The purpose of this study was to (1) examine the spatial (within-sample) uniformity of superconducting behavior and microstructure in YBa2Cu3O7−x specimens over the pore fraction range 0.10–0.25 and (2) determine the viability of using a room-temperature, nondestructive characterization method (ultrasonic velocity imaging) to predict spatial variability. Spatial variations in a.c. susceptibility were observed for specimens containing 0.10 pore fraction. An ultrasonic velocity image constructed from measurements at 1 mm increments across one such specimen revealed microstructural variation between edge and center locations that correlated with variations in a.c. shielding and loss behavior. Optical quantitative image analysis on sample cross sections revealed pore fraction to be the varying microstructural feature.

Diamond pin-on-disk wear of composites of Al2O3 with ZrO2, TiB2, or TiC particles or SiC as particles or whiskers is reported along with such measurements of AIN, Si3N4, TiB2, TiC, and a SiAlON-BN composite at 0.5, 1.0, and 1.5 kg loads. AIN and TiB2 were measured at two or more grain sizes showing wear resistance decreasing with increasing grain size when considered over a substantial grain size range (TiB2). Comparison shows that some dense, fine grained composites can have wear resistance equal to or substantially greater than the most wear resistant constituent alone. Observation of wear mode indicates that plastic deformation generally dominates in fine grain bodies whether they are composites or essentially single phase bodies, with fracturing generally becoming more frequent as grain size increases. However, AIN and Si3N4 were exceptions to this, showing predominantly plastic deformation over the full range of grain sizes considered (6–16 m̈m) which appears to correlate with their surprisingly high wear resistance for their moderate hardness.

Ultrasonic velocity measurement techniques were used to evaluate the effects of oxidation and reduction on the elastic properties, global microstructure and oxygen content of the YBa2Cu3O(7-x) ceramic superconductor for samples ranging from 70 to 90 pct. of theoretical density. Bulk density, velocity, and elastic modulus generally increased with increasing oxygen content upon oxidation, and this behavior was reversible. Velocity image patterns were similar after oxidation and reduction treatments for a 90 pct. dense sample, although the velocity value at any given point on the sample was changed following the treatments. The unchanging pattern correlated with destructive measurements showing that the spatial pore distribution (fraction and size) was not measurably altered after the treatments. Changes in superconducting behavior, crystal structure, and grain structure were observed consistent with changes in oxygen content.

Characteristics such as CTE close to that of silicon, high thermal conductivity, and good dielectric properties make aluminum nitride (A1N) an excellent dielectric for packaging silicon-based high density multichip interconnects. However, there remains many aspects of its behavior that have not been characterized. One such example is the behavior of the various metallizations used within a package. As with Al2O3, these metallizations must contribute toward a hermetic seal separating the die from the environment. However, the chemical behavior of the metallization systems used for Al2O3 may not be compatible with non-oxide ceramics such as A1N. Consequently, these chemical interactions are investigated in view of the requirements for each application within electronic packages. Hermeticity testing results are also included in the discussion.

Excess CuO, BaCuO2, and Y2BaCuO5 (2-1-1) were each separately incorporated into YBa2Cu3O7 (1-2-3) samples, in order to test the sensitivity of powder X-ray diffraction to these common impurity phases. The additions were made by two methods: 1.(1) physical blending, by mixing a phase-pure impurity with phase-pure 1-2-3, and2.(2) chemical addition, by adding the impurities as individual metal nitrates to a stoichiometric YBa2Cu3 nitrate solution, followed by precipitation and calcination. While chemically and physically incorporated CuO display similar X-ray detectabilities, low (2 wt.%) concentrations of chemically added BaCuO2 and 2-1-1 are far harder to detect than their physically blended counterparts. It was also found that nearly 10 at.% of yttrium in excess of stoichiometry (i.e. “1.1-2-3”) can be chemically incorporated before 2-1-1 X-ray peaks are observed.

A systematic study of the relationship between particle dimensions and microwave absorption in micron size powders of superconducting Y1Ba2Cu3O7 reveals that small particles have negligible absorption at T<0.8Tc, and that the transition gets sharper as the grains get bigger. However, when the particles get so large as to incorporate multiple grains, the transition broadens and there is significant absorption down to 0.7 Tc. The temperature dependence in the small (≤10 μm) powders is satisfactorily described by a simple extension of London's theory.