Effect Of Fe Doping Research Articles

Structure and magnetic properties of (La1−xFex)FeO3 (x = 0, 0.25, 0.50) perovskite

The effect of Fe doping of a LaFeO3 orthoferrite nanostructure was investigated, and the structural and magnetic properties of the resulting material were studied. The pure (La1−xFex)FeO3 (x = 0, 0.25, 0.50) nanocrystals with a minimal amount of impurities (≤6%) were successfully produced by the sol–gel technique using La(NO2)3 and Fe(NO2)·34H2O as starting materials. The phase impurities and crystalline structures were characterized through multiphase Rietveld refinement of x-ray diffraction data. The results showed that the average crystallite size of synthesized powders is ∼18 nm. Lanthanum ions have a valence state of La3+ in the (La1−xFex)FeO3, meanwhile inducing the states of mixed character of Fe3+ and Fe4+ in Fe ions, as confirmed by X-ray photoelectron spectroscopy. Magnetometry measurements provided evidence that all the samples, including the parent LaFeO3, are weak ferromagnets; this finding is explained by distortions in the orthoferrite structure, which disturb the ideal antiferromagnetic coupling between Fe3+ ions. Fe substitution for La ions in the parent LaFeO3 structure leads to a significant increase in the saturation magnetization from 5.4 to 10.2 Am2 kg−1, indicating that the double-exchange interaction occurs between Fe3+ and Fe4+ ions.

STRUCTURAL AND ELECTROCHEMICAL PROPERTIES OF Fe-DOPED NiAl2O4 OXIDE

A new spinel solid solution system of Ni1-xFexAl2O4 (0.0 ≤ x ≤ 0.5) was synthesized through sol-gel method. The effect of Fe doping on the nickel aluminate prepared was investigated. The synthesized powders were characterized by means of X-ray diffraction, thermogravimetric and differential thermal analysis, fourier transform infrared spectroscopy, scanning electron microscopy and electrochemical measurements. From the preceding analysis, it can be shown that compounds show a single spinel phase in the temperature range 650-1000°C and the solubility of iron in the NiAl2O4 structure was limited to samples with the iron content x < 0.6. The electrochemical measurements indicate that the catalytic activity is strongly influenced by iron doping. The highest electrode performance is achieved with Ni0.7Fe0.3Al2O4 (i=86.84 mA/cm2) which is ~ 27 times greater than that of NiAl2O4 ( i=3.22 mA/cm2) at E= +0.8V. After one hundred cycles, the stability of the doped electrode with 30% of iron is much better than the undoped electrode.

Влияние допирования железом на структурные, магнитные и электрические характеристики манганитов системы La0,7Sr0,3Mn0,9Zn0,1 – xFexO3 (0 ≤ x ≤ 0,1)

Влияние допирования железом на структурные, магнитные и электрические характеристики манганитов системы La0,7Sr0,3Mn0,9Zn0,1 – xFexO3 (0 ≤ x ≤ 0,1)

Fe doping effect of vanadium oxide films for enhanced switching electrochromic performances

In the present study, Fe-doped V2O5 films showing impressive electrochromic (EC) performance were developed using the sol-gel spin-coating method. To confirm the optimized Fe-doping effect on the V2O5 films for the EC performance, we adjusted the Fe atomic percentages to 0.0, 0.5, 1.0, and 1.5 at%, respectively. With the effect of Fe doping on the V2O5 films, the obtained films resulted in the formation of the oxygen vacancies. As the result, when the optimum Fe atomic percentage was 1.0 at%, the enhanced switching speeds (3.7 s for the bleaching speed and 2.0 s for the coloration speed) and enhanced coloration efficiency value (47.3 cm2/C) compared to the other films were implemented. This can be attributed to the improved electrical conductivity and Li+ diffusion coefficient that led to efficient generation of the EC reaction activity and narrowing the optical bandgap at the coloration state to increase transmittance modulation. Therefore, this unique film can be a promising EC material to improve the performance for the EC devices.

Investigation of the Fe doping effect on the B-site of the layered perovskite PrBa0.8Ca0.2Co2O5+δ for a promising cathode material of the intermediate-temperature solid oxide fuel cells

Layered perovskites can be considered as promising cathode materials for intermediate-temperature solid oxide fuel cell because of their fast oxygen kinetics compared to simple perovskites. Among them, the cobalt-based layered perovskites are considered as very promising cathode materials due to its high conductivity and fast oxygen kinetics, but they are unstable under operating condition. Doping other transition metal such as Fe, Mn, Cu, and Ni can be considered to solve the instability of the cobalt-based layered perovskites.In this paper, we investigated Fe doped cobalt-based layered perovskite, PrBa0.8Ca0.2Co2-xFexO5+δ (x = 0, 0.5, and 1.0), as prospective cathode materials in terms of their crystal structures, thermal expansion behavior, electro- and electro-chemical properties. The PrBa0.8Ca0.2Co1.5Fe0.5O5+δ shows improved maximum power density of 1.89 W cm−2 and polarization resistance of 0.080 Ω cm2 at 600 °C as compared with un-doped PrBa0.8Ca0.2Co2O5+δ while maintaining suppressed thermal expansion. Based on these results, PrBa0.8Ca0.2Co1.5Fe0.5O5+δ can be considered as a promising cathode material for intermediate-temperature solid oxide fuel cell.

Effect of transition metal (TM) doping on structural and magnetic properties in hexagonal YMn0.917TM0.083O3 systems

Suitable TM doping at the Mn site is an important access to manipulate magnetic properties of hexagonal YMnO3, however, it has not yet been systematically explored how the strength of antiferromagnetic interactions and the magnetic transition temperatures (TN) are modified in the doping YMn0.917TM0.083O3 systems. In the work, we have performed first-principles calculations to study the effect of TM doping on the structural and magnetic properties of hexagonal YMn0.917TM0.083O3 bulks; the results are combined with the available experimental results. The calculated results reveal that the planar TM-O bonds and O-TM-O angles of TMO5 bipyramid are both prominent structural features for the transformations of magnetic properties. We have also predicted the Ti, V, Cr and Fe doping effects on magnetic properties and further analyzed the TM electronic structures of TMO5 bipyramid in the YMn0.917TM0.083O3(001)/MgO(001) film configurations, which could provide more understanding towards the designing of new generation multifunctional devices.

Enhanced carrier concentration of Fe doped delafossite CuAlO2 by double-effect: Divalent metal ions doping and excess oxygen

Bulk CuAlO2 compound has been widely studied as a p-type metal oxide semiconductor material due to the simplicity in its synthesis and use of inexpensive raw materials. The Fe doping in CuAlO2 has been demonstrated to enhance the electrical conductivity. An in-depth analysis of the effect of Fe doping in CuAlO2 on the carrier concentration improvement was revealed. Delafossite CuAl1−xFexO2 powders with x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.30 were synthesized by a solid-state reaction method. The X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) studies were used to measure the atomic-ion concentrations and the oxidation state of each element. The variations of carrier concentration corresponded with a ratio of Cu2+/Cu1+ in CuAlO2. We found that the increase of Cu2+/Cu1+ was caused by double effects through divalent metal ions (Fe2+) doping and excess oxygen (O2−δ) in CuAlO2. The maximum carrier concentration of 8.09 × 1017 cm−3 was obtained for the CuAlO2 sample at Fe content of 10 at.%.

Effects of Fe doping on the photoelectrochemical properties of CuO photoelectrodes

In this study, CuO photoelectrodes doped with various iron concentrations were grown by using a modified chemical bath deposition method. We investigated the effects of the iron doping concentration on the morphological, structural, optical, electrical and photoelectrochemical properties of the CuO photoelectrode by using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), UV-visible spectrophotometry (UV-Vis), electrochemical impedance spectroscopy (EIS) and potentiostatic/galvanostatic analysis, respectively. In this study, the smallest dislocation density, highest charge carrier density and lowest charge transfer resistance values were obtained from the sample with an Fe doping concentration of 2 at%. As a result, the maximum photocurrent density value of −1.44 mA/cm2 was obtained at −0.55 V (vs. SCE) from the photoelectrode with an Fe doping concentration of 2 at%, which was 53% higher than that of the undoped CuO photoelectrode.

Role of Fe-Doping Effect in 2-D MoS2 Magnetic Semiconductor

Two 2-D Mo1– x Fe x S2 ( $x = 0, 0.01$ ) nanosheets were fabricated by the hydrothermal method. X-ray diffraction shows both samples are formed in hexagonal $\text{P}6_{3}$ /mmc (2H structure) phase with 2-D morphology. Raman spectra displayed that the peak widths were broadening in the iron-doped sample. AC conductivity experiments revealed that both samples obeyed the small polaron hopping model. The activation energies of $x = 0$ are 0.121(3) and 0.066(1) eV above and below 200 K. Similarly, two different activation energies, 0.140(2) and 0.082(1) eV above and below 240 K are also found in $x = 0.01$ sample. The effect of iron-doped may raise the activation energies of small polaron. Diamagnetism and paramagnetism were observed in pure MoS2 and iron-doped sample, respectively. Magnetic hysteresis experiments show no loop in both samples, which is evidence that there was not any magnetic domain formed. For $x = 0.01$ sample, the Brillouin function is conducted to fit the M–H curve. The fit $ $ of the $x = 0.01$ sample is about 0.038(1) $\mu _{B}/f. u$ ., which matched the value of 1% Fe4+ ( $S = 2$ ) ion-doped.

Effects of Fe doping on anomalous specific heat and XAFS oscillation in antiferromagnetic metal Mn3Si

The specific heat of Mn3−xFexSi was measured over a wide temperature range. Aside from the lattice and electronic specific heat components, another component had a significant contribution to the specific heat at low temperatures in the case of x = 0.2; however, its contribution decreased when x = 1.0. It is observed that the net component was retained at temperatures significantly higher than TN for both x. The XAFS spectra of the Mn K-edge for x = 0 not only indicated a smooth structure near the edge, but also an unusually small amplitude in the extended high energy region; however, these features disappeared with Fe doping. The specific heat and XAFS data were discussed in terms of the charge degree of freedom or electronic inhomogeneity.

Influence of Fe2+/Fe3+ ions in tuning the optical band gap of SnO2 nanoparticles synthesized by TSP method: Surface morphology, structural and optical studies

Fe doped nanostructured SnO2 thin films are prepared by a thermal spray pyrolysis (TSP) method at a substrate temperature (Ts) 450 °C. In addition, an effort is made to comprehend the effect of Fe doping on the surface morphology, micro-structural and optical properties of SnO2 thin film. The result of XRD data confirms that the fabricated SnO2 films are tetragonal cassiterite structure and the lattice parameters are slightly changed with Fe2+/Fe3+ contents. The values of lattice parameters are analogous in Rietveld refinement and DFT function. The lattice strain and stresses value are ranging from 2.07 to 0.13, × 10−3 and 0.71–0.04 respectively. The films are made up of nano-sized crystals with slender and polyhedron shaped particle size ranging from 17.23 to 159.50 nm observed by field emission scanning electron microscope (FESEM), Scherrer's formula and uniform deformation model (UDM). With increasing Fe concentrations, the optical band gap of SnO2 films is decreased from 3.89 to 3.39 eV. Reduction in optical band gap is attributed to the influence of Fe ions and conduction/valence bands of SnO2 structure. Fe doped SnO2 nanostructured film addresses the suitability of the material to have a good potential application in optoelectronic devices.

Synergistic effects of Bi Deficiencies and Fe-doping on the thermoelectric properties and hardness of BiCuSeO ceramics

Synergistic effects of Bi Deficiencies and Fe-doping on the thermoelectric properties and hardness of BiCuSeO ceramics

Fabrication of ferroelectric Fe doped HfO2 epitaxial thin films by ion-beam sputtering method and their characterization

In this study, the effect of Fe doping on the crystal structure and electrical properties in 20-nm-thick HfO2 epitaxial thin films were systematically investigated. X-ray diffraction measurements revealed that undoped HfO2 films were composed of a paraelectric monoclinic phase. On the other hand, the formation of non-centrosymmetric orthorhombic phase was observed in Fe doped HfO2 films and was most promoted at an optimum doping concentration. In addition, high-temperature X-ray diffraction measurements showed that an orthorhombic phase to a highly symmetric phase transition occurs between 500 and 600 °C. Microstructural analysis using scanning transmission electron microscopy revealed multidomain structure consisting of orthorhombic and monoclinic phases. Ferroelectricity depended on Fe doping concentration, and the maximum remanent polarization value was 8.8 µC/cm2. These results indicate that Fe doped HfO2 thin films can be applied as nanoscale ferroelectrics.

Effect of Fe doping on structural and optical properties of ZnO films and nanorods

Fe-doped ZnO thin films were successfully prepared via the sol-gel spin coating method. Both X-ray diffraction and X-ray photoelectron spectroscopy analysis displayed that Fe atoms were successfully incorporated into the ZnO thin films and existed in the form of Fe2+ mostly in 1 at.% Fe-doped ZnO films, and mainly existed in the form of Fe3+ in higher concentration of the films. Scanning electron microscopy images demonstrated the decrease in crystallite size with increasing Fe concentration. The room temperature photoluminescence revealed that electrons transition from a shallow level of Zni to top level of valance band increased, while near band edge (NBE) emission reduced with increasing Fe content, which indicated that Fe doping introduce some impurity levels and/or influence on the existing levels and hence affect the type of transition. Furthermore, the behavior of surface carrier transport and interfacial charge transfer are investigated by the photocatalytic activities and electrochemical impedance spectroscopy for undoped and Fe-doped ZnO films and nanorods, to detect the effects of Fe dopant in the form of Fe2+ and Fe3+ ions on photocatalytic performance.

Effects of Fe doping on photoluminescent and magnetic properties of CaTiO3:Eu3+

In this work, photoluminescent and ferromagnetic bifunctional properties were found in Fe-doped CaTiO3:Eu3+ ceramic materials synthesized via ceramic sintering method. With appropriate amount of Fe doping in CaTiO3:Eu3+ ceramic, both photoluminescent intensities and magnetization strength of samples increase. When doping content of Fe is 0.05 mol%, the ceramic has optimal photoluminescent intensity. After 0.05 mol% Fe-doped CaTiO3:Eu3+ ceramic material experiences 0.15 T external magnetic treatment for 12 h, main red emission at 615 nm ([5D0→7F2]) increases ~80%, and 593 nm emission ([5D0→7F1]) increases ~109%. This study is helpful for understanding effects of Fe doping on photoluminescent and magnetic properties of CaTiO3:Eu3+ ceramic and provides valuable reference for effects of Fe impurities on photoluminescent and magnetic properties of other materials.

Structural and electrochemical properties of LiMn0.6Fe0.4PO4 as a cathode material for flexible lithium-ion batteries and self-charging power pack

Cathode materials with low-cost, environment-friendly, high energy density are critical for lithium-ion batteries (LIBs). Here, the effects of Fe doping on the structure of LiMnPO4 (LMP) are investigated by neutron powder diffraction (NPD). The prepared LiMn0.6Fe0.4PO4/carbon (LMFP/C) shows a higher specific capacity of 90 mAh g-1 at a current density of 1 C, which is about 5 times of that of LiMnPO4/C. It also shows excellent cycling performance for 1000 cycles. The improved electrochemical performance is ascribed to the higher octahedral distortion of (Mn, Fe)O6 and an easiness for Li diffusion due to much less anisotropic ellipsoids for Li in LMFP. We further fabricated a flexible LIB with LMFP/C cathode and an in-situ polymerized electrolyte, which exhibits excellent flexibility and cyclability. The cell shows no obvious performance degradation after bending for 300 times. Moreover, a flexible triboelectric nanogenerator (TENG) was coupled with the flexible cell to form a wearable self-charging power pack. The TENG can harvest mechanical energy and convert it into electrical form, charge the battery to supply energy for a flexible electrochromic membrane. The open circuit voltage (VOC) of the flexible LIB increases from 3.32 V to 3.51 V in about 20 min through daily human motion.

Iron doped ZnO thin films deposited by ultrasonic spray pyrolysis: structural, morphological, optical, electrical and magnetic investigations

In this work, undoped and Fe-doped ZnO thin films at various concentrations (2, 4 and 6 at.%) were deposited onto glass substrate by using ultrasonic spray pyrolysis in order to investigate the effect of Fe doping on the structural, morphological, optical, electrical and magnetic properties of ZnO thin films. X-ray diffractometer (XRD) results revealed that all deposited thin films have hexagonal wurtzite structure and Fe doping led to decrease in mean crystallite size. Atomic force microscopy images showed that thin films were composed of tightly packed grains. Optical examinations indicated that optical transmittance remarkably decreased with the increase in the amount of Fe concentration in thin films. Additionally, optical band gap of deposited films were determined in the range of 3.26–3.29 eV. It was determined that all deposited thin films have n-type conductivity and electrical resistivity increased up to 253.6 Ωcm as a consequence of Fe doping. Vibrating sample magnetometer measurements showed that all films have ferromagnetic behavior.

Effect of Fe and Ti Substitution Doping on Magnetic Property of Monolayer CrSi2: a First-Principle Investigation

First-principle calculations based on spin-polarized density functional theory were performed to investigate the effect of Fe and Ti substitution doping on magnetic property of monolayer CrSi2. The electronic structures, binding energy, magnetic property, total and partial density of states, and spin density of monolayer CrSi2 are scientifically studied. Calculated binding energy reveals that Fe-doped monolayer CrSi2 is more stable than Ti-doped monolayer CrSi2. The local magnetic moment of Fe and Ti atom all decrease compared with atomic moment in free gas phase due to variation of bond interaction and charge transfer. The density of states and spin-density results indicated that local magnetic moment of Fe atom is larger than Ti atom, leading to total magnetic moment of Fe-doped monolayer CrSi2 is bigger than Ti-doped monolayer CrSi2.

Effect of Fe doping on structure and magnetotransport properties of perovskite manganite

Neutron powder diffraction experiments to refine the crystal and magnetic structures of a La0.7Ca0.3Mn0.5Fe0.5O3 compound were carried out at temperatures of 10, 50, 80, 100, 120, 150, 200, 250 and 300 K. The obtained results support the conclusion that there is no long-range ferromagnetic order at all these temperatures. Structural parameters and, especially, the magnetic moments are calculated as a function of temperature. Their polynomial extrapolation is performed. Magnetization and electrical resistivity measurements were also performed in the temperature range of 5–300 K in magnetic fields up to 1 T. Field magnetization is measured to confirm the formation of the spin-glass-like state. These experimental results indicate formation of a complex magnetic state in which the long-range antiferromagnetic G-type phase coexists with short-range ferromagnetic clusters. Electrical conductivity of La0.7Ca0.3Mn0.5Fe0.5O3 demonstrates an anomalous temperature behavior suggesting a switching between different states. Correlation between the critical temperatures of magnetic and electrical transitions is demonstrated. Resistivity data in various theoretical models are processed. We discuss the origin of the unconventional magnetic state, the mechanisms of the electrical conductivity, and the correlation between magnetic and transport properties in this manganite.

On the Sol-Gel Synthesis and Structure, Electronic and Ionic Conductivities and Impedance Behavior of Y, Fe Co-Doped SrTiO&lt;sub&gt;3&lt;/sub&gt; Mixed Conductor

A single phase perovskite, YxSr1−xTi0.6Fe0.4O3-δ(x=0.06-0.09), was fabricated at 1350°C in air by sol-gel method. The effects of Y-and Fe-doping into SrTiO3on phase structure, electrical conductivity, ionic conductivity and its impedance behavior were investigated. The optimized Y0.07Sr0.93Fe0.4Ti0.6O3-δsample exhibits an electrical conductivity of 0.135 S·cm-1at 800 °C. Y-doping decreases the migration energy for oxygen ions, leading to a significant increase in ionic conductivity. The ionic conductivity of Y0.09Sr0.91Ti0.6Fe0.4O3-δsample varies from 0.0052 S· cm-1at 600°C to 0.02 S·cm-1at 800°C. Impedance characteristics over a wide frequency range of 0.01Hz-100 KHz reveal that the resistance of ionic conduction is predominantly influenced by grain boundary, the relaxation time of which decreases with increase of Y-doping amount.