Electrical Properties of Lead Free (1-x)(Na0.5K0.5) NbO3-xLiNbO(3) Piezoelectric Ceramics

This work focuses on the electrical conduction mechanism in a lead free (Na0.5K0.5NbO3; NKN) ceramics system with LiNbO3 content of approximately critical concentration x >= 0.2. Lead free (1-x)(Na0.5K0.5) NbO3 - x(LiNbO3), NKN-LNx (x = 0.1, 0.2) ceramics were synthesized by solid-state reaction method. Crystal structures are confirmed by X-ray diffraction. The electric-mechanical bond coefficient k p decreases and the phase transition temperature T-c increases with increasing x content, as determined by dielectric and piezoelectric measurements. The value of the real dielectric constants epsilon' and k(B)T epsilon '' showed anomalies around T-c (462 degrees C in the NKN-LN0.1 and 500 degrees C in the NKN-LN0.2). For the ionic conduction of mobile ions, the activation energies are obtained as E-I = 1.76 eV (NKN-LN0.1) and E-I = 1.55 eV (NKN-LN0.2), above T-c, and E-II = 0.78 (NKN-LN0.1) and E-II = 0.81 (NKN-LN0.2) below T-c. It is believed that the conduction mechanisms of NKN-LNx ceramics are related to ionic hopping conduction, which may arise mainly due to the jumping of Li+ ions.