Enhancing TCR of La0.81Sr0.19MnO3 ceramics by optimizing sintering duration to degrade cation disorder and grain boundary scattering

The influence of sintering duration ( t s  = 7, 10, 13 and 16 h) on the microstructure, A-site cation disorder ( σ 2 ), hopping conduction mechanism and temperature coefficient of resistance characteristics of La 0.81 Sr 0.19 MnO 3 polycrystalline ceramics were investigated in this work. By systematically adjusting the sintering duration, it is observed that the A-site cation disorder has decreased from σ 2  = 4.23 × 10 −3 ( t s  = 7 h) to σ 2  = 3.71 × 10 −3 ( t s  = 13 h). The changes in the A-site cation disorder increase the ratio of Mn 4+ /Mn 3+ , Mn-O bond lengths and angles of perovskite manganite oxides. The hopping conduction mechanism of the ceramics was examined using the variable range hopping model, and the result verified that the dynamics of charge carriers are significantly impacted by variations in cation disorder. All of the scattering processes in electron-electron, electron-phonon, and electron-magnon in La 0.81 Sr 0.19 MnO 3 ceramics were decreased with cation disorder decreasing. The temperature coefficient of resistivity ( TCR ) achieved its maximum value of 11.19 % K −1 at room temperature (298.56 K) when t s  = 13 h. The value of TCR has increased by 38.32 % from 8.05 % K −1 ( t s  = 10 h) to 11.19 % K −1 ( t s  = 13 h). Therefore, the ceramic has great application potential for infrared bolometers.