STUDY OF THE CRYSTALLIZATION PROCESS OF V ITREOUS SODIUM-TRIMETAPHOSPHATE .1. CRYSTALLOCHEMICAL ASPECT

The influence of annealing parameters (temperature and duration) on th e crystallization process of vitreous sodium-trimetaphosphate has been studied by X-ray diffraction under air-free conditions. The phenomeno n is undoubtly initiated by very small amounts of water being inevitab ly present. A crystalline phase grows on the sample surface with very strong crystallographic orientations, the structure of which being rel ated to the structure of a sodium-trimetaphosphate hydrate. Water is g radually released when annealing temperature and/or duration is increa sed. Crystallization of anhydrous trimetaphosphate occurs first on the surface before spreading over the whole volume of the solid.