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Determination of the Pcmn / Ibm 2 Phase Boundary at High Temperatures in the System Ca 2 Fe 2 O 5 ‐Ca 2 Al 2 O 5
Author(s) -
Fukuda Koichiro,
Ando Hisashi
Publication year - 2002
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.1151-2916.2002.tb00263.x
Subject(s) - phase transition , phase boundary , phase (matter) , analytical chemistry (journal) , crystallography , chemistry , crystal (programming language) , transition temperature , thermal expansion , materials science , mineralogy , condensed matter physics , physics , metallurgy , chromatography , computer science , programming language , superconductivity , organic chemistry
The crystals of Ca 2 (Al x Fe 1− x ) 2 O 5 with 0 ≤ x ≤ 0.4 were examined using powder XRD at temperatures between 25° and 1000°C. The Pcmn to Ibm 2 phase transition was readily detected by the disappearance of the 131 and 151 reflections ( h + k + l odd). Thus, the phase relationship has been determined as combined functions of the temperature and x ‐value. At 25°C, the space group changed from Pcmn (0 ≤ x ≤ 0.23) to Ibm 2 (0.24 ≤ x ≤ 0.40) across x = 0.235. With increased x ‐value, the cell dimensions of both phases steadily decreased, showing the nearly complete continuity at that phase boundary. For the crystal with x = 0 (Ca 2 Fe 2 O 5 ), the cell dimensions steadily increased during heating to 685°C, at which temperature the phase transition occurred. There was a slight discontinuous decrease in cell dimensions just after the transition. Subsequent heating to 1000°C of the Ibm 2 phase led to a steady thermal expansion along the b ‐axis and c ‐axis, while a slight contraction occurred along the a ‐axis up to 800°C.