Кл.слова (ненормированные):
Crystal growth -- Fluoridotitanate -- Mixed valence -- Phase transition -- Optical properties -- Heat capacity
Аннотация: Mixed-valence hydrated fluoridotitanate with idealized formula FeTiF6·6H2O is the main product of fluoride processing of natural mineral ilmenite with hydrofluoric acid. Its single crystals were grown and optical and calorimetric experiments were carried out in the temperature range 200–350 K. Charge re-distribution, Fe2+Ti4+ to Fe3+Ti3+, in the compound studied was evident in XPS spectra. A first order ferroelastic phase transition occurs at temperatures T0↓ = 271.5 K, T0↑ = 274 ÷ 275.5 K with the symmetry change P3‾↔ P1‾. The structural transformation is accompanied by the appearance of a very weak optical anisotropy in the slice (001), a small anomaly of the heat capacity (ΔS = 1.5 J/mol K = 0.2R), and positive baric coefficients dT0/dp ≈ 30 ± 10 K/GPa.
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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, 660036, Russian Federation
Institute of Chemistry, Far Eastern Branch of RAS, Vladivostok, 690022, Russian Federation
Siberian Federal University, Krasnoyarsk, 660074, Russian Federation
Доп.точки доступа:
Mel'nikova, S. V.; Мельникова, Светлана Владимировна; Laptash, N. M.; Gorev, M. V.; Горев, Михаил Васильевич; Pogoreltsev, E. I.; Погорельцев, Евгений Ильич