Suppressed grain boundary scattering effect to enhance electrical transport properties of La0.815Sr0.185MnO3 polycrystalline ceramic via high-temperature sintering process

Polycrystalline La 0.815 Sr 0.185 MnO 3 (LSMO) ceramic was synthesized using the sol-gel method. The effect of varying sintering temperatures (1763, 1783, 1803 and 1823 K) on the microstructure and electrical transport properties were systematically investigated. The samples exhibited a distinct dual-peak metal-insulator transition, with the first peak ( T p1 ) primarily influenced by grain boundary (GB) scattering effect. At lower sintering temperatures, lattice strain induced by the ionic size mismatch between La 3+ and Sr 2+ ions is transferred to the grain boundaries, increasing their contribution to resistivity. As the sintering temperature rises, the grain boundary effect diminish, leading to a suppression of the T p1 peak. Elevated sintering temperatures further promote hybridization effect, enhancing the double exchange mechanism. As the temperature increases, this mechanism gradually becomes dominant, leading to a more pronounced influence of the T p2 peak. Additionally, higher sintering temperatures reduce grain boundary scattering, improving the temperature coefficient of resistivity ( TCR ). At an optimal sintering temperature of 1803 K, the LSMO ceramic achieved a peak TCR of 10.78% K -1 near room temperature (284.8 K), demonstrating strong potential for improved performance in uncooled infrared bolometers or electronic switch devices.