Structure, Infrared and Raman spectroscopic studies of the new Ba(NbV 0.5MIII0.5)(PO4)2 (MIII = Al, Cr, Fe, In) yavapaiite compounds ‘series

Abstract

<jats:p>Synthesis and structural study of the new Ba(NbV 0.50MIII 0.50)(PO4)2 (MIII = Al, Cr, Fe, In) phosphates, abbreviated as [BaNbM], were reported here for the first time. Structures of [BaNbM] compounds, obtained by solid-state reaction in air atmosphere, were determined at room temperature from X-ray powder diffraction using the Rietveld method. The four studied compoundsfeature the yavapaiite-type structure, with space group C2/m ( 3 C2h , N°12) and Z = 2. Their framework can be described as consisting of dense slabs of Nb(M)O6 octahedra and PO4 tetrahedra interconnected via corner-sharing, alternating along the c-axis with layers of Ba cations in ten-fold coordination. Raman and Infrared spectroscopic study were used to obtain further structural information about the nature of bonding in selected compositions. Assignments of Nb-O, M-O and P-O Raman and Infrared bands, in [BaNbM] compounds, were based on those already known in the literature for niobium and phosphates oxides. Some empirical relationships, connecting Raman stretching frequencies to the obtained Nb-O and P-O distance values, were also used for assignments of various Raman bands</jats:p>