Effect of thallium on the crystallization kinetics of the chalcogenide glasses GeSe2 and GeSe4

The structure identification of the quenched compositions GeSe2, GeSe4, GeSe2Tl and GeSe4Tl has been confirmed by energy dispersive X-ray analysis ( EDX), X-ray diffraction ( XRD) and differential thermal analysis ( DTA). The differential thermal analysis curves of the compositions under investigation were recorded at the heating rates 5, 10, 20, 30 and 50 degrees C min(-1). Addition of thallium to GeSe2 and GeSe4 results in decreasing the glass transition temperature T-g, the crystallization temperature T-c and the melting temperature T-m. The effect of heating rates on the transition temperatures ( T-g, T-c and T-m) was studied and the variation of the crystallization peak temperature T-p position was used to calculate the activation energy. The kinetic parameters of crystallization for the devitrification processes have been determined by three methods and discussed on the basis of Johnson - Mehl - Avrami model.