Crystallization kinetics and thermal properties of 20Li2O-80TeO2 glass

In this work, X-ray diffraction, Raman spectroscopy and differential scanning calorimetry techniques were used to understand the crystallization process on 20Li2O-80TeO2 glass. X-ray diffraction results reveal the presence of three distinct alpha γ-TeO2, α-TeO2 and α-Li2Te2O5 crystalline phases in the glass matrix. The Raman spectroscopy band structure of this glass is similar to the one observed in glassy TeO2. Raman results clearly reveal the metastable character of the γ-TeO2 phase in the 20Li2O-80TeO2 glass, whose associated vibration modes disappear completely at temperatures higher than 315 deg. C. On the other hand, the Raman modes associated to α-TeO2 and α-Li2Te2O5 phases persists up to temperatures close to the final stages of the crystallization in the studied glass (around 420 deg. C). From DSC measurements, the activation energies 296 ± 3 and 298 ± 1 kJ mol-1 were associated to γ-TeO2 and α-TeO2 phases crystallization, indicating that these phases crystallizes at temperatures very close in the studied glass.