Ni Co-doping Research Articles

Room temperature dual ferroic behavior induced by (Bi, Ni) co-doping in nanocrystalline Nd0.7Bi0.3Fe1−xNixO3 (0 ≤ x ≤ 0.3)

Nanocrystalline samples of Nd0.7Bi0.3Fe1−xNixO3 (x = 0, 0.1, 0.2, and 0.3) are synthesized using sol-gel auto-combustion process to investigate their structural, electrical, magnetic, and thermal properties. Phase purity and crystallinity of the samples are determined through x-ray diffraction (XRD) data. XRD patterns along with Rietveld refinement reveal orthorhombic structure with Pbnm space group. Unit cell parameters, bond angles, and bond lengths for all the samples have been determined. Crystallite size calculated by Scherrer equation is found to be in the range of 15–21 nm. The characteristic bands in the FTIR spectra further confirm the formation of our samples. FE-SEM images indicate the homogeneous distribution of particles on large scale and Ni-doped samples show some wall-like nanostructure in the morphology. EDX spectra confirm the elemental composition without any impurity element. The polarization versus electric field (P-E) and magnetization versus magnetic field (M-H) loops exhibit the multiferroic nature of the material. The sample with concentration x = 0.2 shows the maximum value of polarization (Pm) while maximum magnetization is achieved for x = 0.1 concentration. The specific heat capacity (Cp), endothermic, and exothermic peaks of the materials have been determined in the broad temperature range with the help of DTA measurements in the controlled nitrogen atmosphere. The Neel temperature of the parent system is found to be 742 K and that decreases up to 573 K on Ni doping.

Structural, optical, magnetic, dielectric, and photocatalytic properties of Sm- and Ni-substituted BiFeO3 nanoparticles

A detailed study on synthesis and optical, magnetic, dielectric, and photocatalytic properties of Multiferroic co-doped Bi1−xSmxFe1−xNixO3 (x = 0.00, 0.02, 0.04, 0.06 and 0.08) (BSFNO) nanoparticles that have been prepared by tartaric acid-based sol–gel technique has been conducted. X-ray diffraction data show that high crystallite could be provided by the sharp peak and mergers of the doublet peaks, for instance (104) and (110), and (006) and (202), which indicates structural transition and XRD pattern shift towards higher angle, indicating structural distortion due to Sm and Ni co-doped BiFeO3. Raman spectroscopy also gives the confirmation of structural distortion and distorted rhombohedral perovskite structure with R3c symmetry. FESEM studies have revealed microstructural and nanocrystalline nature of BSFNO, a nanostructured material, and elemental analysis was done by EDX. The particle size of BSFNO (x = 0.02, 0.04) was analyzed by TEM and the average size of the particle was found to be ~ 50 nm. The identification of elements, chemical shift, oxidation state of elements ,and oxygen vacancies of the Sm and Ni co-doped BiFeO3 (x = 0.02 and 0.06) samples were analyzed by XPS. The calculated energy band gap values for BSFNO, a nanostructured material, were found to be 2.3 eV, 2.03 eV, 2.04 eV, 2.03 eV, 2.04 eV, respectively (from UV–VIS spectra). These results provide preliminary research for optoelectronic device and infrared detector. An enhancement in saturation magnetization has been observed with the substitution of Sm and Ni co-doped in BFO. Similarly enhancement in the dielectric constant (e) and dielectric loss (tanδ) has been observed with the substitution of Sm and Ni co-doping in BFO. The photocatalytic properties enhanced in co-doped BSFNO in comparison to pure BFO. The % efficiency and degradation of co-doped BSFNO increases when compared to pure BFO.

High Temperature Dielectric Response and AC Conductivity Mechanism of (Nd, Ni) codoped BiFeO3

BiFeO3(BFO)and Bi0.9Nd0.1Fe0.9Ni0.1O3 (BNFNO) nanocrystalline samples have been synthesized through the sol-gel auto combustion process. Frequency and temperature dependent dielectric measurements have been performed in order to apprehend the influence of (Nd,Ni) co-doping on the conduction mechanism of pristine BFO.Thereal part of the dielectric constant is found to increase with the Nd and Ni doping, which is accredited to higher space charge polarization induced by the dopant ions.The dielectric constant measured as a function of frequency exhibits a dispersivebehaviour within low frequency region and attains a constant value at higher frequencies. A thermally activated relaxation peak is found at around 500K in the BNFNO samplewhich shifts towards lower temperatures at higher frequencies. The AC conductivity follows the Jonscher’s universal dynamic law, which has been utilized to evaluate the value of frequency exponent ‘s’. The decrease in the value of the ‘s’ parameter with the increase in temperature establishes that the conduction mechanism is governed by the correlated barrier hopping (CBH) model. The ac conductivity data has been utilized to evaluate the minimum hopping distance (Rmin) and the binding energies (Wm) of the electrons in BNFNO. Arrhenius equation has been used to fit the experimental data and activation energy has been evaluated at different temperatures. The Activation energy is found to increase with the increase in the temperatures, owing to the creation of more oxygen vacancies instigated by (Nd, Ni) co-doping.

Effect of (Sn, Ni) co-doping on structural, optical and magnetic properties of ZnS Nanoparticles and thin films

Nanoparticles of Zinc Sulfide (ZnS) co-doped with Tin (Sn) and Nickel (Ni) have been synthesized using solid state reaction and the nanoparticles were then deposited on to glass substates by physical vapour deposition technique. The structural, morphological, optical and magnetic properties of the prepared nanoparticles and thin films were analyzed in detail. Single phase cubic structure was observed for both nanoparticles and thin films. The optical band gap became narrower for co-doped nanoparticles compared to the individually doped nanoparticles. The co-doped thin films showed a maximum transmittance (93%) in the visible region. The co-doped nanoparticles exhibited soft ferromagnetic nature at room temperature, while room temperature paramagnetic nature was observed in co-doped thin films.

Ni/Fe Codoped In2S3 Nanosheet Arrays Boost Photo‐Electrochemical Performance of Planar Si Photocathodes

AbstractThe photo‐electrochemical performance of the Si photocathode is seriously restricted by the severe charge recombination at the Si/electrolyte interface and sluggish hydrogen evolution reaction (HER) kinetics. Herein, a facile hydrothermal process is reported to integrate Ni/Fe codoped In2S3 nanosheet arrays onto the surface of unmodified a p‐Si photocathode for water reduction. The experimental results and density functional theory calculations indicate that the Ni and Fe codoping of In2S3 contributes to small surface transfer impedance, prolonged carrier lifetime, increased charge carrier concentration, and reduced overpotential for HER. Moreover, a p–n junction formed at the interface of Si and Ni/Fe:In2S3 promotes the photogenerated electron–hole separation and reduces the recombination in the bulk. As a result, the Si–Ni/Fe:In2S3 photocathode exhibits high performance with significantly enhanced photocurrent of −80.9 mA cm−2 at −1.3 VRHE and positive onset potential of 0.44 VRHE.

Studies on the effect of Ni and Ba co-doping on CdS nano structures

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Analysis of the co-doping effect of graphene and nano-Ni on grain connectivity and critical current density in MgB2 superconductors

MgB2 bulks codoped with graphene and nickel with a composition of Mg1−xNixB1.9G0.1 (x = 0.02, 0.04 and 0.06) have been synthesized by an in situ reaction method. The combination effect of graphene and Ni codoping on microstructure, critical current density (Jc) and irreversibility field (Hirr) of MgB2 has been studied. Graphene doping is more efficient than other forms of carbon doping for modifying the MgB2 microstructures due to the two-dimensional structures. The doping of Ni is confirmed to eliminate the porosity present in the graphene-doped sample by the assistance of a Mg–Ni eutectic liquid at low temperature. The results clearly indicate that graphene and Ni codoping are cooperative in improving the Jc of MgB2 bulks in the zero fields due to the superior grain connectivity and high density. The flux pinning by carbon substitution and MgNi2.5B2 nano-inclusions is expected to enhance the Jc value at high magnetic fields. However, the positive action has been extremely offset by the aggregation of impurity structures such as MgNi2.5B2, MgO and over-doped graphene. Consequently, a delicate balance between graphene and Ni, homogeneous dispersion of nano-inclusions in MgB2 grains and more lattice defects are further required to increase the flux pinning centers.

Facile preparation of Ti3+/Ni co-doped TiO2 nanotubes photoanode for efficient photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting using TiO2-based nanostructures is one of the most promising strategies for sustainable energy development. Here we reported Ti3+/Ni co-doped TiO2 nanotubes for high-efficiency PEC water-splitting. The co-doped photoanode was prepared through Zn reduction of Ni-doped TiO2 nanotubes grown on TiNi alloy. Ti3+/Ni co-doping modified the energy band structure and narrowed the band gap to 2.84 eV, which enhanced optical absorption, increased the charge carriers, density and promoted charge separation-transport process. A remarkable solar to hydrogen conversion efficiency of 1.51% was achieved, which was about 10 times that of undoped TiO2. This work will facilitate developing novel co-doping approaches of Ti3+ species and other elements for enhancing PEC activity of undoped TiO2 nanotubes.

Theoretical investigation of Ti and Ni co-doping on the anti-disproportionation ability of ZrCo alloy

First-principles calculations are utilized to investigate the effect of Ti and Ni co-doping on the anti-disproportionation ability of ZrCo alloy. In Ti and Ni co-doped ZrCoH3, the Ti-H(8e) bond shows a strong ionic feature and the Ni-H(8e) bond exhibits covalent bonding characteristic. Judged by the Zr-H(8e) bond length, the size of the 8e site and H diffusion barrier out of the 8e site in ZrCoH3, it can be concluded that the Ti + Ni co-doping can impair the anti-disproportionation ability of Ti doping in ZrCo alloy, which uncovers the mechanism of the negative effect of Ni on the Ti-doped ZrCo alloy found in the previous experimental results.

ENHANCED FERROELECTRICITY AND FERROMAGNETISM OF (Y, Ni) CO-DOPED BiFeO3 MATERIALS

In this study, multiferroicMultiferroic Bi1-xYxFe0.975Ni0.025O3 (x = 0.00, 0.05, 0.10, and 0.15) called as (Y, Ni) co-doped BiFeO3 materials were synthesized by a sol-gel method. and characterized by X-ray diffraction diagrams and(XRD), energy-dispersive X-ray (EDX) and vibrating sample magnetization (VSM) measurements demonstrated. The result showed that Bi1-xYxFe0.975Ni0.025O3all investigated materials waspresent a single phase of the perovskite-type rhombohedral structure. Ferromagnetism and ferroelectricity of the Bi1-xYxFe0.975Ni0.025O3 materials have been investigated. Results showed that the co-doping by (Y, Ni) for (Bi, Fe) have affected in enhancing by the (Y, Ni) co-doping, as a result the ferroelectric polarization and magnetization of BiFeO3. The magnetic characterization indicated that the ferromagnetic behavior wasthe initial BiFeO3 materialwere enhanced with increasing concentration of Y3+ for (Y, Ni) co-substituted of BiFeO3. Which could beion. It is attributed to the defferentdifference of the magnetic momentmoments of Ni2+ and Fe3+, and+ ions, as well as the Y3+-Fe3+,+ and Y3+-Ni2+ super-exchange interaction. Theinteractions. The characteristics of the investigated materials, such as remanent magnetization (Mr), saturation magnetization (Ms), remanent polarization (2Pr) and saturation polarization (2Ps) continuously increase upon increasing in the range of x from 0.00 to 0.15. When x = 0.15, the values of Mr and Ms are 0.078 and 0.794 emu/g, respectively. The values of 2Pr and 2Ps are 16.58 and 27.99 µC/cm2, respectively. Origin of ferromagnetic and ferroelectric properties of Bi1-xYxFe0.975Ni0.025O3 materials will be discussed in this paper.

Ni–Mg co-doped ZnO nanoparticles as a novel catalyst for hydroxylation of benzene to phenol

Mg and Ni were introduced as the novel co-doping materials for synthesizing Mg and Ni co-doping ZnO nanoparticles (NPs) through the simple wet chemical method. Photocatalyst properties of Mg and Ni co-doping ZnO NPs were studied by hydroxylation of benzene to phenol at room temperature. Furthermore, the doped Mg and Ni cause the hydroxylation capability of ZnO to be enhanced which can be attributed to the presence of Mg and Ni on the ZnO NPs which greatly increases absorption in under the ultraviolet (UV) light range enabled by the surface plasmon resonance effect from Mg and Ni. In addition, an attempt was made to investigate the effects of several parameters such as hydroxylation reaction time, solvent, and concentration of H2O2 and photocatalyst, and UV irradiation on the hydroxylation yield. Mg and Ni co-doping ZnO NPs showed significant hydroxylation after two recyclings, resulting in 85 and 77% in the first and second recycling processes, respectively.

Ni and Se co-doping increases the power factor and thermoelectric performance of CoSbS

Ni and Se co-doping increases the DOS effective mass and softens the chemical bonding, resulting in the highest ZT ∼ 0.58, 222% improvement over that of CoSbS.

A study of the influences of transition metal (Mn,Ni) co-doping on the morphological, structural and optical properties of nanostructured CdO films

In this paper, a systematic investigations on the effects of transition metals such as Mn and Ni-dopant on physical properties of cadmium oxide (CdO) thin films coated on soda lime glass substrates by using SILAR method have been reported. The characterizations of un-doped, Mn-doped (Cd0.99 Mn0.01O) and Mn/Ni double doped CdO [(Cd0.99−xMn0.01NixO)(0 ≤ x ≤ 0.001)] films were investigated by SEM, EDX, XRD and UV–Vis spectrophotometry to determine the morphological, structural and optical properties, respectively. SEM analysis showed that the surface morphologies of the CdO films were influenced by Mn doping and Mn/Ni co-doping. The EDX result verified the presence of expected elements Cd, O, Mn and Ni in the growing solution. The crystal phases of the samples and their crystallinity quality have been investigated by XRD measurements. The X-ray diffractograms show all the diffraction peaks are highly intense also they demonstrate the preferential orientations of (111) and (200) directions. Optical investigations revealed red shift with Mn doping and Mn/Ni co-doping in the absorbance spectrum.

Double Metal Co-Doping of TiO2Nanoparticles for Improvement of their SERS Activity and Ultrasensitive Detection of Enrofloxacin: Regulation Strategy of Energy Levels

In this paper, the strategy of double metals (Ni and Zn) codoping was carried out for improving SERS activity of TiO2 nanoparticles (NPs). Accordingly, pure TiO2 and different metals doped TiO2 (Zn-TiO2, Ni-TiO2 and Ni−Zn-TiO2) NPs substrates were synthesized by a sol-hydrothermal method. The results show that, compared to the other substrates, 4-mercaptobenzoic acid (4-MBA) probe molecules on the Ni−Zn-TiO2 exhibit the largest SERS enhancement, which is attributed to the contributions of double metals codoping. Ni and Zn codoping can simultaneously result in the abundant surface state levels and metal doping levels in the TiO2 band gap; both of them together promote the charge transfer from TiO2 to molecule and consequent SERS enhancement of probe molecule. And importantly, Ni−Zn-TiO2 NPs can be served as the efficient SERS-active substrate for the detection of enrofloxacin (ENR) drug. Under the optimal test conditions, the limit of detection of ENR on the 1 %Ni-1 %Zn-TiO2 substrate can be reduced to 3×10−10 M, which is far lower than the standard of European Union, and there is a good linear relationship in the wide low concentration range of 1×10−4∼1×10−9 M.

The electronic structure, optical absorption and photocatalytic water splitting of (Fe + Ni)-codoped TiO2: A DFT + U study

The electronic and optical properties of Fe or/and Ni (co)doped anatase and rutile TiO2 were investigated using the spin-polarized density functional theory. Our calculated results indicate that the synergistic effect of (Fe + Ni) codoping can lead to a band gap narrowing and the hybridized states of Fe 3d and Ni 3d appearing in the forbidden gap, which enhances greatly the optical absorption of TiO2 nanomaterials from the ultraviolet-light to the infrared-light region and reduces the recombination of photogenerated electron–hole pairs. In particular, (Fe + Ni) codoping can improve greatly the infrared-light absorption of TiO2 nanomaterials. Furthermore, the researches of electronegativity show that (Fe + Ni)-codoped TiO2 system has a stronger redox power for hydrogen generation by photocatalytic water splitting compared with pure, Fe-doped, and Ni-doped TiO2 systems. These results lead to an outstanding solar energy photocatalytic water splitting for hydrogen generation in (Fe + Ni)-codoped TiO2 photocatalyst.

Effect of Co and Ni codoping on the structural, magnetic, electrical and optical properties of ZnO

Co and Ni codoped ZnO-based dilute magnetic semiconductors having a general formula of Zn0.9Co0.1−xNixO (x=0.0, 0.02, 0.04, 0.06, 0.08 and 0.10) have been prepared using a simple solid-state reaction method. A single-phase hexagonal wurtzite structure, confirmed by X-ray diffraction, has been developed for Zn0.9Co0.1−xNixO (x<0.05), while minor secondary peaks of NiO were detected in samples having x=0.06, 0.08 and 0.10. The study of surface morphology revealed grain sizes in the range of 1.41–0.71μm. Raman spectra in the 200–800cm−1 range have been studied. The direct band gap energy for all the samples was found to be less than that of pure ZnO. Fourier transform infrared spectroscopy and UV–vis spectroscopy confirmed the incorporation of the Co and Ni ions into a ZnO lattice. Magnetic characterisation performed by vibrating sample magnetometer exhibited room-temperature ferromagnetism. Temperature-dependent electrical resistivity measurements were performed using a four-point probe technique.

Effects of Lu and Ni Substitution on Thermoelectric Properties of Ca3Co4O9+δ

Effects of (Lu, Ni) co-doping on the thermoelectric properties of Ca3Co4O9+δ (CCO) have been systematically investigated from 20 K to 350 K. The electrical resistivity and thermopower of (Lu, Ni) co-doped samples increase, while their thermal conductivity is significantly depressed as compared to that of pristine CCO. The figure of merit (ZT) of co-doped samples is higher than those of Lu-doped samples and pristine CCO. A maximum ZT of 0.0185 is achieved at 350 K for Ca2.9Lu0.1Co3.9Ni0.1O9+δ . We demonstrate that the simultaneous increase of spin entropy and phonon scattering induced by (Lu, Ni) co-doping boosts ZT of CCO. This study indicates that (Lu, Ni) co-doping may promise an effective way to improve thermoelectric properties of the CCO system.

Effects of Ni co-doping concentrations on dielectric and magnetic properties of (Co, Ni) co-doped SnO2 nanoparticles

In this work, the dielectric and magnetic properties of (Co, Ni) co-doped SnO2 nanoparticles were studied using ac impedance spectroscopy and magnetic properties measurement system or quantum design superconducting quantum interference device. Results showed that dielectric constant (er), dielectric loss (e″), and ac electrical conductivity (σAC) are strongly frequency dependent. A decrease in frequency was accompanied with an increase in er and e″ values, whereas, a decrease in the dielectric constant was observed with the increase of Ni co-doping concentration. It was found that the dielectric constant and dielectric loss values decrease, whilst AC electrical conductivity increases with increase in co-doping concentration. Magnetization measurements revealed that the Ni co-doped SnO2 samples exhibits room temperature ferromagnetism. The results illustrate that (Co, Ni) co-doped SnO2 nanoparticles have an excellent dielectric, magnetic properties, and high electrical conductivity than those of co-doped samples reported previously, indicating that these (Co, Ni) co-doped SnO2 materials can be suitable for the purpose of high frequency device and spintronic applications.

Structural, morphological, optical properties and wettability of spin-coated copper oxide; influences of film thickness, Ni, and (La, Ni) co-doping

Controlling the properties of nano-sized copper oxide (CuO) is an interesting approach for broadening its multifunctionality. This paper reports the deposition of CuO thin films on ultrasonically cleaned glass substrates. The sol–gel spin coating technique was employed to prepare un-doped films with different thickness, Ni-doped and (La, Ni) co-doped CuO films in the formulas; Cu1−x Ni x O (0 ≤ x ≤ 0.06) and Cu0.94−y Ni0.06La y O (0.02 ≤ y ≤ 0.06). The structural and morphological properties were studied by X-ray diffraction (XRD), Fourier transformation infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). The optical and wetting properties were investigated by UV–Vis spectrophotometer and water contact angle (WCA) measurement, respectively. XRD and FTIR results confirm the synthesis of nanostructured CuO of monoclinic structure. The average crystallite size, D, is dependent on the number of the coated layers of the pure CuO film. The value of D increased from 22.2 nm for the four-layered CuO film to 24.2 nm upon the incorporation of 6 % Ni content. Then, it decreased to 11.4 nm after the co-doping with 6 % La. Ni doping improved the (002) preferential orientation and La co-doping reduced the crystallinity of the films. The films are hydrophilic and their wetting properties were enhanced by increasing the film thickness and La incorporation. Ni and La co-doping could efficiently control transmittance, optical band gap, and the refractive index of the films. The existence of stable copper oxide films at room temperature with band gaps around 2.0 eV supports their use in catalysts and gas sensing applications as well as in optoelectronics and solar technologies.

Effects of Ni and Mn doping on physicochemical and electrochemical performances of LiFePO4/C

The LiNixFe1−xPO4/C (x = 0.00, 0.01, 0.02, 0.03, 0.04), LiMnyFe1−yPO4/C (y = 0.00, 0.01, 0.02, 0.03, 0.04) and LiNi0.02Mn0.03FePO4 composites have been successfully synthesized by a simple solid-state method. The structure, morphology and electrochemical property of the as-prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and charge/discharge tests. The XRD patterns indicate that doping with Ni2+ or Mn2+ do not affect the structure of olivine LiFePO4. The results of electrochemical performance measurements reveal that the LiNi0.02Fe0.98PO4/C shows the best electrochemical performance among all of the single Ni-doped samples. Meanwhile, comparing with other single Mn-doped materials, the LiMn0.03Fe0.97PO4/C show the highest initial discharge capacity and excellent cyclic stability. In order to further improve the electrochemical performance of LiFePO4/C, LiNi0.02Mn0.03Fe0.95PO4/C composite with Ni and Mn co-doping was also synthesized by the same route. Relative to other samples, the LiNi0.02Mn0.03Fe0.95PO4/C delivers higher initial discharge capacity of 164.3 mAh g−1 at a rate of 0.1 C. Moreover, it also exhibits excellent cyclic stability with capacity retention of 98.7% cycled at 1 C after 100 cycles. CV shows that the Ni and Mn dual-doping reduce the electrode polarization, which may be the important factors for improving the electrochemical properties of the cathode materials.