Calculations of Avrami exponent and applicability of Johnson–Mehl–Avrami model on crystallization in Er:LiY(PO3)4 phosphate glass

Preparation and thermal properties of Er3+-doped lithium–yttrium meta-phosphate glasses with a nominal composition of Er:LiY(PO3)4 were studied as a new scintillating material for neutron detection. The glassy Er:LiY(PO3)4 ingots 10 × 10 × 25 mm3 in size were prepared by quenching of the molten mixture of the starting lithium carbonate, yttrium phosphate, and phosphorus oxide in stoichiometric relations. Crystallization kinetics was experimentally studied on powder samples with particle sizes ranging from 96 to 106 μm, 200 to 212 μm, and on bulk glassy samples using the non-isothermal differential scanning calorimetry. The evaluation of the measured data was performed using the Johnson–Mehl–Avrami, Matusita and Augis–Bennett models, and the y(α) and z(α) functions. In the case of the powder samples, the model analysis of the measured data showed that the crystallization mechanism was primarily performed through volume nucleation followed by 2D and 3D growth and in the bulk one by the surface and volume nucleation with 1D growth. Obtained kinetic parameters were used for reconstruction of the crystallization peaks using various models and compared with actual experimental data.