Тип публикации: статья из журнала
Год издания: 2013
Идентификатор DOI: 10.1016/j.jssc.2013.01.038
Ключевые слова: Phase transitions, Iron fluorides, Defect pyrochlore, Differential scanning calorimeters, Displacive transformation, Narrow temperature ranges, Orthorhombic structures, Phase transition mechanisms, Structural phase transition, Defects, Differential scanning calorimetry, X ray powder diffraction, Fluorine compounds
Аннотация: For the first time, structural phase transitions induced by the temperature were found in A(x)N(x)(II)M((1-x))(III)F(3),,)F-3 fluorides with the defect pyrochlore structure (Fd (3) over barm, Z=8). The room temperature structure of CsFe2F6 was determined using X-ray powder diffraction technique. This phase was found to be ordered wПоказать полностьюith the Pnma space group. The study of the temperature stability of orthorhombic structure by differential scanning calorimeter between 100 K and 700 K has shown a succession of phase transitions. The Pnma (Z=4)-> Imma (Z=4)-> I4(1)/amd (Z=4)-> Fd (3) over barm (Z=8) structural sequence was proposed to occur within a rather narrow temperature range 500-560 K. The mechanism of structural transition has been mainly associated with the rotation of (MF6) octahedra and small displacements of some Fe atoms. This assumption is in good agreement with the low experimental entropy value, which is characteristic for displacive transformations. (C) 2013 Elsevier Inc. All rights reserved.
Журнал: JOURNAL OF SOLID STATE CHEMISTRY
Выпуск журнала: Vol. 200
Номера страниц: 157-164
ISSN журнала: 00224596
Место издания: SAN DIEGO
Издатель: ACADEMIC PRESS INC ELSEVIER SCIENCE