Influences of secondary phases on ferroelectric properties of Bi(Na,K)TiO3 ceramics

The effect of secondary phases on ferroelectric properties of Bi0.5(Na0.8K0.2)0.5TiO3 (BNKT) is studied. Ceramic powders are prepared by the solid-state reaction method where the influence of different sintering temperatures is also studied. Then, samples are characterized by X-ray diffraction (XRD), Raman microspectroscopy, Scanning Electron Microscopy and impedance spectroscopy. Through XRD and Raman results, the perovskite structure is detected; together with small peaks corresponding to a secondary phase associated with a K2−xNaxTi6O13-based phase. The secondary phases amount increases with the sintering temperature, yielding different combinations of K2−xNaxTi6O13- and Bi0.5(Na1−yKy)0.5TiO3-based phases. Moreover, the content of the secondary phase improves the d33 piezoelectric constant and dielectric properties of BNKT ceramics. These results can benefit the understanding of BNKT ceramics and the expanding of their applications range.