DEVELOPMENT OF THE NONLINEAR-OPTICAL CRYSTAL CSTIOASO4 .1. STRUCTURAL STABILITY

We have systematically investigated the structural stability of the KTiOPO4 family of crystals, specifically of CsTiOAsO4. High temperature differential thermal analysis (DTA) reveals for the first time that CsTiOAsO4 thermally decomposes into, a non-stiochiometric, Cs-deficient cubic compound at approximately 960-degrees-C. This decomposition is actually more general, and is observed in two other KTiOPO4 isomorphs, namely RbTiOPO4 and TITiOPO4. A ''threatened-structure model'' is proposed to explain the decomposition and evidence supporting the validity of this model are presented. The model further explains the observed anomaly in CsTiOAsO4'S Crystal growth properties using various fluxes. CsTiOASO4's relatively low decomposition temperature creates problems for bulk crystal growth and methods for reducing these growth problems are proposed.