Direct Calorimetric Measurement of Enthalpies of Phase Transitions at 2000°–2400°C in Yttria and Zirconia
High-temperature differential thermal analysis provided data on phase transitions in zirconia and yttria. The tetragonal form of ZrO2 transforms to the cubic fluorite structure at 2311°±15°C with an enthalpy of 3.4±3.1 kJ/mol. Cubic C-type Y2O3 transforms, probably to the fluorite structure, at 2308°±15°C with ΔH=47.7±3.0 kJ/mol. This high-temperature polymorph melts at 2382°±15°C with an enthalpy of fusion of 35.6±3.0 kJ/mol.
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