Crystallisation kinetics of a cesium iron phosphate glass

The crystallisation kinetics of 36 mol% Cs2O–26 mol% Fe2O3–P2O5 glass was studied by differential scanning calorimetry under non-isothermal conditions at various heating rates. X-ray diffraction technique was employed to understand the product of crystallisation. This glass crystallises to a mixture of CsFe(P2O7), Cs7Fe7(PO4)8O2 and Cs3PO4. The activation energy of the crystallisation process was determined by classical multi heating rate methods like Kissinger, Mahadevan and Augis–Bennet. Heating rate dependence of the activation energy was observed when the data were analysed using Coats and Redfern method. This dependence of the activation energy was evaluated by the application of Kissinger–Akahira–Sunrose isoconversional method. It was observed that the activation energy of crystallisation was found to vary with the degree of conversion. The value of Avrami exponent ‘n’ obtained was 4, suggesting the mechanism of crystallisation to be bulk nucleation and three-dimensional growth.