Phase selection in the undercooled peritectic Y 3Fe 5O 12 melt

Abstract

Containerless solidification of peritectic Y 3Fe 5O 12 garnet (YIG) was examined using an aero-acoustic levitator to investigate the direct growth of YIG from the undercooled melt. Although the melt was undercooled below the peritectic temperature ( T p), YFeO 3 perovskite (YIP) was primarily solidified in the spontaneously nucleated specimen. The phase selection theory based on the competitive growth indicates that YIG never solidifies directly from the undercooled melt even when the melt is undercooled much below T p. However, when the melt undercooled below T p was dropped onto the copper chill plate with high thermal conductivity, YIG solidified around the chill plate as a primary phase. On the other hand, for the undercooled melt dropped onto the quartz glass chill plate with low thermal conductivity, YIP primarily solidified. These results suggest that the high cooling rate achieved by the copper chill plate prevented the nucleation of YIP and led to the direct growth of YIG, which is explained by the phase selection based on the competitive nucleation rate.