Determination of crystallization kinetics parameters of a Li 1.5Al0.5Ge1.5(PO4)3 (LAGP) glass by differential scanning calorimetry

Abstract

Crystallization kinetics parameters of a stoichiometric glass with the composition Li1.5Al0.5Ge1.5(PO 4)3 were investigated by subjecting parallelepipedonal samples (3 × 3 × 1.5 mm) to heat treatment in a differential scanning calorimeter at different heating rates (3, 5, 8 and 10 °C/min). The data were analyzed using Ligero's and Kissinger's methods to determine the activation energy (E) of crystallization, which yielded, respectively, E = 415 ± 37 kJ/mol and 378 ± 19 kJ/mol. Ligero's method was also employed to calculate the Avrami coefficient (n), which was found to be n = 3.0. A second set of samples were heat-treated in a tubular furnace at temperatures above the glass transition temperature, Tg, to induce crystallization. The X-ray diffraction analysis of these samples indicated the presence of LiGe 2(PO4)3 which displays a NASICON-type structure. An analysis by optical microscopy revealed the presence of spheric crystals located primarily in the volume, in agreement with the crystallization mechanism predicted by the Avrami coefficient.