Synthesis, crystal structure and ionic conductivity of a new open-framework arsenate K0.405Bi0.865AsO4

Abstract

K0.405Bi0.865AsO4 compound has been prepared via solid state reaction. Its structure was determined using single crystal X-ray diffraction data. The space group was P31 with a = 7.237(1) Ǻ, c = 6.790(2) Ǻ and Z = 3. The crystal structure was made of BiO8 polyedra sharing corners and edges with AsO4 tetrahedra. The structure can be described as infinite anionic layers parallel to the (100) plane, connected via As–O–Bi bridges to form a three dimensional framework. This architecture delimits tunnels running along the [001] direction where the potassium ions are included. The structure model was confirmed by bond valence sum (BVS) and charge distribution (CD) methods. The electrical properties of the compound were determined by impedance spectroscopy. The conductivity increases from 1.607 × 10−7 S cm−1 at 300 °C to 1.023 × 10−4 S cm−1 at 677 °C. The activation energy deduced from the slope is 0.88 eV. Potassium pathways migrations in the anionic frameworks were simulated using the bond valence sum map (BVSM) model. The noncentrosymmetry of the space group was confirmed by second harmonic generation experiments carried out at 1.06 μm on a powder sample.