Thermal and structural investigations of x Li2 O-(1?x)Bi2 O3 (0.25 ? x ? 0.35) glasses

In this paper, we have studied the nonisothermal and isothermal crystallization kinetics of xLi2O-(1?x)Bi2O3 (0.25 ? x ? 0.35) glasses, using differential scanning calorimetry. Both the energies of glass transition and crystallization are estimated, using the Ozawa and Kissinger methods for nonisothermal crystallization. The modified Johnson-Mehl-Avrami (JMA) equation is used to estimate the nature of nucleation and crystal growth during the nonisothermal crystallization. The nature of nucleation and crystal growth is also determined by the Sestak-Berggren model for the non-isothermal crystallization. On the other hand, the JMA equation describes the diffusion controlled growth of crystallites for isothermal crystallization. Nature of crystal growth is identified by scanning electron micrographs both non-isothermally and isothermally. In situ low frequency Raman spectra are analyzed to determine the degree of amorphous nature below onset of crystallization temperature for the glasses. Transition from local ordering to high range ordering of BiO6 octahedral units after crystallization is also identified, using Raman susceptibility spectra.