Doping effects and role conversion of CeO2 in 0.3PZN–0.7PZT ternary piezoelectric ceramics with enhanced electrical properties

Abstract

In this work, the rare-earth doped ternary lead zirconate titanate ceramics with chemical formula of [0.3Pb(Zn1/3Nb2/3)O3–0.7Pb(Zr0.52Ti0.48)O3] + x wt% CeO2 (x=0–0.5, abbreviated as 0.3PZN–0.7PZT–xCe) were synthesized by a conventional solid-state reaction route, specific attentions was focused on the effects of CeO2 dopants on the structures and electrical properties of the 0.3PZN–0.7PZT ceramics, revealing the role conversion of CeO2 dopants with its doping amount (x). When less CeO2 (x≤0.2) is introduced into 0.3PZN–0.7PZT, the prepared ceramics are identified as the coexistence of rhombohedral and tetragonal phases, also involved with an increased grain size and a reduced atomic ratio of Pb/(Zr+Ti+Zn+Nb). The increased remanent polarization (Pr) and deceased coercive filed (Ec), as well as improved dielectric permittivity (εr) and piezoelectric coefficient (d33) demonstrate the donor substitution of Ce3+ for Pb2+ at the A-site of perovskite lattice. Conversely, the introduction of excessive CeO2 (x>0.2) causes a reversal evolution in the electrical properties of ceramics, suggesting that some of the introduced cerium element tends to become Ce4+, which equivalently substitutes for Zr4+ at the B-site. Additionally, the diffused phase transition (DPT) behaviors of the 0.3PZN–0.7PZT–xCe ceramics were investigated by the modified Curie–Weiss Law. The sample with x=0.2 shows reduced DPT character and optimized electrical properties, including TC=297 °C, εr=1400, d33=480 pC/N, tanδ=1.6%, kp=65%, d33×g33=16.32×10–12 m2/N, Pr=38.3 μC/cm2 and Ec=1.02 kV/mm. These enhanced electrical properties not only are contributed by the donor substitution effect of Ce3+, but also benefit from the optimized morphotropic phase boundary that is close to the tetragonal-rich side.