Obtained large room-temperature TCR of La0.67Ca0.25Sr0.08MnO3 ceramics by optimizing sintering temperature

Abstract

Over the past few decades, perovskite manganese oxide Lax(CaSr)1-xMnO3 has presented new opportunities for uncooled infrared bolometers due to its exceptional electrical transport performance. In this study, La0.67Ca0.25Sr0.08MnO3 (LCSMO) ceramics were prepared at different sintering temperatures (Ts, Ts = 1450, 1470, 1490, 1510, 1530 °C) by changing the previous sol-gel preparation process parameters. The research results indicated that the tolerance factor (τ) of the ceramics is τ = 0.935, and all ceramics exhibit a Pnma space group perovskite structure with excellent crystallinity. LCSMO ceramics exhibit good crystal quality and higher room-temperature TCR (14.58 % K−1) at Ts = 1510 °C. As Ts increases, the grain size, Mn–O bond length (dMn-O), Mn–O–Mn bond angle (θMn-O-Mn) and cell volume (V) of ceramics have a slight affected. The decrease of grain boundary scattering, electron-electron scattering, and strong coupling between electrons, so the peak resistivity value of all sintered samples firstly decreases and then increases with the increase in Ts, which effectively yields ceramics with high TCR. The peak TCR value (TCRmax) increased from 8.38 % K−1 (Ts = 1450 °C) at 296.91 K to 14.58 % K−1 (Ts = 1510 °C) at 298.18 K. On the same component, the TCRmax was increased by 42 % from 8.38 % K−1 to 14.58 % K−1 at Ts = 1450 °C–1510 °C. The high room-temperature TCR of LCSMO is expected to be used in advanced uncooled infrared bolometers, providing a basis for studying the influence of Ts on the electrical transport performance of ceramics.