Unusual sequence of phase transitions in (NH4)(3)TiF7 detected by optic and calorimetric studies

Описание

Тип публикации: статья из журнала

Год издания: 2014

Идентификатор DOI: 10.1016/j.jfluchem.2014.05.016

Ключевые слова: Cubic fluorides, Phase transitions, Crystal-optic, Calorimetry, Calorimetry, Crystal-optic, Cubic fluorides, Phase transitions

Аннотация: For the first time structural transformations were observed for one of the compounds belonging to the family of double salt fluorides A(3)MeF(7) = A(2)MeF(6)center dot AF. Single crystals of (NR4)(3)TiF7 = (NH4)(2)TiF6 center dot NH4F were grown by evaporation of the aqueous solution. Polarizing optical observations, heat capacity Показать полностьюand birefringence Delta n = (n(o) - n(e)) measurements were performed in a wide temperature range 100-400 K. Two reversible, first order structural phase transitions were found to be followed by an unusual sequence of symmetry changes: cubic (G(3)) (T-2 down arrow = 287.5 K; T-2 up arrow = 291-310 K) P4/mnc (G(2)) (T-1 down arrow = 358.5 K; T-1 up arrow = 360 K) 4/m (G(1)). The twin structures observed were described assuming the existence of cubic parent phase G(0) with Pm (3) over barm symmetry. (C) 2014 Elsevier B.V. All rights reserved.

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Издание

Журнал: JOURNAL OF FLUORINE CHEMISTRY

Выпуск журнала: Vol. 165

Номера страниц: 14-19

ISSN журнала: 00221139

Место издания: LAUSANNE

Издатель: ELSEVIER SCIENCE SA

Авторы

  • Mel'Nikova S.V. (L.V. Kirensky Institute of Physics, Siberian Department of RAS)
  • Pogoreltsev E.I. (Kirensky Institute of Physics, Building 38)
  • Flerov I.N. (Siberian Federal University)
  • Laptash N.M. (Institute of Chemistry, Far Eastern Department of RAS)

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