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Title: Thermal transformation of quaternary compounds in NaF-CaF{sub 2}-AlF{sub 3} system

Abstract

Details of quaternary compounds formation in the system NaF-CaF{sub 2}-AlF{sub 3} are specified. To achieve this aim, the samples of phases NaCaAlF{sub 6} and Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} have been obtained by high-temperature solid-phase synthesis. Their thermal behavior when heated up to 800 deg. C has been studied using the methods of high-temperature X-ray diffraction (XRD) and thermal analysis (TA). The system under consideration can be regarded as a quasibinary section CaF{sub 2}-NaAlF{sub 4}, where at T=745-750 deg. C invariant equilibrium is implemented with the phases CaF{sub 2}-NaCaAlF{sub 6}-Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14}-(liquid melt)-(NaAlF{sub 4}). The peculiarity of the equilibrium is NaAlF{sub 4} metastability at normal pressure. Below the equilibrium temperature the quaternary phase Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} is stable and NaCaAlF{sub 6} above this temperature. The phase NaCaAlF{sub 6} fixed by rapid quenching from high temperatures and when heated up to 640 deg. C decomposes, yielding Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14}. Further heating in vacuum at temperature up to 740 deg. C results in decomposition of Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} into CaF{sub 2} and Na{sub 3}AlF{sub 6}. The expected reverse transformation of Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} into NaCaAlF{sub 6} has not been observed under experimentalmore » conditions. Transformations in bulk samples reveal direct and reverse transformation of quaternary phases. Synopsis: Thermal transformation of the quaternary compounds in system (NaF-CaF{sub 2}-AlF{sub 3}) was investigated using high-temperature X-ray diffraction (XRD) and thermal analysis (TA). In the system the invariant equilibrium is implemented with the phases CaF{sub 2}-NaCaAlF{sub 6}-Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14}-(liquid melt)-(NaAlF{sub 4}) at T=745-750 deg. C. - Graphical Abstract: The paper concerns of a small piece of the ternary system (NaF-CaF{sub 2}-AlF{sub 3}) which is very important for aluminum production. Details of phase relations were not fully understand up till now because of experimental difficulties: aggressive reagents and high temperature. However, the phase diagram is very important for production control.« less

Authors:
 [1];  [2]
  1. Institute of Chemistry and Chemical Technology SB RAS, K. Marx St., 42, Krasnoyarsk 660049 (Russian Federation)
  2. Siberian Federal University, Svobodny Str., 79, Krasnoyarsk 660041 (Russian Federation)
Publication Date:
OSTI Identifier:
21370547
Resource Type:
Journal Article
Journal Name:
Journal of Solid State Chemistry
Additional Journal Information:
Journal Volume: 182; Journal Issue: 8; Other Information: DOI: 10.1016/j.jssc.2009.05.043; PII: S0022-4596(09)00248-5; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Journal ID: ISSN 0022-4596
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALUMINIUM FLUORIDES; CALCIUM FLUORIDES; DECOMPOSITION; EQUILIBRIUM; HEATING; PHASE DIAGRAMS; QUENCHING; SODIUM FLUORIDES; SYNTHESIS; TEMPERATURE RANGE 0400-1000 K; TEMPERATURE RANGE 1000-4000 K; THERMAL ANALYSIS; X-RAY DIFFRACTION; ALKALI METAL COMPOUNDS; ALKALINE EARTH METAL COMPOUNDS; ALUMINIUM COMPOUNDS; CALCIUM COMPOUNDS; CALCIUM HALIDES; CHEMICAL REACTIONS; COHERENT SCATTERING; DIAGRAMS; DIFFRACTION; FLUORIDES; FLUORINE COMPOUNDS; HALIDES; HALOGEN COMPOUNDS; INFORMATION; SCATTERING; SODIUM COMPOUNDS; TEMPERATURE RANGE

Citation Formats

Zaitseva, Julia N, Yakimov, Igor S, Kirik, Sergei D., E-mail: kirik@icct.r, and Siberian Federal University, Svobodny Str., 79, Krasnoyarsk 660041. Thermal transformation of quaternary compounds in NaF-CaF{sub 2}-AlF{sub 3} system. United States: N. p., 2009. Web. doi:10.1016/j.jssc.2009.05.043.
Zaitseva, Julia N, Yakimov, Igor S, Kirik, Sergei D., E-mail: kirik@icct.r, & Siberian Federal University, Svobodny Str., 79, Krasnoyarsk 660041. Thermal transformation of quaternary compounds in NaF-CaF{sub 2}-AlF{sub 3} system. United States. https://doi.org/10.1016/j.jssc.2009.05.043
Zaitseva, Julia N, Yakimov, Igor S, Kirik, Sergei D., E-mail: kirik@icct.r, and Siberian Federal University, Svobodny Str., 79, Krasnoyarsk 660041. 2009. "Thermal transformation of quaternary compounds in NaF-CaF{sub 2}-AlF{sub 3} system". United States. https://doi.org/10.1016/j.jssc.2009.05.043.
@article{osti_21370547,
title = {Thermal transformation of quaternary compounds in NaF-CaF{sub 2}-AlF{sub 3} system},
author = {Zaitseva, Julia N and Yakimov, Igor S and Kirik, Sergei D., E-mail: kirik@icct.r and Siberian Federal University, Svobodny Str., 79, Krasnoyarsk 660041},
abstractNote = {Details of quaternary compounds formation in the system NaF-CaF{sub 2}-AlF{sub 3} are specified. To achieve this aim, the samples of phases NaCaAlF{sub 6} and Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} have been obtained by high-temperature solid-phase synthesis. Their thermal behavior when heated up to 800 deg. C has been studied using the methods of high-temperature X-ray diffraction (XRD) and thermal analysis (TA). The system under consideration can be regarded as a quasibinary section CaF{sub 2}-NaAlF{sub 4}, where at T=745-750 deg. C invariant equilibrium is implemented with the phases CaF{sub 2}-NaCaAlF{sub 6}-Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14}-(liquid melt)-(NaAlF{sub 4}). The peculiarity of the equilibrium is NaAlF{sub 4} metastability at normal pressure. Below the equilibrium temperature the quaternary phase Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} is stable and NaCaAlF{sub 6} above this temperature. The phase NaCaAlF{sub 6} fixed by rapid quenching from high temperatures and when heated up to 640 deg. C decomposes, yielding Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14}. Further heating in vacuum at temperature up to 740 deg. C results in decomposition of Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} into CaF{sub 2} and Na{sub 3}AlF{sub 6}. The expected reverse transformation of Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} into NaCaAlF{sub 6} has not been observed under experimental conditions. Transformations in bulk samples reveal direct and reverse transformation of quaternary phases. Synopsis: Thermal transformation of the quaternary compounds in system (NaF-CaF{sub 2}-AlF{sub 3}) was investigated using high-temperature X-ray diffraction (XRD) and thermal analysis (TA). In the system the invariant equilibrium is implemented with the phases CaF{sub 2}-NaCaAlF{sub 6}-Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14}-(liquid melt)-(NaAlF{sub 4}) at T=745-750 deg. C. - Graphical Abstract: The paper concerns of a small piece of the ternary system (NaF-CaF{sub 2}-AlF{sub 3}) which is very important for aluminum production. Details of phase relations were not fully understand up till now because of experimental difficulties: aggressive reagents and high temperature. However, the phase diagram is very important for production control.},
doi = {10.1016/j.jssc.2009.05.043},
url = {https://www.osti.gov/biblio/21370547}, journal = {Journal of Solid State Chemistry},
issn = {0022-4596},
number = 8,
volume = 182,
place = {United States},
year = {Sat Aug 15 00:00:00 EDT 2009},
month = {Sat Aug 15 00:00:00 EDT 2009}
}