Isothermal crystallization kinetics of lithium-tantalate glass: Nanocrystal prepared by glass phase

Abstract

We have investigated the formation kinetics of nanocrystals from LiTaO3 (LT) glass. The glass sample was prepared by using the polymerized complex method with no addition of a glass former. The thermal characteristics and the structural transformations of pure LT glass have been studied by means of differential scanning calorimetry and in-situ synchrotron X-ray diffraction, and the surface morphology have been studied by using scanning electron microscopy. A temperaturedependent incubation time is observed. After this incubation time, the isothermal kinetics of the crystallization process is described by the Johnson-Mehl-Avrami-Kolmogorov equation, resulting in an Avrami exponent, n, of ∼2.75. The result indicates that the crystallization mechanism is diffusion-controlled growth at an increasing nucleation rate. The effective activation energy deduced from the time of 30 to 50% transformations is 9.2 eV and, based on the relationship ΔEeff = En + bcEg, turns out to arise from the activation energies of 3.3 eV for nucleation and 3.9 eV for growth.