To investigate excess Na+ effect, Bi0.5(Na0.78+xK0.22)0.5TiO3 (0≤x≤0.05) (BNKT) ceramics were prepared by using a conventional solid-state reaction method. The structure and ferroelectric properties of BNKT ceramics were characterized by XRD (X-ray diffraction) and polarization dependence by external electric field. Also, the temperature dependence of dielectric constant and loss were studied. From these results, it was found that appropriate excess Na+ into BNKT ceramics compensate the volatility and induce dense ceramics. The enhanced piezoelectric coefficient (158 pC/N) and depolarization temperature (202℃) were obtained for the x=0.01 composition.
