Temperature Dependence on Mechanical, Dielectric, and Electric Field-Induced Strain Properties of Lead-Free BNST Ceramics

Abstract

In this research, temperature dependence on the phase evolution, physical, microstructure, mechanical, dielectric, and electric field-induced strain responses of the Bi0.41Na0.35Sr0.21TiO3 or BNST ceramics were investigated. The BNST ceramic was prepared by a conventional mixed oxide method and sintered at various temperatures from 1100 °C to 1175 °C in order to clarify the optimal sintering temperature for all propereties. X-ray diffraction results showed that all ceramics exhibited a single perovskite without any secondary phases. A mixed between tetragonal and rhombohedral phases were identified for all ceramics. Grain size tended to increase with increasing the sintering temperature. The mechanical improvement was related with the change in densification. The optimum relative density (95.83 %), mechanical (HV = 6.43 GPa, HK = 5.12 GPa, E = 107.57 GPa, and KIC = 2.42 MPa.m1/2), and dielectric properties (ε′ = 1752, tan δ = 0.0514, and δA = 100 K), were obtained for the ceramic sintered at 1125 - 1150 °C. In addition, the obtimum sintering temperature of 1125 - 1150 °C were also found to improve the electric field-induced strain response (Smax = 0.14 % and d*33 = 285 pm/V), and the electrostrictive coefficient (Q33 = 0.0199 m4/C2).