Structural, optical, thermal and conducting properties of V_2-xLi_xO_5-δ (0.15 ≤ x ≤ 0.30) systems

Lithium-doped vanadates (V_2-xLi_xO_5-δ (0.15 ≤ x ≤ 0.30)) are synthesized by melt-quench method. The physical, structural, optical, thermal and conducting properties of as-quenched samples are investigated using various experimental techniques to study their suitability for electrolyte in battery/solid oxide fuel cell application. X-ray diffraction (XRD) patterns confirm the formation of three different crystalline phases. FTIR and Raman spectra indicate that the doping of Li₂O into V₂O₅ leads to a transition from VO₅ into VO₄ structural unit. The optical diffused reflectance spectra revealed that the optical band gap (E_g) decreases from 2.2 to 2.08 eV while Urbach energy (E_U) increases (0.31-0.41 eV) with the addition of Li₂O content in place of vanadium. The thermal stability is studied by thermogravimetric analyser (TGA). The DC conductivity of the present samples is increased from 0.08 to 0.12 Scm^-1 at 450 °C with Li₂O doping. These materials can be used as electrolyte for battery/solid oxide fuel cell due to their good conductivity (~0.12 Scm^-1) at 450 °C.