Impedance Spectroscopy of Lead-free Bi0.5(Na0.78K0.22)0.5TiO3-(Na0.5K0.5)NbO3 Piezoelectric Ceramics

A lead-free piezoelectric 0.97Bi(0.5)(Na0.78K0.22)(0.5)TiO3-0.03(Na0.5K0.5)NbO3 (BNKTN-3) polycrystalline ceramic was synthesized by using a solid-state reaction method. X-ray diffraction (XRD) indicated the formation of a BNKTN-3 single phase having tetragonal symmetry. The temperature dependences of the dielectric properties of BNKTN-3 were investigated in the temperature range of 30 - 550 degrees C at various frequencies (0.01 kHz - 1 MHz), and its electrical properties were investigated by using complex impedance spectroscopy. Analyzing the complex impedance relaxation by using a Cole-Cole plot, we found the frequency dependence of the impedance relaxations to be one impedance arc in the complex impedance plot. The responses of electrical conduction are discussed in relation to grain effect upon equivalent circuit model.