Impedance spectroscopy studies of orthorhombic FeNbO₄

Abstract

Electrical characterization of the FeNbO₄ compound, with orthorhombic structure, has been carried out. Compact bodies were prepared by sol-gel and ceramic routes. Pellets for electrical measurement were sintered in air, and samples for electrical tests were electroded with platinum, gold and silver paste. Equivalent circuit models were established that fit the impedance spectroscopy data with good agreement. Comparison of impedance responses showed that samples prepared by different routes have similar electrical behaviour. These measurements, in conjunction with I–V characteristic curves, indicate the existence of a small bulk resistance, which does not change at the higher experimental temperatures considered. Interfacial impedances due to the metallic contact regions contribute the greatest part of the overall impedance. The response of the sample with different electrode materials (platinum, gold, silver) was studied. I–V characteristic curves indicate a space charge-limited current phenomenon at the platinum contact, followed by a charge avalanche process at higher voltages.