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An effect of microstructure on magnetoresistive properties of manganite ceramics (La0.65Sr0.35)0.8Mn1.2O3±Δ with superstoichiometric manganese has been studied after sintering in the temperature range of 800–1500 °C. Increase in sintering temperature to 1400 °C, an enormous growth of grains, densification of material, and rise in magnetoresistance peak from 1% to 4.8% are observed. At the same time, sintering at 1500 °C leads to a sharp increase in the grain size more than 100 μm, release of excess manganese on grain boundaries, and almost two times magnetoresistance peak rise. We propose that such radical changes are due to the presence of superstoichiometric manganese which plays a crucial role in the formation of ceramics microstructure and properties.

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