Non-Isothermal Crystallization of Lithium Germanophosphate Glass Studied by Different Kinetic Methods

Crystallization kinetics of 22.5Li(2)O center dot 10Al(2)O(3)center dot 30GeO(2)center dot 37.5P(2)O(5) (mol%) glass was studied under non-isothermal condition using the differential thermal analysis (DTA). The study was performed by using the first crystallization peak temperature (T-p1) which belongs to the precipitation of LiGe2(PO4)(3) phase in the glass. The activation energy of glass crystallization (E-a) was determined using different isokinetic methods. The dependence of E-a on the degree of glass-crystal transformation (alpha) was studied using model-free isoconversional linear integral KAS (Kissinger-Akahira-Sunose) and FWO (Flynn-Wall-Ozawa) methods. It was shown that the E-a varies with a and hence with temperature and consequently the glass/crystal transformation can be described as a complex process involving different mechanisms of nucleation and growth.