Preparation and Thermal Expansion Behavior of Pollucite Powders by Sol-Gel Processing

[出版社版]rights: 社団法人日本セラミックス協会 rights: 本文データは学協会の許諾に基づきCiNiiから複製したものである relation: IsVersionOf: http://ci.nii.ac.jp/naid/110002291037/Pollucite (Cs_2O・Al_2O_3・4SiO_2) powders were prepared from a combination of Al_2O_3 sol, SiO_2 sol and CsNO_3 starting Materials by sol-gel processing, and a stable region of single phase pollucite was investigated. The pollucite powders of single phase were synthesized when Cs_2O : SiO_2 and Al2O_3 : SiO_2 molar ratios were 0.91-1.02 : 4 and 0.96-2.38 : 4, respectively, by standerdizing SiO_2 molar ratio. The lattice parameters at room temperature were affected mainly by the Cs_2O/SiO_2 ratio. It was confirmed by a high temperature X-ray diffractometry that the thermal expansion for the pollucite powders is greatly affected by the change of compositions: The thermal expansion coefficient decreased with decreasing Cs_2O/SiO_2 ratio from room temperature to 200℃, and increased with increasing Al_2O_3/SiO_2 ratio above 600℃. An increasing tendency of the latter has turned out to be caused by a slight amount of α-Al_2O_3 formed in the course of calcination. However, such behavior was not observed at the Cs_2O/Al_2O_3 ratio of less than 1