Study on Mn3O4 - La1-xCaxMnO3 composite ceramics with high temperature coefficient of resistance in large temperature range

La 1- x Ca x MnO 3 , as a candidate for thermal radiation detectors, has received more attention due to the quest for a higher temperature coefficient of resistance (TCR), however, the narrow high-TCR temperature range greatly limits its application in uncooled bolometer. In this paper, Mn 3 O 4 - La 1- x Ca x MnO 3 ( x  = 0–0.33) composite ceramics were prepared using the sol-gel method. A suitable TCR was achieved over a wide temperature range, including room temperature, by adjusting the Ca content. As the Ca content decreased, the resistivity ( ρ ) of the composite gradually increased at 300 K, and the positive TCR (PTC) peak shifted to a lower temperature. However, the negative TCR (NTC) was enhanced over a wider temperature range. When x  = 0.05, the maximal NTC was −3.2%·K −1 within the range of 172 K–350 K and |TCR| > 2%·K −1 , spanning a large temperature range around 180 K, including room temperature. These results strongly indicate that the composite, such as Mn 3 O 4 - La 1- x Ca x MnO 3 , provides a new idea for uncooled bolometer/night vision. Graphical Abstract