Influence of Cesium Nitrate and Heating Rate on Densification and Microstructure of Cs‐Deficient Pollucite Sintered Body

Abstract

Cs‐deficient pollucite, Cs0.9Al0.9Si2.1O6, a sintered body with a low thermal expansion coefficient of 1.26 × 10−6 K−1 in the temperature range of 298 to 1273 K, has been fabricated using calcined powders with an amorphous phase. The calcined powder was prepared by heating mixtures of CsNO3, γ‐Al2O3, and amorphous SiO2 powders at 798 K in air for 20 h, repeated 10 times. The repetition of the heat treatment at 798 K was performed to decompose CsNO3 thoroughly in the mixed raw powders and to obtain calcined powders with a high specific surface area. The relative density of the sintered bodies fabricated from the green compact of the amorphous calcined powder increased with increasing sintering temperature and heating rate. The sintered body with a relative density of ca. 96%, of a well‐crystallized pollucite single phase and with the grain size in the range of 0.75–4.75 μm, was fabricated by heating the green compact of the amorphous powders at 1673 K in air for 20 h at a heating rate of 20 K/min.