A study of phase stability in the Lu2O3-Al2O3 system

Differential thermal analysis (DTA) of LuAlO3 perovskite phase was performed in argon/hydrogen atmosphere in the temperature range up to 2100 °C. Single-phase LuAlO3 perovskite crystals grown by the vertical Bridgman method were used in measurements. Under thermal conditions excluding phase decomposition in the course of measurements, a single endothermal peak at 1847 °C (corresponding to the melting of pure perovskite phase) and a single exothermal peak at 1834 °C (corresponding to the solidification of the perovskite phase) were registered. DTA measurements were performed with single crystal garnet (Lu3Al5O12) and polycrystalline monoclinic (Lu4Al2O9) as well. Thermal instabilities of LuAlO3 and monoclinic Lu4Al2O9 phases were reinvestigated by x-ray diffraction and micro-probe spectral analysis. Indexing of the LuAlO3 perovskite, so far not reported, is done.