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X‐ray Powder Diffraction Structural Phase‐Transition Study of La(Cr 1‐x Mn x )O 3 (x = 0 to 0.25) Using the Rietveld Method of Analysis
Author(s) -
Howard Scott A.,
Yau JenKuan,
Anderson Harlan U.
Publication year - 1992
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.1151-2916.1992.tb04247.x
Subject(s) - orthorhombic crystal system , crystallography , rietveld refinement , x ray crystallography , materials science , phase (matter) , octahedron , ionic radius , phase transition , powder diffraction , ion , ionic bonding , transition temperature , analytical chemistry (journal) , diffraction , crystal structure , chemistry , thermodynamics , physics , condensed matter physics , organic chemistry , chromatography , optics , superconductivity
The La(Cr 1‐x Mn x )O 3 (x = 0 to 0.25) system exhibited a displacive phase transformation from an orthorhombic to a rhombohedral structure at temperatures ranging from about 256°C at x = 0 to 305°C at x = 0.25. The Rietveld method of X‐ray analysis was used to determine structural characteristics and to assay phase concentrations when multiple phases were present. Indications were that the Mn ions on the B site affected the transition temperature through an ionic size effect; i.e., Mn 3+ , with a larger ionic size than Cr 3+ , increased the transition temperature while the presence of the smaller Mn 4+ ions reduced it. A hysteresis was also observed with respect to the phase transformation as a function of temperature. The phase transformation was associated with a change in the rotation of the oxygen octahedra from an antiphase to an in‐phase tilt sequence.