Effect Of Cr Doping Research Articles

Effect of doping on SGS and weak half-metallic properties of inverse Heusler Alloys

Heusler alloys with Mn and Co have been found to exhibit interesting electronic and magnetic properties. Mn2CoAl is well known SGS compound while Mn2CoGa has weak half metallic character. By using plane wave pseudo-potential method, we studied the effect of Fe and Cr doping on half-metalicity and magnetism of these compounds. The calculated values of formation of energies and cohesive energies confirms the stability of parent and doped compounds. The doping destroys the SGS nature of Mn2CoAl while the small-scale doping enhance the half-metallicity of Mn2CoGa making it perfect half-metal. In case of Mn2CoAl, the doping decrease the band gap while increase in band width is noticed for Mn2CoGa. The half-metallicity is destroyed in both cases when the doping level is beyond certain degree. Moreover, we have also computed magnetic behavior of Mn2CoZ alloys and we found that total magnetic moments of dopped samples have higher values than that of pristine compounds.

Highly improved electrocatalytic activity of NiSx: Effects of Cr-doping and phase transition

Hydrogen evolution reaction (HER) is a vital step for electrochemical energy conversion technologies. However, developing cost-efficient electrocatalysts remains a huge challenge. Here, we report that Cr-doped NiSx (Cr-NiSx) in situ grown on Ni foam via a hydrothermal sulfurization reaction can be an ultra-highly efficient and low-cost electrocatalyst for HER in alkaline condition. We find that the Cr-doping can trigger the formation of NiS and NiS1.19, leading to the suppression of Ni3S2 in the nanostructure. We show that Cr-NiSx exhibits an excellent HER activity with an ultralow overpotential of 81 mV at 10 mA cm−2, better than those of most nickel sulfide catalysts, and good stability. Our combined experimental and computational study reveals that the excellent performance is contributed by: (1) stabilized NiSx phase, (2) strongly improved conductivity, (3) greatly enhanced active sites, and (4) reduced Gibbs free energy for hydrogen adsorption (ΔGH) due to the Cr-doping. We believe that this work provides a simple approach to design cost-effective and ultra-highly efficient HER electrocatalysts for practical applications.

Cr doping effect on the structural, optoelectrical and photocatalytic properties of RF sputtered TiO2 thin films from a powder target

In this study, thin films of pure and chromium doped TiO2 were deposited by RF magnetron sputtering technique with recourse to a low cost powder target. The dopant concentration was varied from 0 to 6 wt%. The structural, optical, electrical and photocatalytic properties of the sputtered deposited films were systematically investigated on the basis of the incorporated Cr content. XRD analysis revealed that the elaborated films are polycrystalline and have a preferential orientation along the (110) plane, characteristic of the rutile phase. The optical measurements showed a good homogeneity of the films and a high transmission that reached 85% in the visible range. The high transparency of these films allows their use as an optical window in thin film solar cells. Optical band gap decreased from 3.44 eV to 3.32 eV with the increase of the Cr content. In addition, the impedance spectroscopy analysis showed that the conductivity increases along with increasing frequency and temperature, and that the conduction mechanism follows the correlated barrier hopping model. The test of the catalytic efficiency of the chromium-doped TiO2 thin films at different concentrations demonstrated a degradation of the methylene blue (MB) and an improvement of the photocatalytic activity and that the 6 wt% doped thin films have the best photocatalytic activity.

Effect of Cr and Zr doping of TiO2 on the opto-electrical properties of dye sensitized solar cells

In this research, we report on the effect of doping TiO2 with chromium and zirconium on the opto-electrical parameters of dye sensitized solar cells (DSSCs). TiO2 films were elaborated by sol-gel and spin-coating routes. Levels of doping agents are 1 %, 3 % and 5 % of atomic ratio. X-Ray diffraction patterns show that when TiO2 is doped with Zr, the sole anatase phase with a preferential orientation along (101) is present. However, doping with Cr leads to the formation of both rutile and anatase phases. Measurements of the transmission spectra show a high transparency for all samples. The band gap energy Eg evaluated from ellipsometric measurements decreases with increasing Cr content and remained approximately unchanged with increasing Zr content. Transmission electron microscopy analysis shows a polycrystalline films. By comparing AM1.5 current density-voltage characteristics of fabricated DSSCs with pure and Cr and Zr doped TiO2 films, results show that the best cell performances are obtained with the 1 % Cr-doping level. Therefore, we obtain high values of the open circuit voltage reaching 1350 mV and a 70 % fill factor.

Effect of chromium doping on Na3V2(PO4)2F3@C as promising positive electrode for sodium-ion batteries

Cr-doped Na3V2(PO4)2F3@C samples, obtained by a one-step sol-gel method, are studied as cathode materials for sodium-ion batteries. Their structural and morphological properties induced by Cr incorporation are determined by powerful solid-state techniques including X-ray diffraction, electron microscopy, and Raman and XPS spectroscopies. Galvanostatic tests reveal the beneficial effects of low-level Cr doping in Na3V2(PO4)2F3, mainly improving the kinetic response of the electrode materials at the highest studied rates. These results are correlated to low cell internal resistances and cell polarization between charge and discharge. Eventually, a full sodium-ion cell is essayed as a proof of concept to evidence the reliability of these cathode materials in practical conditions.

WITHDRAWN: Effect of Cr and Zr doping of TiO2 on the opto-electrical properties of dye sensitized solar cells

WITHDRAWN: Effect of Cr and Zr doping of TiO2 on the opto-electrical properties of dye sensitized solar cells

Improved sensing response of nanostructured CuO thin films towards sweat rate monitoring: Effect of Cr doping

In this research, we have studied the effect of chromium doping of CuO on the main physical properties and hydration level sensing ability of thin-film samples synthesized by SILAR method on soda-lime glass substrates. The structural, morphological and optical properties as well as hydration level sensing behavior of pristine and CrxCu1-xO (x = 0.01 and 0.02) films were investigated under different Cr concentrations. Optical and structural analysis verified the Cr-doping into CuO films without degrading the uniformity of the metal oxide semiconductor structure. It was shown that the resistivity increases with Cr-doping, which was attributed to the additional holes introduced to the semiconductor crystal. Sweat sensing response of the metal oxide films improved significantly with doping (sensing response from 0.45 to 8.50 for heavy doping). Transient analysis of the sweat response also showed that response time is less than 60 s. We conclude that Cr-doping improves the sensing performance of CuO thin films and offers to be implemented in sweat sensing devices as the sensing material.

Effects of Cr-doping on the morphology and optical properties in Zn2GeO4 (ZGO) nanorods prepared by hydrothermal method

The undoped Zn2GeO4 nanorods and the Cr-doped Zn2GeO4 nanorods were successfully prepared by the hydrothermal method. The structure, the optical characteristics properties of nano phosphor powders were studied by X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, photoluminescence spectroscopy, FESEM. The results indicated that Cr ions substituted for Ge ions and the Cr doping expanded for the unit cell of the crystal lattice. The band gap energy found to be decreased with increasing Cr doping concentration. At a wavelength of 250–320 nm excitation, Cr3+ doped Zn2GeO4 phosphors showed bluishwhite emission at 510 nm. The concentration of Cr3+ ions in Zn2GeO4:Cr3+ played important roles in the evolution of the length of nanorods, photoluminescence intensity and quality of nano crystal. This result contributed optimization of Cr3+ doped nano phosphors with 5% mol. The possible mechanism of substitution of ion Cr in Zn2GeO4 nano crystalline has also been discussed.

Cr-doping effects on optical and magnetic properties of BaSn1−xCrxO3

Polycrystalline bulk samples of BaSn1−xCrxO3 with different Cr concentrations were prepared by standard solid state reaction method. The effects of Cr concentration on crystal structure of BaSn1−xCrxO3, as well as optical and magnetic properties were investigated. Powder X-ray diffraction (XRD) shows that each of these samples possess a perovskite structure with $$ Pm\bar{3}m $$ space group. The Cr ions are located at the substitution Sn sites as revealed by the XRD, Diffuse reflectance spectra and Raman spectra. Moreover, it is found that room-temperature ferromagnetism (FM) can be reversed by annealing in the nitrogen atmosphere. This can be well explained by a modified model of F-center mediated FM.

Thermochromic, threshold switching, and optical properties of Cr-doped VO2 thin films

In this paper, undoped and Cr-doped VO2 thin films were fabricated and deposited onto Al2O3 substrates using a sol-gel method. Then, the effects of Cr-doping on the thermochromic, and optical properties of the thin films were investigated. Doping with Cr ions gradually increased the metal-insulator transition (MIT) temperature of the films, while the luminous transmittance (Tlum) and the sol modulation efficiency (ΔTsol) gradually decreased. Additionally, Pt/VO2/ITO devices and Cr-doped VO2 devices were prepared to study their threshold switching (TS) properties. For devices fabricated with Cr-doped VO2 films, both the threshold voltage (Vth+) and the OFF-state current decreased as the amount of Cr doping increased. In contrast, the ON/OFF ratio increased from 104 to 105. These results provide insight into the potential for using VO2 in thermochromic, optical, and TS applications.

Synergetic effects of impurities and alloying element Cr on oxidation and dissolution corrosion of Ni (111) surfaces: A DFT study

Using density-functional calculations, we studied the interactions between interstitial impurities (H, O, N, S, and P) and Ni (111) surfaces doped, or not, with Cr, and studied the effect of Cr doping on the dissolution corrosion resistance of Ni(111) surfaces. The aim of this work was to study, at the atomic scale, the effects of Cr on the segregation behaviors of impurities and the synergetic effects between co-doped atoms on the resistance to dissolution corrosion of Ni (111) surfaces. The results indicate that impurities S, P, O, and H prefer to be trapped at near-surface sites, that Cr was uniformly distributed in the Ni crystal and can affect the segregation behavior of impurities S and P to move toward the surface, and it affects impurities N and O such that they shift from the surface to the subsurface. The formation of near-surface Cr nitrides (speculated to be Cr2N based on the results obtained for particular co-doped surfaces) was also noted. Introducing Cr enhances the structural stability of the Ni (111) surface and protects it from being corroded when impurities are present. The elementary processes studied afforded microscopic insights into the formation of a Cr-depleted zone, a phenomenon that leads to local corrosion of the Ni alloy surface. The results of our theoretical calculations explain some of the experimental results previously observed at the atomic scale.

Effects of Cr Doping on Structural, Morphological, Optical, Humidity Sensing and Catalytic Properties of Magnetic Co3O4

Effects of Cr Doping on Structural, Morphological, Optical, Humidity Sensing and Catalytic Properties of Magnetic Co₃O₄

Morphological, surface and optical properties of spin-coated IrOx films; influence of spin speed, annealing and (Cr, La) codoping

Iridium oxide (IrOx) is a fascinating metal oxide with superior chemical/physical properties. The present report is an attempt to tune the surface and optical properties of IrOx to widen its industrial and technological applications. The influences of substrates' rotational speed (RS), annealing temperature (AT), Cr-doping and (Cr, La) codoping on the surface morphology and wettability, structural as well as the optical properties of spin-coated IrOx films are discussed. Raman spectra of the films show a characteristic phonon mode at 552 cm−1, arising from the Ir–Ox stretching and influenced significantly by the preparative conditions (RS and AT) as well as (Cr, La) codoping. Energy-dispersive X-ray spectra were obtained to confirm the chemical compositions of prepared IrOx nanostructure thin films. Field emission-scanning electron microscopy images reveal the growth of undoped, Cr-doped and (Cr, La) codoped nanorod-like IrOx structures. The annealed film at 500 °C and Cr-doped films showed the nanoporous nature of the grown nanorod-like structures. The films are hydrophilic and follow the Wenzel model. The wetting ability is enhanced by decreasing RS and increasing AT. Increasing RS results in increasing the transmittance (T%) due to decreasing the films' thickness. At wavelength λ = 103 nm, the deposited film shows T% = 53.2 and the film annealed at 500 °C exhibits T% = 44.3. The optical band gap (Egop) increased with increasing RS and decreased with increasing AT. Cr-doping redshifted Egop from 2.95 to 2.85 eV, while codoping with La blue shifted Egop to 3.14 eV. The effect of Cr and La doping on the optical constants of IrOx films was investigated and compared with those of other transition metal oxide films because no data are available in the literature for IrOx films.

Study the structural and optical properties of titanium oxide thin film, doped with chromium prepared in Sol-Gel method

This paper presents the effect of Cr doping on the optical and structural properties of TiO2 films synthesized by sol-gel and deposited by the dip- coating technique. The characteristics of pure and Cr-doped TiO2 were studied by absorption and X-ray diffraction measurement. The spectrum of UV absorption of TiO2 chromium concentrations indicates a red shift; therefore, the energy gap decreases with increased doping. The minimum value of energy gap (2.5 eV) is found at concentration of 4 %. XRD measurements show that the anatase phase is shown for all thin films. Surface morphology measurement by atomic force microscope (AFM) showed that the roughness of thin films decrease with doping and has a minimum value with 4 wt % doping ratio.

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.

Effect of Cr-doping on the physicochemical properties of blue TiO2 and its application in dye-sensitized solar cells via low-temperature fabrication process

Cr-doped blue TiO2 (Cr-BTiO2) nanoparticles were fabricated at room temperature using lithium-ethylenediamine (Li-EDA) as reducing agent. The addition of Li-EDA promotes the selective reduction of the rutile phase of TiO2 into the amorphous phase keeping anatase phase unaltered. Hence, the phase-selective reduction of TiO2 leads to the formation of blue TiO2 nanoparticles. Synthesized samples were characterized by equipment fitted with modern technology. The shifting of (101) peak to a lower angle (2θ) in Cr-BTiO2 in X-ray diffraction (XRD) pattern suggests the successful doping of chromium into TiO2 lattices. In Raman spectra, the shifting of the active Eg peak of Cr-BTiO2 nanoparticles to higher wavenumber also suggests the successful substitution of Ti by Cr. The blue TiO2 and Cr-BTiO2 show increased absorption of light in the visible region compared to TiO2 (P25). The modified TiO2 samples have improved electron-hole separation tendency as predicted by the photoluminescence spectra (PL). Also, doping of Cr- into TiO2 lattice results the formation of oxygen vacancy as detected by X-ray photoelectron spectroscopy (XPS). Among all samples, Cr-BTiO2 demonstrated improvement in Jsc and overall incident photon to current conversion efficiency. Therefore, the synthetic effect is thus responsible for the enhancement in efficiency of Cr-BTiO2 towards the dye-sensitized solar cell (DSSC) by 2.5 and 1.5 times higher than the P25 and blue TiO2, respectively.

Effects of Cr Doping Concentration on Structural, Morphology, Mechanical and Magnetic Properties of Electrodeposited NiCoCr Thin Films

In this report, effects of Cr doping on structural, morphological, mechanical and magnetic properties of Ni–Co–Cr alloy thin films have been prepared by electrodeposition method with different concentration. The influence of Cr substitution on the formation of phases, structure, morphology, hardness and magnetic properties of the electrodeposited films are studied by X-ray diffraction (XRD), scanning electron microscope (SEM), Vickers hardness tester (VHT) and vibrating sample magnetometer (VSM). The SEM micrographs of the electrodeposited films with different concentration of Cr have no micro-cracks with uniform surface morphology. The predominant peaks in XRD spectra of Ni–Co–Cr alloy thin films reveal nanostructure. The VHT result clearly showed that thin films coated with high concentration of Cr have highest hardness value. The magnetic properties such as saturation magnetization and coercivity influenced more by varying the concentration of Cr.

Effects of Cr doping on the mechanical properties of AlN films grown by the co-sputtering technique

We report the mechanical properties of Cr-doped AlN thin films synthesized by reactive magnetron co-sputtering technique with different Cr concentrations (0, 2, 4, 6 and 11 at%). Surface chemical analysis and crystal structure studies of Cr doped AlN films are carried out using X-ray photoelectron spectroscopy (XPS) and grazing incidence X-ray diffraction (GIXRD) techniques. All these films are crystallized with wurtzite structure and grown predominantly along a-axis orientation in the absence of secondary phases belonging to Cr. The surface morphology and RMS roughness are measured by atomic force microscope (AFM). The residual stress of these films exhibit a tensile behavior and it decreases with Cr concentration as calculated by sin2ψ technique. Indentation hardness of these films is measured by nanoindentation technique, which is ranged from 17.5 to 23.0 GPa. However, indentation modulus is enhanced with Cr concentration due to strong p-d hybridization between Cr and N atoms. Indentation impression of these films exhibit a sink-in behavior and gives an evidence of high elastic recovery without radial cracks.

Electronic sensitization of CuO thin films by Cr-doping for enhanced gas sensor response at low detection limit

In this paper we investigate the effect of Cr-doping on the electronic structure of CuO and Cr-doped CuO thin films, which are deposited by DC-pulsed magnetron sputtering at 100 °C. Density Functional Theory calculations explain the effect of Cr dopant, which is introduction of the shallow donor band that decreases the charge carrier concentration. The Cr dopant is shown to be responsible for enhanced sensor response and selectivity towards acetone in ideal (dry air) and in realistic conditions (high relative humidity environment). The chemical and phase compositions are investigated by means of Energy Dispersive x-ray spectroscopy, x-ray Photoelectron Spectroscopy and Grazing Incidence x-ray Diffraction. The surface topography and microstructure are analysed by Scanning Electron Microscopy and Atomic Force Microscopy. The high level of control of the whole fabrication process of Cr-doped CuO thin films in one step and its feasibility for industrial up-scaling, open up a way for the commercial application of this material in gas sensing, catalysis, photovoltaics, using this cost-effective technology.

Effect of chromium doping on the structure and band gap of Bi3.15Nd0.85Ti3O12 thin films

The Bi3.15Nd0.85Ti3O12 (BNdT) and Cr-doped BNdT films on quartz substrates were prepared by a sol-gel process and the effects of Cr doping on the structure and band gap of BNdT were examined. Cr-doping does not change the three-layered perovskite structure of BNdT but transforms the grain morphology from equiaxed grains to rectangular grains. The utilization of visible light is increased by Cr doping and the large band gap reduction (∼1.1 eV) was obtained, which is analyzed from the electronegativity and the distortion caused by substitution. The present work provides an available way to make ferroelectric (FE) BNdT getting more extensively applied in the new photovoltaic cells and other novel optoelectronic devices.