The comprehensive study of the relationship between electrical transport mechanisms and peak TCR for La0.89−xCaxSr0.11MnO3 films

Abstract

At present, perovskite manganite films are at the frontier of the uncooled bolometer materials technology. It is of great significance to explore the perovskite manganite with high temperature coefficient of resistivity (TCR) at room temperature and the influencing factors of peak TCR value. Herein, perovskite manganite films with the formula of La_0.89−xCa_xSr_0.11MnO₃ (LCSMO) were prepared by a facile spin-coating method with improved sintering temperature. The testing results indicated that Mn-O bond length, Mn⁴⁺ content, and grain size of films decreased as x decreased. The combination of strengthening semiconductivity and reducing the metal–insulator transition temperature enabled the film to achieve a high TCR with a maximum value of 13.37 %/K and resulted in a T_k of 293.02 K when x  = 0.18. Specifically, the improved peak TCR value of the La_0.71Ca_0.18Sr_0.11MnO₃ film can be explained by its high hopping activation energy, lower theoretical Curie Temperature and mobility, as well as electron scattering mediated by La³⁺ doping. Basically, inhibiting the metal–insulator transition temperature, lower metallicity resistivity, and higher semiconductor resistivity play a crucial role in controlling the peak TCR value. This finding provides a theoretical basis for explaining ρ–T curve variation trend from the fundamental perspective of semiconductor transport properties.