Non-isothermal crystallization kinetics of the BaTiO3-KNbO3-SiO2 glass

We have investigated the non-isothermal formation kinetics of nanocrystals from the BaTiO3-KNbO3-SiO2 (BKSO) glass at temperatures from room temperature to 800 °C. The thermal characteristics and the structural transformations of the BKSO glass have been studied by means of a differential thermal analysis and X-ray diffraction. The crystallization of BKSO glass is found to accompany a single-step occurrence of a tetragonal Ba3TiNb4O15 nanocrystal structure. During the crystallization, a nanocrystals with a size of ∼40 nm at the initial stage grow with increasing temperature and reach a size of ∼120 nm by the time the crystallization finishes. We use the non-isothermal model of Johnson-Mehl-Avrami-Kolmogorov to characterize the kinetics of the crystallization process for the BKSO glass. The Avrami exponent of 3.5 indicates that the crystallization mechanisms is an increasing nucleation rate with diffusion-controlled growth. In the view of applications, providing information on how to control the size of nanograins systematically by simply controlling the annealing temperature of the glass state, as described in this study, should be useful.