Devitrification kinetics of PbGeO3.

The devitrification of glassy PbGeO₃ was studied and interpreted by means of isothermal and non-isothermal Johnson-Mehl-Avrami equations. In the case of the non-isothermal approach, several approximated equations proposed by various authors were considered in order to obtain both the activation energy E _a and the Avrami morphological coefficient n of the crystallisation process. A critical discussion of the Avrami coefficient on the basis of experimental morphological evidence is also presented. [ABSTRACT FROM AUTHOR]