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 °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 °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.