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

Abstract

Calcined powders were prepared for sintering of cubic Cs_0.9Al_0.9Si_2.1O₆ 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 Cs_0.9Al_0.9Si_2.1O₆ green body was significantly enhanced using the amorphous calcined powder. The relative density of the Cs_0.9Al_0.9Si_2.1O₆ 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 Cs_0.9Al_0.9Si_2.1O₆ sintered body showed linear thermal expansion without hysteresis, resulting in a thermal expansion rate of ca. 0.13% at 1273K.