Increasing Fe Doping Concentration Research Articles

Enhanced Potentiometric Hydrogen Sensing Response Based on the Ba0.5Sr0.5Co1-yFeyO3-δ Electrode with Unusual Polarity.

In this work, unusual potentiometric hydrogen sensing of mixed conducting Ba0.5Sr0.5Co0.8Fe0.2O3-δ was reported. Inspired by the unusual polarity, a dual sensing electrode (SE) potentiometric hydrogen sensor was fabricated by pairing Ba0.5Sr0.5Co0.8Fe0.2O3-δ with electronic conducting ZnO to enhance the hydrogen response. Hydrogen sensing measurements suggested that significantly higher response, larger sensitivity, and lower limit of detection (LOD) were achieved by the dual SE sensor when compared with the single SE sensor based on Ba0.5Sr0.5Co0.8Fe0.2O3-δ or ZnO. A high response of 97.3 mV for 500 ppm hydrogen and a low LOD of 2.5 ppm were obtained by the dual SE sensor at 450 °C. Furthermore, the effect of the Fe doping concentration in Ba0.5Sr0.5Co1-yFeyO3-δ (y = 0.2, 0.5, and 0.8) on hydrogen sensing response was investigated. The potentiometric response values to hydrogen increased monotonically with increasing Fe doping concentration. With the Fe/Co atomic ratio increased from 0.25 to 4, the responses to 500 ppm hydrogen raised by 69.6 and 94% at 350 and 450 °C, respectively. The sensing behaviors of unusual Ba0.5Sr0.5Co1-yFeyO3-δ may be ascribed to the predominant surface electrostatic effect. These results show that mixed conducting Ba0.5Sr0.5Co1-yFeyO3-δ is desirable for developing high-performance dual SE hydrogen sensors.

Tuning of electrical, magnetic, and topological properties of magnetic Weyl semimetal MnGe by Fe doping

We report on the tuning of electrical, magnetic, and topological properties of the magnetic Weyl semimetal (MnGe) by Fe doping at the Mn site, MnFeGe (δ = 0, 0.30, and 0.62). Fe doping significantly changes the electrical and magnetic properties of MnGe. The resistivity of the parent compound displays metallic behavior, the system with δ = 0.30 of Fe doping exhibits semiconducting or bad-metallic behavior, and the system with δ = 0.62 of Fe doping demonstrates a metal–insulator transition at around 100 K. Further, we observe that the Fe doping increases in-plane ferromagnetism, magnetocrystalline anisotropy, and induces a spin-glass state at low temperatures. Surprisingly, topological Hall state has been noticed at a Fe doping of δ = 0.30 that is not found in the parent compound or with δ = 0.62 of Fe doping. In addition, spontaneous anomalous Hall effect observed in the parent system is significantly reduced with increasing Fe doping concentration.

Effects of Fe doping on the magnetic and absorption spectrum of graphene-like ZnO monolayer from first-principles calculations

The stability, electronic structure, magnetic properties, and absorption spectrum of Fe doped ZnO monolayer have been investigated by first-principles calculation. The results show that Fe doped ZnO monolayer systems are stability. The band gap of ZnO monolayer is narrowed by Fe atom doping, and with the increase of Fe doping concentration, the band gap becomes more narrow(2.900 eV) in Zn14Fe2O16 monolayer, which may be due to the formation of the local built-in magnetic field by Fe atom doped in ZnO monolayer systems. Both of Zn15Fe1O16 and Zn14Fe2O16 monolayer systems are magnetic. The Curie temperature value has been estimated to be 916 K in figuration I of Zn14Fe2O16 monolayer systems. Moreover, the absorption spectrum has a red-shift in the wavelength range of 320–800 nm by Fe doping. These calculation results are helpful for the design of photoelectric and spintronic devices.

Weak-visible-light-driven Fe doped TiO2 photocatalyst prepared by coprecipitation method and degradation of methyl orange

Fe doped TiO2 nanoparticles were synthesized by coprecipitation method under calcination temperatures between 200 °C and 400 °C with different Fe doping concentration from 0 to 1.8 at.%. The crystal structure, morphology, optical properties, energy band gap (Eg) and photocatalytic performance of synthesized nanoparticles were calculated and characterized by first-principles calculations, XRD, TG-DSC, FTIR, FESEM, EDS, TEM, SAED, XPS, UV–Vis and PL spectroscopy. Results showed that Fe doped TiO2 nanoparticles had pure anatase structure with spherical morphology of 4–12 nm in crystallite size which increased with calcination temperatures. The Eg of Fe doped TiO2 was decreased from 3.07 eV to 2.71 eV by the increase of Fe doping concentration. The maximum degradation efficiency of methyl orange (MO) was as high as 46.3% for Fe doped TiO2 nanoparticles calcined at 300 °C with Fe doping concentration of 0.3 at.% under 15 W visible light irradiation.

Defect‐mediated optical properties of Fe‐substituted TiO2 nanoparticles

AbstractHere, sol–gel derived Fe–TiO2 anatase nanoparticles with varying concentrations of Ti(1–x)FexO2 (x = 0%, 1%, 5%, 10%) were prepared. The structural, morphological, and optical properties of prepared samples were studied. X‐ray diffraction (XRD) patterns show the formation of pure anatase phase. The mean crystallite size of Fe–TiO2 decreases with increase in the concentration of Fe. Fourier transform infrared spectroscopy (FTIR) spectra confirmed the presence of Ti–O vibrational band for all the samples. In Raman spectrum, peak broadening and red shifting linked with Eg ∼144 cm–1 divulge the Fe substitution at Ti sites into host lattice structure. Photoluminescence (PL) spectra verified nine peaks related to near band‐edge emission and various defect states. The UV–vis diffuse reflectance spectra represent redshift and reduction in the bandgap energy. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations show that the size of the grains decreases with increase in Fe doping concentration. The study shows that Fe‐doped TiO2 anatase phase nanoparticles are suitable for photocatalytic activity and solar cell applications.

Effect of Fe doping on the structural, dielectric, and magnetic properties of Li V(1-X) Fe x O3 (x = 0,0.1,0.3) ceramics

The present work is on the structural, dielectric and magnetic properties of LiV(1-x)Fex O3 (x = 0,0.1,0.3) ceramics samples. The Rietveld refinement of XRD pattern reveal that the crystal structure of all samples are monoclinic with space group C2/c. Structural studies also suggests that Li site disorder increases with increase in Fe doping concentration, leads to the formation of minor phase of Li3VO4. The Raman spectra shows red shift with increase in Fe content to parent LiVO3. The dielectric constant at low-frequency increase with Fe doping content and undulates at high frequency range due to grain boundary effect. The magnetic properties of LiVO3 has been significantly changed with Fe doping. The diamagnetic behavior of parent material changes to weak ferromagnetic nature when doping with Fe.

Structural, optical and electrical properties of spray-deposited Fe-doped nanocrystalline ZnS0.2Se0.8 thin films

ABSTRACT In this work, ZnS0.2Se0.8 thin films doped with Fe of various concentrations were spray deposited to investigate the influence of Fe doping concentration on the most significative structural, morphological, optical and electrical properties. An X-ray diffraction study showed that all films were polycrystalline and had a cubic zinc blende crystal structure. SEM showed that the Fe-doped ZnS0.2Se0.8 thin films had a spherical-like structure with agglomeration of grains and that their particle size was slightly increased. EDAX confirmed that the ZnS0.2Se0.8 lattice was doped with Fe. An optical study indicated that there was a direct allowed type transition. The band gap of ZnS0.2Se0.8 thin films sharply increased to 3.25 eV with Fe doping upto 0.2 mol% and then gradually decreased with increasing Fe doping concentration. DC electrical resistivity measurements confirmed that the films were semiconducting; with a minimum resistivity of 0.617 × 105 Ω-cm. Hall Effect and thermoelectric power measurements confirmed n-type conductivity.

A synergistic boost of photo-activity of ZnO for photocatalytic degradation of methylene blue by Ag decoration and Fe doping

Fe-doped Ag-ZnO (Zn0.97FexAg0.03-xO) nanoparticles (NPs) were synthesized by a two-step polymer network gel method. By modulating the Fe, Ag concentration to acquire the strongest spectral absorption and the most efficient charge separation efficiency, the photocatalytic performance of ZnO for methylene blue (MB) degradation can be improved synergistically and remarkably. The spectral absorption and the photo-generated charge carrier separation properties of ZnO are enhanced by introducing Fe and Ag. The Fe2+ to Fe3+ valence state transformation is observed in the case of increasing Fe doping concentration. Especially, sample Zn0.97Fe0.005Ag0.025O (FZA-0.5) exhibits the strongest spectral absorption, the weakest photoluminescence (PL) emission, and displays the strongest surface photo-voltage (SPV) signal. Compared with pure ZnO, these favorable features of FZA-0.5 lead to the degradation efficiency of MB under UV and visible light being ~2.7 and ~5.0 times higher, respectively. Besides, the introduced Fe2+ on ZnO surface seems more beneficial for the photocatalytic enhancement. We show a strategy for synthesizing high performance and low-cost ZnO-based photocatalysts by trace transition metal doping to reduce the decoration of noble metal.

Multiferroic and phonon properties of pure and ion doped CoCr2O4 - Bulk and nanoparticles

Using a microscopic model we have studied different properties of pure and ion doped CoCr2O4 - bulk and NPs. The magnetization Ms and the Curie temperature TC decrease with decreasing particle size. By Fe doping Ms and TC increase with enhancing Fe concentration x whereas by Mg doping we obtain the opposite effect. In the first case there is a compressive strain, in the second one - a tensile strain due to the different radii of the doping ions compared to the host ones. This leads to different exchange interaction constants in the doped states. The polarization Ps increases with increasing Fe doping concentration x. Two anomalies are observed in the specific heat Cp, at TC = 98 K, and TS = 25 K, which are not so sharp applying h. The temperature, magnetic field, size and doping dependence of the phonon energy ω0 = 685 cm−1 and damping are also investigated.

Hydrothermal synthesis and optical properties of Fe doped ZnO nanorods

ZnO nanopowders with hexagonal wurtzite structure were synthesized by hydrothermal method with different concentrations of Fe. X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy The morphology, structure and optical properties of the samples were tested and characterized by XPS and (photoluminescence) PL spectra.The results show that the crystal structure of wurtzite ZnO does not change with the increase of Fe doping concentration, and Fe ions do not change into ZnO lattice instead of Zn ions. At the same time, the uniformity of flower-like ZnO nanorods deteriorates, Fe doping A small number of single nanorods with smaller sizes appeared in the hetero-ZnO nanorods.The PL spectrum shows that as the Fe doping concentration increases, the UV luminescence peak of the sample does not change significantly, and the intensity of the luminescence peak decreases first and then increases, indicating that the defect of the sample first decreases and then increases.When the concentration of Fe doping is 1.5%, the prepared ZnO flower-like nanorods have a relatively low visible luminescence peak, which has a small defect.

Optimized Fe-doped ZnO nanoparticles for magneto-opto device applications

Magnetic impurity in wide bandgap semiconductors incorporate magneto-electro-optical properties. For the vast application and demand of future market devices; Fe-doped ZnO (Fe-ZnO) powders at different Fe doping concentrations were synthesized by solid-state reaction route. 3%Fe-doped ZnO thin films were also grown using solution route as a powder sample of 3%Fe-ZnO was found to be the Room Temperature Ferromagnetic (RTFM). X-ray Diffraction (XRD) patterns showed the increase in secondary phases from single phase wurtzite ZnO structure with increase in Fe concentration. UV-Vis absorption spectroscopy (UV-Vis) showed decrease in bandgap. In Photoluminescence (PL) spectra quenching is observed as Fe3+ ions occupies the photogenerated Zn ion with an increase in doping concentration. SEM analysis revealed the spherical morphology of nanoparticles ranges in 50 nm. Agglomerations of the Fe2+/Fe3+ ions leads to paramagnetism with an increase in Fe doping. Vibrating Sample Magnetometer (VSM) showed that only 3%Fe-ZnO sample was found to be RTFM whereas paramagnetic behavior dominates with the increase in Fe doping concentration. Since, the type of synthesis route adopted doesn’t have a control of physical and chemical property of any material; Rather the choice of dopant (magnetic-Fe) and the host (optical-ZnO) in an optimized ratio can proves to be a single material with magnetic-optical properties. This material as combination of two properties proves to be a potential for spintronic and biosensor-based device applications both in non-medical and medical areas.

Enhanced photocatalytic Activity of Ferromagnetic Fe-doped NiO nanoparticles

The Ni1-xFexO (x = 0.00, 0.02, 0.04, 0.06 and 0.08) nanoparticles (NPs) has been synthesized via composite hydroxide mediated (CHM) synthesis approach. The single phase formation of NiO NPs was achieved without any impurity phase confirmed by XRD and average crystallite size showed minor decreasing trend with increasing Fe doping concentration. FTIR spectra showed dip in 417-432 cm−1 range which confirmed the existence of Ni-O bonding. In Raman spectra, the weak two-magnon (2 M) band at 1472 cm−1 in pure NiO NPs indicate suppressed antiferromagnetism (AFM) due to smaller average crystallite size and superparamagnetic contribution from the uncompensated surface/core spins. The absence of 2 M band in Fe doped samples is due to onset of ferromagnetism in these NPs. The M-H loops showed the room temperature ferromagnetism in Fe doped samples due to double exchange interaction of mixed valance states of Fe. The energy band gap showed minor increasing trend with increasing Fe doping concentration and is mainly attributed to Moss-Burstein effect. The photocatalytic activity showed an increasing trend with increasing Fe doping due to generation oxygen vacancies which served as energy traps and restricted the electron-hole recombination. Therefore, the bifunctional ferromagnetic Fe doped NiO NPs are more favourable for photocatalysis along with their ability of collection for re-use in the degradation process.

Structural, optical and photoluminescence studies of sol-gel synthesized pure and iron doped TiO2 photocatalysts

Pure and Iron doped TiO2 nanoparticles were synthesized using the sol-gel method. These materials were characterized by X-ray diffractometer (XRD), high-resolution transmission electron microscope (HR-TEM), scanning electron microscope (SEM), Energy dispersive X-ray (EDX), UV–Vis diffuse reflectance spectroscopy (DRS), Fourier-transform infrared (FTIR), Raman and fluorescence spectrometer. XRD analysis revealed that all the samples were a single phase with anatase nanocrystallite structures. The crystallite size of titania reduced from 9.64 nm to 7 nm with Fe doping. The HRTEM images of the TiO2 and 3% Fe doped TiO2 have revealed that all the particles have a spherical shape with an average particle size of 10 nm and 8 nm respectively. The characteristic peak at 482 cm−1 of the TiO bond stretching vibrations can be evidently observed from FTIR analysis. The Raman blue shift was found in the Fe doped TiO2 samples. Fe-doped TiO2 nanoparticles showed a significant red-shift in band edge as compared with pure TiO2 nanoparticles. The redshift of band gap was detected in Fe doped TiO2 nanoparticles. The photoluminescence (PL) emission intensity of Fe doped TiO2 nanoparticles decreases with an increase in Fe doping concentration. The photocatalytic efficiencies of the Fe-doped TiO2 nanoparticles have shown a strong photocatalytic activity (PCA) response. At constant irradiation time, the Fe-doped titania nanoparticles display more catalytic activity compared to undoped TiO2. The photodegradation efficiencies typically decline with an increase in the concentration of Fe+3 doping for the decolorization of methylene blue (MB) under visible light irradiation.

Surface Photocatalytic Research of Fe -doped TiO2 (001) Based On the First-principles

In this paper, the first-principles based on density functional theory was used to study the Fe/TiO2(001) band gap width and adsorption energy of C6H6 molecules at different positions on the surface of the molecule with different doping methods and different Fe content. Calculation of the band structure and density of states of Fe-doped TiO2 nanoparticles shows that, the surface gap doping is more favorable than the substitution doping to reduce the band gap of TiO2, and when the doping concentration is 6.122%, the maximum reduction of the band gap width is 59.3% higher than that of pure TiO2. According to the comparement of adsorption energy, it works out that the benzene molecule is mainly about horizontal adsorption on the surface of TiO2(001). Within the scope of the study, with the increase of Fe doping concentration, The adsorption energy does not decrease as the band gap, when the Fe atoms doping concentration is 4.167%, the maximum increase of adsorption energy is 63.2%.

Preparation of Fe doped ZnO thin films and their structural, magnetic, electrical characterization

Fe doped ZnO thin films having chemical composition of Zn(1-x)FexO (x = 0.0, 0.05, 0.10, 0.15, 0.20) from one molar concentration of precursor sol was synthesized over glass substrate by sol-gel spin coating method. The XRD analysis of the samples reveals the wurtzite ZnO crystallite size reduces from 18.2 nm to 11.4 nm with the increase in Fe content from x = 0 to 0.20. The cubic spinel ZnFe2O4 is identified in the XRD pattern of high (x = 0.20) Fe containing sample. FESEM micrographs reveal that the average particle size reduces from 49.41 to 27.72 nm with the increase in Fe content from x = 0 to 0.20. Whereas, SPM images show that increasing Fe content reduces surface roughness of the films. TEM analysis of Fe (x = 0.10) doped ZnO system supports the phase identification by XRD and particle size analysis by FESEM. The VSM analysis reveals magnetization (Mr) of the samples from the M-H curve. SQUID analysis reveals magnetic properties indicating the formation of room temperature ferromagnetic material (RTFM). The value of saturation magnetization increases from 0.01 to 1.1 emu/gm with the increase in Fe content from 0 to 0.20. Electrical conductivity measurement of the thin film sample using four probe technique indicates that films are semiconducting in nature with electrical resistance (R) of the films varying from 99.8 to 163.3 Ω with the increase in Fe doping concentration from 0 to 0.10.

Visible light irradiated photocatalytic and magnetic properties of Fe-doped SnS2 nanopowders

Fe-doped SnS2 (SnS2:Fe) nanopowders were synthesized by cost effective chemical method and characterized by thermo gravimetric-differential thermal analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and vibrating sample magnetometer techniques. The photocatalytic activity was evaluated for the degradation of congo red dye under visible light irradiation. XRD studies indicate that both the undoped and doped SnS2 nanopowders exhibit hexagonal crystal structure with a strong (1 0 1) preferential growth. Nanosized grains are evinced from the TEM images. XPS spectra confirmed the presence of Fe in the doped samples. Photodegradation efficiency increased with increase in Fe doping concentration and the SnS2:Fe nanopowder with 10 wt% Fe doping concentration exhibits a maximum efficiency of 93.94% after 180 min light irradiation. Ferromagnetic ordering of pure SnS2 improved with Fe doping. The outcome of the results indicated that Fe-doped SnS2 nanopowders are well suited as diluted magnetic semiconductor and also can be used as an efficient photocatalyst.

Synthesis and magnetic properties of (Fe, Sn) co-doped In2O3 nanoparticles

The iron (Fe) and tin (Sn) co-doped indium oxide (In2O3) nanoparticles at different Fe doping concentrations were prepared by solid state reaction and studied for their structural, optical and magnetic properties. The XRD patterns confirmed the cubic structure of all the undoped and co-doped samples. The average crystallite size decreased on increasing from 41 to 32 nm by increase of Fe doping concentration from 5 to 15 at.%. The optical band gap of the samples was found to decrease from 2.89 to 2.77 eV by increasing the Fe dopant concentration. The magnetic properties of the nanoparticles were studied using vibrating sample magnetometer at room temperature and at 100 K by applying the field ±75,000 Oe perpendicular to the sample. The magnetization increased with increase of applied magnetic field and no saturation was observed in all the samples. The similar behavior was observed for the nanoparticles studied at 100 K.

Structural, optical and room temperature ferromagnetic properties of Sn1−xFexO2 thin films using flash evaporation technique

Iron doped tin oxide thin films (Sn1−xFexO2) at x = 0.00, 0.03, 0.05, 0.07,0.10 and 0.15 were prepared onto Corning 7059 substrates using flash evaporation technique and studied the effect of iron (Fe) doping concentration on structural, optical and magnetic properties of the prepared thin films. From the X-ray diffraction patterns, it was found that the Sn1−xFexO2 thin films were polycrystalline with tetragonal structure. The crystallite sizes of the films were calculated using Scherrer’s relation and found that it was about 25 nm. The chemical composition and oxidation states of the elements were found using energy dispersive analysis of X-rays and X-ray photoelectron spectroscopy. From this it was confirmed that the Fe was substituted Sn sites and is in Fe+3states. The optical band gap of the films decreased from 3.98 to 3.76 eV with increase of Fe doping concentration. The pure SnO2 thin films exhibited diamagnetism whereas Sn1−xFexO2 thin films exhibited ferromagnetism at room temperature. A magnetic (Ms), coercivity (Hci) and retentivity (Mr) were found to be 13.062 emu/cm3, 114.98 G, 7.487 × 10−6 emu/cm3, respectively Sn1−xFexO2 thin films at x = 0.07.

Effect of Fe-doping on the structural, optical and magnetic properties of ZnO nanostructures synthesised by co-precipitation method

Nanoparticles of Zn1−xFexO (0≤x≤0.2) were prepared by co-precipitation method followed by drying at 200°C. Tween-80, a non-ionic surfactant, not reported in earlier studies was used during preparation process. X-ray diffraction analysis showed the formation of wurtzite ZnO phase nanostructures. The Rietveld analysis confirmed the formation of hexagonal wurtzite structure for all dopant levels without any impurity. Morphological observations using scanning electron microscopy show the formation of nanoparticles with remarkable morphologies. Photoluminescence spectra revealed emission bands in both UV and visible regions due to the defect centres acting as trap levels. Optical studies carried out by diffuse reflectance spectroscopy (DRS) indicated a decrease in the value of the band gap with increasing Fe doping concentration. The elemental composition of Zn, Fe and O quantitatively obtained from EDAX analysis confirmed the purity of the as-prepared nanopowders and that the chemical composition is close to the starting stoichiometries. Magnetization–Field (M–H) hysteresis curves revealed the appearance of ferromagnetic behaviour, where the magnetic characteristics such as coercivity and saturation magnetization values, were found to be sensitive to Fe doping level.

Chemical spray pyrolysis deposition of transparent and conducting Fe doped CdO thin films for ethanol sensor

Transparent conducting cadmium oxide (CdO) and Fe (0.5, 1, 1.5 and 2wt%) doped CdO thin films were deposited on glass substrate using facile chemical spray pyrolysis technique. The influence of Fe doping on the structural, morphological, optical and electrical properties of CdO thin films were systematically investigated using different characterization techniques such as X-ray diffraction (XRD), atomic force microscope (AFM), UV–vis transmittance and Hall measurement respectively. The XRD patterns clearly reveal the pure and Fe doped CdO films are polycrystalline nature along with cubic crystal structure. AFM images show the roughness of the CdO thin film decreases with respect to Fe doping concentration. The surface structure of the 1wt% Fe doped CdO film was investigated by X-ray photoelectron spectroscopy (XPS). Optical transmittance of the CdO thin film decreases with increasing of Fe doping concentration. The optical band gap value of the CdO thin film gradually decreases from 2.61 to 2.18eV with increasing Fe doping concentration. From Hall measurement, the minimum value of resistivity is obtained for (7.67×10−4Ωcm) 1wt% of Fe doped CdO thin film. Finally, the ethanol sensor behaviour was observed using home-built sensor unit. The maximum ethanol gas response of 56.12% is observed for 1wt% of Fe doped CdO thin films. This result suggests the Fe doped CdO is one of the promising material in sensor applications.