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

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 ( T k ) at room temperature. Herein, La 0.7 Ca 0.3− x K x MnO 3 (LCKMO, 0.22 ≤ x  ≤ 0.28) films were fabricated on La 0.3 Sr 0.7 Al 0.65 Ta 0.35 O 3 (00 l ) 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 La 1− x Ca x MnO 3 with the high T k of La 1− x K x MnO 3 by optimizing the K doping level. The results show that LCKMO films are a promising candidate for fabricating uncooled infrared bolometers.