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Crystal structure of two phosphates belonging to the Sb2O5-Cr2O3-P2O5 system

Abderrahim Aatiq, Rachid Bakri, Btissame Haggouch, My Rachid Tigha,Said Benmokhtar1, Rodolphe Heyd

Structures of the two SbV 1.50CrIII 0.50 (PO4)3 and (SbV 0.50CrIII 0.50) P2O7 phases, obtained by solid state reaction in air atmosphere at 950°C, were determined at roomtemperature fromX-ray powder diffraction using the Rietveldmethod. SbV 1.50CrIII 0.50 (PO4)3 belongs to the Nasicon-type structure (R 3 c space group, Z = 6, ahex. = 8.2770(1) Å and chex. = 22.0605(2) Å). Their structure is built up by corner-sharing Sb(Cr)O6 octahedra and PO4 tetrahedra. XRD patterns of (Sb0.50Cr0.50) P2O7 is indexed on a cubic unit cell similar to that of ZrP2O7 (Pa 3 space group; Z = 4, a = 7.818(2) Å.). Their structure is built up from corner-shared SbO6 or CrO6 octahedra and P2O7 groups. Within the structure, each P2O7 shares its six vertices with Sb(Cr)O, octahedra and each Sb(Cr)O6 octahedra is connected to six P2O7 groups.