Preparation and crystal structure of Sb V 1.50 In III 0.50 (PO 4 ) 3 and (Sb V 0.50 In III 0.50 )P 2 O 7

Synthesis and structure of two phosphates belonging to the ternary Sb 2 O 5 –In 2 O 3 –P 2 O 5 system are realized. Structures of Sb V 1.50 In III 0.50 (PO 4 ) 3 and (Sb V 0.50 In III 0.50 )P 2 O 7 phases, obtained by solid state reaction in air at 950 °C, were determined at room temperature from X-ray powder diffraction using the Rietveld method. Sb V 1.50 In III 0.50 (PO 4 ) 3 have a monoclinic (space group P 2 1 / n ) distortion of the Sc 2 (W O 4 ) 3 -type framework. Its structure is constituted by corner-shared SbO 6 or InO 6 octahedra and PO 4 tetrahedra. Monoclinic unit cell parameters are a =11.801(2) Å, b =8.623(1) Å, c =8.372(1) Å, and β=90.93(1)°. (Sb 0.50 In 0.50 )P 2 O 7 is isotypic with (Sb 0.50 Fe 0.50 )P 2 O 7 and crystallizes in orthorhombic system (space group Pna 2 1 ) with a =7.9389(1) Å, b =16.0664(2) Å, and c =7.9777(1) Å. Its structure is built up from corner-shared SbO 6 or InO 6 octahedra and P 2 O 7 groups (two group-types). Each P 2 O 7 group shares its six vertices with three SbO 6 and three InO 6 octahedra, and each octahedron is connected to six P 2 O 7 groups.