The TeO2-rich part of the TeO2-Ga2O3 system:: equilibrium and non-equilibrium phase diagram

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 degreesC +/- 5 degreesC of the crystalline compound Ga2Te4O11 (DeltaH(P) = 18.1 +/- 2 kJ mol(-1)) and to the equilibrium Ga2Te4O11 <-> LP + Ga2O3. The eutectic reaction (23 mol% GaO1.5, T-E = 600 +/- 5 degreesC, DeltaH(E) = 22.2 +/- 2 kJ mol(-1)) corresponds to the equilibrium TeO2 + Ga2Te4O11 <-> L-E. 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 (approximate to -14 degreesC). 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.