Electron-lattice coupling effect to improve electrical transport properties of La0.7Ca0.3−xKxMnO3 (0.22 ≤ x ≤ 0.28) films via large-radius K doping

Abstract

For uncooled infrared bolometers, the traditional thermal sensing materials such as vanadium oxide and amorphous silicon have a relative low value of temperature coefficient of resistivity (TCR). In contrast, perovskite manganese oxide films exhibit 3–5 times higher TCR values than traditional materials. The important challenge is to achieve both high TCR and peak TCR temperatures (Tk) at room temperature. Herein, La0.7Ca0.3−xKxMnO3 (LCKMO, 0.22 ≤ x ≤ 0.28) films were fabricated on La0.3Sr0.7Al0.65Ta0.35O3 (00l) substrates using a combined sol–gel and spin coating process. It was found that by optimizing the K doping amount at x = 0.24, on the one hand, double exchange mechanism becomes the strongest. On the other hand, with minimal lattice strain, electron scattering is inhibited, and the electron-lattice coupling effect improves. Furthermore, the film exhibits a dense surface structure and a uniform distribution of grains. Finally, TCR value reaches 15.95 % K−1 at the corresponding temperature of 283.28 K. Obviously, the prepared LCKMO films effectively combine the high TCR of La1−xCaxMnO3 with the high Tk of La1−xKxMnO3 by optimizing the K doping level. The results show that LCKMO films are a promising candidate for fabricating uncooled infrared bolometers.