An arsenate with the α-CrPO4 structure type, NaCa1-xNi3-2xAl2x(AsO4)3 (x = 0.23): crystal structure, charge-distribution and bond-valence-sum analyses.

Author(s) Ben Smail, R.; Zid, M.Faouzi
Journal Acta Crystallogr C Struct Chem
Date Published 2017 Nov 01
Abstract

Since the discovery of electrochemically active LiFePO4, materials with tunnel and layered structures built up of transition metals and polyanions have become the subject of much research. A new quaternary arsenate, sodium calcium trinickel aluminium triarsenate, NaCa1-xNi3-2xAl2x(AsO4)3 (x = 0.23), was synthesized using the flux method in air at 1023 K and its crystal structure was determined from single-crystal X-ray diffraction (XRD) data. This material was also characterized by qualitative energy-dispersive X-ray spectroscopy (EDS) analysis and IR spectroscopy. The crystal structure belongs to the α-CrPO4 type with the space group Imma. The structure is described as a three-dimensional framework built up of corner-edge-sharing NiO6, (Ni,Al)O6 and AsO4 polyhedra, with channels running along the [100] and [010] directions, in which the sodium and calcium cations are located. The proposed structural model has been validated by bond-valence-sum (BVS) and charge-distribution (CHARDI) tools. The sodium ionic conduction pathways in the anionic framework were investigated by means of the bond-valence site energy (BVSE) model, which predicted that the studied material will probably be a very poor Na+ ion conductor (bond-valence activation energy ∼7 eV).

DOI 10.1107/S2053229617013213
ISSN 2053-2296
Citation Acta Crystallogr C Struct Chem. 2017;73(Pt 11):896904.

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