Correlation of Microstructures and Conductivities of Ferroelectric Ceramics Using Complex Impedance Spectroscopy

The microstructures and conductivities of lead-free ceramics [Bi(0.5)(Na(1-x)K(x))(0.5)]TiO(3) with x = 0.18 (BNKT) and lead-based ceramics of x(0.94PbZn(1/3)Nb(2/3)O(3) + 0.06BaTiO(3)) + (1 - x)PbZr(y)Ti(1-y)O(3) with x = 0.5, y = 0.52 (PBZNZT) were investigated. Experimental results show that the activation energy of grain boundary conductivity is higher than that of grain conductivity for the BNKT system, indicating that the Bi(2)O(3) evaporation of grains induces an easy conduction path through grains. However, the activation energy of grain boundary conductivity is lower than that of grain conductivity for the PBZNZT system, which might be attributed to the charged particles in the amorphous phase at grain boundaries, participating in the conduction process. A conduction model of both grain and grain boundary conductivities was proposed, and the microstructural characteristics and AC impedance data of ferroelectric ceramics correlate fairly well, suggesting that impedance spectroscopy is an efficient characterization technique for the grain boundary engineering of ferroelectric ceramics. (C) 2010 The Japan Society of Applied Physics DOI: 10.1143/JJAP.49.061505