High temperature dielectric and impedance spectroscopy study of LaCo0.7Nb0.3O3

We report the high temperature dielectric and ac impedance spectroscopy investigation of Nb substituted LaCo0.7Nb0.3O3 polycrystalline sample. The maximum dielectric constant value was observed & AP;1400 at around 400 K where the peak value shows a decreasing trend at higher temperatures and frequency. Similar variation was reflected in the dielectric loss behavior with temperature, which shows the thermal activation of the charge carriers in the material. The analysis of high temperature impedance spectroscopy data shows the grain and grain boundary contributions by fitting the Nyquist plots to the equivalent circuit. From the analysis of the impedance and modulus spectra, it was possible to discern between the effects of overlapping grains, grain boundaries, and electrode interfaces. The relaxation time decreases with an increase in the temperature and the activation energy changes from 0.44 eV to 0.56 eV at around 400 K, which is due to involvement of thermal activation in the conduction of charge carriers.