Abstract
A new member of sodium metal diphosphate-diarsenate, Na2CuP1.5As0.5O7, was synthesized as polycrystalline powder by a solid-state route. X-ray diffraction followed by Rietveld refinement show that the studied material, isostructural with beta-Na2CuP2O7, crystallizes in the monoclinic system of the C2/c space group with the unit cell parameters a = 14.798(2) angstrom; b = 5.729(3) angstrom; c = 8.075(2) angstrom; beta = 115.00(3)degrees. The structure of the studied material is formed by Cu2P4O15 groups connected via oxygen atoms that results in infinite chains, wavy saw-toothed along the [001] direction, with Na+ ions located in the inter-chain space. Thermal study using DSC analysis shows that the studied material is stable up to the melting point at 688 degrees C. The electrical investigation, using impedance spectroscopy in the 260-380 degrees C temperature range, shows that the Na2CuP1.5As0.5O7 compound is a fast-ion conductor with sigma(350) degrees C = 2.28 10(-5) Scm(-1) and Ea = 0.6 eV. Na+ ions pathways simulation using bond-valence site energy (BVSE) supports the fast three-dimensional mobility of the sodium cations in the inter-chain space.