Room-temperature TCR and low-field MR of La0.7Ca0.3-xSrxMnO3 (0.06 ≤ x ≤ 0.1) polycrystalline ceramics

In this study, La0.7Ca0.3-xSrxMnO3 (LCSMO, 0.06 <= x <= 0.1) ceramics were synthesized via a sol-gel method. The perovskite microstructure, electrical transport properties, low-field magnetoresistance (MR) and peak temperature coefficient of resistivity (TCR) behaviors of the as-obtained materials were all studied and the results were discussed. Grain size of LCSMO ceramics expanded as more Sr was added but grain boundaries (GBs) decreased. Field emission scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS) and vibrating sample magnetometry (VSM) analyses suggested that addition of Sr greatly enhanced the electrical/magnetic properties of the prepared specimens. The metal-insulator transition temperature rose as doping concentration x enhanced, and increased Ca2+ substitution led to reduced peaks of MR and TCR. For single-phase LCSMO, large room-temperature TCR and low-field MR effects (0.8 T magnetic field) were obtained by controlling the level of Sr2+ substituted Ca2+. For x = 0.095, the optimized room-temperature TCR and MR reached 13.78% K-1 (299.2 K) and 26.41% (302.6 K), respectively. Overall, LCSMO ceramics have broad application prospects in photoelectronic or magnetic devices at room-temperature.