Structure,infrared and Raman spectroscopic studies of newly synthetic AII(SbV0.50FeIII0.50)(PO4)2 (ABa,Sr, Pb) phosphates with yavapaiite structure

The synthesis and structural study of three new A^II(Sb^V_0.5Fe^III_0.5)(PO₄)₂ (ABa, Sr, Pb) phosphates belonging to the ASbFePO system were reported here for the first time. Structures of Ba], Sr] and Pb] compounds, obtained by solid state reaction in air atmosphere, were determined at room temperature from X-ray powder diffraction using the Rietveld method. Ba^II(Sb^V_0.5Fe^III_0.5)(PO₄)₂ features the yavapaiite-type structure, with space group C2/m, Z = 2 and a = 8.1568(4) Å; b = 5.1996(3) Å c = 7.8290(4) Å; β = 94.53(1)°. A^II(Sb^V_0.5Fe^III_0.5)(PO₄)₂ (ASr, Pb) compounds have a distorted yavapaiite structure with space group C2/c, Z = 4 and a = 16.5215(2) Å; b = 5.1891(1) Å c = 8.0489(1) Å; β = 115.70(1)° for Sr]; a = 16.6925(2) Å; b = 5.1832(1) Å c = 8.1215(1) Å; β = 115.03(1)° for Pb]. Raman and Infrared spectroscopic study was used to obtain further structural information about the nature of bonding in selected compositions.