Synthesis, structural and electrical properties of a new cobalt arsenate NaCo2As3O10

The title compound sodium dicobalt triarsenate NaCo2As3O10 has been synthesized by solid state reaction. Crystal structure and electrical properties were studied by X-ray diffraction and complex impedance spectroscopy, respectively. The obtained structural model is supported by charge-distribution (CHARDI) analysis and bond-valence-sum (BVS) validations tools. The structure (triclinic, P-1, a=6.800 (8) angstrom, b=7.816 (9) angstrom, c=8.718 (3) angstrom, alpha=108.03 (2)degrees, beta=108.48 (3)degrees, gamma=100.11 (2)degrees) can be described as a three-dimensional framework resulted from corner-connection between cobalt metallic chains running along [-110] and As3O10 groups; the negative charge is balanced by Na+ ions which house the two tunnels parallel to a and b axes. Ball milling was used as mechanical means to reduce the particles sizes of the synthesized powder. At the optimal sintering temperature of 650 degrees C, 85% of the relative density was obtained. The conductivity measurements show that NaCo2As3O10 is a cationic conductor with an activation energy of 0.48 eV and a conductivity of sigma=1.2 x 10(-5) S cm(-1) at 310 degrees C. The BVS model is extended to simulate the ionic migration pathways of alkali cations in the anionic framework. (C) 2014 Elsevier Inc. All rights reserved.