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Analysis of yttrium oxide exchange samples

Description: Report detailing the results of several yttrium oxide analyses. Four different institutions were given 50 grams of yttrium oxide to analyze following the Yttrium Analytical Conference on November 7th and 8th, 1956. This report details the results of those four different institutions.
Date: February 1958
Creator: Rodden, Clement J.
Partner: UNT Libraries Government Documents Department

Crystal and magnetic structure of stoichiometric YFe{sub 2}O{sub 4}

Description: Crystal structure of stoichiometric YFe{sub 2}O{sub 4} powder was studied by high-resolution neutron diffraction at room temperature, 225 K and 80 K. Rietveld refinements of the diffraction patterns give reasonable fits with space group R{bar 3}m (hexagonal) for room temperature, and with P{bar 1} (triclinic) for 225 K. However, the 80 K pattern cannot be fitted at all with the same triclinic symmetry, indicating that the structure is much more complicated. The magnetic reflection has been separated from those complex nuclear peaks by the polarization analysis. The magnetic structure is also fairly complicated both at 225 K and at 80 K.
Date: August 1, 1994
Creator: Katano, S.; Funahashi, S.; Matsumoto, T.; Iida, J.; Tanaka, M. & Cable, J.W.
Partner: UNT Libraries Government Documents Department

Aqueous precipitation: Population balance modeling and control in multi-cation systems

Description: Efficient separation of metal species from aqueous streams by precipitation techniques requires a fundamental understanding of the processes that occur during precipitation. These processes include particle nucleation, particle growth by solute deposition, agglomerate formation, and agglomerate breakup. Population balance method has been used to develop a kinetic model that accounts for these competing kinetic processes. The usefulness of the model is illustrated through its application to precipitation of yttrium hydroxynitrate, YHN. Kinetic parameters calculated from the model equations and system-specific solution chemistry are used to describe several aspects of the effect of pH on YHN precipitation. Implications for simultaneous precipitation of more than one cation type are discussed with examples. Effects of solution chemistry, precipitator design, and solvent choice are considered.
Date: March 1996
Creator: Voigt, J. A.
Partner: UNT Libraries Government Documents Department

Atomic structure of the {sigma}5 (210)/[001] symmetric tilt grain boundary in yttrium aluminum garnet

Description: The {Sigma}5(210)/[100] symmetric tilt grain boundary in YAG was produced by UHV diffusion bonding precisely oriented single crystals. The boundary has been characterized by HREM along two different directions, parallel and perpendicular to the tilt axis. Models of the atomic structure of the boundary were formed following the Coincident Site Lattice scheme. The resulting models are equivalent to twins formed at the atomic scale. The high resolution images show no rigid crystal translations away from the perfect mirror reflection relation. Comparison of the simulated images using the atomic model as input with the experimental images identifies the plane of mirror symmetry. The atomic model is shown to be in good agreement with the experimental images when viewed parallel to tilt axis, but disagrees with the images perpendicular to tilt axis. Agreement between simulated and experimental images can be improved by changing the composition of the grain boundary with respect to the bulk. To reach a more certain conclusion on the structure of the grain boundary will require additional theoretical calculations.
Date: June 24, 1996
Creator: Campbell, G.H. & King, W.E.
Partner: UNT Libraries Government Documents Department

Thin film synthesis of novel electrode materials for solid-oxide fuel cells

Description: Electrode materials for solid-oxide fuel cells are developed using sputter deposition. A thin film anode is formed by co-deposition of nickel and yttria-stabilized zirconia. This approach is suitable for composition grading and the provision of a mixed-conducting interracial layer to the electrolyte layer. Similarly, synthesis of a thin film cathode proceeds by co-deposition of silver and yttria- stabilized zirconia. The sputter deposition of a thin film solid- oxide fuel cell is next demonstrated. The thin film fuel cell microstructure is examined using scanning electron microscopy whereas the cell performance is characterized through current-voltage measurement and corresponding impedance spectroscopy.
Date: December 1, 1997
Creator: Jankowski, A.F. & Morse, J.D.
Partner: UNT Libraries Government Documents Department

Combustion synthesis and engineering nanoparticles for electronic, structural and superconductor applications. Final report, May 31, 1992--May 30, 1996

Description: Dense, nanocrystalline ceramic articles of doped ZrO{sub 2} (for use in solid electrolytes, oxygen sensors, electrode materials, thermal barrier coatings, etc.), BaTiO{sub 3} (for capacitor applications), and YBa{sub 2}Cu{sub 3}O{sub 7-x} (a high-temperature superconductor with uses, e.g., in magnetic flux trapping and high-speed capacitor applications) were prepared by the new nanofabrication process that has been developed in this research program. The process consists of two steps: synthesis of ceramic nanoparticles, and fabrication of dense ceramic articles that possess nanocrystalline features. The synthesis step is capable of producing 10-nanometer-diameter crystallites of doped ZrO{sub 2}, and of being scaled up to kilogram/hour production rates. The fabrication step produced dense, ultrafine-grained articles at significantly reduced sintering temperatures and times--representing a factor of 10-100 reduction in process energy requirements. The process has thus been shown to be technically feasible, while a preliminary engineering cost analysis of a pilot plant-scale version of the process indicates that it is both a cost- and an energy-efficient method of producing nanoparticles and nanocrystalline ceramics from those nanoparticles. One U.S. patent for this process has been allowed, and an additional five (continuation-in-part) applications have been filed. Technology transfer efforts have begun, through ongoing discussions with representatives from three manufacturing concerns.
Date: May 30, 1996
Creator: Stangle, G.C.; Schulze, W.A. & Amarakoon, V.R.W.
Partner: UNT Libraries Government Documents Department

Pseudogap and Incommensurate Magnetic Fluctuations in YBa{sub 2}Cu{sub 3}O{sub 6.6}

Description: Unpolarized inelastic neutron scattering is used to study the temperature and wave vector dependence of the dynamical magnetic susceptibility, {xi}`` (q,{omega}), of a well characterized single crystal YBa{sub 2}Cu{sub 3}O{sub 6.6} (T{sub c} = 62.7 K). We find that a pseudogap opens in the spin fluctuation spectrum at temperatures well above T{sub c}. We speculate that the appearance of the low frequency incommensurate fluctuations is associated with the opening of the pseudogap. To within the error of the measurements, a gap in the spin fluctuation spectrum is found in the superconducting state.
Date: July 24, 1997
Creator: Dai, P., Mook, H.A.,
Partner: UNT Libraries Government Documents Department

Flux pinning in two-dimensional high temperature superconductors

Description: Various types of high temperature superconducting single crystals (TI-2223, Bi-2212, and Y-123 with oxygen contents between 6.4 and 6.64) were investigated by SQUID magnetometry. Both materials show very {open_quotes}low{close_quotes} lying irreversibility lines (Hllc), which follow an exponential law-and rise rapidly below T/T{sub c}=0.5. High critical current P densities are found only at low temperatures, e.g. J{sub c} is about 2.7{circ}10{sup 10}Am{sup -2} at 1 T and 5 K in TI-2223. A comparison of the condensation energy provided by different types of defects with the thermal energy gives evidence for pinning of individual pancakes by the as-grown defect structure.
Date: October 1, 1996
Creator: Brandstaetter, G.; Sauerzopf, F.M.; Weber, H.W. & Veal, B.W.
Partner: UNT Libraries Government Documents Department

Neutron scattering studies of the magnetic fluctuations in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}

Description: Neutron scattering measurements have been made on the spin fluctuations in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} for different oxygen doping levels. Incommensurability is clearly observed for oxygen concentrations of 6.6 and 6.7 and is suggested for the 6.93. Measurements of the resonance for the O6.6 concentration show that it exists in a broadened and less intense form at temperatures much higher than Tc.
Date: November 5, 1997
Creator: Mook, H.A.; Dai, P.; Hunt, R.D. & Dogan, F.
Partner: UNT Libraries Government Documents Department

REVIEW OF THERMAL CONDUCTIVITY AND HEAT TRANSFER IN UO$sub 2$

Description: The theories of heal transfer in insulators are viewed and discussed relevant to UO/sub 2/. As the rate of heat transfer from a reactor core is determined largely by the thermal conductivity of the fuuel, this coefficient is of paramount importance in improving the efficiency of an installation. There is no theoretical basis to expect small or moderate chemical additions to increase the thermal conductivity of UO/sub 2 when the oxide is classed as an insulator. Large additions of a phase having a high thermal conductivity have been found to increase the net conductivity. Such systems were two phase and had poor sintering cjaracterostocs/ cpmsoderomg UO/sub 2 as a potential oxidic semiconducotor, there is possibility of increasing the themnal conductivity by proper doping. Thermal conduction by intrinsic carriers was treated experimentally and theoretically, and the conductiivity values of the two cases do not presently agree, ie., the Wiedemann-Franz law is not obeyed. The extrinsic case such as a doped urements indicate that doping UO/sub 2/ with Y/sup +3/ and Nb/sup +5/ increases the thermal conductivity. These data are sparce; the magnitude of the increase and its dependence upon impurity concentration and temperature have not been determined. (auth)
Date: September 1, 1958
Creator: Tennery, V.J.
Partner: UNT Libraries Government Documents Department

High power 2 {micro}m wing-pumped Tm{sup 3+}:YAG laser

Description: Using a scalable diode end-pumping technology developed at Lawrence Livermore National Laboratory the authors have demonstrated a compact Tm{sup 3+}:YAG laser capable of generating greater than 50 W of cw 2 {micro}m laser output power. The design and operational characteristics of this laser will be discussed.
Date: January 1, 1996
Creator: Beach, R.J.; Sutton, S.B.; Honea, E.C.; Skidmore, J.A. & Emanuel, M.A.
Partner: UNT Libraries Government Documents Department

Optical tuning a dichroic multilayer for a high fluence laser application

Description: We report on the design and successful fabrication of a dichroic multilayer stack using a procedure that allowed shifting from high reflectance to high transmittance within 89 rim and surviving high laser fluences. A design approach based on quarter-wave thick layers allowed the multilayer stack to be optically tuned in the last layers of the stack. In our case, this necessitated removing the samples from the coating chamber for a transmittance scan prior to depositing the last layers. This procedure is not commonly practiced due to thermal stress-induced failures in an oxide multilayer. However, D.J. Smith and co-workers reported that reactive e-beam evaporated hafnia from a Hf source produced laser-resistant coatings that had less coating stress compared to coatings evaporated from a HfO{sub 2} source. Tuned dichroic coatings were made that had high transmittance at 941 rim and high reflectance at 1030 nm. The coating was exposed for 5 minutes to a 100 kW/cm{sup 2} 1064 nm (180-ns pulsewidth, 10.7 kHz) laser beam and survived without microscopic damage. The same coating survived a 140 kW/cm{sup 2} of laser intensity without catastrophic damage before optical tuning were performed.
Date: October 11, 1995
Creator: R. Chow, Loomis, G.E.; Bibeau, C.; Molau, N.E.; Kanz, V.K. & Beach, R.J.
Partner: UNT Libraries Government Documents Department

Sol-gel process for preparing YBa{sub 2}Cu{sub 4}O{sub 8} precursors from Y, Ba, and Cu acidic acetates/ammonia/ascorbic acid systems

Description: Sols were prepared by addition of ammonia to acidic acetate solutions of Y{sup 3+}, Ba{sup 2+}, and Cu{sup 2+}. Ascorbic acid was added to a part of the sol. The resultant sols were gelled to a shard, a film, or microspheres by evaporation at 60 C or by extraction of water from drops of emulsion suspended in 2-ethylhexanol-1. Addition of ethanol to the sols facilitated the formation of gel films, fabricated by a dipping technique, on glass or silver substrates. At 100 C, gels that were formed in the presence of ascorbic acid were perfectly amorphous, in contrast to the crystalline acetate gels. Conversion of the amorphous ascorbate gels to final products was easier than for the acetate gels. The quality of coatings prepared from ascorbate gels was superior to that of acetate gel coatings.
Date: August 1, 1995
Creator: Deptula, A.; Lada, W.; Olczak, T.; Goretta, K.C.; Di Bartolomeo, A. & Casadio, S.
Partner: UNT Libraries Government Documents Department

Low-voltage cathodoluminescence of europium-activated yttrium orthovanadate

Description: Emissive flat panel display systems operating in full color demand higher performance at low voltages (ca. 501000 V) from cathodoluminescent (CL) phosphors than cathode ray tubes require. Hydrothermal synthesis has been suggested as a route to phosphors with improved efficiencies, lower voltage thresholds, and increased saturation power. This hypothesis was tested in europium-doped yttrium orthovanadate (YVO{sub 4}:Eu), an efficient, red emitting CL phosphor. The CL efficiency of YVO{sub 4}:Eu crystallized from aqueous solution at 200{degrees}C is relatively low until it is annealed. The distribution of particle sizes in the low-temperature phosphor is similar to that in material made via a solid-state route, but crystallites remain much smaller (ca. 400 {Angstrom}) until they are annealed. These observations, along with the anomalously strong dependence of CL intensity on europium concentration, support a model in which efficiency principally depends on crystallite size. CL efficiency of both solid state and hydrothermal YVO{sub 4}:Eu increases with voltage at constant power. Surface-bound electrons are likely the dominant influence on efficiency at voltages near threshold. Saturation power is independent of synthetic route. It is apparent that the CL properties of hydrothermally synthesized YVO{sub 4}:Eu are essentially the same as those of YVO{sub 4}:Eu produced via conventional, high-temperature routes.
Date: March 1, 1995
Creator: Phillips, M.L.F.
Partner: UNT Libraries Government Documents Department

Effect of flux flow on current distribution and heat generation in composite superconductors during a thermal disturbance

Description: An analytical investigation of current distribution and heat generation rate in composite superconductors, incorporating the effects of flux flow during disturbances, is carried out. Equations describing current density in the superconductor and the heat generation rate per unit volume of the composite conductor in the current sharing regime are derived. The results show that when the superconductor is in the flux-flow state, the current density and the heat generation rate depend only on a dimensionless parameter {phi}{sub f} = ({rho}{sub n}/{rho}{sub st})[H/H{sub c2(0)}](l-{lambda})/{lambda}. When the thermal disturbance is relatively small and {phi}{sub f} >> 1, the current density in the superconductor remains at the critical current density with all the excess transferred to the stabilizer and the heat generation rate is equal to that usually employed for low temperature superconductors. When the thermal disturbance is large and {phi}{sub f} >> 1, the current density in the superconductor can be greater than the critical current density and the heat generation rate equals the critical generation rate, independent of whether the superconductor is in the flux-flow state or the normal state. For moderate and large thermal disturbances and {phi}{sub f} =1, which is applicable to high-temperature superconductors because of high H{sub c2}(0), the heat generation rate is q = q{sub c}/2 if the Superconductor is in the flux-flow state and q = q{sub c} if the superconductor is in the normal state. An argument is provided to indicate when and Linder what circumstances will all the excess current be transferred to the stabilizer while the current in the superconductor remains at the critical current during a thermal disturbance. The differences between hi-h- and low-temperature superconductors and its implication for cryogenic stability are discussed. Data on critical currents and thermal runaway of sintered YBa{sub 2}Cu{sub 3}O{sub 7} with unoriented grains are presented.
Date: September 1, 1994
Creator: Cha, Y.S.; Hull, J.R. & Askew, T.R.
Partner: UNT Libraries Government Documents Department

Modulated spin and charge densities in cuprate superconductors

Description: Neutron scattering experiments have played a crucial role in characterizing the spin and charge correlations in copper-oxide superconductors. While the data are often interpreted with respect to specific theories of the cuprates, an attempt is made here to distinguish those facts that can be extracted empirically, and the connections that can be made with minimal assumptions.
Date: August 1, 1997
Creator: Tranquada, J.M.
Partner: UNT Libraries Government Documents Department

Characterization of novel powder and thin film RGB phosphors for field emissions display application

Description: The spectral response, brightness and outgassing characteristics of new, low-voltage phosphors for application in field-emission flat-panel displays, are presented. The tested phosphor materials include combustion synthesized powders and thin films prepared by RF-diode or magnetron sputtering, laser ablation and molecular beam epitaxy. These cathodoluminescent materials are tested with e-beam excitation at currents up to 50 {mu}A within the 200-2000V (e.g. {open_quotes}low-voltage{close_quotes}) and 3-8 kV (e.g. {open_quotes}medium voltage{close_quotes}) ranges. The spectral coordinates are compared to commercial low-voltage P22 phosphors. Phosphor outgassing, as a function of time is measured with a residual gas analyzer at fixed 50 {mu}A beam current in the low-voltage range. We find that levels of outgassing stabilize to low values after the first few hours of excitation. The desorption rates measured for powder phosphor layers with different thickness are compared to desorption from thin films.
Date: December 31, 1996
Creator: Chakhovskoi, A.G.; Hunt, C.E.; Malinowski, M.E.; Felter, T.E. & Talin, A.A.
Partner: UNT Libraries Government Documents Department

The interaction of vortices with twin boundaries

Description: Twin boundaries provide a convenient defect for investigating vortex dynamics in superconductors. They occur naturally in YBa{sub 2}Cu{sub 3}O{sub 7}, with well defined planar geometries. They are a strong pinning defect, and at the temperature of the melting transition they are the dominant pinning sites in clean crystals. Twin boundaries are easily seen in polarized light, making their location and number directly observable without special equipment. Finally, they present a highly anisotropic pinning potential to the vortices, creating the possibility of interesting new behavior. In this paper, we describe experiments using twin boundaries to probe two effects in vortex dynamics: a new peak effect in the critical current occurring in the solid state just below the melting transition, and anisotropic pinning by planar defects.
Date: May 1, 1995
Creator: Crabtree, G. W.; Kwok, W. K.; Welp, U.; Fendrich, J.; van der Beek, C. J.; Vlasko-Vlasov, V. K. et al.
Partner: UNT Libraries Government Documents Department

A High Resolution Electron Beam Profile Monitor

Description: A new beam diagnostic to measure transverse profiles of electron beams is described. This profile monitor uses a Yttrium:Aluminum:Garnet (YAG) crystal doped with a visible light scintillator to produce an image of the transverse beam distribution. The advantage of this material over traditional fluorescent screens is that it is formed from a single crystal, and therefore has improved spatial resolution. The current system is limited to a resolution of about 10 microns. Improvements in the optical transport will enable measurements of RMS beam sizes of less than 1 micron. The total cost of the system is modest.
Date: December 31, 1997
Creator: Graves, W.S.; Johnson, E.D. & O`Shea, P.G.
Partner: UNT Libraries Government Documents Department

The choice: Welding with CO{sub 2} or Nd:YAG lasers

Description: The recent commercial availability of multi-kilowatt Nd:YAG lasers has opened new avenues for rapid laser processing as well as intensified the competition (cost effectiveness) between CO{sub 2} and Nd:YAG laser systems. Vendors offering Nd:YAG laser systems may claim lower operating costs (than CO{sub 2}) and fiberoptic beam delivery flexibility while CO{sub 2} systems vendors may emphasize lower capital cost and well established processing requirements and experience. The capital and operating costs of a laser system are impacted by demand and supply economics and technological advances. Frequently the total cost of a workcell using a laser for processing has to be considered rather than the laser system alone. Consequently it is not very practical to approach the selection of a laser system based on its capital cost and estimated operating cost only. This presentation describes a more pragmatic approach to aid the user in the selection of the optimal multi-kilowatt laser system for a particular processing requirement with emphasis on welding. CO{sub 2} laser systems are well established on the factory floor. Consequently, emphasis is given to the comparative application of Nd:YAG lasers, process requirements and performance. Requirements for the laser welding of different metals are examined in the context of hardware (laser system and beam delivery) selection and examples of welding speeds that can be achieved using CO{sub 2} and Nd:YAG lasers are examined.
Date: May 1, 1995
Creator: Leong, K.H.
Partner: UNT Libraries Government Documents Department

Dual-rod Yb: YAG laser for high-power and high-brightness applications

Description: The authors describe a diode-pumped Yb:YAG laser producing 1,080 W cw with 27.5% optical-optical efficiency and 532 W Q-switched with M{sup 2} = 2.2 and 17% optical-optical efficiency. The laser uses two composite Yb:YAG rods separated by a 90 degree quartz rotator for bifocusing compensation. A microlensed diode array end-pumps each rod using a hollow lens duct for pump delivery. By changing resonator parameters, they can adjust the fundamental mode size and the output beam quality. Using a flattened gaussian intensity profile to calculate the mode fill efficiency and clipping losses, the authors compare experimental data to modeled output power vs beam quality.
Date: March 13, 2000
Creator: Honea, E C; Beach, R; Mitchell, S C; Skidmore, J A; Emanuel, M A; Sutton, S B et al.
Partner: UNT Libraries Government Documents Department

Garnet phosphors prepared via hydrothermal synthesis

Description: This project studied hydrothermal synthesis as a route to producing green-emitting cathodoluminescent phosphorus isostructural with yttrium aluminum garnet (Y{sub 3}Al{sub 5}O{sub 12}, or YAG). Aqueous precipitation of Y, Gd, Al, Ga, and Tb salts produced amorphous gels, which were heated with water at 600 C and 3,200 bar to produce crystalline YAG:Tb, Y{sub 3}Ga{sub 5}O{sub 12}:Tb, Y{sub 3}Al{sub 3}Ga{sub 2}O{sub 12}:Tb, and Gd{sub 3}Ga{sub 5}O{sub 12}:Tb powders. Process parameters were identified that yielded submicron YAG:Tb and Y{sub 3}Ga{sub 5}O{sub 12}:Tb powders without grinding. Cathodoluminescent efficiencies were measured as functions of power density at 600 V, using both the hydrothermal garnets and identical phosphor compositions synthesized at high temperatures. Saturation behavior was independent of synthetic technique, however, the hydrothermal phosphorus were less susceptible to damage (irreversible efficiency loss) at very high power densities (up to 0.1 W/cm{sup 2}). The fine grain sizes available with hydrothermal synthesis make it an attractive method for preparing garnet phosphorus for field emission, projection, and head-up displays.
Date: May 1, 1996
Creator: Phillips, M.L.F.; Walko, R.J. & Shea, L.E.
Partner: UNT Libraries Government Documents Department

Fabrication of High Current YBa<sub>2</sub>Cu<sub>3</sub>O(sub>7-y</sub>) Coated Conductors Using Rolling-Assisted Biaxially Textured Substrates

Description: High critical current YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-y</sub> (referred to as YBCO) coated conductors were fabricated with a layer sequence of YBCO/YSZ/CeO<sub>2</sub>/Ni. The cube (100) texture in the starting Ni substrates was obtained by cold rolling followed by recrystallization. A thin CeO<sub>2</sub> (Cerium Oxide) layer with a thickness of 100-200 Å was grown epitaxially on the biaxially textured-Ni substrates using an e-beam evaporation technique. This was followed by the growth of a thick (<= 0.77 µm) YSZ (Yttria Stabilized Zirconia) layer using either e-beam evaporation or rf magnetron sputtering. The e-beam CeO<sub>2</sub> film had a dense microstructure. The microstructure of the e-beam YSZ film was porous whereas the sputtered YSZ film was dense. The YBCO films were grown by pulsed laser deposition on both e-beam and sputtered YSZ layers. A transport critical current density of ~ 1 x l0<sup>6</sup> A/cm<sup>2</sup> at 77 K was obtained for ~ 0.8 µm thick YBCO Rims on both YSZ surfaces in zero field. To demonstrate the quality and compatibility of the e-beam CeO<sub>2</sub> layers; YBCO films were also grown on CeO<sub>2</sub>-buffered YSZ (100) single crystal substrates using e-beam co-evaporated Y-BaF<sub>2</sub>-Cu precursors followed by a post-annealing process. A transport critical current density of over 1 x lO<sup>6</sup>A/cm<sup>2</sup> at 77 K was obtained on a ~ 0.3 µm thick YBCO film in zero field.
Date: June 1, 1999
Creator: Christen, D.K.; Feenstra, R.; Kroeger, D.M.; Lee, D.F.; List, F.A.; Martin, P.M. et al.
Partner: UNT Libraries Government Documents Department

Demonstration of High Current Density YBCO Coated Conductors on RE<sub>2</sub>O<sub>3</sub>-Buffered Ni Substrates with Two New Alternative Architectures

Description: In continuation of our effort to develop single buffer layer architectures for YBCO (YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-<font face="symbol">g</font>) coated tape conductors, we have studied RE<sub>2</sub>O<sub>3</sub> (RE = Y, and rare earths) as candidate materials. Three types of crystal structures including the preferred cubic phase are known for the rare earth oxides. High quality simple cubic RE<sub>2</sub>O<sub>3</sub> buffer layers were grown epitaxiahy on {100}<001> textured Ni substrates using both reactive evaporation and sol-gel processing. Detailed X-ray studies have shown that the Y<sub>2</sub>O<sub>3</sub>, Eu<sub>2</sub>O<sub>3</sub>, Gd<sub>2</sub>O<sub>3</sub>, and Yb<sub>2</sub>O<sub>3</sub> were grown with a single epitaxial orientation. SEM micrographs indicated that both e-beam and sol-gel grown films were dense, continuous and crack free. High J<sub>c</sub> YBCO films were grown on RE<sub>2</sub>O<sub>3</sub>-buffered Ni substrates with sputtered cap layers. Two new alternative buffer layer architectures were developed. A high J<sub>c</sub> of 1.8 MA/cm<sup>2</sup> at 77 K and self-field was obtained on YBCO films with a layer sequence of YBCO (pulsed laser deposition)/Yb<sub>2</sub>O<sub>3</sub> (sputtered)/Y<sub>2</sub>O<sub>3</sub> (e-beam)/Ni. Also, a high J<sub>c</sub> of over 1 MA/cm<sup>2</sup> at 77 K and self-field was obtained on YBCO films with a layer sequence of YBCO (ex-situ BaF<sub>2</sub> process)/CeO<sub>2</sub> (sputtered)YSZ sputtered)/RE<sub>2</sub>O<sub>3</sub> (sol-gel or e-beam)Ni. The performance of sol-gel grown buffers approached the quality of e-beam grown buffers.
Date: July 12, 1999
Creator: Beach, D. B.; Chirayil, T. G.; Christen, D. K.; Cui, X.; Feenstra, R.; Goyal, A. et al.
Partner: UNT Libraries Government Documents Department