Formation process of Sr-celsian from precursor zeolites

Abstract

Two kinds of zeolites with different crystal structures with the same chemical composition of SrO·Al2O3·2SiO 2·xH2O prepared by an ion-exchange technique were used as a precursor of Sr-celsian. One was Sr-exchanged zeolite A (Sr-A), the other was Sr-exchanged Linde F zeolite (Sr-F). The Sr-A almost became an amorphous material at 400°C, and then generates a small amount of Sr-hexacelsian from the amorphous material at 500°C. The amount of Sr-hexacelsian steeply increased and a small amount of Sr-monocelsian also formed at 1000°C. On the other hand, the Sr-F nearly becomes an amorphous material at 300°C, and then Sr-hexacelsian mainly formed along with a small amount of Sr-monocelsian above 1000°C. In both of the Sr-exchanged zeolites, a single phase of Sr-monocelsian was obtained finally at 1300°C, owing to the hexacelsian - to - monocel-sian phase transformation. The reason for the crystallization of Sr-hexacelsian at 500°C only from Sr-A was explained in terms of the similarity in framework structures of zeolite A and Sr-hexacelsian. © 2009 The Ceramic Society of Japan. All rights reserved.