DEVITRIFICATION IN SODIUM DISILICATE GLASSES CONTAINING IRON.

Systematic studies of thermally induced structural transformation in (Na//20 multiplied by (times) 2SiO//2)//1// minus //x(Fe//2O//3)//x glass with 0. 05 less than equivalent to x less than equivalent to 0. 3 have been carried out by x-ray diffraction, extended x-ray absorption fine structure, and Mossbauer effect spectroscopy techniques. On the basis of the diffraction analysis, this glass system devitrifies at elevated temperature to form three major crystalline phases, gamma -Na//2Si//2O//5, alpha -Fe//2O//3, and Na//5Fe(SiO//3)//4, plus several minor ones. The weight fractions of those crystalline phases under different heat treatment conditions have been determined by a matrix flushing method using x-ray diffraction.