Enhanced Electrical Properties of La$_{0.7}$(Ca$_{0.2}$Sr$_{0.1}$) MnO$_{3}$ Polycrystalline Composites with Ag Addition

Abstract

La$_{0.7}$(Ca$_{0.2}$Sr$_{0.1}$)MnO$_{3}$:Ag$_{x }$(LCSMO:Ag$_{x}$, x = 0, 0.1, 0.2 and 0.3, mol%) polycrystalline composites were prepared by a solid-state reaction method. With the increasing of Ag addition, the temperature coefficient of resistance (TCR) and the metal-to-insulator transition temperature ($T_\mathrm{p}$) reach the maximum values of 9.1 % K$^{-1}$ and 258 K for LCSMO:Ag$_{x}$ (x = 0.3) sample, which can be used as a candidate of bolometer or infrared detectors. The improvement of Mn$^{4+}$ concentration and grain connectivity by Ag addition is responsible for the enhancement of $T_\mathrm{p}$ and TCR values. The fitting curves of electrical resistivity show that the low temperature region ($T < T_\mathrm{p}$) is fitted with grain/domain boundary, electron–electron, and magnon scattering mechanisms, as well as the high temperature region ($T > T_\mathrm{p}$) is fitted with adiabatic small-polaron hopping mechanism.