Optimization of temperature coefficient of resistivity and magnetoresistance of La0.67Ca0.33Mn0.98Fe0.02O3: Agx ceramics by Ag adjustment

Abstract

High-quality La0.67Ca0.33Mn0.98Fe0.02O3: Agx ceramics were prepared by sol-gel and solid-phase methods. Ag and Ag+ were found to be present in the system after Ag doping, exhibiting a significant effect on the crystal structure and the concentration of Mn3+/Mn4+. Ag provided the desired conductive pathway, promoted the connectivity between grains, and improved the electrical conductivity of the ceramic. With the increase of Ag doping, the resistivity gradually decreased, while the Curie and the metal-insulator transition temperatures gradually increased. The temperature coefficient of resistivity (TCR) and the magnetoresistance (MR) were greatly improved. At x = 0.15, the peak TCR reached 75.4%·K−1, and the peak MR reached 87.0%. In order to adjust the TCR and MR, the contents of Ag and Ag+ were optimized by controlling the amount of Ag doping. The results demonstrated that Ag doping can regulate the metal-insulator transition and ferromagnetic-paramagnetic transition of the system effectively.