(Pr0.75La0.25)0.7Sr0.3MnO3:Agx (0 ≤ x ≤ 0.25) polycrystalline ceramics with room-temperature TCR improvement for uncooled infrared bolometers

• Published in: Ceramics international Vol. 46; no. 11; pp. 19028 - 19037
• Main Authors: Pu, Xingrui, Li, Hongjiang, Chu, Kaili, Duan, Yunbiao, Li, Zhidong, Liu, Xiang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2020
• Subjects: (Pr0.75La0.25)0.7Sr0.3MnO3:Agx ceramics; Perovskite manganites; Room-temperature; Temperature coefficient of resistivity (TCR); Uncooled infrared bolometers; (Pr0.75La0.25)0.7Sr0.3MnO3:Agx ceramics; Uncooled infrared bolometers; Perovskite manganites; Room-temperature; Temperature coefficient of resistivity (TCR)
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2020.04.233

In this work, perovskite manganite (Pr0.75La0.25)0.7Sr0.3MnO3:Agx (PLSMO:Agx, x = 0, 0.05, 0.10, 0.15, 0.20 and 0.25) ceramics were successfully prepared by sol-gel route and solid-state reaction. The surface morphologies, peak temperature variation behaviors of temperature coefficient of resistivity (TCR), microstructural and electrical transport properties of all the specimens were analyzed by various testing methods like XRD, SEM, EDS, R-T and XPS. XRD Rietveld refinement data demonstrated that Mn–O bond length, Mn–O–Mn bond angles and the unit cell volume increased along with the rise in x. Consequently, the bandwidth describing the overlap between the O2p and Mn3d orbitals reduced, and this change further affected the electrical transport properties. Scanning electron microscopy (SEM) images indicated that silver was helpful in increasing the grain size. The metal-insulator transition temperature increased due to the enhancement in double exchange (DE) interaction. X-ray photoelectron spectroscopy (XPS) fitting data (percentage of Mn4+ and O2−) along with XRD Rietveld refinement data confirmed the enhancement in DE interaction. The most remarkable thing was that the reduction in resistivity occurred gradually, which resulted in a significant improvement in the TCR. The TCR value achieved 11.35% K−1 with the peak temperature being 300.69 K (room-temperature ~ 300 K) at x = 0.15. Obviously, obtaining a large room-temperature TCR value (≥10% K−1) in praseodymium perovskite oxides was encouraging since such results have not been explored previously. Overall, the proposed PLSMO:Ag0.15 ceramic with large room-temperature TCR value look prospective candidates for future advanced uncooled infrared bolometers.