Effect Of Cu Substitution Research Articles

Effect of Cu substitution on morphological optical and electrochemical properties of Co3O4 nanoparticles by co-precipitation method

In this present study, pure Co3O4 and Cu-substituted Co3O4 nanoparticles (NPs) were prepared by a simple co-precipitation method and their structural, morphological, optical, and electrochemical properties were assessed. X-ray diffraction (XRD) analysis indicated that the synthesized samples had a cubic structure with the formation of a secondary phase (CuO) was detected at a higher Cu concentration. The average crystallite was decreased with increasing Cu content. Fourier transform infra-red (FT-IR) analysis revealed that the presence of vibrational bands in Cu-substituted Co3O4 NPs. The morphological study of the pure Co3O4 and Cu-substituted Co3O4 NPs revealed that the hexagonal structure with porous morphology confirmed by Field emission scanning electron microscopy (FESEM). High resolution transmission electron microscope (HR-TEM) analysis with spotty diffraction rings showed that pure Co3O4 and Cu-substituted Co3O4 NPs were polycrystalline in nature. The optical properties of synthesized samples exhibited strong absorption edges, and bandgap values were found to be increased from 3.60 to 3.75 eV. Cyclic voltammetry (CV) was employed to investigate the electrochemical properties of the synthesized materials. The CV curves exhibited pseudocapacitive behavior, and 2 % Cu substituted Co3O4 electrode had a high higher specific capacitance value than pure Co3O4 electrode.

Correction: Effect of Cu substitution on the structural, magnetic, and dc electrical resistivity response of Co0.5Mg0.5-xCuxFe2O4 nanoferrites

Correction: Effect of Cu substitution on the structural, magnetic, and dc electrical resistivity response of Co0.5Mg0.5-xCuxFe2O4 nanoferrites

Effect of Cu substitution on magnetic and photocatalytic properties of Mn–ZnFe2O4 nanoparticles

The citrate approach was employed to successfully synthesize Mn0.4Zn0.6−xCuxFe2O4 (MZCF) with a nanostructured shape. A thorough examination was conducted on the microstructural, magnetic, and optical properties of the nanoparticles obtained. The X-ray diffraction (XRD) patterns revealed that all of the compositions exhibit a high degree of single-phase spinel formation. The experimental findings indicate that the introduction of copper ions leads to a reduction in both lattice constant and porosity, while concurrently resulting in an increase in the theoretical X-ray and bulk densities. The analysis of UV–Vis spectroscopy indicated that MZCF exhibited a direct band gap falling within the range of 1.61–1.78 eV. The magnetic characteristics were assessed through the analysis of hysteresis plots. The introduction of copper (Cu) content leads to notable improvements in the saturation (Ms) and remanent magnetization (Mr) values, which range from 40.21 to 58.78 and 4.46–10.54 emu/g, respectively. The assessment of the microwave frequency response has verified the appropriateness of MZCF nanoferrites for application within the frequency spectrum spanning from 8 to 13 gigahertz. The nanoparticles exhibit improved magnetic properties, suggesting their potential appropriateness for applications involving high-frequency microwave absorption and switching. Furthermore, the nanoparticles Mn0.4Zn0.6Fe2O4 and Mn0.4Zn0.2Cu0.4Fe2O4 were subjected to analysis utilizing a solar light simulator in order to induce degradation of MB dye.

Cu-mediated broadening of the absorption band of quaternary Cu–Ag–In–S/CdSe type-II core/shell quantum dot-sensitized solar cells with an efficiency of 12.51% under 0.25 sun

We report the effects of Cu substitution on the photovoltaic performance of (a) single-layered Cu–Ag–In–S and (b) core/shell Cu–Ag–In–S/CdSe quantum-dot sensitized solar cells (QDSSCs).

Microstructure, magnetic properties, and loss performance of the Cu-substituted MnZn ferrites

While the Cu substitution in NiCuZn ferrites is known to enhance densification and increase the initial permeability (μi), little is known about its effects in the MnZn based ferrites, which naturally possess a higher saturation magnetization (Ms) and μi. In this study, the effects of Cu substitution for Mn on the power MnZn ferrites (Mn0.71-xCuxZn0.22Fe2.07O4, x = 0.00–0.35) are investigated. With increasing Cu content, enhanced density, reduced porosity, and significant grain growth are observed. The cation distribution was determined using the Rietveld refinement, showing the strong tendency of Cu2+ ions to occupy the octahedral sites of the spinel lattice. The magnetization curves show reduced Ms with increasing Cu content. The magnetic anisotropy (|K|) was also determined from the magnetization curves using the law of approach to saturation and is seen to be increased by the increasing Cu content. The reduced Ms and increased |K| lead to the dramatic reduction of μi from 2503 (x = 0.00) to 151 (x = 0.35) at room temperature. Despite the reduced Ms at room temperature, the Curie temperature (TC) is seen to increase with increasing Cu content from x = 0.05 to x = 0.35, indicating the relocation of cations at an elevated temperature. The cut-off frequency (fr) is increased with increasing Cu content, which corresponds to the reduced μi. Moreover, the core loss (Pcv) of the MnCuZn ferrites was tested at 100kHz/200 mT, 200kHz/125 mT, and 300kHz/100 mT at room temperature, and is found to deteriorate with the increasing Cu content.

Effects of Cu substitution on photocatalytic performance of ZnO nanorods synthesised via hydrothermal route for the degradation of chlorobenzene

ABSTRACT In the present study, photocatalytic material ZnO nanorod and 20%Cu-substituted ZnO nanorod synthesised via hydrothermal route by using Zn(NO3)2.6 H2O and CuCl2.2 H2O as the source of zinc and copper, respectively. Cu present in 20%Cu-substituted ZnO NRs photocatalytic material led to reducing in the band gap of pure ZnO and enhanced the efficiency of photocatalytic material. Sample purity and crystallinity were investigated by XRD study. The surface study and extent of doping were examined by the SEM-EDX analysis.20%Cu-substituted ZnO NRs showed enriched degradation efficiency of 100 ppm chlorobenzene solution than ZnO NRs at pH 5 in 120 min under visible light.

First-principles calculation analysis and photovoltaic properties of Cu compound-added perovskite solar cells

Experiments and first-principles calculations were performed to investigate the effects of Cu substitution in CH3NH3PbI3 perovskite crystals. The first-principles calculations indicated that the energy level of the Cu d orbital formed above the VB maximum would be an acceptor or defect level. The effect of Cu addition on device properties was investigated, and the device with added 2% Cu provided higher efficiencies than the standard device. On the other hand, the decrease in short-circuit current density with increasing Cu content would be attributed to the defect level of the Cu d orbitals. First-principles calculations and experimental results provided insight into the function of Cu in CH3NH3-based perovskite crystals.

Effect of copper substitution on the electrochemical properties of high entropy layered oxides cathode materials for sodium-ion batteries

Layered oxide cathode materials in batteries usually experience complex phase transition during intercalating-deintercalating reaction, leading to poor cycle stability. However, high entropy oxides (HEOs) which can suppress the intermediate phase change have been reported with stable crystal structure and improved cycle stability as cathode materials for sodium-ion batteries (SIBs). Here we synthesize a non-toxic Cu substituted HEOs NaNi0.4-xCuxFe0.2Mn0.2Ti0.2O2 (x = 0, 0.1, 0.2, 0.3, 0.4) via high temperature solid-state reaction, and the effect of Cu substitution is analyzed in detail. NaNi0.3Cu0.1Fe0.2Mn0.2Ti0.2O2 delivers an initial specific capacity of 123.6 mA h g−1 at 0.1C rate corresponding to a capacity retention of 90.05 % after 50 cycles, while NaNi0.4Fe0.2Mn0.2Ti0.2O2 delivers a reversible an initial specific capacity of 129.1 mA h g-1corresponding to a capacity retention of 74.83 %. Cu substitution inhibits the phase transition and improve cycle stability of the material during cycling without sacrificing much capacity. This result constitutes a step forward in increasing the practicality of SIBs.

Effect of Cu Substitution in P′2- and P2-Type Sodium Manganese-Based Oxides

Layered manganese oxides have been considerably studied toward sustainable sodium-ion battery materials. There has been a focus on the specific roles of Cu as a member of substituents in sodium manganese oxides. Herein, the effects of Cu substitution for Mn in P′2- and P2-type Na0.67[CuxMn1–x]O2 (0 ≤ x ≤ 0.33) are systematically investigated, focusing on the cooperative Jahn–Teller distortion of Mn3+ and Cu2+ ions. P2-type Na0.67[Cu0.2Mn0.8]O2 is selected to gain further insights on oxygen redox along with P2-type Na0.67[Cu0.1Mg0.1Mn0.8]O2 and P2-type Na0.67[Cu0.1Zn0.1Mn0.8]O2. Comparative studies among the three materials reveal that the type of substituent(s) for Mn has no impact on the activation of oxygen redox. In contrast, the nature and the concentration of substituted element(s) influence structural evolution during charge/discharge. P2-type Na0.67[Cu0.2Mn0.8O2] maintains a P2 phase without any secondary phase at the bulk and local scales at the end of charge to 4.5 V, leading to suppressed voltage hysteresis. At the end of discharge to 1.5 V, the presence of higher Cu2+ in P2-type Na0.67[Cu0.2Mn0.8]O2 results in a distorted P′2 phase with a distortion degree of 10.6(1)%. This can induce a large lattice stress related to the lattice mismatch between P2 and P′2, which jeopardizes cyclability.

Effect of Cu substitution on anion redox behaviour in P3-type sodium manganese oxides

Sodium layered oxides which display oxygen anion redox behaviour are considered promising positive electrodes for sodium-ion batteries because they offer increased specific capacities. However, they suffer from irreversible structural changes resulting in significant capacity loss and limited oxygen redox reversibility. Here the effect of Cu substitution on the electrochemical performance of P3-type sodium manganese oxide is examined by evaluating the structural and electronic structural evolution upon cycling, supported by density functional theory (DFT) calculations. Over the voltage range 1.8–3.8 V vs. Na/Na+, where the redox reactions of the transition metal ions contribute entirely towards the charge compensation mechanism, stable cycling performance is maintained, showing a capacity retention of 90% of the initial discharge capacity of 166 mA h g−1 after 40 cycles at 10 mA g−1. Over an extended voltage range of 1.8–4.3 V vs. Na/Na+, oxygen anion redox is invoked, with a voltage hysteresis of 110 mV and a greater initial discharge capacity of 195 mA h g−1 at 10 mA g−1 is reached. Ex-situ powder x-ray diffraction patterns reveal distortion of the P3 structure to P′3 after charge to 4.3 V, and then transformation to O′3 upon discharge to 1.8 V, which contributes towards the capacity fade observed between the voltage range 1.8–4.3 V. DFT with projected density of states calculations reveal a strong covalency between the copper and oxygen atoms which facilitate both the cationic and anionic redox reactions in P3-type Na0.67Mn0.9Cu0.1O2.

Effect of Cu Substitution and Heat Treatment on Phase Formation and Magnetic Properties of Sm12Co88-xCux Melt-Spun Ribbons.

The phase structure and microstructure of Sm12Co88−xCux (x = 0, 2, 4, 6, 8, 10; at.%) as-cast alloys and melt-spun ribbons prepared via the arc-melting method and melt-spun technology were studied experimentally by X-ray diffraction (XRD) and scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). The results reveal that the Sm12Co88−xCux (x = 0) as-cast alloy contains Sm2Co17 and Sm5Co19 phases, while the Sm12Co88−xCux (x = 2) as-cast alloy is composed of Sm2Co17, Sm2Co7 and Sm(Co, Cu)5 phases. Sm2Co17 and Sm(Co, Cu)5 phases are detected in Sm12Co88−xCux (x = 4, 6, 8, 10) as-cast alloys. Meanwhile, Sm12Co88−xCux ribbons show a single SmCo7 phase, which is still formed in the ribbons annealed at 1023 K for one hour. After annealed at 1123 K for two hours, cooled slowly down to 673 K at 0.5 K/min and then kept for four hours, the ribbons are composed of Sm2Co17 and Sm(Co, Cu)5 phases. The magnetic measurements of Sm12Co88−xCux ribbons were performed by vibrating sample magnetometer (VSM). The results exhibit that the maximum magnetic energy product ((BH)max), the coercivity (Hcj) and the remanence (Br) of the Sm12Co88−xCux ribbons increase generally with the increase in Cu substitution. In particular, the magnetic properties of the ribbons annealed at 1123 K and 673 K increase significantly with the increase in Cu substitution, resulting from the increase in the volume fraction of the formed Sm(Co, Cu)5 phase after heat treatment.

Evolution of magnetic and transport properties in the Cu-doped pyrochlore iridateEu2(Ir1−xCux)2O7

We have investigated the effect of Cu substitution in Eu2(Ir1-xCux)2O7 with the help of magnetic and transport property measurements. XPS measurement reveals that each Cu2+ converts Ir4+ to double amount of Ir5+ ions. The metal-insulator transition temperature (T_MI) is obtained around 120 K. In the insulating phase, at lower temperature below 50 K, the temperature dependent resistivity follows a power law dependence and the magnitude of the exponent increases with Cu concentrations. The temperature dependent thermopower is observed to follow the electrical resistivity down to 50 K, except for a sudden drop in thermopower at temperature below 50 K. We find negligible Hall voltage in the metallic regime of the samples but a sudden Hall voltage is developed below 50 K. We observe bifurcation in zero field cooled and field cooled (ZFC-FC) magnetization below irreversibility temperature, exchange bias and negative magnetoresistance at 3 K and the magnitude of all these properties increases with Cu concentrations. In the insulating region (below 6 K) there exists a linear specific heat and its coefficient decreases with Cu doping which indicates the reduction of spinon contribution with Cu doping.

Effect of Cu substitution on the type of magnetic phase transition and magnetocaloric effect in the ErCo2-xCux compounds

In this paper, the crystal structure, magnetic phase transition and magnetocaloric properties of the ErCo2-xCux (x = 0.12, 0.24, 0.36 and 0.48) compounds have been investigated in detail. All of the compounds crystallize in the C15 cubic Laves structure (MgCu2-type) with the Fd-3 m space group. The substitution of Cu for Co is accompanied by an increase of the Curie temperature Tc from 31.5 K to 68 K for x varying from 0.12 to 0.48. The nature of the magnetic phase transition, determined by the results of the Arrott plots and Landau theory, changed from a first order to a second order in the ErCo2-xCux compounds with the Cu content increasing. The isothermal entropy change -∆SM is calculated according to isothermal magnetization measurements using Maxwell’s relation. For an applied magnetic field change of 0–5 T, the -∆SM decreased from 30 J kg−1 K−1 for x = 0.12 to 10.9 J kg−1 K−1 for x = 0.48, whereas the working temperature range became wider due to that the magnetic transition type changed from a first order to a second order, which is a benefit for the application of the magnetic refrigeration. The corresponding refrigerant capacity RC values are 270.8 J kg−1, 194.1 J kg−1, 261.8 J kg−1 and 264.8 J kg−1, respectively.

The effects of Cu-substitution and high-pressure synthesis on phase transitions in Ni2MnGa Heusler alloys

The magnetic, structural, and thermal behaviors of the Cu-doped Heusler alloy Ni2Mn1−xCuxGa (0 ⩽ x ⩽ 0.4) were studied as a function of concentration x. As the Cu concentration increased, the structural transition temperatures increased, whereas the chemical order-disorder transitions and melting points decreased. The experimental results from temperature dependent X-ray diffraction reveal different crystal structures of the martensite phase at low temperatures for samples with different x, but all the samples ultimately crystallized in the L21 cubic crystal structure upon heating above their respective structural transitions. The experimental data were used to construct a comprehensive magnetic and structural phase diagram as a function of x from below their respective structural transition temperatures to their melting temperatures. The XRD analysis shows that the observed volume reduction is associated with the increasing structural transition temperature. Therefore, one of the samples was annealed under high pressure to permanently reduce its volume, and the correlation between the increasing structural transition temperatures and volumes was confirmed.

Effect of Cu Substitution on Magnetic Properties of Co0.6Ni0.4Fe2O4 Nanoferrites

This work is focusing on synthesizing the cobalt nanoferrite materials substituted by copper forming Co0.6Ni0.4-xCuxFe2O4 with x = 0.0, 0.1, and 0.3 using the sol-gel auto-combustion method. The phase analysis of XRD showed the spinel structure with the lattice parameter in the range 8.36-8.39 Å. FESEM image showed the grain size initially decreasing and then increasing with Cu concentration. The FTIR curve's two absorption bands in the specified range of frequency assured the spinel nano ferrite structure. The values of remanent ratios obtained from VSM showed their isotropic nature forming single domain ferrimagnetic particles.

Effect of Cu substitution on magnetic and DC electrical resistivity properties of Ni–Zn nanoferrites

Effect of Cu substitution on magnetic and DC electrical resistivity properties of Ni–Zn nanoferrites

Effect of Cu substitution on the structural, magnetic, and dc electrical resistivity response of Co0.5Mg0.5-xCuxFe2O4 nanoferrites

Effect of Cu substitution on the structural, magnetic, and dc electrical resistivity response of Co0.5Mg0.5-xCuxFe2O4 nanoferrites

Martensitic transformation and magnetocaloric effect in Mn<sub>50</sub>Ni<sub>32</sub><sub>–</sub><sub><italic>x</italic></sub>Cu<sub><italic>x</italic></sub>Co<sub>8</sub>Ti<sub>10</sub> Heusler alloy ribbons

<p indent="0mm">The effects of Cu substitution and annealing on the martensitic transformation behavior and magnetocaloric properties in all-<italic>d</italic>-metal Mn₅₀Ni_32–_{<italic>x</italic>}Cu_{<italic>x</italic>}Co₈Ti₁₀ (<italic>x</italic>=1, 2) alloy ribbons have been mainly investigated. After the substitution, it is observed that the martensitic transformation temperature of the alloys, which was extremely sensitive to the Cu content, was reduced. Moreover, the ferromagnetism of austenite increased, increasing the magnetization difference across the martensitic transformation. The magnetic-field-induced metamagnetic martensitic transformation also occurred. The magnetic entropy change gradually increased, and the effective refrigeration capacity increased by more than twice than that of the Cu-free substitution. Moreover, the sample with <italic>x</italic>=1 was utilized as the research object to study the effect of annealing on the martensitic transformation. After annealing, the martensitic transformation became slow and the austenite ferromagnetism decreased. The change in the magnetization across the phase transition was also reduced. The magnetic-field-induced metamagnetic martensitic transformation was also weakened. Consequently, the magnetic entropy change was greatly reduced. However, the effective refrigeration capacity did not reduce significantly because the refrigeration temperature interval increased largely. In this paper, the physical mechanisms of the effects of Cu substitution and annealing on the martensitic transformation were discussed from the change in the <italic>d</italic>-<italic>d</italic> interaction and the precipitation in the <italic>γ</italic>-phase, respectively.

Specific heat of Cu substituted GdNiSi

The specific heat of magnetic regenerator materials affects the efficiency of cryocoolers below 10 K. GdNiSi with the orthorhombic TiNiSi-type structure shows antiferromagnetic order at 11 K. To tune the magnetic transition temperature below 10 K, Cu substituted GdNiSi alloys were prepared. Powder X-ray diffraction and specific heat measurements were performed to study the effect of Cu substitution on the crystal structure and magnetic transition temperature. Increasing Cu content, the secondary phase which may be the hexagonal BeZrSi-type GdNi1−x Cu x Si is observed. The peak of the specific heat for x ≤ 0.2 was shifted higher temperature (13 K) due to the magnetic transition, though the unit cell volume of the TiNiSi-type structure slightly increased with increasing x. This result possibly originates from the increase of the RKKY interaction for the sinusoidal curve due to an increase of the intersite distance of Gd-ions.

Effect of Cu Incorporation on Structure, Densification and Magnetic Properties of Polycrystalline Li&amp;lt;sub&amp;gt;&amp;lt;i&amp;gt;x&amp;lt;/i&amp;gt;&amp;lt;/sub&amp;gt;Ni&amp;lt;sub&amp;gt;0.2&amp;lt;/sub&amp;gt;Zn&amp;lt;sub&amp;gt;0.8-2&amp;lt;i&amp;gt;x&amp;lt;/i&amp;gt;&amp;lt;/sub&amp;gt;Fe&amp;lt;sub&amp;gt;2+&amp;lt;i&amp;gt;x&amp;lt;/i&amp;gt;&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; Ceramics

The polycrystalline LixNi0.2Zn0.8-2xFex+2O4 and LixNi0.1Cu0.1Zn0.8-2xFex+2O4 (x = 0.0, 0.1, 0.2, and 0.3) ferrites were synthesized by the standard solid-state reaction method. The compound was sintered at 1150˚C for 5 hours. The effect of Cu substitution and its impact on the crystal structure, microstructure, complex initial permeability and magnetization of the Ni-Zn ferrites were studied. The effect of Li+ incorporation on the properties mentioned above was also investigated. X-ray diffraction patterns of the samples indicated a single cubic spinel structure for both the compound. No effect of Cu addition on crystal structure was observed. The density of the ferrites was found to be enhanced because of adding Li whereas the porosity of the samples decreased with the content of Li ions. The average value of grain size increased with the addition of Li content. The samples having Cu ions formed bigger size grains. Frequency-dependent complex initial permeability, loss tangent, and relative quality factor were studied at room temperature using an Impedance analyzer in the range of 100 Hz - 120 MHz regions. In the low-frequency region, the prepared samples exhibited a high value of permeability and after a certain frequency, the permeability falls. The value of permeability enhanced with the increase in Li whereas loss tangent was found to be reduced. The relative quality factor graphs described that the compound has excellent frequency stability up to a certain frequency which is suitable to be used in inductors, resistors, capacitors, etc. Initial permeability for LixNi0.1Cu0.1Zn0.8-2xFex+2O4 ferrites was found high than LixNi0.2Zn0.8-2xFex+2O4 which might be attributed to having bigger size grains of Cu containing samples because of easy movement of domain wall in bigger size grains. The values of saturation magnetization (Ms) were calculated for both compounds from M-H hysteresis loops and it enhanced with the increase in Li content which might be related to the modification of predominant exchange interactions between the cations. The Cu-containing compound exhibited higher values of saturation magnetization. The cation distribution reflects this increment because ferromagnetic Ni2+ and paramagnetic Cu2+ ions occupied in the B-sites and the diamagnetic Zn and paramagnetic Li occupied in the A-sites; therefore, net magnetic moments increased gradually. The studied materials might be used as an alternative to Pb-based compounds and would be environment friendly.