Effect of Oxygen Vacancy Concentration on the Electrical Properties and Microstructure of Bi4Ti3O12 Ceramics: Experimental and First-Principles Investigation.

This paper investigates the impact of sintering temperature on oxygen vacancy concentration and its subsequent effect on the microstructure and electrical properties of Bi4Ti3O12 (BIT) ceramics. To further clarify these effects, VASP software was employed to simulate BIT ceramics with varying oxygen vacancy concentrations.The experimental results demonstrate that sintering temperature significantly influences the oxygen vacancy concentration. At the optimal sintering temperature of 1080 °C, the BIT ceramics exhibit a balanced microstructure with a grain size of 4.16 μm, the lowest measured oxygen vacancy concentration of 18.44%, and a piezoelectric coefficient (d33) of 9.8 pC/N. Additionally, the dielectric loss (tanδ) remains below 0.2 at 500 °C, indicating excellent thermal stability. VASP-based simulations reveal that increasing the oxygen vacancy concentration from 18.56% to 44.55% results in a significant collapse of the band gap (from 2.8 eV → 1.0 eV) and a transition in conductivity type from p-type to n-type. This shift induces a leakage current-dominated threshold effect, leading to a decrease in piezoelectric properties (d33 reduced from 9.8 to 6.9 pC/N). Atomic-scale density of states (DOS) analyses indicate that the delocalization of Ti3+ and the weakening of Bi-O hybridization collectively induce lattice distortion and ferroelectric inconsistency. These changes are correlated with an increase in dielectric loss and a slight reduction in Curie temperature (from 620 °C → 618 °C). In conclusion, this study comprehensively elucidates the influence of oxygen vacancy concentration on the microstructure and electrical properties of BIT ceramics. The findings provide a theoretical foundation and practical insights for designing high-performance piezoelectric ceramics.