Synthesis, structure and magnetic properties of the new oxygen-deficient perovskite Na3MnV2O7.5

The new ternary vanadate Na3MnV2O7.5 has been synthesized by solid state reaction route. Its crystal structure was determined from both powder X-ray diffraction data and high-resolution transmission electron microscopy (HRTEM) analysis. Na3MnV2O7.5 (P2/c, a = 7.4004(4) angstrom, b = 5.6065(3) angstrom, c = 17.0876(11) angstrom, beta = 90.0114(2)degrees, and Z = 4) crystallizes with a new type of oxygen-deficient perovskite ABO(3-delta) (delta = 1/2) with the sodium atoms occupying the A site and the vanadium and manganese atoms perfectly ordered in the B site. In Na3MnV2O7.5 the manganese and the vanadium atoms are octahedral and tetrahedral coordinated, respectively. The MnO6 and VO4 polyhedra share edges and form a perovskite 3D-framework with high disorder of the oxygen atoms. HRTEM confirmed this structural model. Na3MnV2O7.5 was characterized by magnetic susceptibility and specific heat measurements. It is anti-ferromagnetic with no magnetic ordering down to 2 K. (C) 2011 Elsevier Masson SAS. All rights reserved.