The cathodoluminescence from Eu3+ and Tb3+ in the orthoborates of In, Sc, Y, La, Gd, and Lu is examined. The host InBO3 is shown to be particularly effective for both activators. Observed spectral details of the luminescence are related to effects of crystal symmetry on electronic transitions.

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Preparation and properties are described for ZnO varistors which clamp at sufficiently low voltages (≊10 V) for overvoltage protection of integrated circuits. The desired electrical characteristics have been obtained by microstructure control using alumina as a ZnO grain growth enhancer. Pulse degradation studies on these low voltage varistor compositions suggest that degradation occurs by premature failure of weak depletion layers and excessive current concentration at microstructural flaws. Capacitance–voltage measurements can be employed to detect these artifacts and predict the possibility of varistor failure during high current surges. A nondestructive scheme for varistor evaluation is outlined which utilizes the rate of change of capacitance and dissipation factor with dc bias voltage both above and below the varistor breakdown voltage.

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The effect of oxygen content of silicon nitride powders on the properties of resulting ceramics was studied by physically and chemically treating the powder to modify its surface oxygen content. These powders were compounded with yttria and hot-pressed into dense ceramics. Strength and oxidation resistance of these ceramics were measured and correlated with the powder and ceramic compositions as well as the resulting intergranular phases. Results showed that the phases varied with slight differences in the initial powder oxygen content as predicted, and that strength could be correlated to initial oxygen concentration. Best results were obtained when the oxygen content was increased by thermal oxidation. A Taguchi Methods experimental study designed to optimize the thermal treatment resulted in silicon nitride ceramics with strength improvements of 22 and 37% at ambient temperature and 1370°C, respectively. Oxidation resistance was also improved.