The superconducting phase Ba2YCu4O8 has been synthesized (as a bulk powder) in flowing oxygen. This was achieved by using the anionic oxidation/reduction method (or the SCD method), in which an aqueous solution containing oxidizing (NO−3 salts) and reducing components (e.g., acetate salts) is spray dried into an intimate mixture. At 300 °C, an internal exothermic oxidation/reduction reaction completely converts the spray-dried powder into the corresponding mixed oxides in one reaction step. Because the resultant mixed oxide powder is homogeneous on a fine scale, the final oxide phase can subsequently be produced at lower temperatures and shorter reaction times. Using this method, ∼93–94% phase pure Ba2YCu4O8 (as determined by x-ray diffraction) has been synthesized in flowing oxygen. Pellets of Ba2YCu4O4 fabricated from the mixed oxides were prepared and partially sintered by firing at 800 °C in flowing oxygen for 50 h. Resistivity and magnetic (AC) susceptibility measurements show onset Tc's of 82–84 and 72–73 K, respectively.

We report the results on x-ray diffraction and magnetic susceptibility study of Y–Ba–(Cu1−xScx)–O. The materials were prepared in a stoichiometry corresponding to Y1Ba2(Cu1−xScx)3O7. Although x-ray analysis reveals the increasing presence of a subtle second phase with increasing Sc content, the superconducting transition temperature and resistivity did not change substantially in the composition range 0.0  x ≤ 0.15. In contrast, the magnetic susceptibility studies showed dramatic changes. Although Sc3+ has no spin by itself, an enhanced paramagnetic Curie susceptibility was observed above Tc with a moment of 1.5 μB per Sc. At 16 K a sharp cusp is observed in the temperature dependent susceptibility corresponding to the onset of a three-dimensionally ordered antiferromagnetic state. These results are discussed in terms of an additional previously unreported phase of Y–Ba–(Cu–Sc)–O that has an antiferromagnetic Néel temperature of 16 K. For composition of x = 1.0, a new phase is formed which is nonmagnetic.

The annihilation of thermal donors in silicon by rapid thermal annealing (RTA) has been studied with deep-level transient spectroscopy. The electron trap AO (Ec – 0.13 eV) observed after heat treatment at 450 °C for 10 h, which is identified with the thermal donor, disappears by RTA at 800 °C for 10 s. However, four electron traps, A1 (Ec 0.18 eV), A2 (Ec – 0.25 eV), A3 (Ec – 0.36 eV), and A4 (Ec – 0.52 eV), with the concentration of ∼1012 cm−3 are produced after annihilation of thermal donors by RTA. These traps are also observed in silicon which receives only RTA at 800 °C. This indicates that traps A1–A4 are thermal stress induced or quenched-in defects by RTA, not secondary defects resulting from annealing of thermal donors.

A method for the complete removal of twins from single crystals of superconducting YBa2Cu3O7−x is described. The process depends on ferroelastic behavior found to exist in the phase, and should be generally applicable to the layered perovskite-type phases containing accommodation twins resulting from a tetragonal-to-orthorhombic transformation on cooling. The twin-free, superconducting single crystals will enable investigation of a–b anisotropy of properties as well as crystal structure determination without complication by the presence of microtwins.

Power compensated differential scanning calorimetry, transmission electron microscopy, and density measurements were used to characterize relaxation phenomena associated with structural transitions in electron beam evaporated amorphous silicon thin films. Two transitions were observed in the amorphous films upon heating: a broad exothermic process below 600 K and an endothermic step beginning at 600 K. The broad exothermic process is due to the relief of bond distortions. The endothermic step is related to homogenization and densification of the structure of the amorphous silicon.

The chemical interactions between the YBa2Cu3O7−x high Tc superconductor and various substrates (Si, Al2O3, ZrO2, SrTiO3, MgO, Ag, Cu, and Nb) were studied. Powders of the orthorhombic YBa2Cu3O7−x (123) phase and each of the various substrates were mixed, pressed into pellets, and subjected to either one of the following heat treatments in flowing oxygen: 600 °C for 11 h, 800 °C for 10 h, 945 °C for 5 h, and 945 °C for 17 h. The reacted samples were characterized by qualitative and quantitative x-ray diffraction, scanning electron microscopy with EDAX, electrical resistivity, and magnetic susceptibility measurements. For all substrates studied, the extent of reaction is much more significant at 945 °C than at 800 °C and 600 °C. The reaction products, in general, are some Ba compounds, CuO (and Cu2O), and the Y2BaCuO5 (211) phase. The reaction with Si results in a morphology of layers of 123/211/Ba2SiO4/CuO/Si. Reactions with Al2O3 and ZrO2 result in similar products and morphologies. Reaction with SrTiO3 results in the replacement of Ba by Sr and the formation of a Ba–Ti–Y–Cu unknown phase. With MgO, the chemical reaction results in the enrichment of MgO with Cu and the formation of an apparently glassy Ba–Cu phase. With the metallic substrates Ag, Cu, and Nb, Ag shows no interaction at all, Cu results in the formation of CuO (and Cu2O), whereas the Nb samples completely disintegrated. By comparing the percentage of remaining 123 phase in samples reacted at 945 ° for 17 h, a reactivity scale in decreasing order was obtained as Nb > Si > ZrO2  Al2O3 > SrTiO3 > MgO  Cu > Ag. It is suggested that the chemical reactivity of the Y–Ba–Cu oxide superconductor is mostly controlled by the highly electropositive Ba2+ ions.

The lower yield strengths of Ni3Al and mild steel and their respective relationships to (grain size)−0.8 and (grain size)−0.5 are explained in terms of work hardening within Lüders bands.

We investigated the stability of the CsCl-type compounds AlRu, SiRu, NiTi, and CuEr under heavy deformation by high-energy ball milling. As a result, nanocrystalline intermetallic compounds have been synthesized with a microstructure showing a mixture of highly strained crystallites (5–12 nm) with random orientation. Thermal analysis of the samples indicates stored deformation energies of 5–10 kJ/mole stored by incorporation of lattice defects, chemical disorder and grain boundaries, and an increase of the heat capacity of up to 13%. Chemical disordering of the crystal is monitored by means of the long-range order parameter. The observed decrease in chemical order can be explained by the high grain boundary density of nanocrystalline metals.

Liquid binary alloys Cs–Sb and Cs–As are able to intercalate into graphite, provided that their compositions are neither too rich nor too poor in cesium. Several phases, whose stage varies between 1 and 4 in the case of antimony, and between 1 and 3 in the case of arsenic, have been observed. These new ternary compounds have been characterized by x-ray measurements.

The structural energy differences between cubic LI2 and tetragonal DO22 crystal structures are calculated for MAl3 compounds, where M is a group III, IV, or V transition metal. The stability of the DO22 structure relative to L12 increases rapidly as the transition-metal d-electron count increases. Typical values of E(DO22) – E(L12) are 0.1–0.15 eV/atom (9600–14500 J/g-atom) for group III,  0.05 eV/atom ( 4800 J/g-atom) for group IV, and ∼ –0.2 eV/atom (∼ –19000 J/g-atom) for group V trialuminides. Similar trends are calculated for the DO23/L12 energy difference. The calculated electronic densities of states (DOS) show that each structure has a minimum in the DOS distribution at a characteristic d-electron count. The preferred crystal structure for a given compound is the one in which the Fermi level lies in the minimum.

The effect of heating YBa2Cu3Ox in vacuum to 600 °C has been studied using photoelectron spectroscopy and diamagnetic susceptibility measurements. Evidence of two chemically distinct copper and barium species is found in single phase samples at room temperature cleaned by gentle heating at 450 °C. Such annealing also increases the volume diamagnetic susceptibility of the samples which suggests that the preferred stoichiometry of growth does not lead to an optimum superconducting phase. Samples cleaned by vacuum scraping or ion bombardment reveal more amorphous XPS structure and are less indicative of bulk properties.

We present the results of an electron microscopy study of Pb-substitution in bulk Bi–Sr–Ca–Cu–O superconductors. We observe grains with c-axis lattice parameters of 30.8 Å (2212 phase), 36.7 Å (2223 phase), and 43.2 Å (2234 phase) containing no intergrowth defects. The existence of two separate incommensurate superstructures, Q1 and Q2, which were previously observed in Pb-doped ceramics and single crystals, has been confirmed in this study. It is found that superlattice reflections from the Q2,-modulated structure in the 2223 phase are much weaker than those from the Q2-modulation, whereas the diffraction intensities of the Q1- and Q2-modulations in the 2212 phase are similar. We also show that the periodicity along the b-axis of the Q2-modulation increases with increasing Pb-substitution, contrary to the implications of a previously suggested structural model.

Fourier transform infrared (FTIR) absorption spectra were measured for various glasses in the Bi–Zn–Fe–B–O system, and interpreted upon the basis of glass structure. Spectral changes were noted with variations in the composition for these glasses that were related to changes in the atomic arrangement of the boron oxide portion of the glass network. The changes in glass transformation temperature with changes in glass composition were discussed in terms of structural data.

We have used transmission electron microscopy and optical microscopy to examine the effect that grain size and heat treatment have on twinning and microcracking in polycrystalline Y1Ba2Cu3O7−δ. It is shown that isothermal oxygenation heat treatments produce twin structures consisting of parallel twins, with a characteristic spacing that increases with increasing grain size. Slow cooling through the temperature range where the orthorhombic-to-tetragonal transformation induces twinning, however, produces a structure consisting of a hierarchical arrangement of intersecting twins, the scale of which appears to be independent of grain size. It is also shown that the microcracking induced by anisotropic changes in grain dimensions on cooling or during oxygenation can be suppressed if the grain size of the material is kept below about 1 μm. The results are examined in the light of current models for transformation twinning and microcracking and the models used to access the effect other processing variables such as oxygen content, doping or heat treatment may have on the microstructure of Y1Ba2Cu3O7−δ.

In the processing of the high temperature superconductors RE1Ba2Cu3O7−x a knowledge of the liquidus temperatures is required in order to avoid liquid formation during the initial reactions of the starting materials. We have investigated the invariant points on the liquidus surface of the RE–Ba–Cu–O systems for RE = Y, Er, Gd, and Nd in oxygen, air, and argon, While the temperatures of the low melting reactions are almost independent of the rare earth species, they are heavily dependent on oxygen partial pressure. In addition, the peritectic decomposition temperature of the REBa2Cu3O7 phase was found to be a function of rare earth with a significantly higher value for the Nd compound than for the other rare earths.

Thin films of Y–Ba–Cu–O and Yb–Ba–Cu–O, 0.5–1.5 μm in thickness, were deposited onto (211) and (100) SrTiO3 single crystal substrates by metalorganic deposition (MOD). After deposition the samples were annealed either by conventional furnace annealing or rapid thermal annealing (RTA). The microstructures of these films were then characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive x-ray spectrometry (EDS). Grain size of the annealed films varied from 0.25 to 1.0 μm. Improved superconducting properties were found for the RTA samples, compared to furnace annealing, and were attributed to larger grain size, little strontium diffusion into the thin films from the substrate, and highly preferred orientation of the 1:2:3 phase.

Percolation networks were observed in an immiscible Ag–Co alloy system after the Ag30Co70 alloy films were irradiated to a dose of 1 × 1016 Xe+/cm2 with 200 Kev Xe+ at room temperature. Fractal dimension D as well as percolation threshold Pc were calculated and exhibited good agreement with the results of the percolation theory. The mechanism of the formation of the ion-induced percolation structures is also discussed.

The electrical conductivity and thermopower of the cuprate, Y1Ba2Cu3Ox, have been measured as functions of temperature and oxygen partial pressure over the ranges of 400 °C–700 °C and 10−4 atm—1 atm, respectively. It has been confirmed that, as temperature increases, conduction mechanism changes from metallic to p-type to n-type semiconducting. It has been found that the p-n transition occurs at a specific value for oxygen content (x = 6.35) irrespective of temperature and that the thermopower in the p-type region is insensitive to temperature. The latter leads to a charge transfer mechanism of correlated hopping of holes. Mechanisms of hole generation due to oxygen nonstoichiometry are found to be different in the tetragonal and the orthorhombic phase of the cuprate.

The epitactic nature of the growth of YBa2Cu3O6+x (YBCO) superconducting thin films on ceramic substrates has been studied using high-resolution electron microscopy (HREM) and selected-area diffraction (SAD) of cross-sectional specimens. The films were grown in situ on (001)-oriented MgO and (001)-oriented Y2O3-stabilized cubic ZrO2 (YSZ) single-crystal substrates by electron beam evaporation. Both of these materials have large lattice misfits with respect to YBCO. Different orientation relationships were observed for films grown on the two types of substrates. These orientation relationships are shown to provide the best matching of the oxygen sublattices across the substrate-film interfaces. A crystalline intermediate layer, 6 nm thick, between the YBCO film and YSZ substrate was observed by HREM and shown by EDS to be a Ba-enriched phase, possibly barium zirconate formed by a reaction. In contrast, the YBCO–MgO interface was found to be sharp and free of any intermediate layers.

This paper compares the properties of yttrium barium cuprate bulk specimens prepared by means of solid-state sintering on one hand and of growth from a largely molten state on the other. The current paper focuses on magnetization measurements at 77 K which show specimens made by the latter method to have high remanence magnetization values.