Abstract
The transport properties of p-type polycrystalline La2Cu1−xMxO4 (MCo and Mn) have been investigated in the high temperature domain above room temperature up to 973 K. The electrical resistivity of La2Cu1−xMxO4 undergoes a temperature driven semiconducting (insulating) to metallic transition at high temperature (∼750 K) and a doping induced metal to semiconductor transition at room temperature. The Arrhenius plot of the ln(ρ/T)∼1/T shows a conducting mechanism and in the La2Cu1−xMxO4 (M:Co and Mn) a transition temperature was found at around 750 K similar to what was observed in the La2−xRExCuO4 (RE: Pr, Nd and Y) system. We therefore suggest that in these doped ceramics the metal–insulator (semiconductor) transition at ∼750 K should be attributed to combined effects of a strong phonon scattering mechanism due to thermal activation, oxygen vacancies and structural disorders. Furthermore, a site-dependent influence of electrical resistivity in La2CuO4-based ceramics was distinguished by combining thermoelectric measurements and X-ray absorption spectroscopy. The doping induced transition is then associated with large imperfections present in the CuO2 layer, consistent with a dominant role of the single CuO2 layer in the charge transport mechanism of La2CuO4-based materials.
Published Version
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