Double B perovskite-type series in the system La0.6Ca0.4Mn1-xMexO3-δ with Me=Fe, Co, Ni and x=0-0.6 were synthesized in air by solid state reactions at 1200℃ 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.
Dresden University of Technology, D-01062 Dresden, Germany Dresden University of Technology, D-01062 Dresden, Germany Meinsberg Kurt-Schwabe Research Institute Meinsberg Kurt-Schwabe Research Institute, Kurt-Schwabe-Straβe 4, D-04720 Ziegra-Knobelsdorf, German Lviv Polytechnic National University, 79013 Lviv, Ukraine Max Planck Institute for Chemical Physics of Solids, Nothnitzer Str.40 01187 Dresden, Germany Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Rd., Shanghai, 200050, Chin