Phase Transition in Niobophosphate Glass-Ceramic

Phase transition during crystallization of glass to glass-ceramic in system P2O5-CaO-Nb2O5-Na2O was studied. Several heating rates were compared – 1, 2, 5, 11 and 20°Cmin-1. DTA, XRD, FTIR and Raman analyses were performed. Niobophosphate glass-ceramic is found to form utterly different crystalline phases depending on maximal heating temperature, heating rate and time of maximal temperature maintenance. Crystallization temperatures of the same phases are strongly dependent on heating rate, while crystallinity of obtained phases is not. At lower temperatures poorly crystalline phosphates (Ca3(PO4)2, Ca10Na(PO4)7, Ca2P2O7) and niobates (NaNbO3 and Nb2O5) are identified. At higher temperatures…