Transitions between P2(1), P6(3)(root 3A), and P6(3)22 modifications of SrAl2O4 by in situ high-temperature X-ray and neutron diffraction

resumo

The results of in situ high-temperature X-ray and neutron powder diffraction experiments reconcile inconsistencies in previous reports on the symmetry of high-temperature phases of SrAl2O4. The material undergoes two reversible phase transitions P2(1) <-> P6(3)(root 3A) and P6(3)(root 3A) <-> P6(3)22 at similar to 680 and similar to 860 degrees C, respectively, and the latter one is experimentally observed and characterized for the first time. The higher symmetry above the P6(3)(root 3A) <-> P6(3)22 transition is gained by disordering off-center split site of oxygen atoms around trigonal axis rather than by unbending Al-O-Al angle to the ideal value 180 degrees. The analysis of the literature suggests that it is a common feature of the P6(3)22 phases of stuffed tridymites. (c) 2007 Elsevier Inc. All rights reserved.

palavras-chave

CRYSTAL-STRUCTURE; PHASE-TRANSITIONS; GALLATE; ALUMINATE; FRAMEWORK; CHEMISTRY; COMPOUND; DISORDER; BEHAVIOR; BARIUM

categoria

Chemistry

autores

Avdeev, M; YakovIev, S; Yaremchenko, AA; Kharton, VV

nossos autores

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