Crystallization kinetics and thermal properties of 20Li(2)O-80TeO(2) glass

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

In this work, X-ray diffraction, Raman spectroscopy and differential scanning calorimetry techniques were used to understand the crystallization process on 20Li(2)O-80TeO(2) glass. X-ray diffraction results reveal the presence of three distinct alpha gamma-TeO2, alpha-TeO2 and alpha-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 gamma-TeO2 phase in the 20Li(2)O-80TeO(2) glass, whose associated vibration modes disappear completely at temperatures higher than 315 degrees C. on the other hand, the Raman modes associated to alpha-TeO2 and alpha-Li2Te2O5 phases persists up to temperatures close to the final stages of the crystallization in the studied glass (around 420 degrees C). From DSC measurements, the activation energies 296 +/- 3 and 298 +/- 1 kJ mol(-1) were associated to gamma-TeO2 and alpha-TeO2 phases crystallization, indicating that these phases crystallizes at temperatures very close in the studied glass. (C) 2009 Elsevier Ltd. All rights reserved.