Non-isothermal crystallization kinetics of BaTiO3–(Li2B4O7–ZnO) glass

Abstract

We have investigated the non-isothermal formation kinetics of nanocrystals from BaTiO3–(Li2B4O7–ZnO) (BTLBZO) glass in the temperature range 303–873 K. Thermal characteristics and structural transformations of the BTLBZO glass, formed through precursors of Li2B4O7, ZnO, and BaTiO3, have been studied by means of differential scanning calorimetry and X-ray diffraction. It is found that crystallization of glass accompanies a sequential two-step occurrence of rhombohedral ZnTiO3 and orthorhombic Ba3Zn7Ti12O34 structures. We use the non-isothermal models of the Johnson–Mehl–Avrami–Kolmogorov, Kissinger, and Ozawa equations to characterize the kinetics of the crystallization process from the BTLBZO glass. The Avrami exponents of 3.5 and 2.5, for the first and second crystallization on heating the glass, indicate that the crystallization mechanisms belong to increasing and constant nucleation rates, respectively, with the diffusion-controlled growth. The activation energies of crystallization, obtained from those non-isothermal three models, show similar values to each other, ensuring the validity of applying equations to the non-isothermal analysis of crystallization kinetics from glass. Isoconversional analysis shows that there involves a complex mechanism at the late stage of crystallization.