Enhanced room-temperature MR and TCR in polycrystalline La0.67(Ca0.33−xSrx)MnO3 ceramics by oxygen assisted sintering

Abstract Polycrystalline La 0.67 (Ca 0.33- x Sr x )MnO 3 (LCSMO, x = 0, 0.03, 0.06, 0.09, 0.12, and 0.15) ceramics were prepared by sol-gel method. Microstructures, electrical/magnetic transport properties, temperature coefficient of resistance ( TCR ) and magnetoresistance ( MR ) behaviors, were all investigated. X-ray diffraction (XRD) results showed that all samples crystallized in single phases without detectable secondary phases. At Sr doping ( x ) above 0.12, crystal structures transformed from orthorhombic phase (space group of Pnma ) to rhombohedral phase (space group of R 3 c ). As x content further rose, metal-insulator transition temperature ( T p ) increased and maximum values of TCR and MR decreased. Further data revealed that TCR and MR peaks were controlled by Sr doping level x . In addition, room temperature MR and TCR of LCSMO ceramics were enhanced under oxygen assisted sintering. At Sr doping x = 0.09, the value of T p attained room temperature (301.8 K), and the maximum values of TCR and MR reached 10.5% K −1 and 43.0%, respectively. These properties were related to combination of double exchange (DE) and Jahn−Teller effects. LCSMO materials may have promising future use in photoelectric (uncooled bolometer or infrared detectors) or magnetic devices (uncooled magnetic sensors) at room temperature.