Phosphates of Zirconium and Metals (Ni, Cu, Co, and Mn) in the Oxidation State of +2: Synthesis and Structure

Abstract

The formation of phases and the structure of phosphates in the M_0.5 + _xM′_xZr₂ − _x(PO₄)₃ systems (M = Co, Mn; M′ = Ni, Cu; 0 ≤x ≤ 2) were studied. The formation of complex phosphate phases synthesized by the sol-gel method was investigated by X-ray diffraction, electron microscopy, microprobe analysis, and IR spectroscopy. The formation of limited solid solution crystallizing in the Sc₂(WO₄)₃ structural type was established in the studied systems. The regularities of changes in their crystallographic characteristics depending on the chemical composition were elucidated. The crystal structure of Mn_1.2Ni_0.7Zr_1.3(PO₄)₃ was refined by the Rietveld method using powder X-ray diffraction data (space group P2₁/n, Z = 4, a = 8.8317(13) Å, b = 8.9350(11) Å, c = 12.4893(17) Å, β = 90.027(26)°, V = 985.55(23) ų). The obtained data on the formation of M_0.5 + _xM′_xZr₂ − _x(PO₄)₃ solid solutions (M = Co, Mn; M′ = Ni, Cu) broadened the phase formation picture for the known phosphates with octahedral-tetrahedral {[L₂(PO₄)₃]^p−}_3∞ type frameworks and characterized the general trends in the size dependence of the structure of phosphates and the limits of solid solutions.