Syntheses, structures and properties of metal phosphates Pb2Mg(PO4)2, Pb4Zn8(PO4)8 and α-BaZn2(PO4)2

Pb2Mg(PO4)(2), Pb4Zn8(PO4)(8) and alpha-BaZn2(PO4)(2) have been synthesized by the standard solid-state reaction and their structures were determined by single crystal X-ray diffraction for the first time. Pb2Mg(PO4)(2), Pb4Zn8(PO4)(8) and alpha-BaZn2(PO4)(2) crystallize in the monoclinic crystal system, P2(1)/c, C2/c and the trigonal crystal system, P (3) over bar m1, respectively. The structure of Pb2Mg(PO4)(2) possesses a three-dimensional framework consisting of MgO6 octahedra and PO4 tetrahedra and the Pb2+ cations reside in the [Mg6P6O12] tunnels. Pb4Zn8(PO4)(8) and alpha-BaZn2(PO4)(2) are two-dimensional layered structures with [Zn4P4O16](infinity) layers for Pb4Zn8(PO4)(8) and [Zn3P3O12](infinity) honeycomb double layers for alpha-BaZn2(PO4)(2). And in the structure of Pb4Zn8(PO4)(8), there are four different Zn-P-O layers, which is reported for the first time in zinc phosphates. In addition, thermal property analysis, and UV-Vis-NIR diffuse reflectance and infrared spectroscopy were also performed. First-principles theoretical studies were also conducted to aid the understanding of their band structures and densities of states.