Phase Selection in the Undercooled Melts of R1VInO(3) (R=rare earth) Using Containerless Solidification Technique

The low oxygen partial pressure Po-2 of an ambient atmosphere is considerably effective for phase selection in the RMnO3 system, since the Mn ion changes its valence states depending on Po-2. Containerless solidification of the undercooled RMnO3 melt was carried out to study phase formation behavior under precisely controlled Po-2. The orthorhombic and hexagonal RMnO3 phases were solidified from an undercooled melt at Po-2=10(5) Pa. X-ray diffraction patterns and cross-sectioned microstructure revealed the existence of orthorhombic and hexagonal RMnO3. Thermodynamic stabilities were studied at various temperatures. The oxygen deficiencies in the as -solidified samples were calculated through annealing at 10(5) Pa using TG-DTA. These results suggest that the containerless solidification is one of the most suitable methods for phase equilibrium study under controlled Po-2.