Electric field-induced strain response of lead-free Fe2O3 nanoparticles-modified Bi0.5(Na0.80K0.20)0.5TiO3-0.03(Ba0.70Sr0.03)TiO3 piezoelectric ceramics

In this research, the effects of Fe2O3 nanoparticles additive on the phase evolution, dielectric, ferroelectric, piezoelectric and electric field-induced strain responses of BNKT-based piezoelectric ceramics were systematically investigated. The Bi0.5(Na0.80K0.20)0.5TiO3-0.03(Ba0.70Sr0.03)TiO3 or BNKT-0.03BSrT piezoelectric ceramics with the addition of 0-2 vol% Fe2O3 nanoparticles were prepared by a solid-state reaction method. Optimum sintering temperature was found to be 1125 °C for 2 h at which all compositions had high densities of 5.73-5.80 g/cm3. All compositions exhibited a perovskite structure with no impurity. The XRD result showed coexisting rhombohedral and tetragonal phases throughout the entire compositional range with the rhombohedral phase becoming dominant at higher Fe2O3 content. The addition of Fe2O3 promoted the diffuse phase transition in the system that is characteristic of a relaxor-like mechanism and interrupted the polarization which leads to a reduction in the remanent polarization and coercive field. However, the destabilization of the ferroelectric order is accompanied by a significant increase in electric field-induced strain response for the studied system. A large electric field-induced strains (Smax) of 0.38% and a normalized strain coefficient (d*33 = Smax/Emax) of 760 pm/V were obtained for the 1 vol% Fe2O3 ceramic. The obtained results indicate that the addition of Fe2O3 significantly enhances the field-induced strain in BNKT-0.03BST ceramics, and the studied material is considered as a promising candidate for lead-free electromechanical actuator applications.