The TeO₂-rich part of the TeO₂–Ga₂O₃system: equilibrium and non-equilibrium phase diagram

Abstract

The TeO2-rich part of the TeO2–Ga2O3 system has been investigated, under equilibrium and non-equilibrium conditions, by temperature programmed X-ray diffraction and differential scanning calorimetry (DSC). Two invariant equilibria have been detected: one peritectic reaction and one eutectic reaction. The peritectic reaction corresponds to the incongruent melting at 620 °C ± 5 °C of the crystalline compound Ga2Te4O11 (ΔHP = 18.1 ± 2 kJ mol−1) and to the equilibrium Ga2Te4O11 ↔ LP + Ga2O3. The eutectic reaction (23 mol% GaO1.5, TE = 600 ± 5 °C, ΔHE = 22.2 ± 2 kJ mol−1) corresponds to the equilibrium TeO2 + Ga2Te4O11 ↔ LE. The glass forming domain ranges from 5 to 30 mol% GaO1.5, and can be extended from 0 to 35 mol% by quenching the melt in a freezing mixture, consisting of ice, ethanol and NaCl (≈−14 °C). The thermal behaviour of glasses has been studied. The glass transition and crystallization temperatures, and the phases which appear during the crystallization have been identified.