Improved room‐temperature TCR and MR of La0.9−xKxCa0.1MnO3 ceramics by A-sites vacancy and disorder degree adjustment

Herein, polycrystalline La0.9−xKxCa0.1MnO3 (LKCMO) ceramics (A-sites = La, K, and Ca, 0.05 ≤ x ≤ 0.25) are successfully synthesized via the sol–gel process. The effects of vacancy and disorder degree (δ2) of A-sites cations on electromagnetic transport properties are investigated and performed by using a combination of double-exchange (DE) mechanism, phenomenological percolation (PP) model and Jahn–Teller (JT) effects. The results show that K+ ions, occupying the A-sites, leading to the A-sites vacancy and δ2 of A-sites cations, significantly influence the DE mechanism, JT effect and PP model. A-sites vacancy is confirmed by energy-dispersive spectroscopy and X-ray photoemission spectroscopy. The simultaneous presence of La3+, Ca2+ and K+ ions at A-sites influenced the δ2 of A-sites cations. At the optimal doping content x = 0.15, the maximum temperature coefficient of resistivity (TCR) is 9.7% K− 1 at 291.4 K, and the maximum magnetoresistance (MR) value is 35.2% at 295.03 K, respectively. In summary, LKCMO ceramics achieve room-temperature TCR and MR by A-sites vacancy and δ2 of A-sites cations adjustment, promising applications in uncooled infrared bolometer and magnetic sensors.