High-density sol-gel derived, cold-isostatically pressed La0.67Ca0.27Sr0.06MnO3 polycrystalline ceramics and their room-temperature TCR improvement.

In this study, high-density La 0.67 Ca 0.27 Sr 0.06 MnO 3 (LCSMO) ceramics were successfully obtained by sol-gel method followed by cold isostatic pressing (CIP) under 250 MPa. Effects of sintering temperature (T S , 1250 °C ≤ T S ≤ 1450 °C) on structure, surface chemical, electrical, and optical properties of as-obtained LCSMO ceramics were investigated by X-ray diffraction (XRD, BDX3200), X-ray photoemission spectroscopy (XPS, Thermo Fisher Scientific), a four-probe system (East changing ET9005), Fourier transform infrared spectrometry (FTIR, TENSOR 27), Raman microscopy (RENISHAW inVia) and UV–vis spectrophotometry (HITACHI U-4100), respectively. All prepared samples showed orthorhombic structure with Pnma space group. As T S increased, grain size gradually rose from 2.71 to 7.30 μm. XRD refinement, Raman, and FTIR all depicted constant of bond angle and length of Mn–O. Hence, variation in T S did not cause lattice distortion inside samples. The best electrical properties were obtained at 1450 °C, where resistivity (ρ) fell below 0.008 Ω cm and temperature coefficient of resistivity (TCR) reached 13.0% K−1 at 289.2 K (room temperature).It is worth noting that electrical performance was indeed improved due to high densities of samples under processing of CIP. Overall, the change in T S from 1250 to 1450 °C greatly influenced electrical behaviors but showed little effect on structural and optical properties of LCSMO ceramics. [ABSTRACT FROM AUTHOR]