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BaSr(NH 4 )Mg 5 F 15 , a Tetragonal Tungsten Bronze Structure with Ammonium Barium Disorder and its Solid Solutions Ba x Sr 2−x (NH 4 )Mg 5 F 15 (x = 1.8−0.6)
Author(s) -
Kubel F.,
Pantazi M.
Publication year - 2007
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200600380
Subject(s) - tetragonal crystal system , barium , solid solution , tungsten , materials science , nanocrystalline material , crystal structure , crystallography , crystallite , inorganic chemistry , fluoride , ammonium fluoride , analytical chemistry (journal) , octahedron , powder diffraction , aqueous solution , chemistry , metallurgy , chromatography
The new fluoride BaSr(NH 4 )Mg 5 F 15 precipitates as a nanocrystalline powder from aqueous solutions of the alkaline earth ions and ammonium fluoride. The compound crystallizes in the tetragonal tungsten bronze structure type with lattice parameters of a,b = 12.4492(14) Å and c = 3.9421(4) Å (space group P 4/ mbm [Nr. 127], structure refinement from powder data, R Bragg = 4.0 %). Corner‐linked magnesium‐fluoride octahedra form a channel structure which contains one empty triangular channel, one channel filled with Sr 2+ [CN = 8+4] and one channel with disordered Ba 2+ and NH 4 + (ratio 1:1) with CN = 7+8. Solid solutions between the composition limits Ba(Ba 0.8 Sr 0.2 )(NH 4 )Mg 5 F 15 and (Ba 0.6 Sr 0.4 )Sr(NH 4 )Mg 5 F 15 were obtained. The crystallite size increases from 15 to 75 nm with increasing barium concentration. The thermal stability between 350 to 450 °C depends on the amount of absorbed (NH 4 )F. Heated samples show luminescence and phosphorescence.