Рубрики:
CRYSTAL-STRUCTURE
DIFFRACTION
NH4F
Кл.слова (ненормированные):
Cubic fluorides -- Phase transitions -- Crystal-optic -- Calorimetry
CRYSTAL-STRUCTURE
DIFFRACTION
NH4F
Кл.слова (ненормированные):
Cubic fluorides -- Phase transitions -- Crystal-optic -- Calorimetry
Аннотация: For the first time structural transformations were observed for one of the compounds belonging to the family of double salt fluorides A3MeF7 = A2MeF6·AF. Single crystals of (NH4)3TiF7 = (NH4)2TiF6·NH4F were grown by evaporation of the aqueous solution. Polarizing optical observations, heat capacity and birefringence Δn = (no − ne) 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 (G3) (T2↓ = 287.5 K; T2↑ = 291–310 K) ↔ P4/mnc (G2) (T1↓ = 358.5 K; T1↑ = 360 K) ↔ 4/m (G1). The twin structures observed were described assuming the existence of cubic parent phase G0 with P m 3 ¯ m symmetry.
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Держатели документа:
RAS, LV Kirensky Phys Inst, Siberian Dept, Krasnoyarsk 660036, Russia
Siberian Fed Univ, Krasnoyarsk 660074, Russia
Russian Acad Sci, Inst Chem, Far Eastern Dept, Vladivostok 690022, Russia
Доп.точки доступа:
Mel'nikova, S. V.; Мельникова, Светлана Владимировна; Pogoreltsev, E. I.; Погорельцев, Евгений Ильич; Flerov, I. N.; Флёров, Игорь Николаевич; Laptash, N. M.; Russian Foundation for Basic Research [12-02-00056]; Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation [NSh-924.2014.2]