Thermal Property and Phase Transition of the Synthesized New Cubic Leucite-type Compounds

Abstract

New cubic leucite-type compounds, CsMSi₂O₆ (M=B_0.2Al_0.8,Al_0.2Fe_0.8), Cs₂MSi₅O₁₂ (M=Cd, Mg, Ni, Zn) have been synthesized by the two-stage heat treatment of the solid-state reaction. The thermal expansion properties of the synthesized leucite-type compounds have been studied with HTXRD and LTXRD in the temperature range of 123 to 1273 K. The thermal expansion rate of CsB_0.2Al_0.8Si₂O₆ was found to be considerably smaller than that of CsAlSi₂O₆, while the thermal expansion property of Cs₂MSi₅O₁₂ (M=Mg, Zn, Cd) was found to have a linear relationship in the temperature range of 298 to 1273 K. By using Rietveld analysis it was found that the thermal expansion rate decreased with increasing the Si—O—M(Si) angle for cubic leucite-type compounds at 298 K, and that the phase transitions of CsAlSi₂O₆ and Cs_0.9Al_0.9Si_2.1O₆ were due to the relationship between the bond angle of Si—O—M(Si) of the three-dimensional framework structure and the space ratio in the unit cell at 298 K.