Effect Of Cr Substitution Research Articles

Effect of Cr substitution in ZnFe2O4 nanoparticles on the electron transfer at electrochemical interfaces

In this study, we explored the effect of Cr³⁺ substitution by partially and fully replacing Fe³⁺ in the normal spinel ZnFe₂O₄ crystal structure at electrochemical interfaces. The resulting ZnCrₓFe₂₋ₓO₄ nanomaterials exhibited an average particle size between 20 and 50 nm with a spherical morphology. The materials also demonstrated energy band gaps ranging from 2.1 to 3.1 eV. X-ray diffraction (XRD) analysis confirmed that all the synthesized materials maintained a normal spinel structure, attributed to the octahedral site preference energy (OSPE) of Zn²⁺, Fe³⁺, and Cr³⁺ ions. Electrochemical performance assessments revealed that the ZnFe₂O₄-based sensor achieved a sensitivity of (37.8 ± 0.2) μA/mM with a kinetic rate constant of (13.1 ± 2.8) ms⁻¹, while the ZnCr₂O₄-based sensor exhibited a sensitivity of (32.4 ± 0.5) μA/mM and a kinetic rate constant of (3.73 ± 0.55) ms⁻¹ in the detection of paracetamol, whereas ZnCrFeO4 sensor has produced the second-best sensitivity (35.7 ± 0.1 μA/mM) and the rate constant (4.53 ± 0.54 ms⁻¹) with the lowest limit of detection (1.94 ± 0.01 μM). These differences in electrochemical performance were correlated with the variations in the energy band gaps caused by the restructuring of the normal spinel structure. Our findings indicate that the ZnFe₂O₄ sensor has a higher potential for direct electron transfer, whereas the other sensors are more likely to facilitate surface-mediated electron transfer.

Effect of phase composition and cluster structure on de-/hydriding kinetics of as-cast and heat-treated Ti33V37Mn30-xCrx alloys

To enhance the hydrogen storage property, elements Mn in Ti33V37Mn30 alloy were partially substituted with varying concentrations of elements Cr. The Ti33V37Mn24Cr6 variant, which exhibited superior performance, was selected for further analysis. Ti33V37Mn24Cr6 samples were first heat-treated separately at 773K, 973K and 1173K for 2h, and then water-quenched. The effect of Cr substitution and heat treatment on the microstructure and de-/hydriding properties of Ti33V37Mn30-xCrx alloys were investigated. As-cast alloys were composed of BCC phases mainly, along with some C14 Laves phases and Ti-rich phases. The lattice parameter of BCC phases in Ti33V37Mn24Cr6 increased to 3.053 Å. Cr substitution changed the tetrahedral gap of the alloy. At 298K, the initial hydrogen absorption capacity and the maximum hydrogen desorption capacity of Ti33V37Mn24Cr6 were raised to 3.07 wt% and 1.81 wt%, respectively. The lattice parameter of Ti33V37Mn24Cr6 alloys heat-treated at 773K also enlarged to 3.056 Å. Elevating the heat treatment temperature to 973K and 1173K significantly raised the proportion of C14 Laves phases in the alloy. Hydrogen storage performance of heat-treated alloys was examined at 298K. The results suggested that the heat-treated alloys could be fully activated after one hydrogen ab-/desorption cycle. Ti33V37Mn24Cr6 alloy heat-treated at 773K achieved the maximum hydrogen desorption capacity of 1.83 wt%, with an accelerated hydrogen ab-/desorption rate.

Effect of Cr substitution on nickel spinel ferrite’s surface morphology, structure, antibacterial activity and magnetic properties

This study reports the sol–gel auto-combustion (SGACT) synthesis of Cr-substituted NiFe2O4 nanoferrites with a composition, of CrxNi(1−x)Fe2O4 (where x = 0.000, 0.025, 0.050, 0.100, 0.150, 0.200), and it examines the effects of chromium on spinel ferrite’s structure and properties. The doping of Cr at the nickel site is first reported in the present study. The computed crystallite size “t” from the XRD results was found in the range of 34.2–40.4 nm, whereas, FESEM plots show larger-sized grains due to the aggregation of a large number of crystallites for the produced nanoferrites. Maximum saturation magnetization of 42.44 emu/g was attained by the Cr0.050Ni0.950Fe2O4 (x = 0.050) specimen, whereas, the Cr0.200Ni0.800Fe2O4 (x = 0.200) specimen attains the maximum coercivity in the current study. All these excellent values of magnetic parameters make our SGACT-produced nanoferrites useful for magnetic recording media applications. In S. aureus, Cr0.200Ni0.800Fe2O4 nanoparticles showed the highest zone of inhibition (ZOI) whereas, Cr0.050Ni0.950Fe2O4 nanoparticles showed the least ZOI. On the other hand, in E. coli, Cr0.850Ni0.150Fe2O4, Cr0.200Ni0.800Fe2O4 and Cr0.050Ni0.950Fe2O4 nanoparticles showed good ZOI. This makes our developed nanoferrites beneficial for biological applications as antibacterial agents.

Effect of Cr substitution on the magnetocaloric properties and corrosion resistance of (Mn,Fe)2(P,Si) alloys

This study investigated the effects on the magnetocaloric properties and corrosion resistance of Cr substitution for Fe in (Mn,Fe)2(P,Si) alloys. The characteristics of the first-order phase transition and the crystal structure were maintained, even after Cr substitution. In particular, a discontinuous change in the lattice parameters was exhibited during the transition from the ferromagnetic to paramagnetic phase at the Curie temperature. Increasing the Cr content reduced the Curie temperature and isothermal entropy change. The thermal hysteresis gradually increased by increasing the Cr content. Meanwhile, the small Cr content maintained the adiabatic temperature change and improved the corrosion resistance. Therefore, the tuning of the Cr content in (Mn,Fe)2(P,Si) alloys can provide possible applications due to their notable magnetocaloric properties and improved corrosion resistance.

The effect of Cr-substitution on the structural, electronic and magnetic properties of rutile VO2

The effect of Cr-substitution on the structural, electronic and magnetic properties of rutile VO2 is investigated in this study. Pure VO2 is found to be a nonmagnetic metal, whereas all three Cr- substituted compounds [V1-xCrxO2 (VCO) with x = 0.25, 0.5, 0.75] are found to exhibit ferrimagnetic metallic behaviour. However, pure and all VCO compounds encounter metal to half-metal transition for the application of U = 2 eV, showing ferromagnetism. VO2, the VCO compounds V0.75Cr0.25O2 and V0.5Cr0.5O2 undergo metal–insulator transition (MIT) for U = 5 eV, 5.5 eV and 3.5 eV respectively, preserving ferromagnetism. Besides, V0.25Cr0.75O2 preserves its ferromagnetic half-metallic character even application of U as high as 6 eV. The breaking of mirror symmetries in the VO6/CrO6 octahedra induces structural distortions in all three VCO compounds. The MIT in pure VO2 is caused by the transfer of electrons from the V-dyz and dxz states to the dx2- y2 states. The simultaneous effect of structural distortion, V4+- V4+ and Cr3+-V5+ charge ordering and U is responsible for the MIT in V0.75Cr0.25O2. On the other hand, the simulteneous effect of structural distortion, transfer of electrons from V-t2g to Cr-t2g states and U is responsible for the MIT in V0.5Cr0.5O2. Although electron transfer is commenced from V-t2g to Cr-t2g states in V0.25Cr0.75O2, the latter cannot be completely occupied by the transferred electrons, resulting in the non-opening of a band gap near the Fermi level. The p-d hybridization between O-2p and V-3d/Cr-3d states, and V/Cr-O antiferromagnetic coupling facilitates ferromagnetism in insulating VO2, V0.75Cr0.25O2, V0.5Cr0.5O2 and half-metallic V0.25Cr0.75O2.

Effect of Cr Substitution on Magnetic and Magnetocaloric Properties for La0.62Nd0.05Ba0.33MnO3

Effect of Cr Substitution on Magnetic and Magnetocaloric Properties for La0.62Nd0.05Ba0.33MnO3

Effect of Cr substitution on ferrimagnetic and ferroelectric properties of GaFeO3 epitaxial thin films

To control the properties of multiferroic materials, substitution of magnetic elements is a useful technique. In this study, we fabricated GaCrxFe1−xO3 and Ga1−yCryFeO3 films by substituting Cr3+ (3d3) ions in GaFeO3 for magnetic Fe3+ (3d5) and nonmagnetic Ga3+ (d10) sites, respectively. The effect of the Cr substitution on the magnetic and dielectric properties was systematically investigated. The obtained GaCrxFe1−xO3 and Ga1−yCryFeO3 films (x ≤ 1/4 and y ≤ 1/2) simultaneously exhibit ferrimagnetism and ferroelectricity. For the GaCrxFe1−xO3 films, the magnetic transition temperature (TC) and magnetic anisotropy decrease with increasing x. On the other hand, for the Ga1−yCryFeO3 films, TC increases with increasing y. Unlike the GaFeO3 film, the Cr-substituted GFO films show a peak in the magnetization versus temperature curves and exhibit a sudden decrease in the coercive field near the peak, probably due to the formation of Fe3+–O–Cr3+ coupling which prefers to form ferromagnetic interactions in the antiferromagnetic Fe3+–O–Fe3+ networks. Furthermore, we found that the Cr-substituted GaFeO3 films show out-of-plane ferroelectricity at room temperature.

Surface modification and enhanced multiferroic behavior of BiFe0.25Cr0.75O3 films with different thickness over Pt(111)/Ti/SiO2/Si substrate

Polycrystalline BiFe0.25Cr0.75O3 thin films have been fabricated via a chemical deposition technique at various thicknesses (60-, 130-, 190-, 240 nm). The effect of Cr substitution on BiFeO3 structures have been briefly discussed by performing X-ray diffraction and SAED pattern. The nature of the films surface at different thicknesses were briefly discussed using scanning electron microscope and transmission electron microscope. Roughness and other amplitude parameters of the film at different thickness are studied through atomic force microscopy. The result indicates that, when changing the thickness of the film, the average bond length gets changed causing difference in electrical and magnetic properties. Electrical and dielectric study reveals thickness dependent property and is deeply understood from space charge, oxygen vacancies and super-exchange interaction. Film at 60 nm shows higher magnetization with 8.5042 emu/cm3 and with a retentivity of 3.852 emu/cm3 than the thick film. Further, the spin-cooling behavior and magnetization below room temperature from 2 to 300 K were analyzed briefly for spintronics applications.

Effect of Cr Substitution on the Structure and the Superconductivity in (Tl$_{0.5}$Pb$_{0.5}$)Sr$_2$CuO$_{5+z}$

Effect of Cr Substitution on the Structure and the Superconductivity in (Tl$_{0.5}$Pb$_{0.5}$)Sr$_2$CuO$_{5+z}$

Manipulation of Magnetic Properties of Cr-Substituted Ni Ferrite Synthesized by Conventional Ceramic Technique

A series of polycrystalline Ni–Cr ferrites, with the composition NiCr x Fe 2−x O 4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0), were synthesized by conventional solid state ceramic method. The effect of Cr substitution on the structural, morphological, and magnetic properties of Ni ferrite has been investigated. Formation of single-phase cubic spinel structure of the compositions has been confirmed by X-ray diffraction. The morphological study was performed by scanning electron microscopy, and the average grain size was found to decrease with increasing Cr content. The magnetic properties of the samples were measured using an impedance analyzer and a vibrating sample magnetometer. Saturation magnetization, coercivity, and remanent magnetization have been measured from the hysteresis curves. The value of the saturation magnetization was found to decrease with increasing Cr concentration. The values of coercivity, remanent magnetization, and remanence ratio (M r/M s) ratio were also reported. The Curie temperatures (T c) were determined from the plots of the real part of permeability ( $\mu _{\mathrm {i}}^{/}$ ) versus temperature, and the values were found to be 511, 465, 415, 364, and 338 ∘C for x = 0.0, 0.2, 0.4, 0.6, and 0.8, respectively. The frequency dependence of the $\mu _{\mathrm {i}}^{/}$ , loss factor, and quality factor has been studied as a function of composition in the frequency range 1 kHz–120 MHz. The real part of permeability was observed to be steady up to ∼10 MHz for all the samples. The loss factor (tan δ) of the samples decreased rapidly before 40 kHz and became almost constant with low values after 40 kHz. The values of quality factor have gradually been increased for samples with x ≤ 0.4, whilst the values diminished for samples with x ≥ 0.6.

The effect of Cr substitution on the structural, electronic and magnetic properties of pulsed laser deposited NiFe2O4 thin films

We have studied the structural, electronic and magnetic properties of pulsed laser deposited thin films of Ni1−xCrxFe2O4 (x=0.02 and 0.05) on Si (111) and Si (100) substrates. The films reveal single phase, polycrystalline structure with larger grain size on Si (111) substrate than that on Si (100) substrate. Contrary to the expected inverse spinel structure, x-ray photoemission (XPS) studies reveal the mixed spinel structure. XPS results suggest that Ni and Fe ions exist in 2+ and 3+ states, respectively, and they exist in tetrahedral as well as octahedral sites. The deviation from the inverse spinel leads to modified magnetic properties. It is observed that saturation magnetization drastically drops compared to the expected saturation value for inverse spinel structure. Strain in the films and lattice distortion produced by the Cr doping also appear to influence the magnetic properties.

Effects of Cr substitution on the magnetic and transport properties and electronic states ofSrRuO3epitaxial thin films

The effect of Cr substitution in a SrRuO3 epitaxial thin film on SrTiO3 substrate was investigated by measuring the magnetic and transport properties and the electronic states. The ferromagnetic transition temperature of the SrRu0.9Cr0.1O3 film (166 K) was higher than that of the SrRuO3 film (147 K). Resonant photoemission spectroscopy experimentally revealed that the Cr 3dt2g orbital is hybridized with the Ru 4dt2g orbital in the SrRu0.9Cr0.1O3 film, supporting the assumption that the enhancement of the ferromagnetic transition temperature through Cr substitution stems from the widening of energy bands due to the hybridization of Cr 3dt2g and Ru 4dt2g orbitals. Furthermore, we found that the Hall resistivity of the SrRu0.9Cr0.1O3 film at low temperature is not a linear function of magnetic field in the high-field region where the out-of-plane magnetization was saturated; this result suggests that the SrRu0.9Cr0.1O3 film undergoes a structural transition at low temperature accompanied with the modulation of the Fermi surface.

Structural and magnetic properties of Cr-substituted NiZnCo ferrite nanopowders

Cr-substituted NiZnCo ferrite nanopowders, Ni0.5−xZn0.5CrxCo0.1Fe1.9O4 (0≤x≤0.20), were synthesized by sol–gel auto-combustion method. The effect of Cr substitution on the structural and magnetic properties have been investigated. Differential thermal analysis-thermogravimetry (DTA-TG), X-ray diffraction (XRD), Fourier transform infrared spectro-scopy (FT-IR) and vibrating sample magnetometer (VSM) measurements were used to characterize chemical, structural and magnetic properties. The DTA-TG results indicate that there are three steps of combustion process. FT-IR spectra confirm the formation of spinel structure during the self-propagation combustion. XRD results indicate that the lattice parameter and the X-ray density decrease, and the average crystallite size increase with increasing Cr substitution. And Fe2O3 secondary impurity phase formed with excess Cr substitution. The saturation magnetization increases with the increase of Cr substitution when x≤0.05, and decreased when x>0.05. Meanwhile, the coercivity monotonically decreases with the increase of Cr substitution.

디지털 컬러용 pink-red 고온발색 무기안료의 합성 및 특성평가

최근 각광받고 있는 디지털 프린팅을 이용한 디자인 기법은 세밀한 표현과 다양한 이미지 구현이 가능하고, 원료의 낭비가 적어 효율성이 높은 장점을 가지고 있다. 디지털 프린팅 공정에서는 cyan, magenta, yellow, black이 기본적인 디지털 4원색으로 사용되며, 도자제품에 적용되는 세라믹 안료의 경우 <TEX>$1000^{\circ}C$</TEX> 이상의 고온 소성이 가능하도록 우수한 열적, 유약 안정성과 발색 특성이 요구된다. 본 연구에서는 고상합성법을 이용하여 <TEX>$CaO-SnO_2-Cr_2O_3-SiO_2$</TEX> 조성의 pink-red 고온발색 무기안료를 합성하였다. <TEX>$Ca(Sn,Cr)SiO_5$</TEX> 세라믹 안료의 합성 조건에 따른 물성을 XRD, SEM, PSA, FT-IR를 이용하여 분석하였고, Cr 치환량 변화가 <TEX>$Ca(Sn,Cr)SiO_5$</TEX> 무기 안료의 발색 거동에 미치는 영향을 Uv-vis.와 CIE 표색계 값(<TEX>$L^*a^*b^*$</TEX>)을 기준으로 한 색도측정을 통해 관찰하였다. Digital ink-jet printing system has many advantages such as fast and fine printing of various images, high efficiency and low cost process. Generally digital ink-jet printing requires ceramic pigments of cyan, magenta, yellow and black with thermal and glaze stability above <TEX>$1000^{\circ}C$</TEX> for the application of porcelain product design. In this study, pink-red colored <TEX>$CaO-SnO_2-Cr_2O_3-SiO_2$</TEX> pigment was synthesized using solid state reaction. The synthesis conditions of <TEX>$Ca(Cr,Sn)SiO_5$</TEX> pigment such as annealing temperature, amount of mineralizer and non-stoichiometric composition were optimized. Crystal structure and morphology of the obtained <TEX>$Ca(Cr,Sn)SiO_5$</TEX> pigment were analyzed using XRD, SEM, PSA, FT-IR and effect of Cr substitution on the pigment color was analyzed using Uv-vis. spectrophotometer and CIE <TEX>$L^*a^*b^*$</TEX> measurement.

Size effect on magnetic phase coexistence in Pr0.5Sr0.5Mn1−xCrxO3

Magnetic and transport properties are investigated in Pr0.5Sr0.5Mn1−xCrxO3 (0 x 0.05) focusing on the effect of Cr substitution and particle size dependence. The studies demonstrate that magnetic and transport properties are significantly different for nanocrystalline compound from the bulk. Neutron depolarization and diffraction studies confirm that different fractions of magnetic phase separation between antiferromagnetic and ferromagnetic components, and ferromagnetic domain size give rise to the different magnetic and transport properties. Intriguingly, nanocrystalline compound with x = 0.05 shows apparent signature of arrested state in magnetization and magnetoresistance both in thermal and magnetic field variations which is absent in the bulk counterpart. A spin-glass like state is identified for nano at low temperature, which is argued to be correlated with the arrested or pinning mechanism.

Effect of Cr substitution by Ni on the cycling stability of Mg2Ni alloy using EXAFS

This paper describes the hydrogen storage properties of Mg2Ni0.9Cr0.1 alloy and aims to elucidate the effect of doping Cr on the hydrogen sorption/desorption kinetics upon cycling. Mg2Ni0.9Cr0.1 alloy shows stable absorption capacity, and its absorption/desorption rates further improve after cycling. The calculated activation energy for dehydrogenation was 53 kJ/mol at the 3rd cycle, and decreased to 36 kJ/mol at the 20th cycle. XRD combined with SEM exhibits that Cr dopant substitutes for Mg or Ni after ball milling and the lattice structure remains stable over 20 cycles. EXAFS was used to investigate the local coordination of Ni and Cr atoms in the ball-milled and cycled samples. For the ball-milled sample, the strong Cr–Ni bonds weaken the Cr–Mg bonds, thereby destabilizing all Cr-doped phases. After 20 cycles, the stable Ni1–Mg1 bonds may be dominant and control the structural stability of Mg2Ni phases.

Formation of Tl-1223 phase in Cr substituted (Tl1−xCrx)Ba2Ca2Cu3O9−δ (x=0.3 to 0.9) superconductor

The effect of Cr substitution on the formation of Tl-1223 type phase is reported. Samples with nominal starting composition (Tl1−xCrx)Ba2Ca2Cu3O9 (Tl-1223) for x=0.3–0.9 were prepared using the solid state reaction method. The samples were studied by powder X-ray diffraction method, electrical resistance versus temperature measurements and scanning electron microscopy (SEM). The x=0.3, 0.4 and 0.5 samples showed a mixed Tl-2212 and Tl-1223 phase. The samples with x=0.6, 0.7 and 0.8 showed a single Tl-1223 phase. The x=0.6 sample showed the highest onset temperature of 124K and zero-resistance temperature of 116K. Our results showed that the (Tl,Cr)-1223 phase can be stabilized with Cr substitutions without the use of Sr.

Effect of Cr Substitution on Magnetic Properties of Mg Nanoferrites Synthesized by Citrate‐Gel Auto Combustion Method

A series of Mg‐Cr nanoferrites with the chemical formula MgCrxFe2−xO4 (0.0 ≤ x ≤ 1.0) were synthesized by Citrate‐Gel auto combustion method. The formation of single phase cubic spinel structure of the samples was confirmed by X‐ray diffraction (XRD) analysis. It is observed that with the increase in the paramagnetic Cr content, the particle size of the ferrite compositions has decreased from 23 nm to 7 nm. Faraday magnetic Susceptibility Balance was used to measure the Magnetic susceptibility of synthesized samples that confirmed the paramagnetic nature of the ferrites. Vibrating Sample Magnetometer (VSM) was used to measure the Magnetic properties of nanoferrites under investigation at room temperature under the applied magnetic field of 15 kOe. With the increase in Cr3+ concentration, the saturation magnetization has decreased from 11 emu/g to 1.5 emu/g.

Synthesis of Nanocrystalline (Fe,Cr)3Al Powder by Mechanical Alloying

The formation and structural changes of Fe50Cr25Al25 powder particles during mechanical alloying of Fe-Cr-Al elemental powder were studied. The results showed that in early stages of process, a composite lamellar structure of Fe, Cr, and Al is formed in which the dissolution of Al and Cr atoms in Fe lattice takes place. Upon further milling the solid solution transformed to a hard (935 Hv) intermetallic compound with nanocrystalline (10 nm) structure. The crystallite size, hardness value, structure, and morphology of Fe50Cr25Al25 powder are compared with those previously reported for binary Fe-Al and ternary Fe-Ti-Al systems, and the effect of Cr substitution is discussed.

The application of chromium substituted magnetite as heterogeneous Fenton catalyst for the degradation of aqueous cationic and anionic dyes

In this study, the heterogeneous Fenton degradation of cationic and anionic dyes catalyzed by a series of Cr-containing magnetites (Fe3−xCrxO4, x=0.00, 0.18, 0.33, 0.47 and 0.67) has been investigated under neutral pH conditions. Methylene blue (MB) and acid orange II (AOII) were chosen as models of cationic and anionic contaminants. Emphases were laid on the comparison of degradation characteristic between MB and AOII and the effect of Cr substitution on the degradation efficiency of both dyes. The octahedral occupancy of Cr3+ increased the BET surface area and superficial hydroxyl amount of magnetite, resulting in an improvement of adsorption ability of MB. However, these Cr-containing magnetites showed no adsorption to AOII. The MB degradation, following the Langmuir–Hinshelwood model, was well fitted by zero-order equation while AOII degradation following the Eley–Rideal model, was well fitted with two-stage pseudo-first-order kinetics. The Cr incorporation significantly improved the catalytic activity of magnetite in heterogeneous Fenton reaction, but the extent of improvement varied with the substitution level. These new insights are of high importance for the environmental application of metal substituted magnetites in the purification of textile wastewater.