Electrical properties of MgAl2-2xZrxMxO4 (M = Co, Ni and x=0.00-0.20) synthesized by coprecipitation technique using urea

This paper presents the results of a study concerning the structural and electrical properties of MgAl2-2xZrxMxO4 (x= 0.00-0.20 and M = Co2+ and Ni2+)prepared by a coprecipitation technique using urea as a precipitating agent. The X-ray diffraction data for the pure and its doped samples are consistent with the single-phase spinel and their crystallite sizes are in the range 7-20 +/- 4 nm. The DC resistivity increases from 3.09 x 10(9) Omega cm to 6.73 x 10(9) and 8.06 x 10(9) Omega cm whereas dielectric constant decreases from 5.80 to 5.11 and 4.95 on doping with Zr-Co and Zr-Ni, respectively. The electrical resistivity variations with increase in the dopant contents indicate two types of conduction mechanisms in operation. Several parameters such as, hopping energy (W), metal-semiconductor transition temperature (T-MS) and Debye temperature (theta(D)) have also been determined. The increase in DC resistivity and decrease in dielectric constant suggest that the synthesized materials can be considered for application as an insulating and structural material in fusion reactors. (C) 2008 Elsevier Ltd. All rights reserved.