Microstructural refinement of the YBa2Cu3O7−x/Ag superconductor composite has resulted in a fracture toughness of 3.6 MPa √ms, as measured by single edge notch beam fracture specimens. This represents the highest bulk fracture toughness value published to date for silver compositions near 20%. A combination of grain size and porosity refinement, in addition to control of silver morphology and distribution, permits the development of fracture toughness levels that compare favorably with many structural ceramics such as SiC and Al2O3.

We measured the elastic constants of polycrystalline Y1Ba2Cu3Ox with eleven oxygen contents varying from 6.2 to 6.9. Reported properties include sound velocities; bulk, shear, Young's moduli; Poisson ratio; Debye temperature. After correction to the void-free state, the measurements fail to show a systematic dependence on oxygen content. Focusing on the bulk modulus, all measurements fall below an ionic-crystal model prediction, by 5–50%. We attribute this macroscopic softness to either microcracks or weak grain-boundary mechanical linkages. For the case x = 6.9, we suggest a set of intrinsic elastic constants.

Regrowth of ion-damaged YBa2Cu3O7−δ thin films on LaAlO3 was studied using the ion beam channeling technique. The damaged films can be regrown at a temperature as low as 650 °C, and are stable up to 1000 °C. The regrowth process was found to be thermally activated with a single activation energy of 0.46 eV, contrary to two energies found in a previous study on the films on MgO [J. A. Martinez et al., Appl. Phys. Lett. 57, 189 (1990)].

We have fabricated Ni3Al and NiAl thin films on different substrates by the pulsed laser deposition (PLD) technique. A high energy nanosecond laser beam was directed onto Ni–Al (NiAl, Ni3Al) targets, and the evaporated material was deposited onto substrates placed parallel to the target. The substrate temperature was varied between 300 and 400 °C, and the substrate-target distance was maintained at approximately 5 cm. The films were analyzed using scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and Rutherford backscattering spectrometry. At energy densities slightly above the evaporation threshold, a slight enrichment of Al was observed, while at higher energy densities the film stoichiometry was close (<5%) to the target composition. Barring a few particles, the surface of the films exhibited a smooth morphology. X-ray and TEM results corroborated the formation of Ni3Al and NiAl films from similar target compositions. These films were characterized by small randomly oriented grains with grain size varying between 200 and 400 Å.

A three-step process to produce wear-resistant, composite diamond coatings is presented. Diamonds are deposited by RF thermal plasma CVD, reinforced by an electroplated metal binder, and regrown to form a continuous film. Microscratching and pin-on-disk wear tests indicate that the three-step composite films are more adherent than plasma deposited diamonds alone.

We have performed x-ray diffraction experiments on MBE grown 〈111〉 and 〈001〉 oriented Co (3 Å)/Pt (18 Å) superlattices with the scattering vector Q covering a plane that includes a major component perpendicular and a minor component parallel to the plane of the sample. The superlattice diffraction peaks were found to have a large width parallel to the plane of the film, indicating that there is strong in-plane disorder. These broad peaks were integrated to evaluate more accurately the amount of interdiffusion at the interface, which was found to be similar in both films, contrary to what the conventional x-ray diffraction experiment suggests.

Interdiffusion coefficients (D) were determined in the temperature range 1373 K–1073 K (0.85 Tm−0.65 Tm) from concentration-distance profiles that were generated from Al66Ti25Mn9/Al67Ti25Cr8 diffusion couples. As both of these materials are completely soluble in one another, the couples were treated as pseudobinaries (particularly because the Ti and Al levels were similar), and the Matano approach was used to calculate diffusion coefficients. The variation in D with composition was determined and a minimum was noted at intermediate temperatures and a relative Mn concentration of 0.5. A maximum in activation energy for interdiffusion was also noted at this concentration where Q ≍ 350 kJ/mol.

Recent work by the authors has been extended to demonstrate the formation of solid krypton in single-crystal magnesium oxide. The solid inclusions, which were formed by ion implantation at room temperature, have been identified by electron diffraction. The formation of solid noble gas inclusions at room temperature indicates that they were under a high pressure. This pressure was determined, based on the measured lattice parameter, to be 1.7 GPa.

Laser reflection interferometry (LRI) has been shown to be a useful in situ technique for measuring growth rate of diamond during microwave plasma chemical vapor deposition (MPCVD). Current alternatives to LRI usually involve ex situ analysis such as cross-sectional SEM or profilometry. The ability to measure the growth rate in ‘real-time’ has allowed the variation of processing parameters during a single deposition and thus the extraction of much more information in a fraction of the time. In situ monitoring of growth processes also makes it possible to perform closed loop process control with better reproducibility and quality control. Unfortunately, LRI requires a relatively smooth surface to avoid surface scattering and the commensurate drop in reflected intensity. This problem was remedied by greatly enhancing the diamond particle nucleation via the deposition of an intermediate carbon layer using substrate biasing. When an unscratched silicon wafer is pretreated by biasing negatively relative to ground while in a methane-hydrogen plasma, nucleation densities much higher than those achieved on scratched silicon wafers are obtained. The enhanced nucleation allows a complete film composed of small grains to form in a relatively short time, resulting in a much smoother surface than is obtained from a film grown at lower nucleation densities.

Whiskers of 2212 phase Bi2Sr2Ca1Cu2Ox were prepared by heating in air the powder-compacted pellets of melt-quenched glassy products in BiSrCaCu2Ox containing a small amount of Al2O3. The dissolved and/or physically mixed Al2O3 in the powder-compacted specimen is found to enhance the whisker formation remarkably.

Thin films of the 80 K-phase of BiCaSrCu-oxide superconductor having the composition of Bi2Ca1.05Sr2.1Cu2.19Ox and high degree of crystalline perfection have been grown on c-axis oriented twin free single crystal substrates of NdGaO3. This has been achieved by carefully establishing the growth conditions of the liquid phase epitaxy (LPE) experiments. The temperature regime of 850 °C to 830 °C and quenching of the specimens on the termination of the growth period are found to be pertinent for the growth of quasi-single crystalline superconducting BCSCO films on NdGaO3 substrates. The TEM analysis reveals a single crystalline nature of these films which exhibit 100% reflectivity in infrared regions at liquid nitrogen temperature.

Slow crack growth in CVD diamond has been observed from indentation experiments. Diamond films of 400 μm thickness were prepared by plasma-enhanced CVD on a silicon substrate, subsequently removed from the substrate, and polished for indentation testing. A microhardness tester was used to produce Vickers indentations under low load. Crack length measurements over time revealed susceptibility to slow crack growth in ambient testing conditions. The stress-corrosion susceptibility coefficient, N, was measured as 9.3.

Tracer self-diffusion of Ba and Y and the diffusion of Dy, Ho, and Gd, which substitute for Y, have been measured in polycrystalline YBa2Cu3Ox over temperature and oxygen partial pressure ranges of 850 to 980 °C and 103 to 105 Pa, respectively. The diffusion of Ba is slower than that of oxygen or copper, with a high activation energy of about 890 ± 80 kJ/mole. Large anisotropy has also been observed, with diffusion along the c-axis being more than three orders of magnitude slower than diffusion in randomly oriented polycrystals. Diffusion coefficients of Ba were, within experimental uncertainty, independent of oxygen partial pressure over the range measured. The diffusion coefficients of the Y-site species were nearly identical and an activation energy of about 1.0 MJ/mole was estimated, in agreement with that for high-temperature deformation. Attempts to speed up the kinetics through creation of point defects on the Y site by doping proved to be unsuccessful. These results are compared to cation diffusion in cubic perovskites and simple oxides.

A modified aerosol decomposition method was developed for producing sintered YBa2Cu3O7−δ (1-2-3) pellets having sharp superconducting transition Tc's at ∼90 K, fine grain sizes, and clean grain boundaries. This method used “precursor” powders, which were produced with an aerosol flow reactor at 550 °C, instead of in situ produced 1-2-3 powders commonly processed at 880–1000 °C. As determined by x-ray absorption and powder diffraction studies, the 1-2-3 powders produced by the modified route contain less cation disorders than the in situ produced powders. The disorder is speculated to be the cause of Tc-suppression and broadening. It cannot be removed unless high sintering temperatures were used (>950 °C), which resulted in large grains and impurities and cracks at grain boundaries.

27Al- and 63Cu-NMR measurements have been made on quasicrystalline phases of the Al65Cu20TM15 alloy (TM:Fe, Ru, and Os). There is no temperature dependence on peak shift and line width of either 27Al- or 63Cu-NMR spectra, suggesting that all the quasicrystalline phases are Pauli-paramagnetic. However, the peak shift of both spectra depends upon the constituent transition element in a different way: Al-peak shift increases from Fe through Os while the Cu-peak shift decreases.

For all tetrahedrally bonded semiconductors (five group IV plus nine III-V compounds and nine II-VI compounds), it is shown that the critical pressure needed to transform the semiconductor into the metallic state correlates with the microindentation hardness number. The same is done for five alkaline earth oxides. The critical transition pressures have been estimated from Herzfeld's theory—that is, from the compression at which the dielectric constant diverges to infinity. Experimental transition pressures also correlate with hardness numbers, and they correlate with the activation energies for dislocation motion. Since these transitions are electronic they can be influenced by photons, doping (donors enhance while acceptors inhibit them), currents, surface states, etc. Microindentation also provides a simple experimental tool for observing pressure and/or shear induced transformations.

Diamond-like carbon with silicon (DLC-Si) coatings formed by plasma-assisted chemical vapor deposition showed low friction coefficients of the order of 0.01 against steel without a lubricant, not only in dry atmosphere but also in humid atmosphere, where conventional DLC coatings showed higher friction coefficients of 0.1–0.2. DLC-Si coatings with 1 μm thickness deposited on steel were slid against steel using a conventional ball-on-disk type of apparatus to compare with a low friction mechanism of DLC-Si in dry and humid atmospheres. Analyses of wear scars indicated that formation and/or transfer of graphite-like carbon including hydrogen that originated in a DLC-Si coating occurred in dry atmosphere, while oxidation of contained silicon with water vapor formed silica-sol by sliding in humid atmosphere. The latter, peculiar to DLC-Si, was considered to cause the low friction coefficient in humid atmosphere through adsorbed water on silica.

Hot- and cold-wall chemical vapor deposition (CVD) using the volatile copper(I) compound (hfac)Cu(1,5-COD), where hfac = 1,1,1,5,5,5,-hexafluoroacetylacetonate and 1,5-COD = 1,5-cyclooctadiene, as a precursor was carried out in hot-wall and warm-wall, lamp-heated reactors using SiO2 substrates that had been patterned with Pt or W, over a temperature range 120 °C-250 °C. Deposition was observed onto Pt, W, and SiO2 over this temperature range at rates of up to 3750 Å/min to give copper films that contained no detectable impurities by Auger electron spectroscopy and gave resistivities of 1.9-5.7 μ ohm cm. The volatile by-products formed during deposition were 1,5-COD and Cu(hfac)2 and a mass balance was consistent with the quantitative disproportionation reaction: 2(hfac)Cu(1,5-COD) → Cu + Cu(hfac)2 + 2(1,5-COD). The measured activation energy for this CVD reaction was 26(2) kcal/mol. The absence of selectivity for metal surfaces in the presence of SiO2 is in contrast to CVD results for the related compounds (β-diketonate)Cu(PMe3) where β-diketonate = hfac, 1,1,1-trifluoroacetylacetonate (tfac), and acetylacetonate (acac).

Compositional dependence of the stress + longitudinal field induced magnetic anisotropy (SLFA) in (Co1−xFex)75Si15B10 (0 ⋚ x ⋚ 1), (Co1−xNix)75Si15B10 (x = 0.22) and [Co1−x(Fe0.5Ni0.5)x]75Si15B10 (x = 0.20, 0.50, and 0.80) amorphous alloy ribbons has been studied. The magnetic field was applied parallel to the ribbon axis. Two mechanisms have been invoked in order to explain the microscopic origin of this anisotropy: the directional ordering of atomic pairs, and the tetrahedral holes like 3Co–1Fe and 1Co–3Fe. The last contribution is found to be similar both in its direction and its value with respect to that obtained for stress + transverse field induced anisotropy (STFA) in the same compositions containing Fe, while in the Co–Ni samples only the first contribution is responsible for the SLFA, depending on its direction for the field annealing.

Phase pure YBa2Cu3O7 high transition temperature superconductor powders were synthesized by a new precursor route. This new synthesis procedure is easy, leads to an atomic mixture of the relevant constituents, and is readily adaptable to many other systems or to the doping of existing systems. A gel of yttrium, barium, and copper salts was prepared using organic gelling agents. The gel was then dried and ground, leaving the xerogel precursor. These xerogels are perfectly stable even under high humidity atmospheric conditions and show an amorphous structure when characterized by x-ray diffraction, which is consistent with the existence of an atomic mixture of the three relevant metal salts. The organic gelling agent was selected after optimization studies focused on such issues as ash residue after calcination, solubility, and chemical interference with the metal salts. From a great variety of these gelling agents (agar, xanthan gum, gelatin, alginates, and others), gelatin was chosen as the ideal gelling agent for this specific application. The final product characterization shows very unexpected results. The crystalline phase purity of the YBa2Cu3O7 superconducting phase was about 99%, with no traces of barium carbonate, as expected from pseudo-organic precursors (xerogels). The product shows superconducting properties even before oxygen anneal (Tc ≍ 70 K), and after oxygen annealing of the powders the transition temperature was found to be 91 K, showing a linear behavior of the resistivity versus temperature before the drop at Tc, extrapolating to zero at 0 K. The particle size of these powders is smaller than 1 μm, as shown by SEM.