DEVITRIFICATION OF ND3-DOPED GLASSES IN THE AKERMANITE-GEHLENITE SYSTEM()

The devitrification of glasses in the akermanite-gehlenite system [(C( 2)Al(2-2y)Mg(y)Si1+O-y(7) (0 less than or equal to y less than or equa l to 1)] doped with Nd3+ (2% mol) has been studied. DTA was used to de termine the kinetics of the process. The Avrami law alpha=1-exp(-kl(n) ) with n=1 was found to hold for doped gehlenite. For pure gehlenite, parameter n was determined to be 1.5. The activation energy of the dev itrification process is independent of the presence of neodymium, and it is of the same order of magnitude as that for the viscous flow in m olten silicates (ca. 650-750 kJ . mol(-1).