Cation Distribution in the (Mg 1- xCu x) 3(PO 4) 2 Solid Solution, x = 0.46 and 0.79

• Published in: Journal of solid state chemistry 1994, Vol.108 (1), p.193-197
• Main Authors: Moqine, A., Boukhari, A., Holt, E.M.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Inorganic compounds; Physics; Salts; Single-crystal and powder diffraction; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; X-ray diffraction and scattering
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.1994.1030

Cation distributions in two related structures, (Mg 0.54Cu 0.46) 3(PO 4) 2(I) and (Mg 0.21Cu 0.79) 3(P0 4) 2(II) belonging to the system Mg 3(PO 4) 2-Cu 3(PO 4) 2 have been determined by single-crystal X-ray diffraction. (Mg 0.54Cu 0.46) 3(PO 4) 2I is isotypic with Mg(PO4)2; a = 7.608(3), b = 8.026(5), c = 5.116(3) Å, β = 92.73(4)°, monoclinic, P 2 1/ n, V = 312.0(3) Å3, Z = 2, D calc = 3.374 g cm -3, R = 5.8% for 549 observed reflections. (Mg 0.21Cu 0.79) 3(PO 4) 2II, is isotypic with Cu 3(PO 4) 2, a = 4.845(3), b = 5.265(3) c = 6.246(2) Å, α = 71.98(4), β = 93.04(4), γ = 111.42(4)°, triclinic, P1 bar, V = 140.7(1) Å 3, Z = 1, D calc = 4.198 g cm -3, R = 8.5% for 645 observed reflections. Both structures show mixed Mg/Cu trigonal bipyramidal sites (31% Mg 2+/69% Cu 2+). In I, additional positions of octahedral symmetry are occupied uniquely by Mg 2+ ions. In II, square planar sites contain only Cu 2+ ions.