Effect of Gd doping on electrical transport properties of La0.8Sr0.2MnO3 polycrystalline ceramics

Gd doped La0.8Sr0.2MnO3 (La0.8-xGdxSr0.2MnO3, LGSMO) ceramics were prepared by a sol-gel method. X-ray diffraction (XRD) patterns showed that all samples exhibited distorted perovskite structures, R3c. When the Gd3+ content x > 0.03, the crystal structure changed to orthorhombic, Pnma. Scanning electron microscopy (SEM) images showed that the ceramics characterize high density and grain boundary connectivity, and higher Gd3+ doping decreased the grain size from 26.72 μm to 7.42 μm. The temperature dependence of resistivity showed a transition from a low-temperature metal to a high-temperature insulator. The resistivity increased with Gd doping content, and the metal-insulator transition temperature, TP, increased first and then decreased, while the temperature coefficient of resistance (TCR) of the samples first decreased and then increased with Gd3+, and the magnetoresistance (MR) increased first and then decreased. The peak TCR at x = 0.06 was 5.18%·K−1, and MR at 0.04 was 34.57%. The electrical transport properties of the ceramics were explained based on the double exchange (DE) interaction mechanism. The obtained material may have application prospects in magnetic devices and infrared detectors.