X‐ray diffraction analyses of polycrystalline samples of Ca3TeO6 and Ca3WO6 have shown these compounds to be isostructural with Ca3UO6 (space group P21).

The effect of surface oxygen concentration of silicon nitride powders on the properties of resulting ceramics was studied. A high-purity silicon nitride powder was treated physically and chemically to modify its surface oxygen content. The resulting powders were hot-pressed into dense ceramics using 6 wt% yttria as a sintering aid. 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 show that the phases developed in yttria-containing silicon nitride ceramics vary with slight changes in the initial powder oxygen content, as predicted, and that strength can be correlated to initial oxygen concentration. The mechanical strength vs oxygen content curve has a definite maximum; i.e., there is a small oxygen concentration range at which optimum ceramic strength is realized. Best results are obtained when the oxygen content is increased by thermal oxidation; other techniques such as chemical oxidation or addition of silica are not as effective, particularly in attaining high strength at elevated temperatures.

Experiments aimed at improving the physical properties of transparent polycrystalline lanthanastrengthened yttria (LSY) infrared windows and domes were conducted. The objective was to enhance the thermal shock resistance for aggressive aerothermal environments. The approach included improving the average equibiaxial flexure strength, Weibull modulus, and other relevant physical properties. Initial results of an extensive study on polishing and post-fabrication treatment along with improved powder processing showed an -30% strength improvement without sacrifice in optical properties, leading to an appreciable increase in the calculated survivability. LSY with a low lanthana content significantly enhanced predicted survivability.

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The emission characteristics of phosphors based on alkaline earth tellurates as host lattice are described. The fluorescence of hexavalent uranium in compounds of the formula MnTeO3+n normalwith n=2 normalor 3 , was studied. The spectral energy distribution of the fluorescence is affected by the cationic species and crystal structure of the compound. Two of the more interesting phosphors are Ca3TeO6:U6+ and Ba2TeO5:U6+ which emit in the blue‐green and orange region of the spectrum, respectively. The effect of structural variations on the nature of the emission center in uranium‐activated phosphors is discussed.