Effect of rare earth oxide doping on microstructure and piezoelectric properties of BCTSZ ceramics

The five types of rare earth oxides are introduced as dopants into Ba_0.98Ca_0.02Ti_0.94Sn_0.04Zr_0.02 (BCTSZ) ceramics using the conventional solid-state approach. This leads to the fabrication of lead-free piezoelectric ceramics denoted as (1–x) (Ba_0.98Ca_0.02Ti_0.94Sn_0.04Zr_0.02)-xM₂O₃ (0 mol% ≤ x ≤ 0.12 mol%, M = La, Ce, Pr, Nd, Sm), where the molar fraction x ranges from 0 to 0.12 and M represents the dopant elements La, Ce, Pr, Nd, and Sm. The effect of doping the five different rare earth oxides on the phase structure, microstructure, and electrical properties of BaTiO₃-based piezoelectric ceramics are investigated. The results reveal the formation of the morphotropic phase boundary (MPB) in all ceramics at a M₂O₃ doping concentration of x = 0.06 mol%. Samples with morphotropic phase boundary typically exhibit relatively good piezoelectric properties. In comparison to other rare earth oxides, BCTSZ ceramics doped with Nd₂O₃ demonstrate larger grain sizes and more nano-ferroelectric domains, achieving optimal electrical properties at doping concentration of x = 0.06 mol%. The electrical properties are as follows: d₃₃ = 463 pC/N, k_p = 56.56%, T_O-T = 36.5 °C, T_C = 87.5 °C, ε_r = 3720, and tanδ = 2.07%. The effect of various rare earth oxides on the electrical properties of BaTiO₃-based piezoceramics under different doping contents were studied through numerous experiments.