COLOR AND CHEMICAL HETEROGENEITIES OF GAMMA-[NA]-CE2S3 SOLID-SOLUTIONS

A quantitative estimation of the concentration distribution of sodium in the gamma-Ce2S3 phase doped with sodium has been obtained for the f irst time. A precise determination of the phase homogeneity and of the sodium volume distribution in the micrometric grains has been carried out using a new chemical method, differential dissolution, combined w ith XRD and Raman spectroscopy. Sodium high surface concentration and impurity phases such as sodium or cerium polysulfides in small amounts were found in the samples prepared under different conditions. It was shown that these heterogeneities can he the cause of a significant mo dification of the color of the material. (C) 1998 Elsevier Science S.A .