Cationic Distribution in α-MZr3F15 Series (M = Y, In, Ln, Tl)

• Published in: Journal of solid state chemistry Vol. 118; no. 2; pp. 389 - 396
• Main Authors: Laval, J.P., Gervais, J.F., Fournès, L., Grannec, J., Gravereau, P., Abaouz, A., Yacoubi, A.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01-09-1995; Elsevier
• Subjects: Chemical Sciences; Condensed matter: structure, mechanical and thermal properties; Engineering Sciences; Exact sciences and technology; Inorganic compounds; Material chemistry; Materials; Physics; Salts; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Inorganic compounds; Ternary compounds; Transition element compounds; XRD; Rare earth compounds; Experimental study; Order disorder; Ion distribution; Crystal structure
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.1995.1359

A series of fluorozirconates MZr3F15 was prepared by direct reaction of the binary fluorides, involving trivalent cations with a wide range of sizes: In, Tl, Lu, Yb, Y, Gd, Eu, and Pr (0.80 Å < Rion < 1.13 Å). The samples were synthesized in sealed Pt tubes and heated between 700 and 1000°C, except for TlZr3F15, which was heated at 500°C under F2 flow. Their crystal structure was solved by X-ray diffraction for single crystals of Y and Gd and for powders using the Rietveld method for the other phases. The structure is isotypic with that of BiZr3F15 and corresponds to a three-dimensional network of corner-sharing octahedra and dodecahedra, in a 1:3 proportion (cationic sites 6a and 18e of the R3̄c space group). The cationic distribution in these two sites depends on the size of the M3+ cation:
—Large cations, such as Y3+ and Ln3+, are localized in the 18e site, with Zr4+ distributed on both sites;
—a small cation, such as In3+, is perfectly ordered in an octahedral site, with Zr4+ in a dodecahedral coordination;
—a cation of medium size, such as Tl3+, presents an average distribution, with Zr4+ on both sites.
Structural relationships with anion-excess ReO3-type and with the low-temperature polymorph β-PrZr3F15 are discussed.