Electrical conduction properties of the BZT-BST ceramics

0.5Ba(Zr0.2Ti0.8)O-3-0.5(Ba0.7Sr0.3)TiO3 (BZT-BST) has been explored in recent times for potential applications in energy harvesting, electrocaloric and energy storage. To this end, energy harvesting/conversion and storage applications require an understanding of the conduction and loss mechanisms. The conduction mechanism in BZT-BST ceramics is studied using impedance spectroscopy (IS) at 0.1 Hz-3 MHz and 100-600 degrees C. Impedance study reveals the presence of two types of relaxation processes due to grain and grain boundary contributions. The relaxation time and dc conductivity activation energies are obtained as 1.12/1.3 eV and 1.05/1.2eV for bulk/grain boundary, respectively, and found that oxygen vacancies dominated electrical behavior. The relaxation mechanism follows non-Debye-type behavior. The high resistance of the grain (bulk) in the ferroelectric region does not contribute to the high losses; the losses probably result from the phase transition. Also, BZT-BST ceramics exhibit a negative temperature coefficient of resistance (NTCR) behaviour. From a practical application point of view in the temperature regime of 25-65 degrees C, the loss's contribution is low. The significant contributions of loss result from the response of phase-transition in this temperature range (25-65 degrees C).