Utilization of Ag ions to improve room-temperature TCR of La0.85-Sr0.15Ag MnO3 polycrystalline ceramics

Abstract

In this work, silver-doped La0.85-xSr0.15AgxMnO3 (LSAMO, 0.05 ≤ x ≤ 0.20) polycrystalline ceramics were prepared by the sol-gel method. The experimental characterization of ceramics revealed that Ag ions were bounded with the lattice matrix. The resistivity and the corresponding peak temperature coefficient (TCR) of LSAMO ceramics were systematically tuned by changing the Ag dopant content. Adjusting the proportion of Ag enabled one to vary the metal-insulator transition temperature (TMI) for LSAMO specimens in a wide range, and their peak resistivity temperature (Tp) was increased from 299.6 to 335.7 K. At the same time, the peak TCR value achieved its maximum of 15.2% K−1 at the doping molar ratio x of 0.15 and the peak resistivity temperature (Tk) of 294.1 K. In addition, the electrical transport was described in the context of the small polaron hopping (SPH) model and the phenomenological percolation model (PP) over the metal-insulator transition region. Under the combined action of the Jahn-Teller (JT) effect, the double exchange (DE) mechanism and the PP model, LSAMO ceramics possessing high TCR at room temperature were obtained by varying the amount of Ag doping. The observed properties suggest LSAMO material can be used in advanced uncooled infrared bolometers.