Electrical conductivity and oxygen non-stoichiometry of the double B mixed perovskite series La0.6Ca0.4Mn1 − yMeyO3 − δ with MeFe, Co, Ni and x = 0–0.6

Double B perovskite-type series in the system La0.6Ca0.4Mn1 − xMexO3 − δ with MeFe, Co, Ni and x = 0–0.6 were synthesized in air by solid state reactions at 1200 °C from simple oxides and CaCO3. Almost single phase compositions with small impurities (3–5%) were formed. Replacement of Mn with Me-cations is accompanied by a considerable decrease of electrical conductivity of the prepared ceramics. Lower conductivities of the Me containing compositions compared to La0.6Ca0.4MnO3 − δ are explained by stronger polarization of the -Mn(α + γ)+-Oα−-Me(α − γ)+-Oα−- fragments of the – Oα−-Mnα+ – Oα−-Mnα+ – Oα−-Mn(α + γ) + -Oα−-Me(α − γ)+-Oα−- chains in comparison with the -Oα−-Mnα+-Oα−-Mnα+-Oα−- chains without Me-cations, because of different electronegativity of Me and Mn. The double exchange theory gives strong explanation for this phenomenon. Type and level of the electrical conductivity of the La0.6Ca0.4Mn1 − xMexO3 − δ series are the functions of the [Mn4+]/[Mn3+] and [Me3+]/[Me2+] ratios. Mn4+ and Me2+-cations are possible point defects which determine the p- and n-type conductivity of compositions, respectively.