Crystallization kinetic studies of CaBi₂B₂O₇ glasses by non-isothermal methods

Transparent glasses of CaBi₂B₂O₇ (CBBO) were fabricated via the conventional melt-quenching technique. The amorphous and the glassy nature of the as-quenched samples were, respectively, confirmed by X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC). The glass transition (T _g) and the crystallization parameters (crystallization activation energy (E _cr) and Avrami exponent (n)) were evaluated under non-isothermal conditions using DSC. The heating rate dependent glass transition and the crystallization temperatures were rationalized by Lasocka equation for the as-quenched CBBO glasses. There was a close agreement between the activation energies for the crystallization process determined by Augis and Bennet and Kissinger methods. The variation of local activation energy (E _c(x)) that was determined by Ozawa method increased with the fraction of crystallization (x). The Avrami exponent (n(x)) decreased with the increase in fraction of crystallization (x), suggesting that there was a changeover in the crystallization process from the bulk to the surface.