Dielectric relaxation behaviour of Li and La co-doped NiO ceramics

Li and La co-doped NiO ceramics have been synthesised by conventional ceramic solid-state reaction processing technique. Comprehensive structural, electrical, and dielectric studies were carried out on the samples of formula LixLayNi1-x-yO, where x=0.05 and y=0.03 and 0.05. Their structural characterisation was carried out with X-ray diffraction. The dc electrical measurements were recorded in the temperature range 300-400 K. The dielectric properties were measured in the frequency range 0.25-100 kHz at different temperatures. At room temperature, a colossal low-frequency dielectric permittivity (epsilon' similar to 10(5)-10(6)) was obtained. These colossal-a values are explained in the framework of the core/shell model. Complex-impedance spectroscopy studies on the prepared ceramics show a slight deviation from Debye-type relaxation. In general, the results of the present work suggest doping with rare earths in low concentrations to obtain colossal dielectric permittivity. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.