Linking defect structure to electrical behavior in vanadium-doped CeO2 films: Insights from theory and experiment

This work explores vanadium-doped CeO 2 nanoparticles synthesized via microwave-assisted hydrothermal synthesis. Computational simulation demonstrated a change in the electron density due to the reduction of V 5+ /V 4+ to V 3+ , which creates defect states near the Fermi level and superpolaron formation. This leads to spin-dependent electronic asymmetry and enhanced charge transport via Ce 3+ –O states. The resulting structure explains the increased conductivity and the inverted Arrhenius behavior observed under reducing conditions. Positron Annihilation Lifetime Spectroscopy revealed that V doping in CeO 2 reduces both τ 1 and τ 2 lifetimes, indicating changes in the defect structure of the samples. The data suggests mixed positron annihilation in the defective matrix and neutral vacancy-cation complexes. Vanadium doping further enhances conductivity across all atmospheres by introducing additional vacancies via the Ce 4+ → V 3+ substitution and thermal reduction. In summary, this study demonstrates that vanadium acts as a tunable redox center, coupled with atmosphere-dependent oxygen vacancy dynamics, enabling the maximization of CeO 2 electrical conductivity under reducing conditions. These findings establish V-doped CeO 2 as a highly promising material for advanced gas-sensing applications, particularly for CO detection, where performance is intrinsically linked to the interplay between the vanadium redox state, defect formation, and enhanced electronic transport. • Establishes a direct link between defect chemistry, electronic structure, and charge transport in vanadium-doped CeO 2 films. • Reveals reduction-induced localized defect states and superpolaron formation near the Fermi level through combined DFT and advanced spectroscopy. • Identifies a transition from polaronic to vacancy-mediated conduction, leading to enhanced conductivity under reducing conditions. • Explains the origin of an inverted Arrhenius behavior as a kinetic crossover between low- and high-temperature transport regimes.