Modulation of room-temperature TCR and MR in La_1−xSr_xMnO₃ polycrystalline ceramics via Sr doping

La_1−xSr_xMnO₃ (LSMO) polycrystalline samples with x content from 0.1 to 0.2 were synthesized via the optimized sol–gel method. The effect of Sr doping (x) on crystal structure, surface morphology, magnetic, and electrical transport properties of LSMO ceramics were investigated systematically. X-ray diffraction (XRD) results showed that all samples crystallized in single phases with rhombohedral structure (R\(\bar 3\)c space group), without any detectable impurity phases. With the increase of x content, lattice parameters expanded, whereas grain size of LSMO ceramic enlarged and grain boundaries (GBs) decreased accordingly. For LSMO ceramics with x = 0.16, peak value of temperature coefficient of resistance (TCR) reached 2.7% K⁻¹ as the peak-TCR temperature (T_K) approached room temperature at 292.5 K, as well as the maximum magnetoresistance (MR) value arrived 17.9% at 300.2 K. In addition, peak TCR of LSMO (x= 0.2) was obtained at 6.4% K⁻¹ as T_K at 329.4 K. These properties of modulation TCR and MR at room temperature in LSMO ceramics were interpreted by the interaction of double exchange mechanism and Jahn-Teller effects.