The devitrification of glasses in the akermanite-gehlenite system [(C2Al2−2yMgySi1+yO7 (0≤y≤1)] doped with Nd3+ (2% mol) has been studied. DTA was used to determine the kinetics of the process. The Avrami law α=1-exp(−ktn) withn=1 was found to hold for doped gehlenite. For pure gehlenite, parametern was determined to be 1.5. The activation energy of the devitrification process is independent of the presence of neodymium,
and it is of the same order of magnitude as that for the viscous flow in molten silicates (ca. 650–750 kJ·mol−1).