Superconducting YBa2Cu3O7−y (YBCO) films having a thickness of 1 μm were prepared on SrTiO3(100) and MgO(100) by the dipping-pyrolysis process using a low-p(O2) annealing method. Heat-treatment conditions were varied along the upper limit of the stability region of the YBCO phase. Films on SrTiO3(100) exhibited strong c-axis orientation with sharp rocking curves (FWHM = 0.8°). The highest Tc,zero of 87 K was obtained for the film heat-treated at 750 °C. On the other hand, films on MgO(100) showed broader rocking curves and their Tc's remained lower. Moreover, Ag addition was found to enhance the Tc values (Tc,zero = 91 K) of films on SrTiO3 heat-treated at 750 °C.

Using Bi-based oxide superconductors of the Bi0.96Pb0.24-xSbxSr1.0Ca 1.1 Cu1.6Oy composition which were prepared by the sol-gel method, production of the high-Tc phase and also microstructures of the high-Tc and the low-Tc phases were investigated using the XRD method and the TEM technique. Two superconducting phases showed good linearities of shrinkages of the a, b, and c lattice parameters as the Sb content increased, and so it has been found that Sb can be included in superconducting crystal structures. However, all shrinkages were below 1%. The activation energy of Sb diffusion was estimated from time dependence of changes of the lattice parameters using the Arrhenius plots. Its energy was from 510 to 593 Kj/mol.

The superconducting properties of YBa2Cu3O6+x reacted with various known ratios of O2/CO2 gas mixtures during sintering at different temperatures were studied. Jc was found to decrease drastically upon reaction with CO2, becoming zero at certain CO2 activities. The stability region for the 123 superconductor, as a function of CO2 activity and temperature, was empirically formulated as follows: log pCO2 < (−45,000)/T + 33.4. The grain boundaries in sintered samples with Jc = 0 were investigated with HRTEM in conjunction with EDS. Two distinct types of grain boundaries were observed. Approximately 10% of the grain boundaries were wet by a thin layer of a second phase, deduced to be BaCuO2. The remaining boundaries were sharp grain boundaries. The grain structure near the sharp grain boundaries was tetragonal. These two types of grain boundaries are thought to be responsible for Jc being zero.

We report on oriented and adherent cubic BN films grown on (001) faces of silicon using the method of ion-assisted pulsed laser deposition. The structure of the films is cubic zinc-blende with a lattice constant of 3.62 Å, as determined by infrared absorption and transmission electron microscopy. The films were found to be polycrystalline, and oriented with the cubic BN [110] axis parallel to the Si [001] direction.

Equations for the concentrations of vacancies and antisite defects in ordered alloys in thermodynamic equilibrium at and near stoichiometry have been derived as functions of defect energies and a Lagrangian parameter. While the resulting equations cannot be solved analytically and in general require iterative calculations, an approximation is given that permits simple numerical evaluation with just a minor loss of accuracy. Using defect energies obtained from an embedded-atom method calculation for Cu3Au, it is found that the adjustment for off-stoichiometric compositions is accounted for primarily by the creation of antisite defects rather than vacancies, and the vacancy concentration on Au sites is orders of magnitude less than that on Cu sites. There is a significant increase in the Au vacancy concentration but a slight decrease in the net vacancy content with increasing Cu fraction.

The Cu, In, and Se core-level electron binding energies of the p-type Cu–In–Se–N thin film were larger than those of the n-type Cu–In–Se thin film. The positive shift of the core-electron binding energies for the Cu–In–Se–N film is consistent with that expected from the conduction types of the films. Holes were positioned in the Cu–Se antibonding orbitals of the Cu–In–Se–N film. The analysis using the Auger parameter revealed that the Cu–Se bonding interaction is stronger for the Cu–In–Se–N film than for the Cu–In–Se film.

The effect of the melt-quenching step on the refinement of Y2BaCuO5 (211) particles, and phase transformations during crystallization in the MPMG (Melt-Powder-Melt-Growth) process were investigated. The quenched powders, which mainly consisted of Y2O3 and BaCu2O2, were transformed into the 211 and liquid phases by way of the YBa2Cu3Oy (123) phase. The transformation was examined on samples quenched from various temperatures. Through crystallographic examination using several kinds of precursors, it has been demonstrated that the addition of platinum, which is a contaminant from the crucible during the first partial melting step in the MPMG method, can refine the 211 particles.

YBa2Cu3O7−x–Ag and YBa2Cu3O7−x–SiO2 composite superconductors were prepared by the spray drying method. The composite powder was prepared by calcination of the precursor powder, which was synthesized by spray drying the oxalate slurries and dissolved components. Fine Ag, Ba2SiO4, and other phases were distributed in composite sintered bodies, with the added Ag or SiO2 showing enhanced magnetic properties.

Isotope diffusion and surface analysis has been used to investigate mass transport processes and oxide chemistry during oxidation of Ni3Al alloys in oxygen between 450 and 800 °C. In all cases, the oxide has an outer layer rich in NiO that grows by outward metal diffusion. Below 650 °C, an inner mixed oxide layer allows fast inward oxygen diffusion and growth. A porous inner layer of alumina forms at 700 °C that also allows oxide growth by oxygen in-diffusion. At 800 °C, the alumina becomes protective and halts the inner oxide growth mechanism. When macroalloyed with chromium, oxide chemistry is similar, but with an additional chromium oxide in the outer layer. There is an increased oxidation protection at temperatures ⋚600 °C that results from the inhibition of oxygen in-diffusion as an oxidation process. Above 700 °C, however, protective alumina formation is retarded and faster outward metal diffusion enhances the oxide growth rate when compared to Ni3Al.

Ternary Ni77Al23−yXy (X = Zr or Hf, y = 0.5 or 1) + 500 ppm boron compounds with various grain sizes were welded by a CO2 laser. Fractographic examinations of the heat-affected zone (HAZ) in the welds with or without postweld heat treatment (PWHT) were performed on the impact-fractured specimens. In laser welds, the fracture appearance of the HAZ was mixed transgranular/intergranular modes for fine-grained alloys and intergranular mode for coarse-grained materials. However, an entirely transgranular mode was observed in the base metal regardless of the grain size of the compounds. Boron desegregation at high temperatures during the thermal cycle of welding could be used to explain the fractographic change from originally ductile mode into less-ductile or even brittle fracture in the HAZ. Short-term PWHTs along with slow cooling provided sufficient time for boron segregation back to the grain boundary, resulting in a completely transgranular fracture mode in the fine-grained HAZ. Nevertheless, such a phenomenon was not observed in the HAZ of coarse-grained welds. Cracks in the HAZ of coarse-grained welds after long-term PWHT, if not so severe, could be healed by a sintering process.

Layered structures of DyBa2Cu3O7−x and Dy2O3 grown on (100) and (110) oriented SrTiO3 have been examined in cross section by transmission electron microscopy and energy dispersive spectroscopy to determine the feasibility of fabricating tunnel junctions with these materials. DyBa2Cu3O7−x and Dy2O3 exhibit a clear epitaxial relationship, resulting in heteroepitaxial growth of DyBa2Cu3O7−x on Dy2O3. The interfaces between DyBa2Cu3O7−x and Dy2O3 are structurally sharp, but interdiffusion between the chemical constituents occurs. Nevertheless, these results are a strong indication that high quality high-Tc superconductor tunneling junctions can be fabricated in this system.

The preferred orientation of a series of laser deposited superconducting thin films of YBa2Cu3O7−δ on LaAlO3 substrate has been examined. X-ray measurements (pole figures, χ-scans, ω-scans, rocking curves) reveal an increasingly strong preferred orientation of the polycrystalline material with c-axes perpendicular to the substrate surface as deposition temperature increases. At low temperatures c-axes are predominantly parallel to the substrate surface. Characteristic parameters of the texture types were derived from those measurements. With higher temperatures twinning on (110) was observed. The different texture types are interpreted in terms of a layered film structure.

Superconducting YBa2Cu3Ox films were prepared by rf plasma flash evaporation on MgO(100) single crystals. 4 MHz rf Ar–O2 plasma was used and Y–Ba–Cu–O (YBCO) powder as raw material was fed into the plasma. The growth rate of 730 nm/min was achieved. Texture of the grown films varied from a-axis orientation to c-axis with increasing growth temperature and decreasing growth rate. The films without heat treatment exhibited zero resistance temperature (Tc0) more than 77 K. The deposited films using the stoichiometric powder were slightly poor in Y. The sample using Y-rich powder revealed nearly stoichiometric composition and exhibited a Tc0 of 90.6 K and a critical current density (Jc) of 6.8 × 105 A/cm2 at 77 K in zero applied field.

We analyze the formation of VSi2 at the amorphous-vanadium-silicide/amorphous-Si interface by linear-heating and isothermal calorimetry, and cross-sectional transmission electron microscopy. We show evidence that indicates sporadic VSi2 nucleation with a steady-state nucleation rate after a transient period. The results are contrasted with those obtained for Al2Ni nucleating at the polycrystalline-Al/polycrystalline-Ni interface, where the kinetics appears to be controlled by growth of a fixed number of nuclei at quickly consumed preferred nucleation sites.

Phase compositions and microstructures of melt processed 2212 were studied. 2212 starting powder was cooled from temperatures between 910 °C and 1100 °C in air at rates ranging from 350 K/min to 0.083 K/min. The solidification sequence was established for all cooling rates. Under all conditions the Bi-free (Sr, Ca)CuO2 (01x1) is the primary phase. The one-layer solid solution 11905 nucleates on this phase. The residual liquid solidifies to a glassy state, decomposes into the eutectic of Cu2O and Bi2Sr2.1Ca0.9Ox, or reacts with the primary phase and the 11905 forming 2212 at high, intermediate, or low cooling rates, respectively. Post solidification heat treatment at 850 °C in air leads to partial remelting. The Cu-rich liquid reacts with 11905 and 01x1 forming 2212. Subsequent solid/solid reactions lead to a high volume fraction of 2212 with almost ideal 2 : 2 : 1 : 2 stoichiometry.

First time experimental evidence is presented for the steady state growth of dendrites away from their normal crystallographic growth directions. The evidence is shown for transparent dendrites in the succinonitrile system, which are induced to grow along wetting surfaces. A method for the quantitative characterization of the tips of such dendrites is described and the differences in the secondary arm formation between off-axis and regular dendrites are recorded. The scientific and technological implications of this finding are examined.

Preparation of Bi based high-Tc superconductors having Pb and Sb elements has been attempted using the sol-gel method. Production of the high-Tc phase was promoted by doping a little Sb (0.05 mol) together with Pb. The nominal composition of the system is Bi0.96Pb0.19Sb0.05Sr1.0Ca1.1Cu1.6Oy. It has been found that the reaction scheme of Sb doped samples is different from that of Sb nondoped samples.

The film crystallinity and nature of the interface between Y1Ba2Cu3O7−x (YBCO) films and (100)-oriented MgO substrates are revealed using results from x-ray line broadening analysis, x-ray pole figure analysis, and simple models for interface types. The superconductor film was grown using Activated Reactive Evaporation (ARE) at 675 °C. The results show that the interface can be treated as semicoherent with interfacial dislocations whose spacing depends on the in-plane orientation relationship between YBCO and MgO. For the orientation relationship (100) YBCO parallel to (100) MgO, the spacings between dislocations are 9 lattice spacings of MgO in the a direction and 11 lattice spacings of MgO in the b direction. For the orientation relationship (110) YBCO parallel to (100) MgO, the spacing between dislocations is 2 lattice spacings of MgO (or 4 plane spacings of (200) MgO—see Ref. 10). The x-ray based method used here can be an addition to or a replacement for the cumbersome cross-sectional TEM technique (for the YBCO system) to view the interface.

The unidirectional solidification of the zone melt method was performed in order to clarify the growth mechanism on Y-system superconductors. A sharp faceted interface of YBa2Cu3Oy (123) crystals was obtained in the sample grown at the low growth rate of 1 mm/h. The volume of the 211 phase changed drastically from liquid to 123 crystal. These results lead to the idea that the necessary solute for peritectic reaction is provided through a liquid. Based on this idea, we developed a simple solidification model that is in good agreement with the experimental results.

A series of iron-chromium-nickel alloys was melted under a nitrogen atmosphere at several different pressures. Nitrogen–high pressure melting (N–HPM) was conducted under pressures ranging from 0.1 to 200 MPa. The total nitrogen concentrations achieved in these alloys were proportional to the square root of the nitrogen pressure used during melting. Nitrogen took the form of soluble interstitial nitrogen and metal nitride precipitates, FexN and CrN. Tensile properties of N–HPM alloys were directly proportional to the nitrogen concentration in the alloy.