EFFECT OF THE MELT TEMPERATURE ON THE SOLIDIFICATION PROCESS OF LIQUID GARNETS LN3AL5O12 (LN = DY, Y, AND LU)

The solidification process of liquid garnets Ln3Al5O12 (Ln = Dy, Y, Lu) was probed by differential thermal analysis. A critical temperature T(clg) was evidenced in the liquid. Cooling from temperatures under T(clg) leads to the crystallization of the single garnet phase. Cooling from temperatures above T(clg) leads to the solidification of a mixture of perovskite LnAlO3 and aluminum oxide alpha-Al2O3. For Ln = Y, the results are in agreement with stable and metastable phase diagrams previously proposed. The YAlO3 melt was shown to display a critical temperature T(clp) also. Its metastable solidification from temperatures above T(clp) leads to the formation of the perovskite at around 1550-degrees-C.