nuclear Information System (INIS)

Arai, Masatoshi; Kajimoto, Ryoichi

2007-03-01

A workshop entitled 'Anomalous Electronic States and Physical Properties in High-Temperature Superconductors' was held on November 7-8, 2006 at Institute for Materials Research, Tohoku University. In the workshop, leading scientists in the field of high-T c superconductivity, both experimentalists and theorists, gathered in a hall to report the recent progress of the study, clarify the problems to be solved, and discuss the future prospects. The workshop was jointly organized by Specially Promoted Research of MEXT, Development of the 4D Spaces Access Neutron Spectrometer and Elucidation of the Mechanism of Oxide High-T c Superconductivity' (repr. by M. Arai, JAEA) and by the Inter-university Cooperative Research Program of the Institute for Materials Research, Tohoku University, 'Anomalous Electronic States and Physical Properties in High-Temperature Superconductors' (repr. by T. Tohyama, Kyoto Univ.). This report includes abstracts and materials of the presentations in the workshop. (author)

Nonempirical Calculation of Superconducting Transition Temperatures in Light-Element Superconductors.

Science.gov (United States)

Arita, Ryotaro; Koretsune, Takashi; Sakai, Shiro; Akashi, Ryosuke; Nomura, Yusuke; Sano, Wataru

2017-07-01

Recent progress in the fully nonempirical calculation of the superconducting transition temperature (T c ) is reviewed. Especially, this study focuses on three representative light-element high-T c superconductors, i.e., elemental Li, sulfur hydrides, and alkali-doped fullerides. Here, it is discussed how crucial it is to develop the beyond Migdal-Eliashberg (ME) methods. For Li, a scheme of superconducting density functional theory for the plasmon mechanism is formulated and it is found that T c is dramatically enhanced by considering the frequency dependence of the screened Coulomb interaction. For sulfur hydrides, it is essential to go beyond not only the static approximation for the screened Coulomb interaction, but also the constant density-of-states approximation for electrons, the harmonic approximation for phonons, and the Migdal approximation for the electron-phonon vertex, all of which have been employed in the standard ME calculation. It is also shown that the feedback effect in the self-consistent calculation of the self-energy and the zero point motion considerably affect the calculation of T c . For alkali-doped fullerides, the interplay between electron-phonon coupling and electron correlations becomes more nontrivial. It has been demonstrated that the combination of density functional theory and dynamical mean field theory with the ab initio downfolding scheme for electron-phonon coupled systems works successfully. This study not only reproduces the experimental phase diagram but also obtains a unified view of the high-T c superconductivity and the Mott-Hubbard transition in the fullerides. The results for these high-T c superconductors will provide a firm ground for future materials design of new superconductors. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fracture analysis of a transversely isotropic high temperature superconductor strip based on real fundamental solutions

Science.gov (United States)

Gao, Zhiwen; Zhou, Youhe

2015-04-01

Real fundamental solution for fracture problem of transversely isotropic high temperature superconductor (HTS) strip is obtained. The superconductor E-J constitutive law is characterized by the Bean model where the critical current density is independent of the flux density. Fracture analysis is performed by the methods of singular integral equations which are solved numerically by Gauss-Lobatto-Chybeshev (GSL) collocation method. To guarantee a satisfactory accuracy, the convergence behavior of the kernel function is investigated. Numerical results of fracture parameters are obtained and the effects of the geometric characteristics, applied magnetic field and critical current density on the stress intensity factors (SIF) are discussed.

Design of a high-temperature superconductor current lead for electric utility SMES

International Nuclear Information System (INIS)

Niemann, R.C.; Cha, Y.S.; Hull, J.R.; Rey, C.M.; Dixon, K.D.

1995-01-01

Current leads that rely on high-temperature superconductors (HTSs) to deliver power to devices operating at liquid helium temperature have the potential to reduce refrigeration requirements to levels significantly below those achievable with conventional leads. The design of HTS current leads suitable for use in near-term superconducting magnetic energy storage (SMES) is in progress. The SMES system has an 0.5 MWh energy capacity and a discharge power of 30 MW. Lead-design considerations include safety and reliability, electrical and thermal performance, structural integrity, manufacturability, and cost. Available details of the design, including materials, configuration, and performance predictions, are presented

Fabrication and characterization of low temperature co-fired cordierite glass–ceramics from potassium feldspar

International Nuclear Information System (INIS)

Wu, Jianfang; Li, Zhen; Huang, Yanqiu; Li, Fei; Yang, Qiuran

2014-01-01

Highlights: • Low cost cordierite glass–ceramics were fabricated from potassium feldspar. • The glass–ceramics could be highly densified below 950 °C. • The glass–ceramics exhibit extraordinary properties. • The glass–ceramics can be used as LTCC substrates. • The excess SiO 2 improved the microstructure and properties of the glass–ceramics. -- Abstract: Cordierite glass–ceramics for low temperature co-fired ceramic (LTCC) substrates were fabricated successfully using potassium feldspar as the main raw material. The sintering and crystallization behaviors of the glass–ceramics were investigated by the differential scanning calorimetry (DSC), X-ray diffraction (XRD), and field emission scanning electron microscope (FESEM). The results indicated that the glass–ceramics could be highly densified at 850 °C and the cordierite was the main crystalline phase precipitated from the glasses in the temperature range between 900 and 925 °C. The study also evaluated the physical properties including dielectric properties, thermal expansion and flexural strength of the glass–ceramics. The glass–ceramics showed low dielectric constants in the range of 6–8 and low dielectric losses in the range of 0.0025–0.01. The coefficients of thermal expansion (CTEs) are between 4.32 and 5.48 × 10 −6 K −1 and flexural strength of the glass–ceramics are 90–130 MPa. All of those qualify the glass–ceramics for further research to be used as potential LTCC substrates in the multilayer electronic substrate field. Additionally, the excess SiO 2 acted as a great role in improving the sinterability of the glasses, and the microstructure and dielectric properties of the relevant glass–ceramics

Testing and evaluation of high temperature superconductor current leads

International Nuclear Information System (INIS)

Yadav, Anand; Puntambekar, Avinash; Manekar, M.A.

2009-01-01

National Institute for Inter-disciplinary Science and Technology (NIIST), Council of Scientific and Industrial Research, Trivandrum (formerly Regional Research Laboratory) has accomplished a DAE-BRNS project with Raja Ramanna Centre for Advanced Technology (RRCAT) as principal collaborator for the development of high temperature superconductor (HTS) current leads. These HTS current leads have self-field critical currents (Ic) ranging from 50 A to 1000 A at liquid nitrogen (LN 2 ) temperature. These HTS are made out of silver sheathed Bismuth Strontium Calcium Copper Oxide (BSCCO-2223), for direct application in superconducting (SC) systems involving transportation of high electric currents from power sources at room temperature to superconducting devices at cryogenic temperatures. RRCAT has participated in this project by testing and evaluation of these HTS current leads and carried out actual load trials. In this paper, we will describe the HTS testing setup, tests performed with their testing procedure and the test results. The testing of these HTS has been done with joint effort of Materials Advanced Accelerator Science and Cryogenics Div. and Superconducting Technology Lab (SCT Lab), Advanced Accelerator Module Development Div., using the test facility available at the SCT Lab. (author)

High temperature superconductors at optimal doping

Directory of Open Access Journals (Sweden)

W. E. Pickett

2006-09-01

Full Text Available   Intensive study of the high temperature superconductors has been ongoing for two decades. A great deal of this effort has been devoted to the underdoped regime, where the new and difficult physics of the doped Mott insulator has met extra complications including bilayer coupling/splitting, shadow bands, and hot spots. While these complications continue to unfold, in this short overview the focus is moved to the region of actual high-Tc, that of optimal doping. The focus here also is not on the superconducting state itself, but primarily on the characteristics of the normal state from which the superconducting instability arises, and even these can be given only a broad-brush description. A reminder is given of two issues,(i why the “optimal Tc” varies,for n-layered systems it increases for n up to 3, then decreases for a given n, Tc increases according to the ‘basis’ atom in the order Bi, Tl, Hg (ii how does pressure, or a particular uniaxial strain, increase Tc when the zero-strain system is already optimally doped?

Temperature control system for liquid-fed ceramic melters

International Nuclear Information System (INIS)

Westsik, J.H. Jr.

1986-10-01

A temperature-feedback system has been developed for controlling electrical power to liquid-fed ceramic melters (LFCM). Software, written for a microcomputer-based data acquisition and process monitoring system, compares glass temperatures with a temperature setpoint and adjusts the electrical power accordingly. Included in the control algorithm are steps to reject failed thermocouples, spatially average the glass temperatures, smooth the averaged temperatures over time using a digital filter, and detect foaming in the glass. The temperature control system has proved effective during all phases of melter operation including startup, steady operation, loss of feed, and shutdown. This system replaces current, power, and resistance feedback control systems used previously in controlling the LFCM process

Microwave impedance of epitaxial high-temperature superconductor films

International Nuclear Information System (INIS)

Melkov, G.A.; Malyshev, V.Yu.; Bagada, A.V.

1995-01-01

In the 3 cm band dependences of the epitaxial HTS film surface resistance on the magnitude of ac and dc magnetic fields have been measured. YBa 2 Cu 3 O 7-σ films on sapphire were investigated. It was established that alternating magnetic field produces a stronger impact on the surface resistance than dc field. To explain experimental results the assumption is made that a HTS film is not an ideal superconductor and consists of series-connected sections of various types: sections of an ideal superconductor, sections of low and large resistance intragranular Josephson junctions, shunted by the ideal superconductor, and finally, sections of intergranular Josephson junctions few for epitaxial films. In these conditions the dependences of the surface resistance on dc magnetic field are caused by Abrikosov's vortices moving in ideal superconductive sections, and dependences on the amplitude of ac magnetic field are caused by switching of large resistance junctions to a low resistance state

An overview of rotating machine systems with high-temperature bulk superconductors

Science.gov (United States)

Zhou, Difan; Izumi, Mitsuru; Miki, Motohiro; Felder, Brice; Ida, Tetsuya; Kitano, Masahiro

2012-10-01

The paper contains a review of recent advancements in rotating machines with bulk high-temperature superconductors (HTS). The high critical current density of bulk HTS enables us to design rotating machines with a compact configuration in a practical scheme. The development of an axial-gap-type trapped flux synchronous rotating machine together with the systematic research works at the Tokyo University of Marine Science and Technology since 2001 are briefly introduced. Developments in bulk HTS rotating machines in other research groups are also summarized. The key issues of bulk HTS machines, including material progress of bulk HTS, in situ magnetization, and cooling together with AC loss at low-temperature operation are discussed.

Renormalization effects and phonon density of states in high temperature superconductors

Directory of Open Access Journals (Sweden)

Vinod Ashokan

2013-02-01

Full Text Available Using the versatile double time thermodynamic Green's function approach based on many body theory the renormalized frequencies, phonon energy line widths, shifts and phonon density of states (PDOS are investigated via a newly formulated Hamiltonian (does not include BCS type Hamiltonian that includes the effects of electron-phonon, anharmonicities and that of isotopic impurities. The automatic appearance of pairons, temperature, impurity and electron-phonon coupling of renormalized frequencies, widths, shifts and PDOS emerges as a characteristic feature of present theory. The numerical investigations on PDOS for the YBa2Cu3O7 − δ crystal predicts several new feature of high temperature superconductors (HTS and agreements with experimental observations.

Fracture peculiarities in ceramic tungsten at different temperatures in vacuum

International Nuclear Information System (INIS)

Uskov, E.I.; Babak, A.V.

1981-01-01

Stress-strain diagrams and results of metallographic analyses are presented for the ceramic tungsten samples tested for fracture toughness under conditions of eccentric tension at different temperatures (20...1600 deg C) in vacuum. The tungsten fracture is shown to be of brittle nature within the whole temperature range studied, but the fracture process has its own peculiarities at different test temperatures

Pinning and creep in high-Tc superconductors

International Nuclear Information System (INIS)

Ovchinnikov, Yu.N.; Ivlev, B.I.

1992-01-01

The angular and magnetic field dependence of a critical current parallel to the layers in the layered superconductors is studied. The critical current value is found for a superconductor with strong pinning centers. Quantum flux creep in sufficiently perfect layered high-Tc superconductors is discussed. The cross-over temperature between activated and quantum creep is found. (orig.)

Low-temperature specific heat of the β-pyrochlore oxide superconductors under high pressure

Science.gov (United States)

Isono, T.; Iguchi, D.; Machida, Y.; Izawa, K.; Salce, B.; Flouquet, J.; Ogusu, H.; Yamaura, J.; Hiroi, Z.

2011-01-01

We report the results of the low-temperature specific heat measurements of the single crystalline β-pyrochlore oxide superconductors AOs 2O 6 (A=K, Rb, and Cs) under high pressure up to 13 GPa. We find that superconducting transition temperature ( Tc) monotonically increases for CsOs 2O 6 and RbOs 2O 6, while the one for KOs 2O 6 decreases by applying the pressure. With further increasing the pressure, Tc is suddenly suppressed at the same lattice volume for all compounds, concomitant with the first-order structural phase transition.

Characterization of ceramics and semiconductors using nuclear techniques. Final report of a co-ordinated research project

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-03-01

With the aim of promoting research and facilitating more extensive application of nuclear techniques for material development, the IAEA established in 1994 a Co-ordinated Research Project (CRP) on Characterization of Ceramics and Semiconductors using Nuclear Techniques. This publication reviews and summarizes recent developments in this field and includes an assessment of the current status and trends in nuclear techniques in characterization of inorganic materials of technological importance. The TECDOC presents new achievements on ceramic superconductor behaviour under neutron induced defects, optimization of structure of mineral gels,m low temperature preparation of fine particles of ferrites, crystal luminescence of ceramic composites with improved plastic properties, thin film defects and detoxification of asbestos. The investigation of chemical composition, phase transitions and magnetic properties of ferrites by Moessbauer spectroscopy is largely developed. The document includes 18 individual contributions, each of them has been indexed and provided with an abstract Refs, figs, tabs

Characterization of ceramics and semiconductors using nuclear techniques. Final report of a co-ordinated research project

International Nuclear Information System (INIS)

1999-03-01

With the aim of promoting research and facilitating more extensive application of nuclear techniques for material development, the IAEA established in 1994 a Co-ordinated Research Project (CRP) on Characterization of Ceramics and Semiconductors using Nuclear Techniques. This publication reviews and summarizes recent developments in this field and includes an assessment of the current status and trends in nuclear techniques in characterization of inorganic materials of technological importance. The TECDOC presents new achievements on ceramic superconductor behaviour under neutron induced defects, optimization of structure of mineral gels,m low temperature preparation of fine particles of ferrites, crystal luminescence of ceramic composites with improved plastic properties, thin film defects and detoxification of asbestos. The investigation of chemical composition, phase transitions and magnetic properties of ferrites by Moessbauer spectroscopy is largely developed. The document includes 18 individual contributions, each of them has been indexed and provided with an abstract

Summaries of reports of the 30. Conference on low-temperature physics. Pt. 1. Fundamental questions of superconductivity including HTSC

International Nuclear Information System (INIS)

1994-01-01

Thesis of reporsts of the 30th Conference on low-temperature physics are presented. Fundamental problems of superconductivity are discussed including HTSC in bulk crystals, in thin films of Josephson junctions, ceramics and heterostructures. Specific features of superconductor structure and magnetic properties and also different mechanisms of superconductivity are analyzed

Laser beam joining of non-oxidic ceramics for ultra high temperature resistant joints

International Nuclear Information System (INIS)

Lippmann, W.; Knorr, J.; Wolf, R.; Reinecke, A.M.; Rasper, R.

2004-01-01

The excellent technical properties of silicon carbide (SiC) and silicon nitride (Si 3 N 4 ) ceramics, such as resistance to extreme temperatures, oxidation, mechanical wear, aggressive chemical substances and radioactive radiation and also its high thermal conductivity and good temperature-shock resistance, make these ceramics ideally suited for use in the field of nuclear technology. However, their practical use has been limited so far because of the unavailability of effective joining techniques for these ceramics, especially for high temperature applications. A new joining technology (CERALINK registered ) has been developed in a network project which allowed high temperature resistant and vacuum-tight joining of SiC or Si 3 N 4 ceramics. A power laser is used as heat source, which makes it possible to join ceramic components in free atmosphere in combination with a pure oxidic braze filler. As no furnace is necessary, there are no limitations on the component dimensions by the furnace-geometry. During the joining process, the heated area can be limited to the seam area so that this technology can also be used to encapsulate materials with a low melting point. The seam has a high mechanical strength, it is resistant to a wide range of chemicals and radiation and it is also vacuum-tight. The temperature resistance can be varied by variation of the braze filler composition - usually between 1,400 C and >1,600 C. Beside the optimum filler it is also important to select the suitable laser wavelength. The paper will demonstrate the influence of different wave lengths, i. e. various laser types, on the seam quality. Examples are chosen to illustrate the strengths and limitations of the new technology

Mottness in high-temperature copper-oxide superconductors

International Nuclear Information System (INIS)

Phillips, Philip; Choy, T.-P.; Leigh, Robert G

2009-01-01

The standard theory of metals, Fermi liquid theory, hinges on the key assumption that although the electrons interact, the low-energy excitation spectrum stands in a one-to-one correspondence with that of a non-interacting system. In the normal state of the copper-oxide high-temperature superconductors, drastic deviations from the Fermi liquid picture are obtained, highlighted by a pseudogap, broad spectral features and T-linear resistivity. A successful theory in this context must confront the highly constraining scaling argument which establishes that all 4-Fermi interactions are irrelevant (except for pairing) at a Fermi surface. This argument lays plain that new low-energy degrees of freedom are necessary. This paper focuses on the series of experiments on copper-oxide superconductors which reveal that the number of low-energy addition states per electron per spin exceeds unity, in direct violation of the key Fermi liquid tenet. These experiments point to new degrees of freedom, not made out of the elemental excitations, as the key mechanism by which Fermi liquid theory breaks down in the cuprates. A recent theoretical advance which permits an explicit integration of the high-energy scale in the standard model for the cuprates reveals the source of the new dynamical degrees of freedom at low energies, a charge 2e bosonic field which has nothing to do with pairing but rather represents the mixing with the high-energy scales. We demonstrate explicitly that at half-filling, this new degree of freedom provides a dynamical mechanism for the generation of the charge gap and antiferromagnetism in the insulating phase. At finite doping, many of the anomalies of the normal state of the cuprates including the pseudogap, T-linear resistivity and the mid-infrared band are reproduced. A possible route to superconductivity is explored

Testing and Modeling Ultra-High Temperature Ceramic (UHTC) Materials For Hypersonic Flight

Science.gov (United States)

2011-11-30

Ridge, D. G. Fletcher, C. O. Asma , O. Chazot, and J. Thömel, “Oxidation of ZrB2-SiC Ultra-High Temperature Ceramic Composites in Dissociated Air...Fletcher, C. O. Asma , “Characterization of ZrB2-SiC Ceramics Tested by Plasma Stream Oxidation,” poster, 32 th International Conference...Fahrenholtz, W.G., Hilmas, G.E., Zhu, S.M., Ridge, J., Fletcher, D.G., Asma , C.O., and Thomel, J., "Oxidation of ZrB2-SiC Ultrahigh-Temperature

Potential for use of high-temperature superconductors in fusion reactors

International Nuclear Information System (INIS)

Hull, J.R.

1991-01-01

The present rate of development of high-temperature superconductors (HTSs) is sufficiently rapid that there may be opportunities for their use in contemporary fusion devices such as the International Thermonuclear Experimental Reactor (ITER). The most likely 1application is for delivering power to the superconducting magnets, especially in substituting for the current leads between the temperatures of 4 K and 77K. A second possible application of HTSs is as a liquid-nitrogen-cooled power bus, connecting the power supplies to the magnets, thus reducing the ohmic heating losses over these relatively long cables. A third potential application of HTSs is as an inner high-field winding of the toroidal field coils that would operate at ∼20 K. While the use of higher temperature magnets offers significant advantages to the reactor system, it is unlikely that tested conductors of this type will be available within the ITER time frame. 23 refs., 2 figs

To Crack or Not to Crack: Strain in High Temperature Superconductors

International Nuclear Information System (INIS)

Godeke, Arno

2007-01-01

Round wire Bi 2212 is emerging as a viable successor of Nb3Sn in High Energy Physics and Nuclear Magnetic Resonance, to generate magnetic fields that surpass the intrinsic limitations of Nb3Sn. Rather bold claims are made on achievable magnetic fields in applications using Bi 2212, due to the materials' estimated critical magnetic field of 100 Tor higher. High transport currents in high magnetic fields, however, lead to large stress on, and resulting large strain in the superconductor. The effect of strain on the critical properties of Bi-2212 is far from understood, and strain is, as with Nb3Sn, often treated as a secondary parameter in the design of superconducting magnets. Reversibility of the strain induced change of the critical surface of Nb3Sn, points to an electronic origin of the observed strain dependence. Record breaking high field magnets are enabled by virtue of such reversible behavior. Strain effects on the critical surface of Bi-2212, in contrast, are mainly irreversible and suggest a non-electronic origin of the observed strain dependence, which appears to be dominated by the formation of cracks in the superconductor volumes. A review is presented of available results on the effects of strain on the critical surface of Bi-2212, Bi-2223 and YBCO. It is shown how a generic behavior emerges for the (axial) strain dependence of the critical current density, and how the irreversible reduction of the critical current density is dominated by strain induced crack formation in the superconductor. From this generic model it becomes clear that magnets using high temperature superconductors will be strain limited far before the intrinsic magnetic field limitations will be approached, or possibly even before the magnetic field limitation of Nb3Sn can be surpassed. On a positive note, in a very promising recent result from NIST on the axial strain dependence of the critical current density in extremely well aligned YBCO, reversible behavior was observed. This

Photothermal measurements of superconductors

International Nuclear Information System (INIS)

Kino, G.S.; Wu, X.D.; Kapitulnik, A.; Fishman, I.

1993-01-01

The authors have developed a new photothermal technique to investigate electronic phase transitions of high temperature superconductors. The phase shift of the thermal wave yields the anisotropic thermal diffusivity coefficient of the sample. The amplitude of the photothermal signal is sensitive to electronic phase transitions of the second kind. The technique is completely noncontacting and nondestructive, and is well suited to measure small and fragile single-crystal high-T c superconductors. The measurements give good agreement with fluctuation theory near the transition temperature. They have studied diffusion in, and superconducting fluctuations of, single crystals of YBa 2 Cu 3 O 7-δ and Bi 2 Sr 2 CaCu 2 O 8 . Both systems show fluctuation effects beyond Gaussian fluctuations. While YBa 2 Cu 3 O 7-δ behaves as a three-dimensional anisotropic superconductor, results on Bi 2 Sr 2 CaCu 2 O 8 indicate strong two-dimensional effects

Temperature dependent dielectric relaxation and ac-conductivity of alkali niobate ceramics studied by impedance spectroscopy

Science.gov (United States)

Yadav, Abhinav; Mantry, Snigdha Paramita; Fahad, Mohd.; Sarun, P. M.

2018-05-01

Sodium niobate (NaNbO3) ceramics is prepared by conventional solid state reaction method at sintering temperature 1150 °C for 4 h. The structural information of the material has been investigated by X-ray diffraction (XRD) and Field emission scanning electron microscopy (FE-SEM). The XRD analysis of NaNbO3 ceramics shows an orthorhombic structure. The FE-SEM micrograph of NaNbO3 ceramics exhibit grains with grain sizes ranging between 1 μm to 5 μm. The surface coverage and average grain size of NaNbO3 ceramics are found to be 97.6 % and 2.5 μm, respectively. Frequency dependent electrical properties of NaNbO3 is investigated from room temperature to 500 °C in wide frequency range (100 Hz-5 MHz). Dielectric constant, ac-conductivity, impedance, modulus and Nyquist analysis are performed. The observed dielectric constant (1 kHz) at transition temperature (400 °C) are 975. From conductivity analysis, the estimated activation energy of NaNbO3 ceramics is 0.58 eV at 10 kHz. The result of Nyquist plot shows that the electrical behavior of NaNbO3 ceramics is contributed by grain and grain boundary responses. The impedance and modulus spectrum asserts that the negative temperature coefficient of resistance (NTCR) behavior and non-Debye type relaxation in NaNbO3.

Single-source-precursor Synthesis and High-temperature Behavior of SiC Ceramics Containing Boron

Science.gov (United States)

Gui, Miaomiao; Fang, Yunhui; Yu, Zhaoju

2014-12-01

In this paper, a hyperbranched polyborocarbosilane (HPBCS) was prepared by a one-pot synthesis with Cl2Si(CH3)CH2Cl, Cl3SiCH2Cl and BCl3 as the starting materials. The obtained HPBCS was characterized by GPC, FT-IR and NMR, and was confirmed to have hyperbranched structures. The thermal property of the resulting HPBCS was investigated by TGA. The ceramic yield of the HPBCS is about 84% and that of the counterpart hyperbranched hydridopolycarbosilane is only 45%, indicating that the introduction of boron into the preceramic polymer significantly improved the ceramic yield. With the polymer-derived ceramic route, the final ceramics were annealed at 1800 °C in argon atmosphere for 2 h in order to characterize the microstructure and to evaluate the high-temperature behavior. The final ceramic microstructure was studied by XRD and SEM, indicating that the introduction of boron dramatically inhibits SiC crystallization. The boron-containing SiC ceramic shows excellent high-temperature behavior against decomposition and crystallization at 1800 °C.

Three exciting areas of experimental physical sciences : high temperature superconductors, metal clusters and super molecules of carbon

International Nuclear Information System (INIS)

Rao, C.N.

1992-01-01

The author has narrated his experience in carrying out research in three exciting areas of physical sciences. These areas are : high temperature superconductors, metal clusters and super molecules of carbon. (M.G.B.)

High-temperature superconductors. Les supraconducteurs a haute temperature

Energy Technology Data Exchange (ETDEWEB)

Bontemps, N; Combescot, R; Monod, P [Ecole Normale Superieure, 75 - Paris (France)

1992-02-01

High-tc superconductivity was discovered in 1986. The prospects of being able to dispose of superconductors cooled by liquid nitrogen instead of liquid helium, and fundamental physics questions raised by these new compounds drag an unprecedented scientific mobilization. Today, the super conductive state nature become clearer. But, to all expectations, their normal state nature is proved to present quite more difficulties. 20 refs., 5 figs.

Ceramics baking temperature influence on the dosimetric parameters essential in TL dating

International Nuclear Information System (INIS)

Krumpschmid, K.R.

1986-11-01

Thermoluminescence in quartz is used for dating of ceramics. The main problem is the 'intercept', i.e. the deviation from linearity in the relationship thermoluminescence versus absorbed dose of natural radiation. This deviation is most probably dependent on the fabrication method of the ceramics. In the present work the hypothesis is tested that the most important parameter, in this respect, is the baking temperature. Four types of ceramic bricks were fabricated, with four burning cycles of end temperatures of 550 0 C, 650 0 C, 900 0 C and 1200 0 C respectively, then irradiated and finally underwent the TL-procedure. The results are discussed with regard of the maximum of glow curve, intensity, fading, sensitivity to beta radiation and to additional alpha radiation and the intercept. (qui)

Fabrication of Nb{sub 3}Al superconductor by the optimized mechanical alloying method with low temperature

Energy Technology Data Exchange (ETDEWEB)

Zhang, Y., E-mail: yongzhang@swjtu.cn [Key Laboratory of Magnetic Levitation Technologies and Maglev Trains, Ministry of Education of China, and Superconductivity and New Energy R& D Center, Southwest Jiaotong University, Chengdu 610031 (China); Lin, W.J.; Xu, L.Y.; Yang, D.W.; Chen, Y.L. [Key Laboratory of Magnetic Levitation Technologies and Maglev Trains, Ministry of Education of China, and Superconductivity and New Energy R& D Center, Southwest Jiaotong University, Chengdu 610031 (China); Li, P.Y.; Pan, X.F.; Yan, G. [Western Superconducting Technoligies Co., Ltd., Xi' an 710018 (China); Zhao, Y., E-mail: yzhao@home.swjtu.edu.cn [Key Laboratory of Magnetic Levitation Technologies and Maglev Trains, Ministry of Education of China, and Superconductivity and New Energy R& D Center, Southwest Jiaotong University, Chengdu 610031 (China); School of Materials Science and Engineering, University of New South Wales, Sydney 2052 NSW (Australia)

2016-11-15

Highlights: • Due to a much better strain tolerance than Nb{sub 3}Sn, Nb{sub 3}Al has been considered as an excellent candidate for making high field magnets. At present, the Nb{sub 3}Al superconducting wires were prepared mainly by the Jelly-roll method combined with a rapid heating and quenching (RHQ) heat treatment at around 2000 °C. In this study, Nb{sub 3}Al superconductor with T{sub c} of 15.6 K is directly prepared with a mechanical alloying method followed by a low temperature annealing at 800 to 900 °C. Our results hint the possibility that Nb{sub 3}Al superconducting wire with high performance can be prepared below the melting point of Cu (1080 °C) by a conventional powder in tube (PIT) method, thus effectively avoiding high temperature heat treatment and RHQ device. - Abstract: Mechanical alloying was used to synthesize Nb{sub 3}Al superconductor successfully, and the process was optimization under various preparation conditions. In the current study, Nb{sub 3}Al superconductor with T{sub c} of 15.6 K was directly prepared from high quality Nb (Al) solid solution by mechanical alloying method and heat treatment at a low temperature of 800 to 900 °C. The results showed that Nb{sub 3}Al superconducting wire with high performance could be prepared after heat treatment below the melting point of Cu (1080°C) and using Nb (Al) solid solution and conventional powder in tube (PIT) method, thus effectively avoiding ultra-high temperature heat treatment and special rapid heating and quenching(RHQ) device.

Grain Oriented Perovskite Layer Structure Ceramics for High-Temperature Piezoelectric Applications

Science.gov (United States)

Fuierer, Paul Anton

The perovskite layer structure (PLS) compounds have the general formula (A^{2+}) _2(B^{5+})_2 O_7, or (A^ {3+})_2(B^{4+ })_2O_7, and crystallize in a very anisotropic layered structure consisting of parallel slabs made up of perovskite units. Several of these compounds possess the highest Curie temperatures (T_{rm c} ) of any known ferroelectrics. Two examples are Sr_2Nb_2O _7 with T_{rm c} of 1342^circC, and La_2Ti_2O _7 with T_{rm c} of 1500^circC. This thesis is an investigation of PLS ceramics and their feasibility as a high temperature transducer material. Piezoelectricity in single crystals has been measured, but the containerless float zone apparatus necessary to grow high quality crystals of these refractory compounds is expensive and limited to a small number of research groups. Previous attempts to pole polycrystalline Sr_2Nb _2O_7 have failed, and to this point piezoelectricity has been absent. The initiative taken in this research was to investigate PLS ceramics by way of composition and processing schemes such that polycrystalline bodies could be electrically poled. The ultimate objective then was to demonstrate piezoelectricity in PLS ceramics, especially at high temperatures. Donor-doping of both La_2Ti _2O_7 and Sr_2Nb_2O _7 was found to increase volume resistivities at elevated temperatures, an important parameter to consider during the poling process. Sr_2Ta _2O_7 (T _{rm c} = -107 ^circC) was used to make solid solution compositions with moderately high Curie temperatures, of about 850^circC, and lower coercive fields. A hot-forging technique was employed to produce ceramics with high density (>99% of theoretical) and high degree of grain orientation (>90%). Texturing was characterized by x-ray diffraction and microscopy. Considerable anisotropy was observed in physical and electrical properties, including thermal expansion, resistivity, dielectric constant, and polarization. The direction perpendicular to the forging axis proved to be the

Critical state in the Y-Ba-Cu-O ceramics

International Nuclear Information System (INIS)

Artemov, A.N.; Grishin, A.M.; Korenivskii, V.N.; Ulyanov, A.N.; Khokhlov, V.A.

1990-01-01

This paper reports on the temperature and field dependences of the Y-Ba-Cu-O ceramics susceptibility studied both experimentally and theoretically. These dependence have been used to reconstruct the temperature dependence of the critical current (j c (T) = j c (O)(1 - T/T c1 ) 3/2 , J c (O) = 340 A/cm 2 , T c1 = 94.6 K) and the distribution of the granules with respect to the superconducting transition temperature (with the maximum at T c2 = 95.3 K and ΔT = 1.1 K). Within the critical state concept diamagnetic response of the granular superconductors at fundamental and multiple frequencies has been calculated. The calculation results are in good agreement with the experimentally obtained susceptibility dependences and explain the different dependences of the diamagnetic response on the magnitude of the d.c. field and the amplitude of a.c. field

Theoretical study of cathode surfaces and high-temperature superconductors

Science.gov (United States)

Mueller, Wolfgang

1995-01-01

Calculations are presented for the work functions of BaO on W, Os, Pt, and alloys of Re-W, Os-W, and Ir-W that are in excellent agreement with experiment. The observed emission enhancement for alloy relative to tungsten dispenser cathodes is attributed to properties of the substrate crystal structure and explained by the smaller depolarization of the surface dipole on hexagonal as compared to cubic substrates. For Ba and BaO on W(100), the geometry of the adsorbates has been determined by a comparison of inverse photoemission spectra with calculated densities of unoccupied states based on the fully relativistic embedded cluster approach. Results are also discussed for models of scandate cathodes and the electronic structure of oxygen on W(100) at room and elevated temperatures. A detailed comparison is made for the surface electronic structure of the high-temperature superconductor YBa2Cu3O7 as obtained with non-, quasi-, and fully relativistic cluster calculations.

Evaluating superconductors for microwave applications

International Nuclear Information System (INIS)

Hammond, B.; Bybokas, J.

1989-01-01

It is becoming increasingly obvious that some of the earliest applications for high Tc superconductors will be in the microwave market. While this is a major opportunity for the superconductor community, it also represents a significant challenge. At DC or low frequencies a superconductor can be easily characterized by simple measurements of resistivity and magnetic susceptibility versus temperature. These parameters are fundamental to superconductor characterization and various methods exist for measuring them. The only valid way to determine the microwave characteristics of a superconductor is to measure it at microwave frequencies. It is for this reason that measuring microwave surface resistance has emerged as one of the most demanding and telling tests for materials intended for high frequency applications. In this article, the theory of microwave surface resistance is discussed. Methods for characterizing surface resistance theoretically and by practical implementation are described

Ultralight and fire-resistant ceramic nanofibrous aerogels with temperature-invariant superelasticity.

Science.gov (United States)

Si, Yang; Wang, Xueqin; Dou, Lvye; Yu, Jianyong; Ding, Bin

2018-04-01

Ultralight aerogels that are both highly resilient and compressible have been fabricated from various materials including polymer, carbon, and metal. However, it has remained a great challenge to realize high elasticity in aerogels solely based on ceramic components. We report a scalable strategy to create superelastic lamellar-structured ceramic nanofibrous aerogels (CNFAs) by combining SiO 2 nanofibers with aluminoborosilicate matrices. This approach causes the random-deposited SiO 2 nanofibers to assemble into elastic ceramic aerogels with tunable densities and desired shapes on a large scale. The resulting CNFAs exhibit the integrated properties of flyweight densities of >0.15 mg cm -3 , rapid recovery from 80% strain, zero Poisson's ratio, and temperature-invariant superelasticity to 1100°C. The integral ceramic nature also provided the CNFAs with robust fire resistance and thermal insulation performance. The successful synthesis of these fascinating materials may provide new insights into the development of ceramics in a lightweight, resilient, and structurally adaptive form.

Characteristics of the Mott transition and electronic states of high-temperature cuprate superconductors from the perspective of the Hubbard model

Science.gov (United States)

Kohno, Masanori

2018-04-01

A fundamental issue of the Mott transition is how electrons behaving as single particles carrying spin and charge in a metal change into those exhibiting separated spin and charge excitations (low-energy spin excitation and high-energy charge excitation) in a Mott insulator. This issue has attracted considerable attention particularly in relation to high-temperature cuprate superconductors, which exhibit electronic states near the Mott transition that are difficult to explain in conventional pictures. Here, from a new viewpoint of the Mott transition based on analyses of the Hubbard model, we review anomalous features observed in high-temperature cuprate superconductors near the Mott transition.

Experiments on the rf surface resistance of the perovskite superconductors at 3 GHz

International Nuclear Information System (INIS)

Hein, M.; Klein, N.; Mueller, G.; Piel, H.; Roeth, R.W.

1988-01-01

Since the discovery of the perovskite superconductors many experiments to explore their physical properties have been performed and various potential applications have been considered. The high critical temperature of more than 90 K obtained with Y 1 Ba 2 Cu 3 O/sub 7-δ/ (Y may be substituted by other rare earth elements) makes these superconductors interesting for applications in microwave technology. This has focused the authors interest on the investigation of their rf properties. Due to the sensitivity of the rf surface resistance to surface impurities and remaining non superconducting phases rf measurements are a good means to provide useful information about the quality of sample preparation and about physical properties of the superconductor itself. This contribution reports on the experimental determination of the rf surface resistance of Y 1 Ba 2 Cu 3 O/sub 7-δ/ and Eu 1 Ba 2 Cu 3 O/sub 7-δ/ in the normal and superconducting state at 3 GHz. In the first chapter the preparation of the ceramic samples and initial dc experiments are described. The main part of the paper describes the rf measurements which are performed in a superconducting niobium host cavity. The obtained results for both the surface resistance and the high field performance are discussed with respect to the preparation of the samples and regarding possible applications. 7 references, 7 figures, 2 tables

Ternary superconductors

International Nuclear Information System (INIS)

Giorgi, A.L.

1987-01-01

Ternary superconductors constitute a class of superconducting compounds with exceptional properties such as high transition temperatures (≅ 15.2 K), extremely high critical fields (H c2 >60 Tesla), and the coexistence of superconductivity and long-range magnetic order. This has generated great interest in the scientific community and resulted in a large number of experimental and theoretical investigations in which many new ternary compounds have been discovered. A review of some of the properties of these ternary compounds is presented with particular emphasis on the ternary molybdenum chalcogenides and the ternary rare earth transition metal tetraborides. The effect of partial substitution of a second metal atom to form pseudoternary compounds is examined as well as some of the proposed correlations between the superconducting transition temperature and the structural and electronic properties of the ternary superconductors

Temperature dependence of the mechanical properties of melt-processed Dy-Ba-Cu-O bulk superconductors evaluated by three point bending tests

International Nuclear Information System (INIS)

Katagiri, K; Nyilas, A; Sato, T; Hatakeyama, Y; Hokari, T; Teshima, H; Iwamoto, A; Mito, T

2006-01-01

Dy-Ba-Cu-O bulk superconductor has an excellent capability of trapping magnetic flux and lower heat conductivity at cryogenic temperatures as compared with Y-Ba-Cu-O bulk superconductor. The Young's modulus and the bending strength in the range from room temperature to 7 K were measured by the three-point bending tests using specimens cut from a melt-processed Dy-Ba-Cu-O bulk superconductor. They were tested in a helium gas flow type cryostat at Forschungszentrum Karlsruhe and in a liquid nitrogen bath at Iwate University. The Young's modulus was calculated by either the slope of stress-strain curve or that of the load-deflection curve of the specimen. Although the bending strength measured in the two institutes coincided well, there was a significant discrepancy in the Young's modulus. The Young's modulus and bending strength increased with decrease of temperature down to 7 K. The amount of increase in the Young's modulus and the bending strength were about 32% and 36% of those at room temperature, respectively. The scatter of data for each run was significant and did not depend on temperature. The temperature dependence of the Young's modulus coincided with that in Y-Ba-Cu-O obtained by ultrasonic velocity. The temperature dependence of the Young's modulus and the bending strength was discussed from the view point of interatomic distance of the bulk crystal

Laser treatment of dental ceramic/cement layers: transmitted energy, temperature effects and surface characterisation.

Science.gov (United States)

Pich, Olena; Franzen, René; Gutknecht, Norbert; Wolfart, Stefan

2015-02-01

In the present paper, we investigate the behaviour of different dental materials under laser irradiation. We have used e.max Ceram, e.max ZirCAD, and e.max Press dental ceramics and glass ionomer cement Ketac Cem in the present study. The dental ceramics were prepared in the form of samples with thickness of 0.5-2 mm. We used two lasers [solid-state laser (Er:YAG, Fidelis III+, Fotona) and an 810- nm diode laser (FOX, A.R.C)] for the transillumination of ceramic samples. It has been shown that the laser energy transmitted through the ceramic material decreases to 30-40% of the original values along with an increase in the thickness of the irradiated sample. Pigmented ceramic samples show more laser energy loss compared to the samples containing no pigment. We investigated the temperature evolution in composite sandwiched ceramic/cement samples under laser treatment. The increase in the irradiation time and laser power led to a temperature increase of up to 80 °C. The surfaces of irradiated ceramic samples were examined with X-ray photoelectron spectroscopy to evaluate changes in chemical composition, such as a decrease in the C signal, accompanied by a strong increase in the Zr peak for the Er:YAG laser, while the 810-nm diode laser showed no change in the ratio of elements on the surface.

Signatures of granular superconductivity and Josephson effects in macroscopic measurements: the case of new superconductors

Directory of Open Access Journals (Sweden)

S Senoussi

2006-09-01

Full Text Available   We report systematic investigations of the magnetic superconducting properties of the new superconducting materials (NS: New high temperature superconductors (HTS, Organic superconductors (OS, fullerenes, carbon nanotubes, MgB2 etc. We show that, contrary to conventional superconductors where the superconducting state can be coherent over several tenths of km, the macroscopic coherence range lc of the NS is often as short as 0.1 to 10 µm typically. As a consequence, the magnetic properties are dominated by granular-like effects as well as Josephson coupling between grains. Here, we concentrate on HTS ceramics and organic superconductors exclusively. In the first case we observe three distinct regimes: (i At very low field (H < 5 Oe to say all the grains are coupled via Josephson effect and lc can be considered as infinite. (2 At intermediate field (5 < H < 50 Oe, typically the grains are gradually decoupled by H and/or T. (iii At higher fields all the grains are decoupled and lc roughly coincides with the diameter of the metallurgical grains. The case of OS is more subtle and is connected with a kind of order-disorder transition that occurs in most of them. For instance, in this study, we exploit quenched disorder (after crossing such a transition in the -(BEDT-TTF2Cu[N(CN2]Br layered organic superconductor to get new insights on both the superconducting state (T £ 11.6 K and the glassy transition at Tg, by studying the superconducting properties as functions of annealing time and annealing temperature around the glassy transition. Our main result is that the data can be described by a percolation molecular cluster model in which the topology and the growth of the molecular clusters obey an Ising spin-glass-like model with Tg ≈ 80 K for the hydrogenated compound and Tg ≈ 55 K for the fully deuterated one.

Mechanical behavior of high strength ceramic fibers at high temperatures

Science.gov (United States)

Tressler, R. E.; Pysher, D. J.

1991-01-01

The mechanical behavior of commercially available and developmental ceramic fibers, both oxide and nonoxide, has been experimentally studied at expected use temperatures. In addition, these properties have been compared to results from the literature. Tensile strengths were measured for three SiC-based and three oxide ceramic fibers for temperatures from 25 C to 1400 C. The SiC-based fibers were stronger but less stiff than the oxide fibers at room temperature and retained more of both strength and stiffness to high temperatures. Extensive creep and creep-rupture experiments have been performed on those fibers from this group which had the best strengths above 1200 C in both single filament tests and tests of fiber bundles. The creep rates for the oxides are on the order of two orders of magnitude faster than the polymer derived nonoxide fibers. The most creep resistant filaments available are single crystal c-axis sapphire filaments. Large diameter CVD fabricated SiC fibers are the most creep and rupture resistant nonoxide polycrystalline fibers tested to date.

Synthesis of Highly Uniform and Compact Lithium Zinc Ferrite Ceramics via an Efficient Low Temperature Approach.

Science.gov (United States)

Xu, Fang; Liao, Yulong; Zhang, Dainan; Zhou, Tingchuan; Li, Jie; Gan, Gongwen; Zhang, Huaiwu

2017-04-17

LiZn ferrite ceramics with high saturation magnetization (4πM s ) and low ferromagnetic resonance line widths (ΔH) represent a very critical class of material for microwave ferrite devices. Many existing approaches emphasize promotion of the grain growth (average size is 10-50 μm) of ferrite ceramics to improve the gyromagnetic properties at relatively low sintering temperatures. This paper describes a new strategy for obtaining uniform and compact LiZn ferrite ceramics (average grains size is ∼2 μm) with enhanced magnetic performance by suppressing grain growth in great detail. The LiZn ferrites with a formula of Li 0.415 Zn 0.27 Mn 0.06 Ti 0.1 Fe 2.155 O 4 were prepared by solid reaction routes with two new sintering strategies. Interestingly, results show that uniform, compact, and pure spinel ferrite ceramics were synthesized at a low temperature (∼850 °C) without obvious grain growth. We also find that a fast second sintering treatment (FSST) can further improve their gyromagnetic properties, such as higher 4πM s and lower ΔH. The two new strategies are facile and efficient for densification of LiZn ferrite ceramics via suppressing grain growth at low temperatures. The sintering strategy reported in this study also provides a referential experience for other ceramics, such as soft magnetism ferrite ceramics or dielectric ceramics.

Temperature dependence of velocity of sound in high-Tc superconductors in normal state

International Nuclear Information System (INIS)

Bishoyi, K.C.; Rout, G.C.; Behera, S.N.

2002-01-01

A microscopic theoretical calculation of temperature dependence of velocity of sound in high temperature superconductors is addressed in this paper. The influence of model parameters of the system in its normal phase is investigated through numerical calculations. The results at the room temperature as well as low temperatures (∼ 25 K), are discussed. The dimensionless parameters involved in the calculations are the electron-phonon coupling (g), staggered magnetic field (h), hybridization (V), position of the f-level (d), temperature (t) and the conduction band width (ω). The model Hamiltonian contains the antiferromagnetism in conduction electrons of cooper and the electron-phonon interaction through the hybridization between conduction electrons and f-electrons of impurity atoms. The phonon Green's functions are calculated by Zubarev's technique. The velocity of sound is calculated in the long wavelength and finite temperature limit. (author)

Low critical temperature superconductors for electromagnets; Supraconducteurs a basse temperature critique pour electroaimants

Energy Technology Data Exchange (ETDEWEB)

Devred, A

2002-07-01

After a brief history of the main discoveries in applied superconductivity (section 1), we discuss the structure and properties of NbTi and Nb3 Sn (section 2). Then, we explain why low critical-temperature superconductors are produced under the form of multifilamentary composites (section 3), and we review the manufacturing processes of NbTi and Nb3Sn wires (section 4). We follow by a description of the transition from the superconducting to the normal resistive state of multifilamentary composite wires (section 5) and we detail their magnetization properties section 6). Last, we present the most commonly used cable configurations (section 7) and we provide simple formulae illustrating on a few examples the computation of losses generated under time-varying magnetic fields (section 8). (author)

Nonlinear resistivity in a d-wave superconductor YBa{sub 2}Cu{sub 4}O{sub 8} of sub-micron scale grains

Energy Technology Data Exchange (ETDEWEB)

Deguchi, H; Shoho, T; Kato, Y; Ashida, T; Mito, M; Takagi, S [Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550 (Japan); Hagiwara, M [Faculty of Engineering and Design, Kyoto Institute of Technology, Kyoto 606-8585 (Japan); Koyama, K, E-mail: deguchi@tobata.isc.kyutech.ac.jp [Faculty of Integrated Arts and Science, The University of Tokushima 770-8502 (Japan)

2011-07-20

The d-wave ceramic YBa{sub 2}Cu{sub 4}O{sub 8} superconductor composed of sub-micron size grains is considered as random Josephson-coupled network of 0 and {pi} junctions and shows successive phase transitions. The upper transition occurs inside each grain at T{sub c1} = 82 K and the lower transition occurs among the grains at T{sub c2} = 66 K. We measured the temperature dependence of the current-voltage characteristics of the ceramic YBa{sub 2}Cu{sub 4}O{sub 8} and derived the linear and nonlinear resistivity. The nonlinear resistivity {rho}{sub 2} and {rho}{sub 4} have finite values between T{sub c1} and T{sub c2} and have the peak at the same temperature T{sub p} = 70 K above T{sub c2}. The result agrees with the theoretical one obtained by Li and DomInguez. They interpreted T{sub p} as the crossover temperature from the normal state phase to a chiral paramagnetic one.

Electrical bushing for a superconductor element

Science.gov (United States)

Mirebeau, Pierre; Lallouet, Nicolas; Delplace, Sebastien; Lapierre, Regis

2010-05-04

The invention relates to an electrical bushing serving to make a connection at ambient temperature to a superconductor element situated in an enclosure at cryogenic temperature. The electrical bushing passes successively through an enclosure at intermediate temperature between ambient temperature and cryogenic temperature, and an enclosure at ambient temperature, and it comprises a central electrical conductor surrounded by an electrically insulating sheath. According to the invention, an electrically conductive screen connected to ground potential surrounds the insulating sheath over a section that extends from the end of the bushing that is in contact with the enclosure at cryogenic temperature at least as far as the junction between the enclosure at intermediate temperature and the enclosure at ambient temperature. The invention is more particularly applicable to making a connection to a superconductor cable.

Engineering design of a high-temperature superconductor current lead

International Nuclear Information System (INIS)

Niemann, R.C.; Cha, Y.S.; Hull, J.R.; Daugherty, M.A.; Buckles, W.E.

1993-01-01

As part of the US Department of Energy's Superconductivity Pilot Center Program, Argonne National Laboratory and Superconductivity, Inc., are developing high-temperature superconductor (HTS) current leads suitable for application to superconducting magnetic energy storage systems. The principal objective of the development program is to design, construct, and evaluate the performance of HTS current leads suitable for near-term applications. Supporting objectives are to (1) develop performance criteria; (2) develop a detailed design; (3) analyze performance; (4) gain manufacturing experience in the areas of materials and components procurement, fabrication and assembly, quality assurance, and cost; (5) measure performance of critical components and the overall assembly; (6) identify design uncertainties and develop a program for their study; and (7) develop application-acceptance criteria

Engineering design of a high-temperature superconductor current lead

Science.gov (United States)

Niemann, R. C.; Cha, Y. S.; Hull, J. R.; Daugherty, M. A.; Buckles, W. E.

As part of the US Department of Energy's Superconductivity Pilot Center Program, Argonne National Laboratory and Superconductivity, Inc., are developing high-temperature superconductor (HTS) current leads suitable for application to superconducting magnetic energy storage systems. The principal objective of the development program is to design, construct, and evaluate the performance of HTS current leads suitable for near-term applications. Supporting objectives are to (1) develop performance criteria; (2) develop a detailed design; (3) analyze performance; (4) gain manufacturing experience in the areas of materials and components procurement, fabrication and assembly, quality assurance, and cost; (5) measure performance of critical components and the overall assembly; (6) identify design uncertainties and develop a program for their study; and (7) develop application-acceptance criteria.

Neutron irradiation effects in advanced superconductors

International Nuclear Information System (INIS)

Yoshida, H.; Kodaka, H.; Miyata, K.; Hayashi, Y.; Atobe, K.

1988-01-01

This paper reports the effects of neutron irradiation on superconducting transitions studied by susceptibility and resistivity measurements for A15 type compounds, Laves-phase compounds and oxide superconductors. For A15 superconductors, the transition temperature (T c ) decreased with increasing neutron fluence and showed large drop started at about 5 x 10 18 n/cm 2 (E > 0.1 MeV). Post-irradiation annealing gave recovery of T c , but the behaviors were different for the materials with different composition and microstructure. The Laves-phase compounds showed less degradation than the A15 superconductors. For oxide superconductors very sensitive transition change was observed, including the radiation-induced superconductivity

The Goettingen high-Tc superconductivity research pool: the effects of structure and structural defects on the performance of high-Tc superconductors. Final reports

International Nuclear Information System (INIS)

1992-02-01

The compilation presents the final reports prepared by the various teams of the Goettingen research pool for high-Tc superconductivity. The reports are entitled: Structure and phase transition in high-Tc superconductors (Krebs/Freyhardt). Preparation and critical properties of high-Tc superconductors (Freyhardt/Heinemann/Zimmermann). EMC measurements in high-Tc superconductors (Bormann/Noelting). Phase analysis of the various phases observed in the preparation of high-Tc superconductors (Faupel/Hehenkamp). Positron annihilation in high-Tc superconductors (Hehenkamp). Preparation and characterization of thin films consisting of superconducting oxide ceramics (v. Minnigerode/Samwer). High-Tc superconductivity in monocrystals (Winzer/Beuermann). Microwave conductivity in high-Tc superconductors (Helberg). High-resolution structural analyses in high-Tc superconductors (Kupcik/Bente). Synthesis, structural analyses and spectroscopy of high-Tc superconductors (Bente). Synthesis, monocrystal growing, crystal structure of high-Tc superconductors (Schwarzmann). Ion-beam-aided studies in high-Tc superconductors (Uhrmacher). (orig./MM) [de

Charge and spin transport in mesoscopic superconductors

Directory of Open Access Journals (Sweden)

M. J. Wolf

2014-02-01

Full Text Available Background: Non-equilibrium charge transport in superconductors has been investigated intensely in the 1970s and 1980s, mostly in the vicinity of the critical temperature. Much less attention has been paid to low temperatures and the role of the quasiparticle spin.Results: We report here on nonlocal transport in superconductor hybrid structures at very low temperatures. By comparing the nonlocal conductance obtained by using ferromagnetic and normal-metal detectors, we discriminate charge and spin degrees of freedom. We observe spin injection and long-range transport of pure, chargeless spin currents in the regime of large Zeeman splitting. We elucidate charge and spin transport by comparison to theoretical models.Conclusion: The observed long-range chargeless spin transport opens a new path to manipulate and utilize the quasiparticle spin in superconductor nanostructures.

Atomic hydrogen effects on high-Tc superconductors

International Nuclear Information System (INIS)

Frantskevich, N.V.; Ulyashin, A.G.; Alifanov, A.V.; Stepanenko, A.V.; Fedotova, V.V.

1999-01-01

The atomic hydrogen effects on the properties of bulk high-temperature superconductors were investigated. It is shown that the insertion of the atomic hydrogen into the bulk of these materials from a DC plasma leads to the increase of the critical current density J c for YBaCuO(123) as well as for BiSrCaCuO(2223) high-temperature superconductors. It is found that the hydrogenation of the He implanted samples with following annealing leads to the optically detected blistering on the surface. It means that the textured thin subsurface layers of high-temperature superconductors can be formed by this method. The improvement of superconductivity by atomic hydrogen can be explained by the passivation of dangling bonds and defects on grain boundaries of these materials

Thermal contact conductance of metallic coated BiCaSrCuO superconductor/copper interfaces at cryogenic temperatures

International Nuclear Information System (INIS)

Ochterbeck, J.M.; Peterson, G.P.; Fletcher, L.S.

1992-01-01

The effects of vapor deposited coatings on the thermal contact conductance of cold pressed, normal state BiCaSrCuO superconductor/oxygen-free copper interfaces were experimentally investigated over a pressure range of 200 to 2,000 kPa. Using traditional vapor deposition processes, thin coatings of indium or lead were applied to the superconductor material to determine the effect on the heat transfer occurring at the interface. The test data indicate that the contact conductance can be enhanced using these coatings, with indium providing the greater enhancement. The experimental program revealed the need for a better understanding and control of the vapor deposition process when using soft metallic coatings. Also, the temperature-dependent microhardness of copper was experimentally determined and found to increase by approximately 35 percent as the temperature decreased from 300 to 85 K. An empirical model was developed to predict the effect of soft coatings on the thermal contact conductance of the superconductor/copper interfaces. When applied, the model agreed well with the data obtained in this investigation at low coating thicknesses but overpredicted the data as the thickness increased. In addition, the model agreed very well with data obtained in a previous investigation for silvercoated nickel substrates at all coating thicknesses

Influence of light curing unit and ceramic thickness on temperature rise during resin cement photo-activation.

Science.gov (United States)

Guiraldo, Ricardo Danil; Consani, Simonides; Mastrofrancisco, Sarina; Consani, Rafael Leonardo Xediek; Sinhoreti, Mario Alexandre Coelho; Correr-Sobrinho, Lourenço

2008-11-01

The aim of this study was to determine the effect of different ceramic thickness on heat generation during resin cement photo-activation by QTH (quartz-tungsten-halogen), LED (light emitting diode), and PAC (plasma arc-curing) LCUs (light curing units). The resin cement used was Rely X ARC (3M-ESPE), and the ceramic was IPS Empress Esthetic (Ivoclar-Vivadent), of which 0.7-, 1.4- and 2.0-mm thick disks, 0.8 mm in diameter were made. Temperature increase was recorded with a type-K thermocouple connected to a digital thermometer (Iopetherm 46). An acrylic resin base was built to guide the thermocouple and support the 1.0-mm thick dentin disk. A 0.1-mm thick black adhesive paper matrix with a perforation 6 mm in diameter was placed on the dentin to contain the resin cement and support the ceramic disks of different thicknesses. Three LCUs were used: QTH, LED and PAC. Nine groups were formed (n=10) according to the interaction: 3 ceramic thicknesses, 1 resin cement and 3 photo-activation methods. Temperature increase data were submitted to Tukey's test (5%). For all ceramic thicknesses, a statistically significant difference in temperature increase was observed among the LCUs, with the highest mean value for the QTH LCU (p0.05). The interaction of higher energy density with smaller ceramic thickness showed higher temperature increase values.

Study of the capacitance technique for measuring high-temperature blade tip clearance on ceramic rotors

Science.gov (United States)

Barranger, John P.

1993-01-01

Higher operating temperatures required for increased engine efficiency can be achieved by using ceramic materials for engine components. Ceramic turbine rotors are subject to the same limitations with regard to gas path efficiency as their superalloy predecessors. In this study, a modified frequency-modulation system is proposed for the measurement of blade tip clearance on ceramic rotors. It is expected to operate up to 1370 C (2500 F), the working temperature of present engines with ceramic turbine rotors. The design of the system addresses two special problems associated with nonmetallic blades: the capacitance is less than that of a metal blade and the effects of temperature may introduce uncertainty with regard to the blade tip material composition. To increase capacitance and stabilize the measurement, a small portion of the rotor is modified by the application of 5-micron-thick platinum films. The platinum surfaces on the probe electrodes and rotor that are exposed to the high-velocity gas stream are coated with an additional 10-micron-thick protective ceramic topcoat. A finite-element method is applied to calculate the capacitance as a function of clearance.

Modeling high-temperature superconductors and metallic alloys on the Intel IPSC/860

Science.gov (United States)

Geist, G. A.; Peyton, B. W.; Shelton, W. A.; Stocks, G. M.

Oak Ridge National Laboratory has embarked on several computational Grand Challenges, which require the close cooperation of physicists, mathematicians, and computer scientists. One of these projects is the determination of the material properties of alloys from first principles and, in particular, the electronic structure of high-temperature superconductors. While the present focus of the project is on superconductivity, the approach is general enough to permit study of other properties of metallic alloys such as strength and magnetic properties. This paper describes the progress to date on this project. We include a description of a self-consistent KKR-CPA method, parallelization of the model, and the incorporation of a dynamic load balancing scheme into the algorithm. We also describe the development and performance of a consolidated KKR-CPA code capable of running on CRAYs, workstations, and several parallel computers without source code modification. Performance of this code on the Intel iPSC/860 is also compared to a CRAY 2, CRAY YMP, and several workstations. Finally, some density of state calculations of two perovskite superconductors are given.

The superconductor revolutions and the (slow) applications evolution

International Nuclear Information System (INIS)

Foner, S.

1990-01-01

The discovery in the 1960's of type 2 superconductors with high critical current densities in high magnetic fields (and the development of NbTi in particular) led to the first revolution. The discovery of high temperature superconductors (HTS) started the second revolution. At this stage ceramists became involved with superconductors. I will assess the status of various superconductor applications, progress of HTS and their possible applications at 4.2K, and near-term needs for superconducting materials operating at 30T in specialized facilities. Reasons for the slow growth of superconductor applications will be reviewed

Effects of Ceramic Density and Sintering Temperature on the Mechanical Properties of a Novel Polymer-Infiltrated Ceramic-Network Zirconia Dental Restorative (Filling) Material.

Science.gov (United States)

Li, Weiyan; Sun, Jian

2018-05-10

BACKGROUND Polymer-infiltrated ceramic-network (PICN) dental material is a new and practical development in orthodontics. Sintering is the process of forming a stable solid mass from a powder by heating without melting. The aim of this study was to evaluate the effects of sintering temperature on the mechanical properties of a PICN zirconia dental material. MATERIAL AND METHODS A dense zirconia ceramic and four PICN zirconia dental materials, with varying porosities, were sintered at three different temperatures; 12 PICN zirconia dental materials based on these porous ceramics were prepared, as well as a pure polymer. After the specimen preparation, flexural strength and elastic modulus values were measured using the three-point bending test, and fracture toughness were determined by the single-edge notched beam (SENB) method. The Vickers hardness test method was used with an indentation strength (IS) test. Scanning electron microscopy (SEM) was used to examine the microstructure of the ceramic surface and the fracture surface. RESULTS Mechanical properties of the PICN dental materials, including flexural strength, elastic modulus, fracture toughness, and hardness, were more similar to the properties of natural teeth when compared with traditional dental ceramic materials, and were affected by the density and sintering temperature. SEM showed that the porous ceramic network became cohesive and that the length of cracks in the PICN dental material was reduced. CONCLUSIONS PICN zirconia dental materials were characterized by similar mechanical properties to natural dental tissues, but further studies are required continue to improve the similarities with natural human enamel and dentin.

Influence of temperature and heat treatment on crack resistance of ceramic tungsten

International Nuclear Information System (INIS)

Uskov, E.I.; Babak, A.V.; Bega, N.D.

1983-01-01

The effect of testing temperature in the range from 20 to 2000 deg C, and recrystallization annealing at 2200 deg C on crack resistance of ceramic tungsten in vacuum, is investigated. The extension diagrams thus obtained have been treated in accordance with the standard technique. The value of the critical crack loading and the stress intensity coefficient have been determined. Structural changes have been controlled with X-ray structural methods. Crack resistance of tungsten increases in the test temperature range from 20 deg C to Tsub(x) which is connected with the increase of mobility of screw components of dislocation loops. At the temperature more than Tsub(x) the plasticity growth of ceramic tungsten takes place simultaneously with grain boundary embrittlement. Recrystallization annealing at 2200 deg C creates the structure resistant to temperature effect; crack resistance being minimum

Tritium release from lithium ceramics at constant temperature

International Nuclear Information System (INIS)

Verrall, R.A.; Miller, J.M.

1992-02-01

Analytic methods for post-irradiation annealing tests to measure tritium release from lithium ceramics at constant temperature are examined. Modifications to the Bertone (1) relations for distinguishing diffusion-controlled release from desorption-controlled release are shown. The methods are applied to tests on sintered LiA10 2 ; first-order desorption is shown to control tritium release for these tests

The usage of ceramics in the manufacture of the lining of temperature sensors for the oil industry

International Nuclear Information System (INIS)

Domingues, R.O.; Yadava, Y.P.; Sanguinetti Ferreira, R.A.

2014-01-01

In the oil production, many types of sensors are used in order to monitor some important parameters such as temperature, pressure and flow. These sensors are subjected to harsh operating conditions. Therefore they must present an inert and stable behavior in these conditions. The temperature sensors that are more suited to the oil industry are the Temperature Detectors by Resistance (TDR), because they have high accuracy and wide temperature range. Usually these devices are built with metals as detectors of temperature by encapsulated resistance in inert ceramics. The main objective of this research is to produce new ceramics of a Ca_2AlZrO_5_,_5 cubic complex perovskite structure for the encapsulation of temperature sensors. The stoichiometric amounts of the constituent chemicals, with a high degree of purity, are homogenized, through a solid state reaction in a high energy ball mill. They are then compacted by uniaxial pressing and calcined at 1200°C for 24 hours. Soon after, the tablet is crushed giving place to a ceramic powder and the analysis of X-ray diffraction is performed. According to the sintering behavior of the ceramic powder, the microstructure and the homogeneity are studied by the Scanning Electron Microscopy. The results are presented in terms of the potential of this ceramic for applications as components of temperature sensors. (author)

Investigation of firing temperature variation in ovens for ceramic-fused-to-metal dental prostheses using swept source optical coherence tomography

Science.gov (United States)

Todor, Raluca; Negrutiu, Meda-Lavinia; Sinescu, Cosmin; Topala, Florin Ionel; Bradu, Adrian; Duma, Virgil-Florin; Romînu, Mihai; Podoleanu, Adrian G.

2018-03-01

One of the most common fabrication techniques for dental ceramics is sintering, a process of heating of the ceramic to ensure densification. This occurs by viscous flow when the firing temperature is reached. Acceptable restorations require the alloy and ceramic to be chemically, thermally, mechanically, and aesthetically compatible. Thermal and mechanical compatibility include a fusing temperature of ceramic that does not cause distortion of the metal substructure. Decalibration of ovens used for firing of the ceramic layers for metal ceramic dental prostheses leads to stress and cracks in the veneering material, and ultimately to the failure of the restoration. 25 metal ceramic prostheses were made for this study. They were divided in five groups, each sintered at a different temperature: a group at the temperature prescribed by the producer, two groups at lower and two groups at higher temperatures set in the ceramic oven. An established noninvasive biomedical imaging method, swept source (SS) optical coherence tomography (OCT) was employed, in order to evaluate the modifications induced when using temperatures different from those prescribed for firing the samples. A quantitative assessment of the probes is performed by en-face OCT images, taken at constant depths inside the samples. The differences in granulation, thus in reflectivity allow for extracting rules-of-thumb to evaluate fast, by using only the prostheses currently produced the current calibration of the ceramic oven. OCT imaging can allow quick identification of the oven decalibration, to avoid producing dental prostheses with defects.

Enhanced green upconversion by controlled ceramization of Er{sup 3+}–Yb{sup 3+} co-doped sodium niobium tellurite glass–ceramics for low temperature sensors

Energy Technology Data Exchange (ETDEWEB)

Suresh Kumar, J., E-mail: suresh@ua.pt; Pavani, K.; Graça, M.P.F.; Soares, M.J.

2014-12-25

Highlights: • Upconversion luminescence improved in glass–ceramics compared to host glass. • Judd–Ofelt and radiative parameters calculated. • NIR decay curve results concur the results of improved luminescence. • Temperature dependent upconversion support the use of materials for sensors. - Abstract: Tellurite based glasses are well-known for their upconversion properties besides having a disadvantage of low mechanical strength dragging them away from practical applications. The present work deals with preparation of sodium niobium tellurite (SNT) glasses using melt quenching method, in which small quantities of boron and silicon in the form of oxides are added to improve their mechanical properties. Controlled heat treatment is performed to ceramize the prepared glasses based on the thermal data given by DTA. XRD and SEM profiles of the glass–ceramics which confirmed the formation of crystalline monoclinic Sodium Tellurium Niobium Oxide (Na{sub 1.4}Nb{sub 3}Te{sub 4.9}O{sub 18}) phase (JCPDS card No. 04–011-7556). Upconversion measurements in the visible region were made for the prepared Er{sup 3+}–Yb{sup 3+} co-doped glasses and glass–ceramics with 980 nm laser excitation varying the laser power and concentration of Er{sup 3+} ions. Results showed that the upconversion luminescence intensity was enhanced by ten times in SNT glass–ceramics compared to that in the SNT glasses. Decay curves give evidence of high performance of glass–ceramics compared to glasses due to ceramization and structural changes. Temperature dependent visible upconversion was performed to test the ability of efficient SNT glass–ceramic at low temperatures and variation of upconversion intensities was studied.

Production of high temperature superconductors and characteristics by infrared and Raman spectroscopy

International Nuclear Information System (INIS)

Thomsen, C.

1991-01-01

This final report, which is partly kept short, is concerned with electron/phonon interaction and the determination of the band gap in high temperature superconductors (YBa 2 Cu 3 O 7 ). The final report is divided into four parts, which reflect the individual working groups: 1. Raman spectroscopy, 2. IR spectroscopy (reflection measurements, isotope effect, superconducting energy gap, behaviour of infrared active phonons), 3. Magnetic field measurements, and 4. Theory (initial calculation of the metal/isolator transfer in BaBiO 3 ). (MM) [de

Possibilities of development photodynamic therapy under high temperature superconductor magnetic field

International Nuclear Information System (INIS)

Sen, Mihir

1996-01-01

After a long extensive research work neutron photon therapy for treatment of acquired immuno-deficiency syndrome (AIDS) was developed. High temperature superconductor magnet was developed and fitted in magnetic resonance imaging system to guide the patient. By this neutron-photon therapy AIDS effected cells are identified prominently. Patient is then injected with light sensitive drug molecules, which only AIDS cell retain. Light from photon (laser) then energizes the drug, which passes that energy to oxygen, which then leads a biochemical attack on the AIDS cells. If all goes well, the AIDS affected cells die. 10 refs., 1 fig

Deficient by oxygen perovskites and superconductor with transition temperature 93 K

International Nuclear Information System (INIS)

Ross, N.L.; Angel, R.J.; Finger, L.W.; Hazen, R.M.; Prewitt, K.T.

1988-01-01

Structural changes in some perovskites deficient by oxygen is reviewd. The structure of the high-temperature YBa 2 Cu 3 O 7-x superconductor is shown to develop usual for perovskites properties and at the same time to possess specific features. The specific feature includes the fact that ordering of vacancies and oxygen atoms is the consequence of Ba 2+ and Y 3+ ordering in positions A. Such ordering causes the removal of oxygen atoms plane from the structure and accurrence of pyramidal-coordinated atoms Cu2 in positions B. 22 refs.; 3 figs.; 2 tabs

Preparation and temperature dependence of electrostriction properties for PMN-based composite ceramics

International Nuclear Information System (INIS)

Zhao Jingbo; Qu Shaobo; Du Hongliang; Zheng Yanju; Xu Zhuo

2009-01-01

Both low- and high-temperature units were prepared by columbite precursor method, and Pb(Mg 1/3 Nb 2/3 )O 3 (PMN)-based ferroelectric composite ceramics were prepared by conventional method, baking-block method and coating method, respectively. The effects of preparation methods on dielectric and electrostriction properties as well as the temperature-dependence property of the obtained composite ceramics were studied. The results show that compared with the samples prepared by traditional blend sintering method, of the samples prepared by baking-block and coating methods have much better dielectric and electrostriction properties. For those prepared by baking-block method, the electrostriction temperature-dependence properties are good in the range of 20-60 deg. C. For those prepared by coating method, the dielectric temperature-dependence properties are also good in the broad range of -30 to 70 deg. C, and the electrostriction temperature properties are better than those prepared by blending-block. Compared with the traditional blending sintering method, the dielectric and electrostriction temperature-dependence properties are much better, which effectively solves the problem of temperature properties existing in present engineering applications.

Pyroelectric Ceramics as Temperature Sensors for Energy System Applications

Science.gov (United States)

Silva, Jorge Luis

Temperature is continuously monitored in energy systems to ensure safe operation temperatures, increase efficiency and avoid high emissions. Most of energy systems operate at high temperature and harsh environments to achieve higher efficiencies, therefore temperature sensing devices that can operate under these conditions are highly desired. The interest has increased in temperature sensors capable to operate and in harsh environments and temperature sensors capable to transmit thermal information wirelessly. One of the solutions for developing harsh environment sensors is to use ceramic materials, especially functional ceramics such as pyroelectrics. Pyroelectric ceramics could be used to develop active sensors for both temperature and pressure due to their capabilities in coupling energy among mechanical, thermal, and electrical domains. In this study, two different pyroelectric materials were used to develop two different temperature sensors systems. First, a high temperature sensor was developed using a lithium niobate (LiNbO3) pyroelectric ceramic. With its Curie temperature of 1210 °C, lithium niobate is capable to maintain its pyroelectric properties at high temperature making it ideal for temperature sensing at high temperature applications. Lithium niobate has been studied previously in the attempt to use its pyroelectric current as the sensing mechanism to measure temperatures up to 500 °C. Pyroelectric coefficient of lithium niobate is a function of temperature as reported in a previous study, therefore a dynamic technique is utilized to measure the pyroelectric coefficient of the lithium niobate used in this study. The pyroelectric coefficient was successfully measured up to 500 °C with coefficients ranging from -8.5 x 10 -5 C/m2 °C at room temperature to -23.70 x 10 -5 C/m2 °C at 500 °C. The lithium niobate sensor was then tested at higher temperatures: 220 °C, 280 °C, 410 °C and 500 °C with 4.31 %, 2.1 %, 0.4 % and 0.6 % deviation

Design and preliminary analysis of in-vessel core catcher made of high-temperature ceramics material in PWR

International Nuclear Information System (INIS)

Xu Hong; Ma Li; Wang Junrong; Zhou Zhiwei

2011-01-01

In order to protect the interior wall of pressure vessel from melting, as an additional way to external reactor vessel cooling (ERVC), a kind of in-vessel core catcher (IVCC) made of high-temperature ceramics material was designed. Through the high-temperature and thermal-resistance characteristic of IVCC, the distributing of heat flux was optimized. The results show that the downward average heat flux from melt in ceramic layer reduces obviously and the interior wall of pressure vessel doesn't melt, keeping its integrity perfectly. Increasing of upward heat flux from metallic layer makes the upper plenum structure's temperature ascend, but the temperature doesn't exceed its melting point. In conclusion, the results indicate the potential feasibility of IVCC made of high-temperature ceramics material. (authors)

Modeling the basic superconductor thermodynamical-statistical characteristics

International Nuclear Information System (INIS)

Palenskis, V.; Maknys, K.

1999-01-01

In accordance with the Landau second-order phase transition and other thermodynamical-statistical relations for superconductors, and using the energy gap as an order parameter in the electron free energy presentation, the fundamental characteristics of electrons, such as the free energy, the total energy, the energy gap, the entropy, and the heat capacity dependences on temperature were obtained. The obtained modeling results, in principle, well reflect the basic low- and high-temperature superconductor characteristics

Method for fabrication of high temperature superconductors

Science.gov (United States)

Balachandran, Uthamalingam [Hinsdale, IL; Ma, Beihai [Naperville, IL; Miller, Dean [Darien, IL

2009-07-14

A layered article of manufacture and a method of manufacturing same is disclosed. A substrate has a biaxially textured MgO crystalline layer having the c-axes thereof inclined with respect to the plane of the substrate deposited thereon. A layer of one or more of YSZ or Y.sub.2O.sub.3 and then a layer of CeO.sub.2 is deposited on the MgO. A crystalline superconductor layer with the c-axes thereof normal to the plane of the substrate is deposited on the CeO.sub.2 layer. Deposition of the MgO layer on the substrate is by the inclined substrate deposition method developed at Argonne National Laboratory. Preferably, the MgO has the c-axes thereof inclined with respect to the normal to the substrate in the range of from about 10.degree. to about 40.degree. and YBCO superconductors are used.

Magnetic-Field-Enhanced Incommensurate Magnetic Order in the Underdoped High-Temperature Superconductor YBa2Cu3O6.45

DEFF Research Database (Denmark)

Haug, D.; Hinkov, V.; Suchaneck, A.

2009-01-01

We present a neutron-scattering study of the static and dynamic spin correlations in the underdoped high-temperature superconductor YBa2Cu3O6.45 in magnetic fields up to 15 T. The field strongly enhances static incommensurate magnetic order at low temperatures and induces a spectral-weight shift...

Fatigue limit of polycrystalline zirconium oxide ceramics: effect of grinding and low-temperature aging

NARCIS (Netherlands)

Pereira, G.K.R.; Silvestri, T.; Amaral, M.; Rippe, M.P.; Kleverlaan, C.J.; Valandro, L.F.

2016-01-01

The following study aimed to evaluate the effect of grinding and low-temperature aging on the fatigue limit of Y-TZP ceramics for frameworks and monolithic restorations. Disc specimens from each ceramic material, Lava Frame (3M ESPE) and Zirlux FC (Ivoclar Vivadent) were manufactured according to

Concepts for using trapped-flux bulk high-temperature superconductor in motors and generators

International Nuclear Information System (INIS)

Hull, John R; Strasik, Michael

2010-01-01

We review previous concepts for using bulk high-temperature superconductors (HTSs) in motors and generators and discuss methods for using trapped-flux (TF) HTSs in motors and generators that have been recently investigated in our laboratory. We examine the expected performance of a brushless motor/generator that uses TF bulk HTSs to provide magnetomotive force, where the stator windings are used to create the TF. A key feature is the use of dysprosium for the stator and rotor cores.

Syntactic intergrowth problems with BCSCO and fabrication difficulties therefrom. [Bismuth-Calcium-Strontium-Copper-Oxide superconductors

Science.gov (United States)

Morgan, P. E. D.; Ratto, J. J.; Housley, R. M.; Porter, J. R.

1988-01-01

EDXS performed on isolated particles of the Bi-Ca-Sr-Cu-O high-temperature ceramic superconductor has verified the presence of significant elemental exchange between the Ca and Sr, and, to a lesser extent, between Cu and Bi. Two primary preparations, identified as primarily 24.4 A and 30.6 A, respectively, are identified. The Cu:Bi ratio in the 30.6 A material is approximately 1:1 for most particles, although only a few particles of the nominally 24.4 A material have the expected 1:2 ratio. No unequivocal assignment of atomic composition to the predominantly 24.4 A or 30.6 A appears possible, if major syntactic problems are present.

Peculiarities of the temperature dependences of trapped magnetic field in Y-HTSC ceramics

International Nuclear Information System (INIS)

Sukhanov, A.A.; Omel'chenko, V.I.

2001-01-01

The temperature dependence H t (T) of trapped magnetic field (TMF) in Y-HTSC ceramics are studied. For the fields-cooled trapping the H t (T) dependences coincide with the dependences of H t on trapping temperature T t . Both dependences fall off monotonously with increasing temperature, and for low fields they reach saturation as temperature is decreased. When the trapping is induced by the field pulse after zero cooling the H t (T t ) dependences show a maximum while the H t (T) curves drop monotonously with increase in temperature. In this case the rate of their dropping increases with decrease in pulse magnitude and the temperature of TMF vanishing decreases with T t and H. The results are discussed and it is shown that contrast to the Been model the theory based on the model of TMF in superconductive loops gives an adequate analytical description of the observed features of the temperature dependences of trapped magnetic field in the Y-HTSC ceramics

Single Crystal Synthesis and STM Studies of High Temperature Superconductors

Science.gov (United States)

Barrientos, Alfonso

1997-01-01

This is a final report for the work initiated in September of 1994 under the grant NAG8-1085 - NASA/OMU, on the fabrication of bulk and single crystal synthesis, specific heat measuring and STM studies of high temperature superconductors. Efforts were made to fabricate bulk and single crystals of mercury based superconducting material. A systematic thermal analysis on the precursors for the corresponding oxides and carbonates were carried out to synthesized bulk samples. Bulk material was used as seed in an attempt to grow single crystals by a two-step self flux process. On the other hand bulk samples were characterized by x-ray diffraction, electrical resistivity and magnetic susceptibility, We studied the specific heat behavior in the range from 80 to 300 K. Some preliminary attempts were made to study the atomic morphology of our samples. As part of our efforts we built an ac susceptibility apparatus for measuring the transition temperature of our sintered samples.

Superconductors in the High School Classroom

Science.gov (United States)

Lincoln, James

2017-01-01

In this article, we discuss the behavior of high-temperature superconductors and how to demonstrate them safely and effectively in the high school or introductory physics classroom. Included here is a discussion of the most relevant physics topics that can be demonstrated, some safety tips, and a bit of the history of superconductors. In an effort…

Flux Pinning and AC Loss in Second Generation High Temperature Superconductor Wires

Energy Technology Data Exchange (ETDEWEB)

Paranthaman, Mariappan Parans [ORNL; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York

2007-01-01

Major advances have been made in the last 18 years in high-temperature superconductor (HTS) reserach and development, resulting in increased use of HTS materials in commerical and pre-commercial electric-power applications. This new and important book addresses the issues related to flux pinning, AC losses and thick YBCO film growth. Written by top most scientists in the world, it presents the current status and issues related to YBCO coated conductors and the need for further fundamental materials science work in YBCO coated conductor. It will be a useful handbook for years to come.

Positron annihilation in a high-temperature superconductor YBa2Cu3O7-δ

International Nuclear Information System (INIS)

Vavryshchuk, Ya.; Levandovski, M.; Rybakov, V.N.; Yutlandov, I.A.

1988-01-01

Positron annihilation as a function of temperature in high-temperature superconductors YBa 2 Cu 3 O 7-δ has been investigated. It is shown that a change in the annihilation capacity at the transition into superconducting state is relatively small. The change of r 1 and r 2 positron lifetimes as well as of the intensity of the component with r 2 -J 2 and Doppler broadening S parameter allows one to assume that transition into superconducting state is accompanied with a certain decrease in electron density and with decreasing number of defects or increasing size of crystalline net

Temperature and carrier density dependence of anisotropy in supercurrent density in layered cuprate superconductors

International Nuclear Information System (INIS)