Enhanced electric-field induced strain in Eu3+ doped 0.67BiFeO3-0.33BaTiO3 lead-free piezoelectric ceramics

Abstract

Lead-free ferroelectric ceramics, 0.67Bi1–xEuxFeO3-0.33BaTiO3 (BF-BT-xEu, x = 0–0.02), were prepared via a solid–state reaction. The effect of Eu3+ doping on the microstructure, dielectric properties, ferroelectric properties, and electric-field-induced strain was investigated. The X-ray diffraction (XRD) results indicate the presence of a mixed phase of tetragonal and rhombohedral at the morphotropic phase boundary (MPB). Doping with an appropriate amount of Eu3+ reduces the Fe2+ content and decreases the leakage current in the binary system. A converse piezoelectric coefficient (d33*) of 392 pm/V is obtained at BF-BT-0.003Eu under an electric field of 60 kV/cm at room temperature, which has a Curie temperature (TC) of 414 °C. The unipolar strain and d33* of BF-BT-0.003Eu ceramics increase to 0.438% and 730 pm/V at 125 °C. The field-induced strain response of the BF-BT-0.003Eu ceramics is greater than that of 0.67BF-0.33BT, mainly due to its optimal grain size, reduction of leakage current, and coexistence of ferroelectric-relaxation phases. BF-BT-0.003Eu ceramic is a lead-free candidate for high-temperature actuator applications.