Simultaneously enhanced insulation and piezoelectricity in Zr-doped BiFeO₃-BaTiO₃ lead-free ceramics

Bismuth ferrite-barium titanate (BF-BT) piezoelectric ceramics typically suffer from high leakage current and dielectric loss, which impede full domain polarization and weaken their piezoelectric response. To address these limitations, BF-BT ceramics were doped with varying amounts of ZrO2 and systematically assessed its effects on phase composition, microstructure, and electromechanical properties. Rietveld refinement of X-ray diffraction (XRD) data shows that the undoped ceramic primarily consist of rhombohedral (R3c) and cubic (Pmm) phases, with the R3c phase accounting for 35.83 %, increasing Zr content steadily raises the R3c fraction. Scanning electron microscopy (SEM) microstructural analysis reveals that average grain size grows with Zr doping, reaches a peak at 0.3 wt% Zr, then decreases at higher levels. Importantly, Zr doping boosts the resistivity at 400 degrees C from 1.3 x 10(2) to 7.4 x 10(4) Omega cm and markedly enhances electrical homogeneity. At 0.3 wt% Zr, the ceramics achieve a peak piezoelectric coefficient (d(33) similar to 204 pC/N) while retaining a relatively high Curie temperature (T-c = 443 degrees C). These findings demonstrate that high-valence Zr4+ doping is an effective strategy to suppress leakage current and improve piezoelectric performance in BF-BT piezoelectric ceramics.