Structural and transport properties of Li-intercalated vanadium pentoxide nanocrystalline films

Abstract

The X-ray diffraction (XRD), transmission electron microscopy, density, electrical and thermoelectric power (TEP) properties of nanocrystalline Li _x V₂O₅ ⋅ nH₂O xerogel films (0 ≤ x ≤ 22 mol.%) were investigated. The films were produced by the sol–gel technique (colloidal route), which was used to enable high-purity, uniform preparation. The relative intensity of the (002) XRD line increased with increasing Li content. The particle size was found to be about 6.0 nm. Electrical conductivity and thermoelectric power were measured parallel to the substrate surface in the temperature range 300–480 K for the as-prepared films. The electrical conductivity showed that all the samples were semiconductors and that conductivity increased with increasing Li content. The conductivity of the present system was primarily determined by hopping carrier mobility, which was found to vary from 6.81 × 10⁻⁶ to 0.33 × 10⁻⁶ cm² V⁻¹ s⁻¹ at 380 K. The carrier density was evaluated to be 8.73 × 10¹⁹–1.118 × 10²¹ cm⁻³. The conduction was confirmed to obey non-adiabatic small polaron hopping. The thermoelectric power, or Seebeck effect, increased with increasing Li content. The results obtained indicate an n-type semiconducting behavior within the temperature range investigated.

Keywords:

• X-ray diffraction
• density, vanadium pentoxide xerogel
• nanocrystalline film
• electrical conductivity
• small polaron hopping
• hopping carrier mobility
• Seebeck effect

Acknowledgement

The authors thank KAST of Saudi Arabia for financial support (Grant No. 29/128).