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Yttria-stabilized zirconia solid oxide electrolyte fuel cells, monolithic solid oxide fuel cells

Description: Small cell size, thin ceramic components, and high operating temperature are the key features of the MSOFC. The small size of individual cells in the monolithic structure increases the active surface area. For example, an MSOFC with channels about 1 mm in diameter has a ratio of active surface area to volume of about 9.4 sq cm/cu cm. This is about seven times the ratio for conventional fuel cells. On this basis alone, an MSOFC with a channel diameter of 1 mm should produce the same power as a c… more
Date: January 1, 1989
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Magnetic ordering in (Y sub 1-x Pr sub x )Ba sub 2 Cu sub 3 O sub 7 as evidenced by muon spin relaxation

Description: Using the zero-field-muon-spin-relaxation ({mu}SR) technique we have found clear evidence for antiferromagnetic ordering of Cu moments within the CuO planes of (Y{sub 1-x}Pr{sub x})Ba{sub 2}Cu{sub 3}O{sub 7}. The Neel temperatures are approximately 285 K, 220 K, 35 K, 30 K, and 20 K for x = 1, 0.8, 0.6, 0.58, and 0.54, respectively. For x = 0.50 we observe a fast-relaxing component of the muon polarization in addition to a long-time tail, reminiscent of spin-glass behavior. This region of the p… more
Date: January 1, 1989
Creator: Cooke, D.W.; Kwok, R.S.; Jahan, M.S.; Lichti, R.L.; Adams, T.D.; Boekema, C. et al.
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Partner: UNT Libraries Government Documents Department
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Anisotropy of oxygen tracer diffusion in YBa sub 2 Cu sub 3 O sub 7-. delta. single crystals

Description: The crystal structure of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} strongly suggests that the diffusion of oxygen in this material will be highly anisotropic, with diffusion in the ab plane being much faster than diffusion parallel to the c axis, and this has been assumed in most analyses of diffusion in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}. The present data confirm this hypothesis; the diffusion coefficient in the ab plane is several orders of magnitude greater than the diffusion coefficient along th… more
Date: September 1, 1989
Creator: Rothman, S. J.; Routbort, J. L.; Liu, J.-Z.; Downey, J. W.; Thompson, L. J.; Fang, Y. et al.
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Partner: UNT Libraries Government Documents Department
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Electron beam induced oxygen in YBa sub 2 Cu sub 3 O sub 7-x superconductors

Description: Thin foils of bulk YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) superconductors were subjected to electron irradiation in a Transmission Electron Microscope (TEM). The resulting disordering of the oxygen atoms and vacancies in the Cu-O planes was monitored by measuring the splitting of the (110) diffraction spots in the (001) diffraction pattern. Samples were irradiated at 83K with 100, 150, 200 and 300kV electrons. The 100kV electrons did not cause any disordering, even after prolonged irradiation. Th… more
Date: January 1, 1989
Creator: Basu, S.N.; Roy, T.; Mitchell, T.E. & Nastasi, M.
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Partner: UNT Libraries Government Documents Department
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Influence of ion beam mixing on the growth of high temperature oxide superconducting thin film

Description: The superconducting properties of high temperature superconductor thin films are dependent on the quality of the substrate used to grow these films. In order to maximize the lattice matching between the superconducting film and the substrate, we have used a YBa{sub 2}Cu{sub 3}O{sub 7} thin film deposited on {l angle}100{r angle} SrTiO{sub 3} as a template. The first film was prepared by coevaporation of Y, BaF{sub 2} and Cu on {l angle}100{r angle} SrTiO{sub 3}, followed by an anneal in wet'' o… more
Date: January 1, 1989
Creator: Bordes, N.; Rollett, A.D.; Cohen, M.R. & Nastasi, M.
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Partner: UNT Libraries Government Documents Department
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Radiation damage calculations for compound materials

Description: Displacement damage calculations can be performed for 40 elements in the energy range up to 20 MeV with the SPECTER computer code. A recent addition to the code, called SPECOMP, can intermix atomic recoil energy distributions for any four elements to calculate the proper displacement damage for compound materials. The calculations take advantage of the atomic recoil data in the SPECTER libraries, which were determined by the DISCS computer code, using evaluated neutron cross section and angular… more
Date: January 1, 1989
Creator: Greenwood, L.R.
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Partner: UNT Libraries Government Documents Department
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Luminescence from defects and impurity centers in yttrium oxide

Description: High-purity (99.999%) Y{sub 2}O{sub 3} powder is used as a starting material for fabricating high-temperature superconductors (HTS), and is frequently found as an unreacted second phase in the final product. We have found that as-received Y{sub 2}O{sub 3} contains Tb{sup 3+} paramagnetic impurity ions as determined by TSL and emission-spectra measurements. Deep luminescence traps (presumably Tb{sup 4+} ions) are formed in Y{sub 2}O{sub 3} when it is exposed to {gamma}-rays, x rays, or fluoresce… more
Date: January 1, 1989
Creator: Jahan, M.S.; Cooke, D.W.; Bennett, B.L.; Hults, W.L.; Maez, M.A.; Ott, K.C. et al.
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Partner: UNT Libraries Government Documents Department
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The influence of the substrate surface on the nucleation and growth of superconducting thin films

Description: The quality of epitaxially grown superconducting thin films is dependent on the nature of the substrate surface. In this study, the surface of <100> oriented SrTiO{sub 3} single crystals was modified by mechanical polishing, thermal annealing and chemical etching. A study of the YBa{sub 2}Cu{sub 3}O{sub 7-x} thin films grown on these substrates showed that high quality superconducting films were obtained when the substrate surface was highly oriented in the <100> direction and was also microsco… more
Date: January 1, 1989
Creator: Basu, S.N.; Bordes, N.; Rollett, A.D.; Cohen, M.R. & Nastasi, M.
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Partner: UNT Libraries Government Documents Department
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Microwave characterization of high-temperature superconductors

Description: Thick (10-15 {mu}m) Tl-Ba-Ca-Cu-O films have been deposited onto yttria-stabilized zirconia and Ag substrates by d.c. magnetron sputtering techniques. Direct deposition onto 1'' diameter yttria-stabilized zirconia yields films with typical 22 GHz surface resistance (R{sub s}) values of 5.2 {plus minus} 2 m{Omega} and 52 {plus minus} 2 m{Omega} at 10 K and 77 K, respectively. For comparison, R{sub s} of Cu at this same frequency is 10 m{Omega} at 4 K and 22 m{Omega} at 77 K. Tl-Ba-Ca-Cu-O films … more
Date: January 1, 1989
Creator: Cooke, D. W.; Gray, E. R.; Arendt, P. N.; Beery, J. G.; Bennett, B. L.; Brown, D. R. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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High Resolution-Angle Resolved Photoemission Studies of High Temperature Superconductors

Description: Recent photoemission studies of Y 123 and Bi 2212 performed with high energy and angular resolution have provided detailed information on the nature of the states near the Fermi level. Measurements of the superconducting gap, band dispersion, and the density of states near the Fermi level in the normal state all support a Fermi liquid description of these materials. 5 refs., 4 figs.
Date: August 1, 1989
Creator: Olson, C. G.; Liu, R.; Lynch, D. W.; Veal, B. W.; Chang, Y. C.; Jiang, P. Z. et al.
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Partner: UNT Libraries Government Documents Department
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Charge transfer and bond lengths in YBa sub 2 Cu sub 3-x M sub x O sub 6+y

Description: We discuss the effects of doping on the Cu chain sites in YBa{sub 2}Cu{sub 3-x}M{sub x}O{sub 6+y}. The relationship between bond lengths obtained from neutron scattering and charge transfer is evaluated in terms of bond valence. In particular, it is concluded that removing an oxygen from the chains transfers one electron to the planes. 24 refs., 3 figs.
Date: January 1, 1989
Creator: Jorgensen, J. D.; Rhyne, J. J.; Neumann, D. A.; Miceli, P. F.; Tarascon, J. M.; Greene, L. H. et al.
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Partner: UNT Libraries Government Documents Department
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Rotational magnetic processes in YB sub 2 Cu sub 3 O sub 7

Description: A polycrystalline superconducting thin-disk sample was rotated in a fixed field ({rvec H}) at 4.2 K, and the vector magnitude and orientation of the total magnetization ({rvec M}) were measured as the sample-rotation angle ({Theta}) was slowly cycled between 0 and 360{degree}. The measured {rvec M} was decomposed into a penetrating (vortex) flux component {rvec M}{sub p} that rotates rigidly with the sample at very small {Theta} and a diamagnetic (shielding) component {rvec M}{sub d} that stays… more
Date: January 1, 1989
Creator: Liu, Liwen; Kouvel, J.S.; Brun, T.O. (Illinois Univ., Chicago, IL (USA). Dept. of Physics & Argonne National Lab., IL (USA))
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Partner: UNT Libraries Government Documents Department
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Magnetic and electronic correlations in YBa sub 2 Cu sub 3 O sub 6+x

Description: YBa{sub 2}Cu{sub 3}O{sub 6+x} is an antiferromagnetic insulator in its tetragonal phase at small x, and it becomes a superconducting metal in the large x orthorhombic phase. The transition between the two phases is controlled by the orientational ordering of CuO{sub x} chain segments and dielectric screening by the BaO layers. In the orthorhombic phase, holes from the chains are transferred to the CuO{sub 2} planes, and the superconducting transition temperature scales with the density of O 2p … more
Date: January 1, 1989
Creator: Tranquada, J.M.
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Partner: UNT Libraries Government Documents Department
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Intergranular and interphase boundaries in ceramics

Description: Interfaces are of great importance in both electronic and structural ceramics. The microstructure and microchemistry of interfaces can be studied by transmission electron microscopy, both high resolution and analytical. Examples are taken from both intergranular and interphase boundaries in ceramics. The former include low angle, twin and 90/degree/ boundaries in YBa/sub 2/Cu/sub 3/O/sub 7/ superconductors. Interphase boundaries include epitactic layers of YBa/sub 2/Cu/sub 3/O/sub 7/on SrTiO/su… more
Date: January 1, 1989
Creator: Mitchell, T.E.; Roy, T. & Unal, O.
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Partner: UNT Libraries Government Documents Department
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Phase separation of holes in antiferromagnets

Description: It is shown that dilute holes in an antiferromagnet are unstable against phase separation into a hole-rich phase and a no-hole phase. When the spin exchange interaction J exceeds a critical value J{sub c}, one phase consists of all holes, the other all electrons. The argument is presented in detail for the t--J model but evidence of phase separation in other models is mentioned. 11 refs.
Date: January 1, 1989
Creator: Emery, V.J.; Kivelson, S.A.; Lin, H.Q. (Brookhaven National Lab., Upton, NY (USA); California Univ., Los Angeles, CA (USA). Dept. of Physics & Brookhaven National Lab., Upton, NY (USA))
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Partner: UNT Libraries Government Documents Department
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The initial scientific program at the NSLS infrared beamline

Description: Unique extraction optics (90 {times} 90 mrads) at the NSLS U4IR line offer high brightness beams at up to mm wavelengths with a {approximately}1ns pulse structure. Radiation from this port has now been carefully characterized and agrees well with calculations, making it 100--1000 times brighter than conventional sources in the middle and far infrared regions. Using rapid scan Michelson interferometers with liquid He cooled bolometer detectors we have been able for the first time to measure mole… more
Date: January 1, 1989
Creator: Williams, G. P.
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Partner: UNT Libraries Government Documents Department
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Rotational spin-glass properties of Tb sub 0. 3 Y sub 0. 7 Ag

Description: This cubic pseudobinary compound with antiferromagnetic order and spin-glass properties below T{sub g} (36 K) was studied by magnetization-vector measurements on a field-cooled (fc) polycrystalline sample disk rotated in various fixed fields ({rvec H}). At 4.2 K, the fc-induced anisotropy field {rvec H}{sub K} is seen to turn rigidly with the sample for all rotational magnetization follows {rvec H}{sub K} very closely, it is deduced that H{sub K} > 100 kOe. At 20 K, {rvec H}{sub K} turns rigidl… more
Date: January 1, 1989
Creator: Said, M.R.; Kouvel, J.S.; Brun, T.O. (Illinois Univ., Chicago, IL (USA). Dept. of Physics & Argonne National Lab., IL (USA))
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Partner: UNT Libraries Government Documents Department
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mu. SR investigation of magnetism and superconductivity in (Y sub 1-x Pr sub x )Ba sub 2 Cu sub 3 O sub 7

Description: Muon spin rotation and relaxation techniques have been used to study the superconductivity and magnetism in (Y{sub 1-x}Pr{sub x})Ba{sub 2}Cu{sub 3}O{sub 7} (0{le}x{le}1) and PrBa{sub 2}Cu{sub 3}O{sub 6}. Clear evidence for magnetic ordering of the Cu moments within the Cu-O planes is seen. Additionally, a lower magnetic transition is observed which, based upon previous work, has been associated with the ordering of Pr moments on the Y sublattice of the YBa{sub 2}Cu{sub 3}O{sub 7} structure. For… more
Date: January 1, 1989
Creator: Cooke, D. W.; Kwok, R. S.; Jahan, M. S.; Lichti, R. L.; Adams, T. R.; Boekema, C. et al.
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Partner: UNT Libraries Government Documents Department
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Partial reduction of re-oxidation processing of Y-Ba-Cu-O sputtered thin films

Description: Thin films of Y--Ba--Cu--O were produced by rf sputtering of YBa{sub 2}Cu{sub 3}O{sub 7-x} ceramic targets, using a variety of plasma compositions, rf power levels, and substrate temperatures. Post annealing of these films in oxygen produced superconducting films with T{sub c} values between 40--60 K, broad transition widths and semiconductor-like electrical behavior above T{sub c}. Subsequent annealing at 850{degree}C in an inert gas with a residual oxygen partial pressure of {le}10 ppM follow… more
Date: January 1, 1989
Creator: Garzon, F.H.; Beery, J.G.; Wilde, D.K. & Raistrick, I.D.
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Partner: UNT Libraries Government Documents Department
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High-frequency cavity applications and measurements of high-temperature superconductors

Description: A potentially important application of high-temperature superconductors will be high-frequency accelerating cavities. Currently these materials are not competitive with Nb at liquid helium temperature or with Cu at room temperature. However, available data on high-quality single crystals suggest that the relatively poor rf properties (high surface resistance and low surface magnetic field) of bulk and film specimens are due to materials properties that can be eliminated by improved processing t… more
Date: January 1, 1989
Creator: Cooke, D.W. & Gray, E.R.
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Partner: UNT Libraries Government Documents Department
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Wear and friction of thin film high temperature oxide superconductors

Description: We have examined the sliding properties of a Nd-Fe-B magnet against a thin film YBa/sub 2/Cu/sub 3/O/sub 7/ superconductor. Pin-on-disk experiments were performed at room temperature and in normal air using a 10 mm magnetic Nd-Fe-B ball loaded to 31.22 g and a sliding speed of approximately 0.57 cm/sec. Such condition produced a steady state friction coefficient of 1.1 +- 0.3. Wear rate measurements indicated that Nd-Fe-B will wear YBa/sub 2/Cu/sub 3/O/sub 7/ at a rate 1.3 /times/ 10/sup /minus… more
Date: January 1, 1989
Creator: Nastasi, M.; Hirvonen, J.-P. & Toivanen, R.O.
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Partner: UNT Libraries Government Documents Department
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Nuclear relaxation rates at copper and oxygen sites in YBa/sub 2/Cu/sub 3/O/sub 7/

Description: We report NMR measurements of the nuclear relaxation rate at all copper and oxygen sites in magnetically aligned powder samples of YBa/sub 2/Cu/sub 3/O/sub 7/. There is no peak in the oxygen relaxation rate below T/sub c/ at any oxygen site supporting the possibility that d-wave pairs are formed in the superconducting state. Comparison of the oxygen and copper rates in the planes reveals a characteristic temperature greater than T/sub c/. 6 refs., 2 figs.
Date: January 1, 1989
Creator: Hammel, P. C.; Takigawa, M.; Heffner, R. H.; Fisk, Z. & Ott, K. C.
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Partner: UNT Libraries Government Documents Department
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Photoemission Spectroscopy of Single Crystal HTSC Materials: A Fermi Liquid Electronic Structure

Description: Photoemission spectra from HTSC materials (primarily 123-type), cleaved and measured at 20K, reveal a rich DOS structure which compares favorably with a calculated band structure, except for a residual 0.5 eV shift which may reflect some correlation effects. Band dispersion is observed throughout the valence bands, with clear evidence for a 0.2 eV wide band dispersing through E/sub F/. The orbital character at E/sub F/ is a mix of Cu-3d and O-2p. There is unambiguous evidence for a large BCS-li… more
Date: January 1, 1989
Creator: Arko, A. J.; List, R. S.; Bartlett, R. J.; Cheong, S. W.; Olson, C. G.; Yang, A. B. et al.
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Partner: UNT Libraries Government Documents Department
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The formation and analysis of thin film high temperature superconductors

Description: Thin films of high temperature superconductors have been fabricated using a variety of physical vapor deposition techniques. Recent results of HTS thin films produced by coevaporation, sputtering and laser deposition will be briefly reviewed. In addition some examples of the utility of high energy ion backscattering for the analysis of film stoichiometry will be given. 34 refs., 6 figs.
Date: January 1, 1989
Creator: Nastasi, M.; Muenchausen, R. E. & Arendt, P. N.
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Partner: UNT Libraries Government Documents Department
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