Structural aspects of the formation of solid solutions in the NaF-KF-AlF3 system
| Autor: | Sergei D. Kirik, Igor S. Yakimov, Peter S. Dubinin, Sergei G. Ruzhnikov, Yulia N. Zaitseva, Alexander S. Samoilo, Oksana E. Piksina |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Potassium
Analytical chemistry chemistry.chemical_element 02 engineering and technology Crystal structure 010402 general chemistry 01 natural sciences law.invention Inorganic Chemistry chemistry.chemical_compound law Phase (matter) Materials Chemistry Calcination Physical and Theoretical Chemistry Thermal analysis Ternary numeral system 021001 nanoscience & nanotechnology Condensed Matter Physics Cryolite 0104 chemical sciences Electronic Optical and Magnetic Materials Crystallography chemistry Ceramics and Composites 0210 nano-technology Solid solution |
| Zdroj: | Journal of Solid State Chemistry. 252:1-7 |
| ISSN: | 0022-4596 |
| DOI: | 10.1016/j.jssc.2017.04.037 |
| Popis: | The formation of solid solutions in the ternary system NaF-KF-AlF 3 has been studied by X-ray diffraction and thermal analysis. Chiolite has been shown to form solid solutions with the composition (Na (5−x) K x )Al 3 F 14 , in the limited range of 0 a ) 7.010 (3) −7.050 (3) A, for ( c ) 10.365 (10) −10.400 (10) A. According to the investigation of the crystal structure, potassium cations substitute sodium only in the 2-fold position in the amount of ~40%. The solid solutions are stable in the range from room to melting point temperature. A wide range of solid solutions based on β-cryolite (Na 3 AlF 6 ) and elpasolite (K 2 NaAlF 6 ) above 540 °C has been studied in detail. It is only the 8-fold cationic position in the β-cryolite structure which appears to have contributed into the substitution in the full range of solid solutions. The solid solution decays into a mixture of α-Na 3 AlF 6 and K 2 NaAlF 6 upon calcination below 540 °C., followed by further cooling without changing the α-Na 3 AlF 6 composition. Elpasolitе initially containing an excess of sodium ions, has yielded cryolite and stoichiometric K 2 NaAlF 6 below 340 °C. The phase K 2 NaAl 3 F 12 present in two polymorphic forms, has not formed a wide range of solid solutions; however, a slight excess of potassium ions has improved the stability of the high-temperature form. |
| Databáze: | OpenAIRE |
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