Giant dielectric permittivity in Li and Pr co-doped NiO ceramics

The objective of the present work is to use rare-earth oxide (Pr oxide) as dopant to Li-doped NiO ceramics in order to obtain giant dielectric permittivity (epsilon') together with low loss factor (tan phi). For that aim, NiO-based ceramics of a formula LixPryNi1-x-yO (LPNO) with x=0.027 and y=0.001 and 0.005 have been synthesized by usual solid-state reaction. Their structural characterization was carried out with X-ray diffraction (XRD) and X-ray fluorescence (XRF). Their bulk dielectric properties at room temperature have been studied in detail. A giant low-frequency dielectric permittivity (e'similar to 10(5)-10(6)) together with a low loss factor (tan delta similar to 0.05-0.08) at room temperature was obtained. The giant values from dielectric permittivity were explained in the framework of core/shell model and the low loss factor was explained by the formation of grain boundaries rich with Pr oxide. Complex-impedance study shows a non-Debye type relaxation in the LPNO compounds. In general, the results of the present work suggest adopting doping with rare earths in low concentrations in order to obtain giant dielectric permittivity together with low loss factor. (C) 2009 Elsevier B.V. All rights reserved.