INVESTIGATION OF THEORETICAL AND PRACTICAL ASPECTS OF THE THERMAL EXPANSION OF CERAMIC MATERIALS. Report No. P1-1273-M-12

Several methods were used to predict the thermal expansion coefficients of pure, single-phase ceramics. The predictions were extended to cover 1700 pure phases. Based upon these calculations a number of phases, predicted to have low values of thermal expansion coefficient, were synthesized and the thermal expansion properties of these materials were measured. Several of these were found to be low-expansion materials. The thermal expansion properties of cubic UP/sub 2/O/sub 7/ are particularly interesting. This material expands with increasing temperature up to about 400 deg C. Above this temperature the crystal contracts, returning to its room temperature length at about 1000 deg C. These properties are believed to be unique. Variation of the thermal expansion anlsotropy by addition of solid solution atoms to several base crystals was attempted. Addition of vanadium to rutile (TiO/sub 2/) resulted in a significant decrease in thermal expansion anisotropy. Vanadium additions to cassiterite (SnO/ sub 2/) which has the same structure as rutile, also caused a significant decrease in thermal expansion anisotropy. (auth)