Raman spectra and ferromagnetism of nanocrystalline Fe-doped Li0.43Nb0.57O3+

Li, You-Yun; Chen, Hao-Long; Kuo, Chia-Liang; Hsieh, Pei-Hsuan; Hwang, Weng-Sing

doi:10.1016/j.ceramint.2016.03.203

Cited by 3 publications

(12 citation statements)

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“…The reported value of Fe +2 -O bond distances is about 2.08 to 2.18, which is higher than that of Fe +3 -O and related to the lattice relaxation, while the valence is changed from Fe +2 to Fe +3 [31,32]. Our results show the same trend.…”

Section: Resultssupporting

confidence: 74%

“…Comparing the Li vacancy model and the model using Equation (7), the increment of the distance of Li-vacancy-Nb is around 0.042 Å in our study. The reported value of Fe +3 –O bond distances is about 1.98 to 2.07 Å, which is smaller than the bond length of Li–O [32]. The bond lengths and bond angles of Li–O and Fe–O in Fe-doped LiNbO 3 are under hybrid calculation in our refinement and denoted as Li/Fe–O in Table 6.…”

Section: Resultsmentioning

confidence: 93%

“…The position of Li in the c axis is reported to be shifting upward by about 0.1 Å in the data of Sanson et al [32]. Since the location of Li ion is relative to the Nb ion along the c axis, a slight upward shift of Li ions could be observed from the increasing distance of Li-vacancy-Nb.…”

Section: Resultsmentioning

confidence: 95%

“…The quantitative characterization and modification of the Fe +2 content by annealing treatments are frequently investigated by the combination of optical absorption spectra, EPR measurement and standard samples for calibrations [28,29,30]. The local distortion induced by the self-trapping action related to the polaron formation was also investigated by some recent XRD results [31] and extended X-ray absorption fine structure (EXAFS) [32]; in these studies a larger lattice relaxation was measured when the Fe +3 changed to Fe +2 . However, the concentration of Fe in these samples is relatively low; there was a lack of data on high doping samples to understand the deformation of the defect structure.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of the Defect Structure of Congruent and Fe-Doped LiNbO3 Powders Synthesized by the Combustion Method

Chen

et al. 2017

Materials

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Fe-doped LiNbO3 synthesized by the combustion method to seek new multiferroic materials exhibits room-temperature ferromagnetism, as reported in our previous work. In this work, the defect structure of congruent and Fe-doped LiNbO3 (0.57–3.3 mol %) powders was investigated in detail by several methods. The molar ratio of [Li]/([Li]+[Nb]) was determined by the Curie temperature (Tc) via DSC. Two peaks of Tc were observed due to phase splitting, and the phase at lower Tc disappears as the Fe doping concentration increases. The coexistence of two different oxidation states of Fe ions in LiNbO3 was probed by XPS and UV-Vis spectroscopy. The Raman spectra exhibit displacements along the c axis of Li and Nb ions, and a deformation of the NbO6 framework owing to Fe doping. Several doping models were applied in the Rietveld refinement of powder X-ray diffraction collected by synchrotron radiation. The fitting by the Nb vacancy model leads to an improbably distorted structure of congruent LiNbO3. In Fe-doped LiNbO3, we conjecture that Li and Nb vacancies coexist in the lattice structure; Fe+2/Fe+3 ions are substituted for Li ions at the regular Li site and may push the anti-site NbLi ion back to the regular Nb site.

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Section: Resultssupporting

confidence: 74%

Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Investigation of the Defect Structure of Congruent and Fe-Doped LiNbO3 Powders Synthesized by the Combustion Method

Chen

et al. 2017

Materials

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“…On the other hand, RS is sensitive to atomic displacements and slight structural modifications by ion substitution [35]. These changes are linked to frequency shifts and band-shape modifications in the Raman spectra [30].…”

Section: Structural and Morphological Properties Of The Lto:fe-lc Andmentioning

confidence: 99%

Iron-Doped Lithium Tantalate Thin Films Deposited by Magnetron Sputtering: A Study of the Iron Role in the Structure and the Derived Magnetic Properties

et al. 2020

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Fe-doped LiTaO3 thin films with a low and high Fe concentration (labeled as LTO:Fe-LC and LTO:Fe-HC, respectively) were deposited by magnetron sputtering from two home-made targets. The dopant directly influenced the crystalline structure of the LiTaO3 thin films, causing the contraction of the unit cell, which was related to the incorporation of Fe3+ ions into the LiTaO3 structure, which occupied Li positions. This substitution was corroborated by Raman spectroscopy, where the bands associated with Li-O bonds broadened in the spectra of the samples. Magnetic hysteresis loops, zero-field cooling curves, and field cooling curves were obtained in a vibrating sample magnetometer. The LTO:Fe-HC sample demonstrates superparamagnetic behavior with a blocking temperature of 100 K, mainly associated with the appearance of Fe clusters in the thin film. On the other hand, a room temperature ferromagnetic behavior was found in the LTO:Fe-LC layer where saturation magnetization (3.80 kAm−1) and magnetic coercivities were not temperature-dependent. Moreover, the crystallinity and morphology of the samples were evaluated by X-ray diffraction and scanning electron microscopy, respectively.

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Structural and Magnetic Behavior of Oxidized and Reduced Fe Doped LiNbO3 Powders

et al. 2018

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Changes in structural and magnetic properties have been systematically induced in lithium niobate (LiNbO 3) powders, Fe-doped with different concentrations and thermally treated in oxidized and reduced states. A rather strong ferromagnetic response at room temperature with a saturation magnetization of 0.96 Am 2 kg −1 was obtained for the higher utilized doping concentration, which is of the order of 1% mol. This may be considered a first report of the manifestation of ferromagnetism in nanocrystalline lithium niobate powders within the regime of very low Fe-doping concentrations. Post-thermal treatment in a controlled atmosphere is key for inducing and detecting this behavior, which can also be explained as the effective recombination of Fe impurities with oxygen vacancies in the surface of the material. Mechanochemical-calcination was employed for the synthesis of LiNbO 3 powders and after that, a diffusion process of 0.44%, 0.89%, 1.47% and 2.20% mass of Fe 2 O 3 was used in the Fe-doping. Oxidation and reduction processes were performed using a controlled atmosphere of ultra-high purity oxygen and hydrogen, respectively. X-ray diffraction and Raman spectroscopy were employed to characterize the materials. The magnetic properties were studied using Vibration Sample magnetometry and Electron Spin Resonance spectroscopy.

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Raman spectra and ferromagnetism of nanocrystalline Fe-doped Li0.43Nb0.57O3+

Cited by 3 publications

References 30 publications

Investigation of the Defect Structure of Congruent and Fe-Doped LiNbO3 Powders Synthesized by the Combustion Method

Investigation of the Defect Structure of Congruent and Fe-Doped LiNbO3 Powders Synthesized by the Combustion Method

Iron-Doped Lithium Tantalate Thin Films Deposited by Magnetron Sputtering: A Study of the Iron Role in the Structure and the Derived Magnetic Properties

Structural and Magnetic Behavior of Oxidized and Reduced Fe Doped LiNbO3 Powders

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