Bivalent Sr2+ doping to improve room-temperature TCR of La0.8-xSrxAg0.2MnO3 polycrystalline ceramics

•TCR of La0.625Sr0.175Ag0.2MnO3 ceramic showed a higher value of 16.9% K−1 at 299.8 K.•Combination of XRD, FTIR and XPS confirmed that the distortion of the MnO6 octahedron.•XPS indicated a noticeable enhancement of the DE effect in the LSAMO composites with doping.•Sr2+ doped LSAMO ceramics with high TCR response have broad application prospects. Rare earth manganites have attractive wide attentions due to their promising applications in infrared bolometers and magnetic information storage. Their temperature coefficient of resistivity (TCR) need further improved so as to achieve its applications at room temperature. In this work, La0.8-xSrxAg0.2MnO3 (LSAMO, x = 0.00, 0.10, 0.15, 0.175, and 0.25) ceramics are fabricated by sol-gel method. Their structure and morphology as well as the optical, electrical and magnetic properties are studied. The structural distortion of Sr doped specimens is identified by the shift of the X-ray diffraction peaks toward the low angles and the red-shift of their Fourier transform infrared spectra. Meanwhile, the Mn4+ ion concentration increases, indicating that the double exchange effect enhances in the ceramics. Furthermore, the TCR values are obviously influenced by the doped Sr content. It enhances from 2.5% K−1 at 211.5 K for La0.8Ag0.2MnO3 to 16.9% K−1 at 299.8 K for La0.625Sr0.175Ag0.2MnO3. The origin of this improvement is attributed to the transformation of rare earth manganites from ferromagnetic metal to paramagnetic insulator and the distortion of MnO6 octahedra. These results uncover the effect of Sr2+ doping on the room-temperature TCR values of ceramics, making it suitable for advanced uncooling device applications.