NUCLEATION AND CRYSTALLIZATION OF WO3 FROM PURE AND PB2+ DOPED NAF FLUXES

DTA runs and flux growth experiments have shown that the crystallizati on temperatures of WO3 from NaF flux are in the range of 1020-1090 deg rees C. Addition of Pb2+ influences the crystal growth and the crystal lization temperatures are altered (within this range). A thermal effec t giving rise to an exothermal DTA peak was observed above the crystal lization temperature. This peak occurs at a higher temperature when le ad ions are present. We propose an explanation based on pre-crystalliz ation clustering and on the number of nucleation sites on the surface of the platinum crucible.