Тип публикации: статья из журнала
Год издания: 2010
Идентификатор DOI: 10.1016/j.jssc.2009.11.034
Ключевые слова: Phase diagram of NaF-AlF3, Synthesis via vapor condensation, Crystal structure from X-ray powder data, Chemical transformations, Chiolite, Crystal forms, Fibrous crystals, High temperature, High temperature X-ray diffraction, Higher temperatures, Main component, Molten salt, NaF-AlF, Sodium ions, Space Groups, Thermal analysis, Thermal stability, Vapor condensation, X-ray powder, Aluminum, Complexation, Condensation, Diffraction, Fused salts, Halide minerals, Metal ions, Phase diagrams, System stability, Ternary systems, Thermoanalysis, Thermodynamic stability, Vapors, X ray powder diffraction, Crystal structure
Аннотация: The compound NaAlF4 has been obtained in the form of thin fibrous Crystals OF fine colorless powder by condensation at 18 degrees C of vapors arising over chiolite Na5Al3F14 or NaCaAlF6, heated up to 800 degrees C. Thermal stability has been investigated by the methods of thermal analysis and high temperature X-ray diffraction. WheПоказать полностьюn heated in air, NaAlF4 is Stable up to 390-400 degrees C, then there is an exothermal solid state decay into Na5Al3F14(s) and AlF3(s). At higher temperature Na5Al3F14(s) decays into Na3AlF6(s) and NaAlF4(g). The crystal structure (space group Cmcm, a=3.6124(1)angstrom, b=14.9469(7)angstrom, c=5.2617(3)angstrom, V=284.10 angstrom(3)) has been determined by X-ray powder diffraction method. In the crystal structure of NaAlF4 the octahedrons [AlF6] are joined through vertices and form corrugated layers. sodium ion layers being located between them. The distances between the atoms of AI-F are in the range 1.791-1.814 angstrom, and those for Na center dot center dot center dot F are in the range 2.297-2.439 angstrom. In spite of limited thermal stability of the crystal form, the compound NaAlF4 is the main component of the gas mixture over solid and molten salts in the ternary system NaF-AlF3-CaF2 and participates in chemical transformations between the phases at high temperature. (C) 2009 Elsevier Inc. All rights reserved.
Журнал: JOURNAL OF SOLID STATE CHEMISTRY
Выпуск журнала: Vol. 183, Is. 2
Номера страниц: 431-436
ISSN журнала: 00224596
Место издания: SAN DIEGO
Издатель: ACADEMIC PRESS INC ELSEVIER SCIENCE