Effect Of Cr Doping Research Articles

First principle investigation of Cr doping effect on the stability of NiFe2O4

NiFe2O4 is a key component of CRUD (corrosion-related undesirable deposits) that may severely degrade the safety and efficiency of nuclear power systems. Recent experimental studies showed that Cr impurity may affect the formation and growth of NiFe2O4-rich deposit on Cr-coated nuclear fuel, demonstrating a promising solution to inhibit the growth of CRUD. However, little theoretical study has been dedicated to revealing the effect of impurity on the formation and growth of NiFe2O4, especially Cr. In this work, density functional theory was utilized to compute the effect of Cr doping on electronic structures of NiFe2O4. The calculation results suggested that the effect of Cr impurity on NiFe2O4 structural stability is site-dependent and provides theoretical evidence that explains the experimental observation of suppressed NiFe2O4-rich CRUD growth on Cr-coated nuclear fuel. We believe that lattice mismatch induced by Cr doping may lead to stress and dislocations, which suppressed further growth of NiFe2O4. Subsequently, the diffusion of Cr facilitates the smooth growth of the interface, suggesting that the diffusion of Cr may be a crucial factor influencing the growth rate of CRUD.

Mg and Cr doped ZnO nanoparticles for oxygen evaluation reaction

This study introduces an innovative approach to developing low-cost materials for renewable energy technologies by synthesizing a novel series of zinc oxide (ZnO)-based nanoparticles, including chromium-doped zinc oxide (ZnOCr) and magnesium-chromium co-doped zinc oxide (ZnOCr-Mg), via the solution combustion method. The novelty of this work lies in the strategic co-doping of ZnO with both Cr and Mg, a combination not extensively explored in the field of electrocatalysis for Oxygen Evolution Reactions (OER). By leveraging this co-doping strategy, the structural, morphological, and electrocatalytic properties of the nanoparticles were systematically analyzed using techniques such as linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA). Among the tested variants, ZnOCr-Mg:5 exhibited a significantly lower overpotential and superior stability, maintaining its catalytic performance over 18,000 s, thus outperforming traditional ZnO catalysts. These findings highlight the synergistic effects of Cr and Mg doping, showcasing ZnOCr-Mg:5 as a highly efficient and durable catalyst for OER, offering a novel and scalable solution for advancing sustainable energy technologies.

Effects of strain and Cr doping on hydrogen adsorption behaviors of α-Fe2O3 oxide film: A density functional theory study

High-strength steels are susceptible to hydrogen embrittlement, a critical failure mode, where the surface oxide film serves as the primary barrier against the permeation of hydrogen. In this study, the density functional theory (DFT) calculations are performed to investigate the effects of strain and Cr doping on the H adsorption characteristics at α-Fe2O3 surface. Calculation results reveal that tensile strain weakens the ionic bond of Fe-O at surface, enhancing H atom adsorption, thereby increasing the risk of oxide film degradation. The compressive strain weakens the H atom adsorption, especially at a compression strain above 3%, significant changes in electronic structure occur, including the shift in density of states and the hybridization of orbitals, resulting in an even higher H adsorption energy. Doping the α-Fe2O3 surface with Cr will enhance the charge transfer with O atoms, as a result reducing the H adsorption capability. Surprisingly, when the compressive strain exceeds 3%, the stability of Cr-doped α-Fe2O3 suddenly declines due to a structure relaxation, coinciding with enhanced H adsorption capability. In addition, the p-band theory in describing the H binding energy in one single specific system under strain is found to be universal. This study underscores the significant role of strain and Cr doping in influencing the H adsorption behavior on oxide films, offering critical insights for the design of hydrogen embrittlement resistant high-strength steels.

Effect of Cr doping on electronic and optical properties of mono/bilayer MoTe2 nanosheets– a first-principles study

The influence of Cr-doping on mono/bilayer MoTe2 nanostructures is studied within the framework of density functional theory (DFT) since doping may be used to effectively tailor the electronic and optical characteristics in a desired manner. Chromium (Cr) seems to modify the electronic properties and energy band gap of MoTe2 considerably. At first, we confirmed the stability of the proposed structure with the support of cohesive formation energy and phonon-band-spectrum. Moreover, doping with Cr on MoTe2 produces a red shift towards far infra-red region in the absorption coefficient, thus making it suitable for far infra-red region applications. Hence, Cr doping is employed in this work. When Cr impurities are substituted in pristine MoTe2 nanostructures, the band structure gets modified. Additionally, the band gap of mono/bilayer MoTe2 nanostructures reduces from 1.143/0.74 eV for pristine MoTe2 to 0.807/0.621 eV for 8 % substitution of Cr. By examining absorption spectra, it was found that the optical characteristics of mono/bilayer MoTe2 changed significantly with doping of Cr impurities. The results of this study provide insight into the band structure, optical, and electronic attributes of mono/bilayer MoTe2 nanostructures that could be further fine-tuned for optoelectronic applications using substitution of Cr impurities.

Enhanced secondary electron emission properties of sputter-deposited MgO–Au composite film via Cr doping

High and stable secondary electron emission yield (SEY) is essential for thin film materials used for electrical signal amplification in electronic devices. To enhance the secondary electron emission (SEE) capability of MgO–Au composite film, Cr-doped MgO–Au film was prepared by magnetron sputtering and the effect of Cr doping on the SEE properties of MgO–Au film was intensively investigated. It was confirmed that the doped Cr element is distributed through the whole composite film in a form of Cr2O3. Compared to the conventional MgO–Au film, the Cr-doped MgO–Au film with a Cr/(Cr + Mg) atomic ratio of 0.71 % achieves a SEY of 7.1 with a 4.4 % rise at the primary electron energy (Ep) of 300 eV and a maximum SEY of 10.9 with a 10.1 % increase at the Ep of 800 eV, and it also has a reduction of 49.2 % in SEE decay rate under continuous electron bombardment. For this novel composite film, the SEY ascension mainly attributes to the MgO grain enlargement and chemical stability enhancement, and the decreased SEE decay rate is associated with the improvements of resistance to electron bombardment and electric conductivity induced by Cr doping.

Effect of Cr-doping on third-order nonlinear optical properties of nanostructured Zn1-xCrxO thin films for Opto-Electronic device applications

Effect of Cr-doping on third-order nonlinear optical properties of nanostructured Zn1-xCrxO thin films for Opto-Electronic device applications

Competitive nature of weak anti-localization and weak localization effect in Cr-doped sputtered topological insulator Bi2Se3 thin film

In the present study, we have investigated the effect of magnetic Cr doping on the transport properties of a sputtered Bi2Se3 thin film on the SrTiO3 (110) substrate. The high-resolution x-ray diffraction and Raman spectroscopy measurements revealed the growth of rhombohedral Bi2Se3 thin films. Further electronic and compositional analysis was done by x-ray photoemission spectroscopy and Rutherford backscattering spectroscopy, and the x-value was estimated to be 0.18 in the Bi2−xCrxSe3 thin film. The variation in the resistivity with temperature (2–300 K) revealed the metallic nature in undoped Bi2Se3 up to 30 K and upturn resistivity below 30 K. The Cr-doped Bi2Se3 resistivity data show a traditional semiconducting nature up to 25 K and take an abrupt upturn resistivity below 25 K. The resistivity behavior of both samples was explained by adopting a model that consists of the total resistance, a combination of bulk and surface resistance in parallel. The bulk bandgap value determined by this method is obtained to be 256 meV in an undoped Bi2Se3 thin film. Magnetoconductance data of the undoped thin film revealed a weak anti-localization (WAL) effect, while the Cr-doped thin film showed a weak localization (WL) effect at low temperatures (<50 K). At low magnetic field and low temperature, a competing nature of WAL and WL effects was prominent in the Cr-doped film. A drastic increase in the electrical resistance suggests that Cr doping can significantly modify the electrical properties of Bi2Se3 thin films, which could have potential applications in futuristic devices.

Effects of Cr doping and size reduction on the structural and magnetic properties of α–CoV2O6

We report the effect of Cr-doping on the structural and magnetic properties of powder α–CoV2O6 samples. Samples were synthesized using a wet chemical synthesis method and calcined at temperatures between 350 ℃ and 500 ℃ to promote phase formation. For α–CoV2O6 and Cr-doped α–CoV2O6 samples, a single phase only occurs when the samples are calcined at 450 ℃ and 500 ℃, respectively, as confirmed using powder x-ray diffraction (XRD). Cr-doping results in a compression distortion of the lattice along the c-axis. Transmission electron microscopy (TEM) measurements indicate that Cr-doping causes a reduction in particle size and particle agglomeration. Metamagnetism was observed in field dependence of magnetization, M(μ0H) for α–Co(V1−xCrx)2O6 samples with 0 ≤ x ≤ 0.05. The hysteresis in M(μ0H) curves for μ0H < 5 T at 2 K indicate that the magnetization is metastable and suggests magnetic irreversibility. Zero-field-cooled (ZFC) and field-cooled (FC) temperature dependence of magnetization, M(T), show antiferromagnetic (AFM) ordering of the α–Co(V1−xCrx)2O6 samples at fields, μ0H ≤ 1 T. Increasing field strength to 2.5 T causes a transition from the AFM state to a ferrimagnetic (FI) state, and an introduction of spin-glass (SG)-like behavior. At 5 T, a transition from the FI state to a ferromagnetic (FM) state and a suppression of SG-like behavior is observed.

Effect of Cr doping and photoresponse properties of photodiode based on CdO thin films

AbstractCadmium oxide (CdO) and chromium (Cr) doped CdO thin films with various Cr wt% contents (0.1, 0.5, 1, 2 at.%) are synthesised on soda lime glass (SLG) substrates. Results from X-ray analysis indicate that all thin films are in cubic nature with (111) preferential orientation. Cr doping does not appear to result in a transition from one crystal phase to another. CdO with the 2.0 wt% Cr doping absorbs much more light than undoped CdO in low wavelength region (&lt; ≈450 nm), giving a maximum absorption peak in the ultraviolet region. Cr doped CdO/p-Si heterojunction shows the Cr wt% content-sensitive rectification property, achieving a high ratio of 105. In addition, Cr doped CdO/p-Si heterojunction exhibits photodiode behavior and possesses an improved photo-to-dark current ratio of ≈153. This work introduces an occasion to develop the optoelectronic devices based on Cr doped CdO thin films.

Experimental and DFT studies on corrosion behaviors of laser-cladded (FeCoNi)75−xCrxB15Si10 high-entropy alloy coatings

The effects of Cr doping on microstructure evolutions and corrosion behaviors of laser-cladded (FeCoNi)75−xCrxB15Si10 (denoted as Crx hereafter, x = 0, 4, 8, 12, 16 at%) high-entropy alloy coatings (HEACs) were investigated. The composition and shape of the borides in interdendrite regions are modified by adding Cr, alleviating the localized corrosion behavior. The corrosion resistance of the HEACs increases continuously as a function of Cr level in 3.5 wt% NaCl solution. The Cr16 coating outperforms the previously reported Ni alloys, stainless steel, and some other high entropy alloys in terms of corrosion resistance, with the highest pitting potential (0.233 V), the lowest corrosion current density value of 9.9 × 10−9 A/cm2 and passive current density (2.138 ×10−8 A/cm2). Based on the experimental analysis and density functional theory (DFT) simulations, the corrosion mechanisms of the Crx HEACs were discussed. The exceptional corrosion resistance of the Cr16 coating can be attributed to its high oxygen adsorption energy and thus facilitates the rapid formation of protective and compact passive films with few defects.

Identifying the photon absorption characteristics of Cr-doped Cu2ZnSnS4 (CZTS:Cr) thin film deposited by Co-sputtering technique

This study investigates the potential of a quaternary compound semiconductor to be realized as the absorber layer for third-generation intermediate band solar cells (IBSCs). In this work, the effects of Cr doping into Cu2ZnSnS4 (CZTS) host material to form intermediate band within the forbidden bandgap were studied. The films were deposited by a co-sputtering technique. It has been found that Cr has a high preference to substitute Zn, followed by Sn, then Cu. Insufficient Cr does not lead to intermediate band but, instead, forms defect states within the bandgap. Excess Cr however deteriorates CZTS (112) peak while at the same time secondary phase of cubic-ZnCr2S4 starts to grow. At sufficient levels of Cr content, absorption coefficient tremendously improved to 105 cm−1, resulting in an additional absorption peak attributed to possible formation of an intermediate band. This intermediate band is located at 1.40 ± 0.02 eV below CBM, while the band gap Eg is 1.55 eV. Further optimization to the sulphurization process reveals that the intermediate band peak, ECIL could be adjusted towards blue or red shift by manipulating Cr and/or sulphur content. This yields a bandgap of 1.52 eV with two intermediate bands positioned at 0.90 eV and 1.20 eV above the VBM. These preliminary findings are beneficial prior to realizing a working device of CZTS:Cr intermediate band solar cell.

Effects of Cr doping on the structural, optical and electrical characterizations of spray-deposited ZnSnO3 thin films

Effects of Cr doping on the structural, optical and electrical characterizations of spray-deposited ZnSnO3 thin films

An in-depth oxidation kinetic study of CuCrxMn1-xO2 (x = 0, 0.1, 0.3) for thermochemical energy storage at medium-high temperature

In this study, we investigated the effect of Cr doping on CuMn2O4/CuMnO2 and established an oxidation (heat release) kinetic model for CuCrxMn1-xO2 (x = 0, 0.1, 0.3) as an extension of our previous research on developing medium-high temperature (500–1000 °C) redox-type thermochemical energy storage materials. Our objective is to develop a reliable model for predicting the heat release power at constant temperature conditions. The as-prepared samples were characterized using XRD Rietveld refinement, SEM-EDS, and XPS analysis to obtain a more precise crystal structure and elemental states. The oxidation kinetic model was established using an isothermal oxidation method which differs from the method (non-isothermal) used in the previous study. Additionally, the pressure term was also taken into consideration. The reaction models and kinetic parameters of CuMnO2, CuCr0.1Mn0.9O2 and CuCr0.3Mn0.7O2 were determined using master plots and Arrhenius plots. Among all sample, CuCr0.1Mn0.9O2 exhibited the smallest oxidation activation energy of 29.932 kJ/mol, which was significantly lower than the previous value obtained using the non-isothermal method. Combining the reaction rate and heat release, CuCr0.1Mn0.9O2 showed the highest instantaneous power output of 4.69 kW/kg at the oxygen partial pressure of 0.5.

Structural and optical properties of sol-gel synthesized TiO2 nanocrystals: Effect of Ni and Cr (co)doping

Nickel and chromium metal ions have been utilized to dope and co-dope titanium dioxide nanocrystals, thereby broadening the light absorption range of titania into the visible light spectrum. The doped and co-doped TiO2 nanocrystals were prepared using sol-gel techniques, with a varied doping concentration that extended from 0.25 to 10.0 wt%.These modified materials underwent comprehensive analysis using standard analytical tools such as X-ray diffraction, Raman spectroscopy, BET surface area measurement, Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy, and fluorescence spectroscopy. Powder XRD technique reveals that the modified catalyst majorly contains the anatase polymorph with the transition metal ion either substituting Ti or located as interstitials in the lattice of TiO2. Raman and UV–Vis absorption spectra of the doped and codoped catalyst a show λmax shift towards longer wavelength when in the metal ion concentration is increased from 0.25 to 10 wt%. FTIR patterns show the stretching and vibration patterns of hydroxyl radicals present in the nanocrystals. The BET surface areas of the doped and codoped TiO2 nanocrystals have substantially higher surface areas compared with that of the undoped TiO2. Electronic structural studies of the TiO2, (Ti,Cr)O2, (Ti,Ni)O2, and (Ti,Ni,Cr)O2 crystals using density functional theory indicated a reduction in the band gap width (Eg) of pure TiO2 when doped with transition metals. Specifically, the indirect bandgap values for Ni(10%), Cr(10%) and NiCr(5% + 5%) doping were 2.96, 2.83, and 2.7 eV, respectively. Furthermore, the photoluminescence intensity substantially decreased with the incorporation of transition metal ions in the TiO2 nanocrystals.

Substantial effect of Cr doping on the third-order nonlinear optical properties of ZnO nanostructures

Here in, the present work we report the influence of Cr doping on the nonlinear properties of hydrothermally prepared ZnO nanoparticles. Structure has been confirmed from XRD analysis and exhibit a hexagonal wurtzite structure. Observed peak shift and decrease in crystallite size observed from XRD analysis confirms the successful Cr doping. FE-SEM images show distorted rod-like morphology and the doping percentages are confirmed from the EDAX spectra. The XPS spectrum confirms the existence of oxygen vacancies, which validates the existence of divalent oxidation states of zinc and the trivalent state of chromium. The calculated bandgap values validate thatZn0.98Cr0.02O nanoparticles exhibit the lowest bandgap energy due to the presence of optically active sub-levels within the bandgap region. Variation in peak intensity was observed from the Raman spectra, which validates the addition of Cr into lattice sites of ZnO. Under continuous wave (CW) laser regime, the Z-scan method was used to determine the third order nonlinearity and demonstrate, Zn0.96Cr0.04O nanoparticle show a combined effect of saturable absorption (SA) and reverse saturation absorption (RSA) under open aperture measurements with an increase in nonlinear absorption coefficient (βeff), and third-order NLO susceptibility (χ(3)) values on increasing Cr3+ doping concentration.

Physical properties and photocatalytic activity of Cr doped TiO2 nanoparticles.

Nanocrystalline Ti1-x Crx O2 (0≤ x ≤0.20) samples are synthesized via acid-modified sol-gel process and characterized with various techniques, such as HRTEM, FESEM, Raman, XPS, DTA and VSM. The TEM image of TiO2 exhibits elongated nanoparticles with an average size of 10 nm. The HRTEM in combination with selected area electron diffraction (SAED) patterns reveals the interplanar spacing and polycrystalline nature of the samples, respectively. FESEM micrographs reveal non-uniform morphologies and less aggregation of the particles in the doped sample. Raman spectra ensure the phase purity of the samples and a blue shift on Cr doping. X-ray photoelectron spectra (XPS) predict the chemical state of the elements and oxygen vacancies in the prepared samples. The room temperature magnetic studies reveal a significant variation in the magnetic parameters on Cr doping in TiO2 . The differential thermal analysis (DTA) shows the structural phase transition at ∼630°C. The photocatalytic performance is studied for the degradation of methylene blue (MB) dye under visible-light irradiation. A higher photocatalytic efficiency is found for the 20% of Cr-doped TiO2 . These studies propose that the appropriate incorporation of Cr ions makes TiO2 very efficient for visible light-driven photocatalysts required for applications in wastewater treatment. In the present study, nanoparticles of TiO2 and Cr doped TiO2 by a cost-effective acid-modified sol-gel process. The effect of Cr doping on the microstructure, thermal, magnetic and photocatalytic properties of TiO2 were explored in detail. The transmission electron microscopy (TEM) images exhibit the presence of elongated nanoparticles with an average size of 10 nm. Field emission scanning electron microscopy (FESEM) was used to study the surface morphology of the synthesized materials, which revealed non-uniform morphologies and less aggregation of the particles in the Cr-doped sample. Energy dispersive x-ray spectroscopy (EDS) confirms the elemental compositions with the appropriate stoichiometry of the elements. Raman spectra ensure the phase purity of the materials and also a blue shift with the incorporation of Cr ions in TiO2 . X-ray photoelectron spectra (XPS) predict the chemical state of the elements and oxygen vacancies in the prepared samples. The magnetic nature of all the synthesized samples was examined through the vibrating sample magnetometer (VSM) and revealed weak ferromagnetic behavior of the samples. These results signify that the oxygen vacancies and defects play a crucial role in developing the ferromagnetic nature of oxide semiconductors. The differential thermal analysis (DTA) shows the structural phase transition at ∼630°C. The photocatalytic performance of the prepared samples was studied for the degradation of methylene blue (MB) dye under irradiation of visible light. A higher photocatalytic efficiency was found for the 20% of Cr-doped TiO2 . These studies propose that the appropriate incorporation of Cr ions makes TiO2 very efficient for visible light-driven photocatalysts required for applications in wastewater treatment. This article is protected by copyright. All rights reserved.

Effect of Cr-Doping on the Structural and Magnetic Properties of Mechanically Alloyed FeCoNiAlMn1-xCrx High-Entropy Alloy Powder.

In this work, the new compositions of FeCoNiAlMn1-xCrx, (0.0 ≤ x ≤ 1.0), a high-entropy alloy powder (HEAP), are prepared by mechanical alloying (MA). The influence of Cr doping on the phase structure, microstructure, and magnetic properties is thoroughly investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry. It is found that this alloy has formed a simple body-centered cubic structure with a minute face-centered cubic structure for Mn to Cr replacement with heat treatment. The lattice parameter, average crystallite size, and grain size decrease by replacing Cr with Mn. The SEM analysis of FeCoNiAlMn showed no grain boundary formation, depicting a single-phase microstructure after MA, similar to XRD. The saturation magnetization first increases (68 emu/g) up to x = 0.6 and then decreases with complete substitution of Cr. Magnetic properties are related to crystallite size. FeCoNiAlMn0.4Cr0.6 HEAP has shown optimum results with better saturation magnetization and coercivity as a soft magnet.

Effect of Cr Doping on Oxidation Resistance and Oxidation Mechanism of TiC Reinforced Steel Matrix Composites: Experiments and First-Principles Calculations

Effect of Cr Doping on Oxidation Resistance and Oxidation Mechanism of TiC Reinforced Steel Matrix Composites: Experiments and First-Principles Calculations

Preparation of Zn1−mXmMn2O4 Material Modified by Zinc Site Doping and Effect of Cr Doping on the Material Morphology

Preparation of Zn1−mXmMn2O4 Material Modified by Zinc Site Doping and Effect of Cr Doping on the Material Morphology

Low-temperature synthesis of ultrafine Cr,Mg-codoped Al2TiO5 nanocrystals as high-temperature green ceramic pigment

Tialite (Al2TiO5) is attracting as a high-temperature ceramic host matrix, but the decomposition of Al2TiO5 at 780–1280 °C is a serious obstacle for practical application. Herein we prepared successfully ultrafine Cr,Mg-codoped Al2TiO5 green ceramic pigment with the nanocrystal sizes less than 50 nm and high-temperature stability of up to 1200 °C via nonhydrolytic sol-gel (NHSG) method followed by heating treatment of 750 °C. The effects of Cr and Mg content on phase composition, crystal structure, thermal stability and color property were well investigated. The optimum Cr,Mg-codoped Al2TiO5 pigment with 20 mol% Mg and 6 mol% Cr exhibited an excellent green color (L* = 76.94, a* = −9.62, b* = 14.17), which can be reasonably maintained in exposed air by a heating treatment at 1200 °C for 10 h or in transparent ceramic glaze at 1200 °C for 30 min. These enhanced performances were mainly attributed to synergistic effect of Cr and Mg doping, which hindered the tendency of Al2TiO5 toward decomposition, indicative of its potential application in high-temperature ceramic decoration.