Enhanced room-temperature TCR of La0.67Ca0.33-xSrxMnO3 (0.06 ≤ x ≤ 0.11) polycrystalline ceramics by Sr content adjustment

Herein, the influence of Sr doping on chemical composition, microstructure, and electrical transport properties of La0.67Ca0.33-xSrxMnO3 (LCSMO, 0.06 <= x <= 0.11) polycrystalline ceramics is systematically investigated. The study was performed by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), elemental mapping, energy dispersive spectrometry (EDS), X-ray photoemission spectroscopy (XPS), and four-probe method (rho-T). XRD results verified the synthesis of high-purity orthogonal perovskite structure with Pnma space group. EDS and XPS results confirmed presence and uniform distribution of La, Ca, Sr, Mn and O. Furthermore, rho-T curves indicated that the resistivity decreased with increasing Sr content, whereas metalinsulator transition temperature (T-MI) gradually increased. Moreover, cell volume (V) and electron bandwidth (W) increased with the increase in Sr content, which effectively reduced the resistivity of LCSMO ceramics. One should note that double exchange (DE) enhancement between Mn3+ and Mn4+ is responsible for gradually increasing T-MI. Finally, maximum TCR value of 14.3% K-1 was achieved at x = 0.08, which rendered TCR peak temperature of 299.0 K. High room-temperature TCR of LCSMO ceramics is promising for next-generation infrared bolometers, operating at room-temperature.