Premium
Formation of Orthorhombic and Multiferroic Hexagonal Phases from an Undercooled RMnO 3 (R=Rare‐Earth Element) Melt Using a Containerless Technique
Author(s) -
Vijaya Kumar Malahalli Shankaregowda,
Higaki Nami,
Kuribayashi Kazuhiko,
Hibiya Taketoshi,
Yoda Shinichi
Publication year - 2011
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2010.04042.x
Subject(s) - orthorhombic crystal system , ionic radius , materials science , supercooling , crystallography , multiferroics , thermogravimetric analysis , crystal structure , ion , ferroelectricity , chemistry , thermodynamics , dielectric , physics , optoelectronics , organic chemistry
Containerless solidification of the undercooled RMnO 3 melt was carried out to study the formation of orthorhombic and hexagonal phases under controlled oxygen partial pressure. The o ‐RMnO 3 (R=La to Gd) perovskite with a space group of Pbnm and h ‐RMnO 3 (R=Dy to Lu) with a space group of P 6 3 cm were solidified from an undercooled melt at=10 5 Pa. The RMnO 3 samples showed the undercooling of 230–380 K at=10 5 Pa. The surface morphologies changed from rough spherical to a smooth faceted planes with a decreasing ionic radius from La (0.1032 nm) to Lu (0.0861 nm). X‐ray diffractometry and scanning electron microscopy results showed the existence of o ‐RMnO 3 and h ‐RMnO 3 . Thermodynamic stabilities of the as‐solidified phases were studied at 10 5 Pa; as a result, the hexagonal phases changed to orthorhombic for the DyMnO 3 and HoMnO 3 systems after annealing at 1673 K. Based on the thermogravimetric analysis results, oxygen deficiency, bulk composition, and tolerance factor were calculated.