COMPLEXITY IN THE SOLIDIFICATION BEHAVIOR OF MOLTEN Y3AL5O12

At high degrees of undercooling, it is shown that the solidification behaviour of molten Y3Al5O12 can depart substantially from that predicted by the equilibrium-phase relationships. This leads to the formation of a two-phase perovskite/α-alumina mixture, which is ceramic and opaque in appearance, in preference to transparent garnet material obtained from melts seeded at or just below the melting point. The structures which develop as a function of undercooling can be interpreted in terms of a pseudo-binary eutectic system formed between YAlO3 and α-alumina. The relevance of these findings to the crystal growth of yttrium aluminium garnet is discussed briefly. © 1979.