Structural phase boundary of BiFeO3–Bi(Zn1/2Ti1/2)O3–BaTiO3 lead-free ceramics and their piezoelectric properties

Abstract

In this article, low dielectric loss pure or Mn-doped BiFeO3–Bi(Zn1/2Ti1/2)O3–BaTiO3 (BF–BZT–BT) lead-free piezoceramics with various compositions were prepared using a refined solid state reaction electroceramic processing. The rhombohedral-pseudocubic structural phase boundary was determined with powder X-ray diffraction method and found dependent on ceramic grain size, which shifts far away from the BF-rich corner with increasing microstructure grain size. In contrast to BF–BT binary system, low dielectric loss was understood by mechanism of reduction of oxygen vacancies with doping MnO2 combined with stabilization of Bi-perovskite phase by adding BZT third member. Full piezoresponse of d 33 ≥ 145 pC/N was obtained in the Mn-doped BF–xBZT–yBT (0.01 < x < 0.05 and 0.27 ≤ y ≤ 0.31) coarse-grained ceramics near the structural phase boundary, in agreement with prediction by relationship of d 33 = aɛ 33 − bɛ 33 2 . Ferroelectric polarization subswitching and related low piezoresponse observed in the BZT-riched ceramics were observed and argued extrinsically resulting from residual internal stresses. Primary experiments showed annealing and subsequent quenching treatment eliminate residual internal stresses and increase piezoresponse for the BZT-riched ceramics.