Synthesis, crystal structure refinement, electrical and magnetic properties of BaV₁₃O₁₈ and SrV₁₃O₁₈

Polycrystalline samples of BaV₁₃O₁₈ and SrV₁₃O₁₈ were prepared by solid-state reaction of BaCO₃, SrCO₃, V₂O₅ and V at 1773-2073 K in flowing Ar. The crystal structures of BaV₁₃O₁₈ (R-3, a_h = 12.6293(10) Å, c_h = 7.0121(4) Å) and SrV₁₃O₁₈ (a_h = 12.5491(7) Å, c_h = 6.9878(3) Å) were refined by the Rietveld method using X-ray diffraction data. BaV₁₃O₁₈ exhibited semiconducting behavior with electrical resistivity from 5.8 × 10^-3 to 2.7 × 10^-3 Ω cm at 100-300 K. Electrical resistivity of SrV₁₃O₁₈ ranged from 1.5 × 10^-3 to 1.8 × 10^-3 Ω cm, and it increased slightly up to around 250 K and decreased above 250 K with increasing temperature. Negative Seebeck coefficients of both compounds at 100-300 K indicated that electron was the dominant carrier. BaV₁₃O₁₈ and SrV₁₃O₁₈ showed paramagnetism with the effective magnetic moment of 0.11 μ_B and 0.15 μ_B, respectively, at 10-100 K.