Large and temperature-insensitive piezoelectric strain in xBiFeO3–(1−x)Ba(Zr0.05Ti0.95)O3 lead-free piezoelectric ceramics

Lead-free piezoelectric materials of xBiFeO3–(1−x)Ba(Zr0.05Ti0.95)O3–1.0 mol%MnO2 (BF–BZT) (0.62 ≤ x ≤ 0.74) were prepared by the traditional solid-state reaction process. The structure and high-temperature dielectric, ferroelectric as well as piezoelectric properties were investigated. X-ray diffraction analysis showed that BF–BZT ceramics exhibited pure perovskite structure with the coexistence of tetragonal and rhombohedral phases. Measurements of temperature-dependent dielectric permittivity revealed that BF–BZT ceramics gradually changed from the classical ferroelectrics to relaxors with increasing BZT content. The Curie temperature TC, coercive electric field Ec (80 kV/cm) and remnant polarization Pr (80 kV/cm) of 0.64BF–0.36BZT ceramics were 370 °C, 27.8 kV/cm and 24.22 μC/cm2, respectively. The unipolar strain of 0.64BF–0.36BZT reached up to 0.29% (d*33 = 485 pm/V), and the variation of temperature-dependent piezoelectric strain for 0.64BF–0.36BZT was about 17% from 50 to 180 °C, which was only 1/3, 1/2 and 1/10 of the BF–BT-, PZT-5H- and BNT-based piezoelectric ceramics, showing excellent thermal stability. These results indicated that BF–BZT ceramics were competitive candidates for lead-free piezoelectric applications.