Microstructure, dielectric and ferroelectric properties of (1−x)(0.94Bi0.5Na0.5TiO3–0.06BaTiO3)–xBiFeO3 lead-free ceramics synthesized via a high energy ball milling method

(1−x)[0.94Bi0.5Na0.5TiO3–0.06BaTiO3]–xBiFeO3 lead-free ceramics (BNBT–xBFO, x = 0, 0.01, 0.03 and 0.07) with fine grain sizes were prepared by solid state reaction of high energy ball milled (HEBM) powders. X-ray diffraction (XRD) patterns exhibited single perovskite structure for the BNBT–xBFO ceramics sintered at an optimum temperature of 1170 °C. Quantitative analysis of the XRD patterns showed that relative amount of tetragonal phase decreased with increasing content of BFO. Due to the effects of HEBM, average grain size of the BNBT–xBFO ceramics was smaller than 1.46 μm and varied with content of BFO. Two dielectric anomalies were observed in ɛr − T curves. The degree of diffuseness of the phase transition around Tm became more evident with increasing content of BFO. The variation in polarization with BFO amount is consistent with that in mean grain size with BFO amount.

Research highlightsIn this paper, (1−x)[0.94Bi0.5Na0.5TiO3–0.06BaTiO3]–xBiFeO3 lead-free ceramics (BNBT–xBFO, x = 0, 0.01, 0.03 and 0.07) with fine grain sizes were prepared by solid state reaction of high energy ball milled (HEBM) powders. X-ray diffraction (XRD) patterns exhibited single perovskite structure for the BNBT–xBFO ceramics sintered at an optimum temperature of 1170 °C. The quantitative analysis of XRD patterns showed that the relative amount of tetragonal phase decreased with increasing content of BFO. Due to the effects of HEBM, average grain size of the BNBT–xBFO ceramics is smaller than 1.46 μm and varies with content of BFO. The content of BFO affects both dielectric and ferroelectric properties of the BNBT–xBFO ceramics. The degree of diffuseness of the phase transition around Tm became more evident with increasing content of BFO. The variation in polarization with BFO amount is consistent with that of mean grain size with BFO amount. It is suggested that the dependence of ferroelectric properties on the amount of BFO is associated with the competitive effects of many factors such as A-site vacancy, oxygen vacancy, percentage of tetragonal phase and grain size.