Influence of A-Site Variation and B-Site Substitution on the Physical Properties of (La,Sr)FeO3 Based Perovskites

Perovskite-type materials have been synthesised and investigated with regards to their physical properties including specific surface area (BET), phase purity, sinter behaviour, coefficient of thermal expansion (CTE) and electrical conductivity. We investigated the effect of Sr variation on La1-xSrxFeO3-delta the influence of A-site stoichiometry on (La0.8Sr0.2)(y)FeO3-delta and the impact of substitution of iron by nickel or copper up to 20 mol%. The over-stoichiometric compositions indicate secondary phases independent of the calcination temperature. Stoichiometric and understoichiometric compositions become single phase perovskites after calcination at 1,200 degrees C. The substitution of Fe by Ni or Cu on the B-site, (Li0.2Sr0.8)(0.95)Ni/CuxFe1-xO3, is viable, but limited to 20 mol%. Cu substitution and under-stoichiometry lower the melting point and thus consequently influence the sintering temperature. The diverse LSF composition as well as Ni/Cu substitutions affects the CTE. The CTE matches quite well with YSZ, by a 15% A-site deficiency, as well as with Ni substitution on the B-site. Compatibility tests at 1,000 degrees C prove that Ni increases the reactivity of LSF with YSZ. In case of the CGO, no indication of reactions or interdiffusion could be observed. The substitution of iron by 20 mol% nickel or copper significantly enhances the electrical conductivity of the basic composition (La0.8Sr0.2)(0.95)FeO3-delta.