Effects of mechanochemical activation on the structural and electrical properties of orthorhombic LuFeO₃ ceramics

Abstract

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.

Crystal Structure and Concentration-Driven Phase Transitions in Lu(1−x)ScxFeO3 (0 ≤ x ≤ 1) Prepared by the Sol–Gel Method

“…Figure 4 a compares 532 nm excited Raman spectra of polycrystalline LuFeO 3 and ScFeO 3 samples sintered at 1100 °C. In the case of orthorhombic orthoferrites with a Pnma space group, one can expect 24 first-order Raman active modes distributed by symmetry in the following way [ 40 , 41 ]: …”

“…The positions of the fundamental bands were very similar to those in the Raman spectrum of a single-crystal LuFeO 3 sample [ 40 ], thus indicating a high phase purity of the studied compound. Based on the frequency value, the vibrational bands below ~200 cm −1 could be considered associated mainly with vibrations of heavy rare-earth ions, the vibrational modes ranging from 200 to 350 cm −1 could be related to tilting motions of FeO 6 octahedra, the bands in the frequency region from 350 to 500 cm −1 belonged mainly to the oxygen bending modes, and the vibrational modes at wavenumbers higher than 500 cm −1 were related to symmetric stretching vibrations of Fe–O bonds [ 41 , 42 ].…”

“…This band had two components located near 523 and 546 cm −1 ; the higher-frequency blue-shifted component clearly appeared for the compound with x = 0.75. Because the vibrational modes in the frequency region above 500 cm −1 are related mainly to Fe–O stretching vibrations [ 41 , 42 ], this may indicate a strengthening of the corresponding bond. It should be noted that the spectral parameters of the strong band near 112 cm −1 remained essentially unchanged, which suggested that the local structure in the vicinity of heavy Lu ions remained similar.…”

Optical and Photocatalytic Properties of Cobalt-Doped LuFeO3 Powders Prepared by Oxalic Acid Assistance

“…The powders prepared by the solid-state reaction method, which usually results in large particle sizes and poor morphology, are seldomly employed to perform photocatalytic experiments. However, the mechanochemical activation-assisted solid-state reaction (MAS) method, a modified solid-state reaction method reported in our previous work [33], enables the preparation of desired powders at a relatively low temperature for a relatively short time. In this paper, we prepared B-site Co-doped LuFeO 3 powders by the MAS method reported in our previous work [33].…”

“…However, the mechanochemical activation-assisted solid-state reaction (MAS) method, a modified solid-state reaction method reported in our previous work [33], enables the preparation of desired powders at a relatively low temperature for a relatively short time. In this paper, we prepared B-site Co-doped LuFeO 3 powders by the MAS method reported in our previous work [33]. The preparation, fine structure, morphology, and optical properties are investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and UV-visible absorbance spectroscopy.…”