Constitution of Stable and Metastable Phase Diagrams for TmFeO₃-ScFeO₃ System by Undercooling Solidification Using the Containerless Technique

Abstract

Spherical samples of Tm_1−xSc_xFeO₃ were solidified from the undercooled melt under the containerless state using an aerodynamic levitation (ADL) furnace. The change of solidification behavior from double recalescence to single recalescence and powder X-ray diffraction (XRD) analysis of as-solidified samples revealed that metastable hexagonal LnFeO₃ (h-LnFeO₃) stabilizes with increasing of mole fraction of Sc. The reason for this stabilization was ascribed to the decrease of the difference in the liquidus temperatures of stable orthorhombic LnFeO₃ (o-LnFeO₃) and metastable h-LnFeO₃ phases. Annealing the as-solidified samples at 1473 K for 1 hour resulted in the two-phase coexistent states of o−LnFeO₃ and garnet (c-A₃B₅O₁₂) at 0 < x < 0.3, c-A₃B₅O₁₂ and h-LnFeO₃ at 0.3 < x < 0.5_, and h-LnFeO₃ and c-ScFeO₃ at 0.5 < x < 1.0. Based on these results, we proposed the quasi phase diagram between TmFeO₃ and ScFeO₃.