Sintering of Pollucite Using Amorphous Powder and Its Low Thermal Expansion Property

Calcined powders were prepared for sintering of cubic Cs0.9Al0.9Si2.1O6 by calcining a mixture of Al2O3/SiO2 fine powder and CsNO3 powder at temperatures of 798 to 1123K for 20h in air. The amorphous phase produced in the case of a lower calcination temperature, while the crystallinity of the calcined powder increased with increasing calcination temperature. Densification of the Cs0.9Al0.9Si2.1O6 green body was significantly enhanced using the amorphous calcined powder. The relative density of the Cs0.9Al0.9Si2.1O6 sintered body reached 94.5% when the green body of the amorphous calcined powder, including a slight amount of CsNO3, was sintered at 1673K for 20h in air. The dense cubic Cs0.9Al0.9Si2.1O6 sintered body showed linear thermal expansion without hysteresis, resulting in a thermal expansion rate of ca. 0.13% at 1273K.