Fe-doped ZnO Powders Research Articles

Photodegradation of methyl orange under solar irradiation on Fe-doped ZnO nanoparticles synthesized using wild olive leaf extract

Abstract Fe-doped ZnO nanoparticles (NPs) with different Fe contents (0.1–5.0 wt%) were prepared using extract of wild olive leaves growing in Saudi Arabia (region of Abha). The biosynthesized NPs were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, scanning electron microscopy, transmission electron microscopy, and photoluminescence (PL). Characterization results showed that undoped ZnO and Fe-doped ZnO powders were crystallized in the wurtzite structure with a small shift for the doped samples. Neither Fe3O4 nor another iron oxide phase was observed in the samples, which proves the incorporation of Fe into the ZnO lattice. Doping has a pronounced effect on the physical and optical properties. Indeed, the size of the crystallites, the energy of the bandgap as well as the intensity of the PL emission decreased with the Fe content. Photocatalytic tests revealed that the doped samples degraded methyl orange (MO) more efficiently than pure ZnO and pure Fe3O4. Moreover, the photocatalytic activity improved with increasing Fe content. The best photocatalyst of the series (Fe–ZnO-5) was found degrading MO by 92.1%, in 90 min in a pseudo-first order reaction.

Defects and dopant alliance towards bound magnetic polarons formation and mixed magnetic characteristics in Fe doped ZnO nanoparticles

Fe doped ZnO powders, Zn1-xFexO (x=0–0.03) confirmed to be single phased using X-ray diffraction (XRD) measurement (step size of 0.01°) revealed a change in oxidation state of Fe with increased fraction of Zinc interstitials, Zni and Oxygen vacancy, Vo defects through Photoelectron spectroscopy and Photoluminescence (PL) studies. The Raman and PL spectra have registered the inclusion of Vo-Zni complex defects also. An ideal position of E2(Low) Raman mode justifies the effectual cationic substitution of Fe species. Inclusion of paramagnetic (PM) component is successfully substantiated through Bound Magnetic Polaron (BMP) model fitting. For x=0.01, a residual PM component is ensured through temperature dependent magnetization, M(T) characteristics as well. A close fit of the Field cooled (FC) branch by the 3-D spin wave model (T=99−300K) points towards the intrinsic nature of ferromagnetism mediated by the effectual substitution of Fe2+ ions and the inclusion of BMPs. At lower temperature (T<99K), a good fit to the Curie-Weiss model (C–W) quantifies an estimated cluster size of the order of 10−3, subtle enough to restrict the introduction of spin glass state, thereby justifying the suitability of these nanoparticles for spintronics applications. Excellent PM properties are achieved for x=0.03 at T=300K.

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.

Structure and Hyperfine Interactions of Fe-Doped ZnO Powder Prepared by Co-Precipitation Method

Structure and Hyperfine Interactions of Fe-Doped ZnO Powder Prepared by Co-Precipitation Method

Effects of a surfactant on the morphology and photocatalytic properties of polycrystalline Fe-doped ZnO powders

In this study, we compared the structural, morphological, and optical properties of a series of Zn1-xFexO (x = 0.00, 0.01, and 0.03) powders synthesized via a hydrothermal route with and without cetyltrimethylammonium bromide as a cationic surfactant. Our results highlighted the critical effects of the surfactant and the iron concentration on the structure, morphology, and optical properties of ZnO. X-ray diffraction, Mössbauer spectroscopy, and X-ray photoelectron spectroscopy analyses indicated the presence of a single phase comprising ZnO with a hexagonal wurtzite structure in all samples and a single oxidation state (+3) for the iron (Fe3+) that replaced Zn2+ in the ZnO structure. Morphological investigations by scanning electron microscopy showed that the surfactant and Fe3+ dopant greatly affected the shape of the ZnO grains, which varied between sheets and rod-like flowers. We found that the morphological and photocatalytic properties of the two series of samples comprising iron-doped ZnO with and without the surfactant were in opposition. We propose a possible growth mechanism for the ZnO polycrystalline grains in the presence of the Fe dopant and/or surfactant. The photocatalytic properties increased for the samples prepared with surfactant as the iron content increased, which was confirmed by ultraviolet-visible reflection measurements. The photocatalytic activities of the samples prepared without surfactant decreased in both the ultraviolet and visible spectral regions as the iron content increased in the samples.

Enhanced photocatalytic activity of fe doped ZnO hierarchical nanosheets on the degradation of p-nitrophenol under visible light

Pure and Fe-doped ZnO nanostructures were prepared by a simple hydrothermal process. The crystallographic analysis showed that Fe-doped ZnO powders were crystallized in the hexagonal wurtzite structure and observed only a small shift in ZnO peaks with Fe dopant. The change in lattice constants of Fe doped-ZnO nanostructures was described according to ionic state of Fe atoms in samples. The pure ZnO powder includes the microspheres with flower-like morphology constructed by the hierarchical nanosheets. The flower-like morphology of pure ZnO hierarchical nanosheets was destructed with increasing Fe dopant concentration above 0.5 at.%. The ultraviolet-Visible spectroscopy analysis of the samples illustrated that Fe ions participate with valence states of 3+ into ZnO lattice. Photoluminescence spectroscopy was used to characterize the intrinsic and extrinsic defects in nanostructures powders. The photocatalytic performance of pure and Fe-doped ZnO nanopowders was investigated by using the decomposition of aqueous p-nitrophenol. The photocatalytic activity improved with increasing the Fe dopant concentration while 5 at.% Fe-ZnO nanopowder had the highest photodegradation rate.

Influence of structural evolution on the magnetic behavior of the nanocrystals of Fe-doped ZnO synthesized by soft chemical route

Soft chemical route has been used for the synthesis of nanocrystalline undoped and 5 wt% Fe-doped ZnO powder. The structural, nano/microstructural, vibrational and magnetic properties of these samples have been studied as a function of calcination temperature (400–1100 °C). X-ray diffraction studies revealed major nanocrystalline wurtzite (ZnO) phase at 400 °C only. As the calcination temperature increases to 700 °C, the evolution of the nanocrystalline secondary cubic spinel ZnFe2O4 along with major phase of ZnO is observed. Interestingly, Fe-doped ZnO calcined at 400 °C has exhibited ferromagnetic behavior at room temperature and both the magnetic parameters (M s , H c ) are larger than those of Fe-doped ZnO calcined at 700 °C. The reduction in the magnetization and coercivity has been evidenced with the increase in the grain size of the secondary cubic spinel ZnFe2O4 phase. These changes are ascribed to the degree of inversion of spinel structure, i.e., occupancy of ferric ions in both sites with different symmetries is proposed to be solely responsible for the unusual behavior. At 1100 °C, zero coercivity is observed due to paramagnetic behavior of bulk cubic spinel ZnFe2O4 phase.

Relationship between ferromagnetism and, structure and morphology in un-doped ZnO and Fe-doped ZnO powders prepared by hydrothermal route

The magnetic properties, in the 5 K–350 K temperature range, were investigated in relationship with the structure and morphology of Zn1−xFexO (x = 0, 0.01, 0.03) powders prepared by hydrothermal route. The magnetization measurements reveal that all powders are ferromagnetic at room temperature, with Curie temperature Tc, higher than 350 K. The coercivity Hc takes values between 58 Oe and 107 Oe at 300 K and, between 217 Oe and 613 Oe at 5 K. The weak magnetization of the un-doped ZnO powder is temperature independent and was associated with the high surface to volume ratio of the powder particles (or the number of surface defects). The saturation magnetization Ms was substantially enhanced (up to a factor of about 20 at 300 K and of about 200 at 5 K) at all temperatures as Fe concentration increased, in spite of reduction of the surface to volume ratio of the powder particles. The Hc vs. T and FC/ZFC curves for the un-doped ZnO show typical ferromagnetic behavior, whereas for the Fe doped powders exhibit Ruderman–Kittel–Kasuya–Yosida (RKKY) - like and spin-glass-like behavior. The observed magnetic phenomena in Fe doped ZnO can be explained on the basis of “donor defects concentration – magnetic cations concentration” phase diagram for dilute magnetic semiconductors.

Coprecipitation Synthesis of Fe-doped ZnO Powders with Enhanced Microwave Absorption Properties

In this work, the Fe-doped ZnO powders have been synthesized by a facile chemical coprecipitation method. The structure, morphology and magnetic properties of the as-prepared powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrum (EDS), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). The results showed that the Fe ions were well incorporated into the crystal lattice of ZnO and had a valence state of [Formula: see text]. The magnetization curves indicated the Fe-doped ZnO presented the ferromagnetic behavior at room temperature. Moreover, the electromagnetic (EM) parameters and microwave absorption properties of Fe-doped ZnO/paraffin wax in the frequency range of 2–18[Formula: see text]GHz were explored. The minimum reflection loss reached [Formula: see text] dB at 6.6 GHz, and the reflection loss less than [Formula: see text] dB was 4.0 GHz (from 11.0[Formula: see text]GHz to 15.0[Formula: see text]GHz) with a thickness of only 2.5 mm. Significantly, the enhanced microwave absorption of the as-prepared powders could be achieved by doping with Fe[Formula: see text] ions or varying the thickness of the absorbers. The mechanism of microwave absorption were attributed to the good impedance matching, the dielectric loss resulted from the crystal lattice defects and the magnetic loss originated from the natural resonance. It is believed that the Fe-doped ZnO powders could be used as potential microwave absorbers.

A Mössbauer and magnetic study of ball milled Fe-doped ZnO Powders

The structural and magnetic properties of Fe-doped ZnO are reported in this study, as obtained by mechanical alloying from elemental powders of ZnO and Fe. The properties of Zn0.90Fe0.10O samples alloying while varying the milling time (6, 12, 24 and 36 h) are also reported. The Rietveld refinement of X-ray Diffraction (XRD) patterns revealed that the system presents two structures: the wurtzite structure of ZnO and the bcc structure of α-Fe. The Mossbauer spectra show that the samples present three components: a ferromagnetic component, associated with the Fe phase and two paramagnetic components, associated with the Fe atoms, which penetrate inside the ZnO matrix behaving as Fe3+ and Fe2+. The milling time contributes to an increase in the paramagnetic sites, and a solubility limit of the Fe atoms in the ZnO lattice was detected. The VSM measurements at room temperature detected ferromagnetic behavior with a saturation magnetization of 11 emu/g and a coercive field of 330 Oe for the sample alloyed over 24 h. A similar behavior was shown by the other samples.

Structural, microstructural and magnetic properties of 1% Fe-doped ZnO powder nanostructures prepared by mechanical alloying

ZnO powder nanoparticles were doped with iron (mixing produced by mechanical alloying). Their structure, microstructure and magnetic properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). ZnO starting pure powder exhibits a hexagonal crystal structure with space group P63mc. Otherwise, with the addition of 1% Fe in the ZnO milled powder, the hexagonal ZnO phase remained unchanged, whereas the microstructural parameters were subject to significant variations due to the introduction of Fe atoms into the ZnO hexagonal matrix to replace oxygen ones. The size of crystallites and microstrains were milling time-dependent.

Preparation, Infrared Emissivity, and Dielectric and Microwave Absorption Properties of Fe-Doped ZnO Powder

Fe-doped ZnO powders have been synthesized by the coprecipitation method using zinc nitrate [Zn(NO3)2·6H2O] as starting material, urea [CO(NH2)2] as precipitator, and ferric nitrate [Fe(NO3)3·9H2O] as doping source. The microstructure of the prepared powders has been characterized by x-ray diffraction and scanning electron microscopy. Results show that, when the molar ratio of Fe to (Zn + Fe) was less than 0.09, the prepared powder was ZnO(Fe) solid solution, and the ZnFe2O4 impurity phase appeared when the Fe doping content was further increased. The electric permittivity in the frequency range of 8.2 GHz to 12.4 GHz and the average infrared emissivity in the wavelength range of 8 μm to 14 μm have been determined for the prepared powders. The average infrared emissivity decreased with increasing Fe doping content. The real (e′) and imaginary part (e″) of the permittivity of the prepared powders showed opposite trends. When the molar ratio of Fe to (Zn + Fe) was 0.03, the prepared Fe-doped ZnO powder demonstrated the best microwave absorption in the frequency range of 8.2 GHz to 12.4 GHz.

Preparation, dielectric property and infrared emissivity of Fe-doped ZnO powder by coprecipitation method at various reaction time

Fe-doped ZnO powders have been synthesized by the coprecipitation method at 600°C with various reaction time, using zinc nitrate as the staring material, urea as the precipitator, and ferric nitrate as the doping source, respectively. The phase and morphology of the prepared powders have been characterized by X-ray diffraction and scanning electron microscopy, respectively. It was found that the prepared product synthesized for 1h had a pure ZnO wurtzite structure and was a ZnO(Fe) solid solution powder. The real part, imaginary part, and dielectric loss of complex permittivity of prepared powders in the frequency range of 8.2–12.4GHz decreased with increasing reaction time. The average infrared emissivities of prepared powders at the waveband range of 8–14μm increased with extending reaction time.

Effect of synthesized temperature on microstructure, infrared emissivity and dielectric property of Fe-doped ZnO powder

Fe-doped ZnO powder has been synthesized by coprecipitation method under different synthesized temperature, using zinc nitrate as the staring material, urea as the precipitator, and ferric nitrate as the doping source, respectively. The prepared powders have been characterized by XRD and SEM. Results show that when the synthesized temperature is below 700 °C the prepared powders are ZnO(Fe) solid solution powders and the ZnFe2O4 impurity phase appeared for the Fe-doped ZnO powder synthesized at 700 °C. The electric permittivities in the frequency range of 8.2–12.4 GHz and average infrared emissivity at the waveband range of 8–14 μm of prepared powders have been determined. The real part and imaginary part of electric permittivities of prepared powders have increased firstly and then decreased with increasing synthesized temperature. The average infrared emissivity has presented the opposite changing trend.

The magnetic properties of FexZn1−xO synthesized via the solid-state reaction route: Experiment and theory

We report on a study of magnetism of Fe-doped ZnO powders and tablets synthesized via the solid-state reaction route. The X-ray diffraction results indicate that the solid solubility of Fe in ZnO was less than 1%. When the concentration of Fe was more than 2%, a second phase of ZnFe2O4 was detected. All samples were ferromagnetic in the room temperature and the Hall effect was observed. Calculations based on the density functional theory (DFT+U) indicated two origins for the observed ferromagnetism. The first source is considered to occur due to the second phase of the inverse spinel-type ZnFe2O4 where the antiferromagnetic states of the Fe2Zn14O16 system were preferred through Fe2+O2−Fe2+ or Fe3+O2−Fe3+ bonding. The second appears to originate from the ferromagnetic states of the Fe2Zn14O16 system with the Fe3+O2−Fe2+ bond. The bond is suggested to form due to the double exchange interaction with the Fe2+ and Fe3+ ions substituting the Zn2+ ions in the ZnO lattice, yielding an intrinsic ferromagnetic oxide semiconductor.

Influence of Fe and Co and Cr Doped Amount on the Photoactivating Property of Nanometer ZnO Powder

Fe and Co and Cr doped nanometer ZnO powder was prepared respectively by coprecipitating method with ZnNO3•6H2O, HCl, NaOH, FeCl3•6H2O, CoCl2•6H2O, CrCl3•6H2O as raw materials. Influence of Fe and Co and Cr doped amount on the photoactivating property of nanometer ZnO photocatalyst powder was studied respectively by methyl orange solution as a reaction model. The particle size and dispersion of Fe-doped ZnO powder was characterized by transmission electron microscope(TEM). The results show that the photoactivating activity of nanometer ZnO powder starts increasing and then decreasing when Fe or Co or Cr doped amount decreases.The photoactivating activity of nanometer ZnO powder is maximum when Fe or Co or Cr doped amount is 0.2 wt.%, the degradation rate of methyl orange is 60.79%, 52.56%, 53.91% after ultraviolet light for 50 minutes, respectively. When Fe doped amount is 0.2wt.%, the degradation rate of methyl orange is the highest, the degradation rate of methyl orange is 60.79%, particle size is 20-30 nanometer and dispersion is good.

Synthesis, Crystal Structural and Electrical Conductivity Properties of Fe-Doped Zinc Oxide Powders at High Temperatures

The synthesis, crystal structure and electrical conductivity properties of Fe-doped ZnO powders (in the range of 0.25{15 mol%) were reported in this paper. I-phase samples, which were indexed as single phase with a hexagonal (wurtzite) structure in the Fe-doped ZnO binary system, were determined by X-ray difiraction (XRD). The solubility limit of Fe in the ZnO lattice is 3 mol% at 950 ‐ C. The above mixed phase was observed. And the impurity phase was determined as the cubic-ZnFe2O4 phase when compared with standard XRD data using the PDF program. This study focused on single I-phase ZnO samples which were synthesized at 950 ‐ C because the limit of the solubility range is the widest at this temperature. The lattice parameters a and c of the I-phase decreased with Fe-doping concentration. The morphology of the I-phase samples was analyzed with a scanning electron microscope. The grain size of the I-phase samples increased with heat treatment and doping concentration. The electrical conductivity of the pure ZnO and single I-phase samples was investigated using the four-probe dc method at 100{950 ‐ C in air atmosphere. The electrical conductivity values of pure ZnO, 0.25 and 3 mol% Fe-doped ZnO samples at 100 ‐ C were 2£10 i6 , 1.7£10 i3 and 6.3£10 i4 S¢cm i1 , and at 950 ‐ C they were 3.4, 8.5 and 4 S¢cm i1 , respectively.

Visible-Light-Assisted HCHO Gas Sensing Based on Fe-Doped Flowerlike ZnO at Room Temperature

In this work, Fe-doped flowerlike ZnO powders with various doping contents were successfully fabricated by a hydrothermal method. The results of X-ray diffraction and UV–vis DRS spectra revealed that the Fe ions have been successfully doped into the crystal lattice of the ZnO host structure, and the optical absorption response of Fe-doped ZnO was extended into the visible region for the incorporation of Fe ions. The room-temperature photoelectric gas sensing of formaldehyde (HCHO) based on the Fe-doped ZnO was also studied under 532 nm light irradiation provided by a green laser pointer. It was found that the as-prepared Fe-doped ZnO samples showed excellent sensitivity, in which the gas response to 5 and 100 ppm formaldehyde can reach to 22% and 287% under 532 nm light irradiation at room temperature, respectively. The sensing mechanism of the obvious visible-light-induced photoelectric gas sensing was discussed with the help of surface photovoltage measurement. Our results demonstrated that visible light irradiation was a promising approach to achieving a large response for gas sensors at room temperature. This work will pave a way for the development of a low-cost practical gas sensor.

Magnetic Properties of Bulk Zn&lt;sub&gt;0.95-X&lt;/sub&gt;Mn&lt;sub&gt;X&lt;/sub&gt;Fe&lt;sub&gt;0.05&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; Prepared by Sol-Gel Method and Subsequent Hot Pressing

Mn, Fe doped ZnO powders (Zn0.95-xMnxFe0.05O2, x≤0.05) were synthesized by an ameliorated sol-gel method, using Zn(CH3COO)2, Mn(CH3COO)2and FeCl2as the raw materials, with the addition of vitamin C as a kind of chemical reducer. The resulting powder was subsequently compacted under pressure of 10 MPa at the temperature of 873K in vacuum. The crystal structure and magnetic properties of Zn0.95-xMnxFe0.05O2powder and bulk samples have been investigated by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). X-ray photoelectron spectroscopy (XPS) was used to study chemical valence of manganese, iron and zinc in the samples. The x-ray diffraction (XRD) results showed that Zn0.95-xMnxFe0.05O (x≤0.05) samples were single phase with the ZnO-like wurtzite structure. No secondary phase was found in the XRD spectrum. X-ray photoelectron spectroscopy (XPS) showed that Fe and Mn existed in Zn0.95-xMnxFe0.05O2samples in Fe2+and Mn2+states. The results of VSM experiment proved the room temperature ferromagnetic properties (RTFP) of Mn, Fe co-doped ZnO samples.

Cu-doping effect on structure and magnetic properties of Fe-doped ZnO powders

Fe-doped and Cu, Fe co-doped ZnO diluted magnetic semiconductors powders were synthesized by sol–gel method. The x-ray diffraction (XRD) results showed that Zn 0.97− x Fe 0.03Cu x O ( x ≤ 0.02) samples were single phase with the ZnO-like wurtzite structure. X-ray photoelectron spectroscopy (XPS) showed that Fe 2+ and Fe 3+ existed in Zn 0.97Fe 0.03O, while Fe 2+, Fe 3+and Cu +, Cu 2+ were found in Zn 0.95Fe 0.03Cu 0.02O. Both Zn 0.97Fe 0.03O and Zn 0.95Fe 0.03Cu 0.02O exhibited ferromagnetic performance at room temperature. But the Cu incorporation reduced the saturation magnetization of Fe-doped ZnO diluted magnetic semiconductors.