Orthorhombic LuFeO 3 is an important member of rare-earth orthoferrites ReFeO 3 whose appealing physical features have drawn much attention due to its various potential applications. In this work, pure phase LuFeO 3 ceramics have been prepared by a mechanochemical activation-assisted solid-state reaction (MAS) method and conventional solid-state reaction (CSS) method for comparison. X-ray Diffraction (XRD) studies demonstrated that the mechanochemical activation process can lower the starting reaction temperature and substantially shorten the time to complete the reaction of LuFeO 3 ceramics. Besides, more homogeneous and highly denser LuFeO 3 ceramics can be obtained using the MAS method revealed by the density measurement and Scanning Electron Microscopy. It was revealed by XRD and Raman measurements that there is a little increase in lattice constant in the MAS sample compared to the CSS sample. The complex impedance spectra illustrated that the MAS sample has a much higher resistance than the CSS sample, which is caused by the higher density and fewer oxygen vacancies verified by X-Ray Photoelectron Spectroscopy.We believe that this study will contribute to solving the common leakage problems in ReFeO 3 ceramics and the investigation of its multiferroic properties.
K E Y W O R D Sleakage, mechanochemical activation, multiferroics, oxygen vacancies, rare-earth orthoferrites 3020 | WANG et Al.
To explore the origin of magnetism, the effect of light Cu-doping on ferromagnetic and photoluminescence properties of ZnO nanocrystals was investigated. These Cu-doped ZnO nanocrystals were prepared using a facile solution method. The Cu2+ and Cu+ ions were incorporated into Zn sites, as revealed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). At the Cu concentration of 0.25 at.%, the saturated magnetization reached the maximum and then decreased with increasing Cu concentration. With increasing Cu concentration, the photoluminescence (PL) spectroscopy indicated the distribution of VO+ and VO++ vacancies nearly unchanged. These results indicate that Cu ions can enhance the long-range ferromagnetic ordering at an ultralow concentration, but antiferromagnetic “Cu+-Vo-Cu2+” couples may also be generated, even at a very low Cu-doping concentration.
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