Synthesis and structural characterization of new cadmium, zinc and iron based pyrophosphate: (Cd,Zn)25Fe(P2O7)2

The novel compound with the following nominal formulation (Cd, Zn)2.5Fe(P2O7)2 has been successfully prepared by the solid state reaction and characterized by single-crystal X-ray diffraction. This phosphate crystallizes in the orthorhombic system with the C2221 space group. Its crystal structure is formed by five types of cationic sites and by two unique (P2O7)4- anionic groups with a staggered conformation. In the structure, three sites are fulfilled by Zn2+ :(Zn(3), Zn(4)) and Fe(1)3+, the fourth site is localized in the Wyckoff position 4a (site symmetry 2 ‥) and is statically occupied by Cd2+ : Zn2+with ratio 0.586(2) : 0.413(8). The last site, localized in 8c Wyckoff position (site symmetry 1) is also occupied by a mixture of the two cations Cd2+ : Zn2+with occupancies of 0.444(6) : 0.555(4).Within this framework, the metallic polyhedra [MOn] (n = 5 or 6) form corrugated layers stacked along the b-axis, and intercalated by P2O7 groups