Electrical Transport and Magnetoresistance Properties of the La0.8Sr0.2Mn1-xCoxO3

<title>Abstract</title> <p> In this experiment, La _0.8 Sr _0.2 Mn _{1− <italic>x</italic>} Co _{<italic>x</italic>} O ₃ ( <italic>x</italic>  = 0, 0.005, 0.01, 0.02, 0.03) (LSMCO) polycrystalline ceramics were mainly prepared by the sol-gel method. The effects of Co doping on the crystal structure, surface morphology, electrical transport properties, and magnetoresistance of the LSMCO polycrystalline ceramics were systematically investigated. X-ray diffraction (XRD) patterns, compared with standard PDF cards, show that the angular positions of all characteristic diffraction peaks are in good agreement, indicating that the as-prepared series of samples crystallize in a typical perovskite structure with a rhombohedral crystal symmetry, and all samples belong to the R-3c space group. Scanning electron microscopy (SEM) observations indicate that the polycrystalline ceramic samples exhibit almost no porosity, well‑defined grain boundaries, similar polygonal grain structures, and compact grain packing. EDS results demonstrate that in the overall elemental mapping, La, Sr, Mn, O, and Co are uniformly distributed throughout the ceramic samples, with no noticeable elemental segregation, enrichment regions, or phase separation. This indicates that the principal elements have achieved homogeneous doping and form a solid solution both within the grains and at the grain boundaries. Temperature Coefficient of Resistance (TCR) measurements indicate that, with increasing doping content, the TCR remains nearly unchanged, while T _k gradually decreases. Magnetoresistance (MR) measurements show that a maximum MR value of 28.61% is achieved at 304.53 K for the doping level of <italic>x</italic>  = 0.005. This study broadens the application prospects of polycrystalline ceramics in magnetic sensors, magnetic storage, thermistors, and other related fields. </p>