Optimization of room-temperature temperature coefficient of resistivity of La0.75-K0.19+Sr0.06MnO3 (0.00 ≤ x ≤ 0.06) ceramics by La and K content adjustment

Herein, La0.75-xK0.19+xSr0.06MnO3 (LKSMO, x = 0.00, 0.02, 0.03, 0.04, and 0.06) polycrystalline ceramics were prepared by sol–gel method. Crystal structure, surface morphology, and electrical properties of these ceramic samples were characterized and analyzed in detail. All LKSMO ceramics had rhombohedral structure (R3¯c space group) with excellent crystallinity and homogeneity. With increasing x value, Mn–O bond lengths were increased, and the number of Mn3+/Mn4+ pairs was reduced in LKSMO samples. Increasing K content in these LKSMO ceramics suppressed double-exchange mechanism and significantly promoted Jahn–Teller effect. Consequently, temperature coefficient of resistivity (TCR) was optimized and the temperature of TCR peak was adjusted to room temperature. By adjusting La and K content ratio at A-site, obtained LKSMO (x = 0.03) ceramics exhibited high TCR (11.4% K−1) at room temperature (292.35 K). These results indicate that La0.72K0.22Sr0.06MnO3 polycrystalline ceramics are suitable materials for the preparation of uncooled infrared bolometers.