Preparation and properties of La0.71Ca0.29Mn1−xCrxO3 polycrystalline composites
La0.71Ca0.29Mn1−xCrxO3 (x = 0, 0.01, 0.03, 0.05 and 0.10) polycrystalline ceramics were synthesized by sol–gel method with methanol as solvent. X-ray diffraction results assisted with Rietveld refinement analysis showed that all samples crystallized in the orthorhombic structure with Pnma space group. The Cr substitution modified not only the Mn–O bond length, but also the Mn–O–Mn bond angle. Scanning electron microscope (SEM) micrographs revealed that the samples had high density and dense grain boundary. Temperature dependence of resistivity (ρ–T) curves showed that all samples had metal–insulator transition (TMI) phenomenon. By the way, TMI decreased with the increase in Cr content. When the sample was applied with a magnetic field, the resistivity decreased and TMI shifted to the higher temperature region. The temperature coefficient of resistivity (TCR) of the sample reached the highest value of 38.9%·K−1 at x = 0.01, indicating that TCR can be subtly improved by slight substitution of Mn-site, thereby the colossal magneto-resistance materials have a huge application potential in bolometer/infrared detection.
This work was supported by the Training project of Kunming university of science and technology (No. KKSY201451080) and National Natural Science Foundation of China (No. 11564021).
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