Effects of doping by copper on electrical properties of LaCrO3 based perovskite

Abstract

The use of nickel-yttria-stabilized zirconia (Ni/YSZ) as anode material for solid oxide fuel cell (SOFC) applications, presents some limitations such as poor stability in reduction/oxidation cycling, and poor sulphur tolerance which results in carbon deposition when utilizing hydrocarbon fuels. Even though lanthanum chromite (LaCrO3 noted LCO) is an excellent alternative to Ni/YSZ, it is rarely used in SOFC applications due to its poor conductivity. In order to further progress in developing LCO materials, this work was conducted to improve the conductivity of LCO by copper doping. In particular, LaCr1-xCuxO3 compounds with x = 0, 0.1, and 0.3 were synthesized via a solid-solid method. The followed preparation process allows obtaining a cubic structure with Pm-3m space group. The substitution of Cr with Cu resulted in a slight increase in lattice parameter a, but no change in structure or space group. Whereas, the band gap energy decreased from 3.68 eV for x = 0–3.06 eV for x = 0.3. The crystallite size increases with doping level. With regard to the obtained data from electrical measurements, a thermally activated and frequency depended conductivity was obtained for all samples. Furthermore, the correlated barrier hopping mechanism was proposed as a conduction mechanism, and an electrical transition from semiconductor to metallic behavior was observed. The conductivity increased also monotonously with Cu content and shows a maximum value of 4.5 S/m for x = 0.3. Besides, the tangent loss shows a maximum value of around 104 for x = 0.1. The LaCr0.7Cu0.3O3 compound could be a good candidate for SOFC applications, while LaCr0.9 Cu0.1O3 can be used as a heating element.