Relaxation and conduction mechanism of BNT-KNN ceramics by impedance study.

Impedance spectra of 0.93BNT-0.07KNN revealed positive and negative temperature coefficient of resistance behaviour up to 400°Cand above 400°C. With the increase of temperature, decreased radii and displaced centres of semicircles from the real axis of impedance Cole-Cole plots suggested non-Debye type relaxation mechanism. Three dielectric relaxation regions: within (i) grain, (ii) grain- grain boundary and (iii) grain boundary were prominent in lower, middle and high temperature regions, respectively. The activation energy ranging from ∼0.79 to 1.2eV, suggested that the conduction carriers were cation and cation, oxygen vacancies in lower and higher temperature regions, respectively. [ABSTRACT FROM AUTHOR]