A novel oxide ion conductor in a doped Bi₂O_3-V₂O₅ system: ab initio structure of a new polymorph of NaBi₃V₂O₁₀ via powder X-ray diffraction

Abstract

The crystal structure of NaBi₃V₂O₁₀ has been determined using the ab initio approach followed by Rietveld refinement via powder X-ray diffraction. The unit cell is triclinic, space group P, with a = 7.1964(4) Å, b = 7.0367(3) Å, c = 5.5139(2) Å, α = 84.440(3)°, β = 113.461(2)°, γ =112.319(2)° , and V =236.46(2) ų. The final refinements gave R_p = 9.94%, R_wp = 13.11%, and R_(I,hkl) = 8.73% for 30 parameters and 4871 data points. These results indicate that this is a polymorph different from that reported previously and represents a new class of oxide ion conductors in solid solution of the Na₂O-Bi₂O₃-V₂O₅ ternary system. The (Bi₂O₂)²⁺ chains extend along the c axis with VO₄ units joining the chains along both a and b directions resulting in a hitherto unknown motif in this class of compounds. The structure hence points to a new mode for the mechanism of oxide ion conduction.