Effects of Bi2O3 additive on sintering process and dielectric, ferroelectric, and piezoelectric properties of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 lead-free piezoceramics

Lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) piezoceramics with Bi2O3 additive were synthesized using solid-state ceramic processing. Various amounts of Bi2O3 (0.05, 0.1, 0.5, and 1.0 mol%) were added after calcination, milled, compacted, and sintered with no compensation at A- or B-sites. Addition of up to 0.5 mol% Bi2O3 was found to greatly enhance the densification and increase the piezoelectric properties, while higher amounts decreased the grain size and induced relaxor-like electrical behavior, obeying the Vogel-Fulcher model. The highest properties were obtained for the BCZT with 0.1 mol% Bi2O3 sintered at 1350 °C: d33 = 325 pC/m, d33* = 509 pm/V (at 3 kV/mm), kp = 0.42, and Pr = 10.4 μC/cm2. The microstructure, phase composition, and local structure were investigated by scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The appearance of the A1g vibration mode in the Raman spectra and the shift of diffraction peaks to lower 2θ values indicate the incorporation of Bi3+ into the B-site of the perovskite BCZT structure.