Sr-ヘキサセルシアン焼結体の作製と単斜晶系への相転移

Abstract

In order to develop dense Sr-hexacelsian and Sr-celsian ceramics， amorphous materials (nSrO-Al[2]O[3]-2SiO[2]，n = 1.0 -1.2) prepared by calcining the mixtures of elutriated pure kaolin with strontium carbonate were pressed and heat-treated between 900 and 1200℃. Heat-treatment of the reactive amorphous powders above 950℃ produced densely sintered hexacelsian ceramics and phase transition of hexacelsian to celsian was observed at higher heat-treatrnent temperatures. With the increase in n value，transition temperature lowered from 1100 to 1000℃. When the stoichiometric specimens( n = 1.0) were heat-treated above 1150℃， cracks appeared at the surface of specimens owing to the phase transition of hexacelsian to celsian. Increase in n value above 1.1 depressed the crack formation and gave a crack-free polycrystals.