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

• A new AII(SbV0.5FeIII0.5)(PO4)2 (ASr, Pb, Ba) family of yavapaiite was described.
• A strategy of structural determination was applied.
• IR and Raman of AIISbV0.5FeIII0.5(PO4)2 (ASr, Pb) was studied.

The synthesis and structural study of three new AII(SbV0.5FeIII0.5)(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. BaII(SbV0.5FeIII0.5)(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)°. AII(SbV0.5FeIII0.5)(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.

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