Crystallization kinetics analysis of BaF2 and BaGdF5 nanocrystals precipitated from oxyfluoride glass systems: A comparative study

Abstract Analysis of crystallization kinetics in glasses is an essential tool to gain control over ceramization to achieve desired functionalities. Here, the non-isothermal kinetics of crystallization in two different oxyfluoride glasses have been analyzed using various well-established kinetic models. Activation energies ( E a ) have been estimated using Kissinger, Augis–Bennett and Ozawa methods while both E a and Avrami index ( n ) were predicted from the Matusita and Avrami–Erofeev models. The values of E a and n as predicted using Avrami–Erofeev model are 285 kJ/mol and 1.18, respectively for the oxyfluoride glass yielding BaF 2 nanocrystals whereas 269 kJ/mol and 1.33 for the glass yielding BaGdF 5 nanocrystals. The Avrami indices predict three dimensional diffusion controlled crystallization through bulk nucleation. Moreover, isothermal prediction facilitated to optimize the ceramization temperature and time for obtaining transparent oxyfluoride glass-ceramics. Furthermore, Model-free kinetics analysis demonstrates initial decrease followed by a subsequent rise in activation energy during crystallisation in both the glass systems.