Impact of Ag doping on the structural, surface morphologic and electrical properties of La0.625(Ca0.285Sr0.09)MnO3 polycrystalline ceramics

Abstract

In this study, Ag-doped La0.625(Ca0.285Sr0.09)MnO3:Agz (LCSMO:Agz, z = 0, 0.1, 0.2, 0.3, and 0.4) polycrystalline ceramics were prepared by sol-gel method, then characterized by various techniques. X-ray diffraction (XRD) showed that all bulk prepared specimens crystalized in LCSMO phase with orthogonal cubic structure (space group of Pnma) and without impurities. Scanning electron microscopy (SEM) revealed good compactness with fewer holes. Average grain sizes and quantity of grain boundaries (GBs) correlated with Ag doping amounts. As z content rose, resistivity dropped, and both peaks temperature coefficient of resistance (TCR) and magnetoresistance (MR) first increased and then decreased. Several previous studies indicated that Ag doping amount could affect TCR and MR peaks. At z = 0.3, TCR peaks reached maxima of 10.27% (289.56 K), at z = 0.1, MR peaks reached maxima of 15.63% (293.08 K). As z increased from 0 to 0.4, the temperature of peak TCR (Tk) was adjusted to room temperature from 289.56 to 294.22 K. TCR peak of La0.625(Ca0.285Sr0.09)MnO3:Agz material was improved at room temperature when compared to values reported in the literature. This could be related to changes in tolerance factor (τ) and average A-site cationic radius (rA). Overall, LCSMO:Agz ceramics look promising for infrared detectors and colossal magnetoresistance (CMR) radiant heating instruments at room temperature.