The melting behavior of lutetium aluminum perovskite LuAlO3LuAlO3

DTA measurements with mixtures of aluminum oxide and lutetium oxide around the 1:11:1 perovskite composition were performed up to 1970∘C. A peak with onset 1901∘C was due to the melting of the eutectic Lu4Al2O9Lu4Al2O9 (monoclinic phase) and LuAlO3LuAlO3 (perovskite). Neither peritectic melting of the perovskite nor its decomposition in the solid phase could be resolved experimentally. The maximum of the eutectic peak size is near x=0.44x=0.44, on the Lu-rich side of the perovskite, which is consistent with the conclusion that LuAlO3LuAlO3 melts peritectically at ca. 1907∘C as proposed by Wu, Pelton, J. Alloys Compd. 179 (1992) 259. Thermodynamic equilibrium calculation reveals that under strongly reducing conditions (oxygen partial pressure <10−13bar) aluminum(III) oxide can be reduced to suboxides or even Al metal. It is shown that under such conditions a new phase field with liquid Al can appear.