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The effect of synthesis method and Sr-dopant amount on the electrical conductivity of strontium-doped lanthanum manganites

Strontium-doped lanthanum manganites (La1-xSrxMnO3, LSMO) are perovskite ceramics that have potential use in devices for energy conversion and storage due to their chemical stability and high electrical conductivity. In this study, LSMO (x = 0, 0.1, 0.2, 0.3) were prepared using two different synthesis methods: citrate-nitrate autocombustion (CNA) and coprecipitation. Upon synthesis, all prepared powders were pressed into pellets (6 mm in diameter) and sintered at 1200 °C/2 h. The formation of the LSMO phase was confirmed by X-ray diffraction analysis and the lattice parameters were determined by Rietveld refinement analysis. The oxygen nonstoichiometry in samples was determined by permanganate titration with Mohr’s salt. The electrical properties of calcined pellets were measured using impedance spectroscopy in a wide temperature (– 80 – 240 °C) and frequency (0.01 Hz – 1 MHz) range. All samples have shown semiconductor behavior, their conductivity rising with temperature and Sr-amount. For all analyzed samples, the conductivity was frequency-independent over the entire frequency range. The non-existence of frequency dependent conductivity indicates undisturbed electrical transport through the grain boundaries and the absence of any effect that could block fast electron transport. Furthermore, it was observed that LSMO samples prepared by the coprecipitation method possess higher conductivity than samples prepared with the CNA method due to the higher oxygen nonstoichiometry. Electrical conductivities of all LSMO samples were in 10–2 – 0.45 Ω–1 cm–1 range, which is comparable to the conductivity of Si.

electrical conductivity ; lanthanum manganite ; strontium

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