New positive mixed alkali effect in V2O5.nH2O nanocrystalline films

Abstract

V₂O₅·nH₂O nanocrystalline films intercalated with Li⁺ and Na⁺ ions were prepared using the sol–gel technique. The compositions of Li_xNa_1-xV₂O₅·nH₂O were varied with 0 ≤ x ≤ 1 mol% to investigate the mixed alkali effect on structural properties, such as density and X-ray diffraction (XRD), as well as DC electrical conductivity and thermoelectric power. XRD analysis revealed that the Li_xNa_1-xV₂O₅·nH₂O films consist of highly oriented nanocrystals. Structural analysis showed that the intercalation of alkali ions did not significantly alter the structure, while the crystallite size and interlayer spacing exhibited a nonlinear dependence on Li content. Density calculations revealed a linear dependence on composition. The variation of DC conductivity showed a maximum conductivity (σ_dc) and minimum activation energy (W_dc) at x = 0.5 mol%, which can be attributed to the mixed alkali effect resulting from the mixing of two alkali oxides. The thermoelectric power (S) and power factor (PF) exhibited nonlinear behavior due to the mixed alkali effect.