Effect Of Mg Doping Research Articles

Gallium Nitride‐based Materials as Promising Catalysts for CO2 Reduction: A DFT Study on the Effect of CO2 Coverage and the Incorporation of Mg Doping or Substitutional In

AbstractCatalytic CO2 conversion to fuels and chemicals is important for mitigating the climate change and reducing the dependence on fossil resources. In order to achieve this goal on a large industrial level, effective catalysts need to be developed. Among them, gallium nitride (GaN) and related Mg‐doped and In‐alloyed systems have been proven as efficient materials for the reduction of highly stable CO2 molecules. This work presents a density functional theory (DFT) investigation, performing periodic boundary condition (PBC) calculations which allow to employ a more extended surface for a detailed analysis of the CO2 coverage, and the effect of Mg doping and In alloying on the CO2 adsorption and its conversion to CO. The results show the great potential of GaN(100) surfaces to simultaneously bind and strongly activate multiple CO2 molecules, which is a crucial aspect for an efficient CO2 conversion process. Moreover, the presence of Mg‐dopant on the top layer is found to be more beneficial for the CO2 adsorption and activation with respect to both the pristine and In‐alloyed system, and this effect is further improved by the inclusion of a second impurity on the top layer. In line with the previous experimental findings, these calculations support the potential of pristine GaN(100) to catalyze the CO2‐to‐CO reduction. The results presented here offer crucial information for the development of more efficient and selective catalysts for the CO2 reduction.

Effects of Mg-doping on distorted structure and enhanced electrochemical performance of V1-Mg O2 nanorods

In this work, a series of V1-xMgxO2 samples (x = 0–0.030) were synthesized by hydrothermal method. The corresponding laws of Mg2+ doping concentration on the microstructures and electrochemical performance of V1-xMgxO2 were studied in detail. The XRD results indicated that the prepared V1-xMgxO2 samples showed monoclinic crystal phase and Mg2+ doping caused lattice distortion in the experimental doping range. The SEM and TEM results showed that all the V1-xMgxO2 samples were nanorods and well-crystallized. The positron lifetime spectra showed that the main defects in the V1-xMgxO2 samples were vacancy clusters. The concentration and size of the defects were affected by the combined action of ion radius and valence state of doped Mg2+. The electrochemical results revealed that the samples showed better electrochemical properties when the Mg2+ doping concentration x is 0.015. The high discharge capacitance of the x = 0.015 sample reached 140.6 F/g and the capacitor retention of this sample was still about 90 % after 1000 cycles.

Effect of Mg-doping and Fe-doping in lead zirconate titanate (PZT) thin films on electrical reliability

Uniformly acceptor doped Pb(Zr0.48Ti0.52)O3 (PZT) films with 2 mol. % Mg or Fe prepared by chemical solution deposition exhibited decreased dielectric constants and remanent polarizations relative to undoped PZT. For highly accelerated lifetime testing (HALT) at 200 °C and an electric field of 300 kV/cm in the field up direction, the HALT lifetimes (t50) for undoped, Mg-doped, and Fe-doped PZT films were shortened from 2.81 ± 0.1 to 0.21 ± 0.1 and 0.54 ± 0.04 h, respectively. Through thermally stimulated depolarization current measurement, significant VO∙∙ electromigration was found in homogeneously Mg-doped PZT thin films, a major factor in their short HALT lifetime. Because the concentration of oxygen vacancies increases with uniform acceptor doping, the lifetime decreases. In contrast, when a thin layer of Mg-doped or Fe-doped PZT was deposited on undoped PZT or Nb-doped PZT (PNZT), the HALT lifetimes were longer than those of pure PZT or PNZT films. This confirms prior work on PNZT films with a Mn-doped top layer, demonstrating that the HALT lifetime increases for composite films when a layer with multivalent acceptors is present near the negative electrode during HALT. In that case, the compensating electrons are trapped, presumably on the multivalent acceptors, thus increasing the lifetime.

Modulating the Energy Band Structure of the Mg-Doped Sr0.5Pr0.5Fe0.2Mg0.2Ti0.6O3-δ Electrolyte with Boosted Ionic Conductivity and Electrochemical Performance for Solid Oxide Fuel Cells.

Achieving fast ionic conductivity in the electrolyte at low operating temperatures while maintaining the stable and high electrochemical performance of solid oxide fuel cells (SOFCs) is challenging. Herein, we propose a new type of electrolyte based on perovskite Sr0.5Pr0.5Fe0.4Ti0.6O3−δ for low-temperature SOFCs. The ionic conducting behavior of the electrolyte is modulated using Mg doping, and three different Sr0.5Pr0.5Fe0.4–xMgxTi0.6O3−δ (x = 0, 0.1, and 0.2) samples are prepared. The synthesized Sr0.5Pr0.5Fe0.2Mg0.2Ti0.6O3−δ (SPFMg0.2T) proved to be an optimal electrolyte material, exhibiting a high ionic conductivity of 0.133 S cm–1 along with an attractive fuel cell performance of 0.83 W cm–2 at 520 °C. We proved that a proper amount of Mg doping (20%) contributes to the creation of an adequate number of oxygen vacancies, which facilitates the fast transport of the oxide ions. Considering its rapid oxide ion transport, the prepared SPFMg0.2T presented heterostructure characteristics in the form of an insulating core and superionic conduction via surface layers. In addition, the effect of Mg doping is intensively investigated to tune the band structure for the transport of charged species. Meanwhile, the concept of energy band alignment is employed to interpret the working principle of the proposed electrolyte. Moreover, the density functional theory is utilized to determine the perovskite structures of SrTiO3−δ and Sr0.5Pr0.5Fe0.4–xMgxTi0.6O3−δ (x = 0, 0.1, and 0.2) and their electronic states. Further, the SPFMg0.2T with 20% Mg doping exhibited low dissociation energy, which ensures the fast and high ionic conduction in the electrolyte. Inclusively, Sr0.5Pr0.5Fe0.4Ti0.6O3−δ is a promising electrolyte for SOFCs, and its performance can be efficiently boosted via Mg doping to modulate the energy band structure.

Effect of Mg doping on the optical properties of nanostructures CdO Thin film

The performance of first principles computations of nanostructured CdO and Cdo:Mg grown by spray pyrolysis method (SPM) was studied, using density functional theory (DFT)). The structural and optical behaviour with XRD and ultraviolet visible spectroscopy. DFT displayed that Cd32O32 cluster and doped magnesium have cubic with rock salt structures. The optical bandgap of nanostructure films were obtained, while theoretically calculated for Mg-doped CdO cubic structures. The optical data displayed that the magnesium doped increase optical energy gap. Moreover, Optical results displayed that reflectivity of the nanostructure films varied from (400–900 nm) range with doping. While experimental transmittance was increased about 55% for 4% and decreased to 48% for 8% concentrations.

Effect of magnesium doping on discontinuous precipitation in age-hardenable copper–titanium alloys

One of the most important goals in the development of Cu-based alloys for electrical engineering applications is the realization of materials with both high mechanical strength and electrical conductivity. Cu-Ti alloys are promising alternatives to Cu-Be alloys, which are expensive and can be hazardous to health. Herein, an age-hardenable binary Cu96Ti4 alloy and its Mg-doped analog were compared by advanced electron microscopy techniques. The mechanical properties of the Mg-doped alloy are superior to those of the binary alloy. The effects of Mg-doping on the microstructure are investigated by atomic-scale scanning transmission electron microscopy combined with energy-dispersive X-ray spectroscopy. The Cu96Ti4 (at.%) solid-solution alloy developed lamellar aggregates when subjected to prolonged aging treatment at 450 °C for 100 h owing to discontinuous precipitation (DP) along the grain boundaries. The DP consisted of a face-centered cubic (FCC) Cu solid-solution phase (denoted as α-Cuss) and a stable Cu4Ti intermetallic phase (β-Cu4Ti). Conversely, while the Cu94Ti4Mg2 counterpart had similar lamellar aggregates, the amount of these aggregates was reduced, and no β-Cu4Ti phase was observed. The lamellar in the Cu94Ti4Mg2 counterpart consisted of two distinct FCC Cuss phases with different Ti-solute contents. Accordingly, the possible effects of Mg doping on the local structures of the DP in the Cu-Ti alloy are explained, and the structural characteristics of the DP that may result in improved mechanical properties is discussed.

Mg substitution effect on the electron affinity of ZnO films

We investigated the effect of Mg doping on the electron affinity of ZnO thin films. MgxZn1−xO (x = 0–0.29) composition-gradient films were deposited on an α-Al2O3(001) substrate using combinatorial pulsed laser deposition. The combinatorial high-throughput analysis of the optical transmittance systematically revealed that the bandgap of ZnO films was tunable between 3.3 and 4.0 eV by doping the ZnO thin films with Mg2+ ions. To investigate the electronic structure, photoelectron yield spectroscopy measurements were performed on the MgxZn1−xO composition-gradient films. The ionization potential, which denotes the distance between the valence band maximum and vacuum level, was independent of the Mg content in the ZnO films. By comparing with the optical bandgap results, the electron affinity was tunable from 4.1 to 3.5 eV by the Mg content in the MgxZn1−xO films.

Effect of Mg Doping on the Physical Properties of Fe2O3 Thin Films for Photocatalytic Devices.

Undoped and Mg-doped (y = [Mg2+]/[Fe3+] = 1, 2, 3, and 4 at.%) Fe2O3 thin films were synthesized by a simple spray pyrolysis technique. The thin films were extensively characterized. X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) analysis confirmed the successful insertion of Mg in the rhombohedral structure of Fe2O3. In addition, scanning electronic microscope (SEM) and confocal microscope (CM) images showed a homogenous texture of the film, which was free of defects. The rough surface of the film obtained by spray pyrolysis is an important feature for photocatalysis and gas sensor applications. The direct band gap of the doped Fe2O3 films obtained for [Mg2+]/[Fe3+] = 3 at.% was Edir = 2.20 eV, which recommends the Mg-doped iron oxide as an optical window or buffer layer in solar cell devices. The photodegradation performance of Mg-doped Fe2O3 was assessed by studying the removal of methylene blue (MB) under sunlight irradiation, with an effective removal efficiency of 90% within 180 min. The excellent photodegradation activity was attributed to the strong absorption of Mg-doped Fe2O3 in the UV and most of the visible light, and to the effective separation of photogenerated charge carriers.

Effect of Mg doping on magnetic, and dielectric properties of NiCr2O4 nanoparticles

The structural, magnetic, and dielectric properties of spinel Magnesium (Mg) doped Nickel chromite (NiCr2O4) nanoparticles (NPs) have been studied in detail. The X-ray powder diffraction exhibited normal spinel phase formation of MgxNi1-xCr2O4 (x = 0, 0.2, 0.4, 0.6, and 1) NPs with a maximum average crystallite size of about 44 nm for x = 0.2 composition. The FTIR spectra of these NPs revealed the characteristic Ni–O and Mg–O and Cr–O bands around 639 cm−1 and 497 cm−1, respectively which confirmed the spinel structure. Temperature-dependent zero field cooled and field cooled graphs of NiCr2O4 NPs showed phase changes from ferrimagnetic to paramagnetic state at 86 K, while MgCr2O4 NPs showed antiferromagnetic (AFM) transition at Neel temperature (TN) at 15 K due to corner-sharing of Cr3+ ions at a tetrahedral lattice site resulting in a highly magnetic frustrated structure. The field dependent magnetization (M − H) loops of MgxNi1-xCr2O4 NPs confirmed the competing AFM interactions and ferrimagnetic interactions resulting in a sharp decreased saturation magnetization with Mg doping. Dielectric constant, dielectric loss, and ac conductivity of these NPs showed size-dependent variation and depicted maximum value at x = 0.2 Mg concentration. In summary, the magnetic and dielectric properties of Mg doped NiCr2O4 NPs were modified by variations in the average crystallite size and magnetic exchange interactions, which may be suitable for different technological applications.

Study of electronic, thermoelectric and optical properties of environment friendly Mg doped CeO2 for energy harvesting devices

According to the recent investigations on transition metal oxides it is shown that they have exceptional thermoelectric and optical properties. In this context, present study reports the effect of Mg doping on the electronic, thermoelectric, and optical properties of CeO2, through experimental and DFT calculations. These results are obtained, supposedly due to the ability of ceria nanoparticles to rapidly store and release oxygen, as it acts as an oxygen buffer. Further optimization can be expected by doping Mg which can increase the electrical conductivity of the ceria nanoparticles, thereby increasing the figure of merit. Effect of Mg can also be seen in the electronic and optical behavior of ceria nanoparticles as the band-structure of the system changes. All these changes result in thermoelectric figure of merit approaching to 2 ± 0.2 at room temperature and above.

Enhancing the catalytic performance of calcium-based catalyst derived from gypsum waste for renewable light fuel production through a pyrolysis process: A study on the effect of magnesium content

The thermochemical conversion of abundant renewable resources through pyrolytic catalysis cracking (PCC) is one of the most promising technologies for producing green biofuels. In this study, the pyrolysis of palm oil was investigated over a sustainable CaO-based catalyst derived from waste gypsum. PCC was conducted in a continuous packed-bed reactor under atmospheric pressure without purge gas. The effects of Mg doping and reaction temperature were also examined. A wet ball milling process was used to prepare the well-mixed catalysts and to subsequently form a heterojunction structure between the CaO and MgO particles. CaO was synthesized using the Ca(OH)2 derived from the reaction between gypsum and sodium hydroxide. The pyrolytic oil was separated from the crude oil to remove water and other impurities. The pyrolytic oil was then distilled following ASTM D86, and the three separated products were classified as bio-gasoline, bio-kerosene, and bio-diesel. The highest renewable light fuel volume (bio-gasoline and bio-kerosene) of about 75% (74 %wt.) was obtained at a reaction temperature of 525 °C with 10% MgCO3 content. The percent volume of light fuel increased with increasing reaction temperature. Renewable light fuel production over the Mg-doped CaO-based catalyst was related to both the Mg content and reaction temperature.

Effect of Magnesium Doping on Voltage Decay of Nickel‐Rich Cathode Materials

AbstractStructural degradation is the main challenge of Nickel‐rich cathodes, leading to capacity and voltage fading, especially at high cut‐off voltages. Herein, LiNi0.94‐xCo0.06MgxO2 (x=0, 0.01, 0.02) samples have been prepared by high‐temperature solid‐state reaction method. The effects of Mg doping on its crystalline structure, and electrochemical performance have been studied by various characterizations analysis. We notice that Mg doping can not only tighten the structure/interface stability of the cathode, but also accelerates the Li+ diffusion, thereby significantly achieving its high voltage/cycle stability. High‐voltage (4.5 V) electrochemical results show that Mg‐doped LiNi0.94Co0.06O2 (1 % Mg) can achieve a high reversible capacity of 217.5 mAh g−1 at 0.2 C, high cycle retention rate of 80.5 % after 100 cycles at 0.2 C, inhibits average voltage decay, suppress resistance rise and boosted rate performance. Our work provides a solid strategy for improving the structure and voltage decay of nickel‐rich cathode materials for future high‐energy lithium‐ion batteries.

Effects of Mg doping on structural and optoelectronic properties of p-type semiconductor CuCrO2 thin films

In this study, CuCrO2 thin films are doped with Mg. In the experiment, the Mg content of CuCr1−xMgxO2 (x = 0, 0.015, 0.035, 0.055, 0.075, and 0.095) is increased gradually from 0.2 at% (x = 0.015) to 2.17 at% (x = 0.095) for increased carrier concentration and electrical conductivity. The amounts of Cu, Cr, and O in the CuCrO2 thin films diverge from the atomic stoichiometric ratio (Cu/Cr/O ratio = 25:25:50). In particular, the thin films contain less Cu and Cr and more O than this ratio, which is suitable for p-type conduction. The results show that Mg is present in the lattice sites of delafossite CuCrO2 and that Mg doping influences the structural and photoelectric properties. By increasing the amount of Mg, the root-mean-square roughness of the thin films decreases from 23.4 to 16.6 nm. In addition, an appropriate increase of Mg doping in the CuCrO2 thin films yields enhanced transmittance of visible light and enhanced absorption of ultraviolet light (300–400 nm). With the increasing amount of Mg, the band gap of CuCrO2 increases from 3.09 eV (undoped, x = 0) to 3.12 eV (x = 0.095). The experiment shows that replacing Cr3+ with Mg2+ effectively increases the concentration of carriers, leading to a 64-fold increase in electrical conductivity from 2.43 × 10−2 to 1.56 (Ω-cm)−1. A mechanism based on point defects for electrical conduction of hole carriers is proposed. Mg-doped CuCrO2 is thus a candidate for an optoelectronic semiconductor with desirable properties.

Effect of Mg Doping on SnO2 Energy Band and Power Conversion Efficiency of Dye-Sensitized Solar Cells

In this work, Mg-doped SnO2 materials with different molar ratios were synthesized by hydrothermal method. Based on the UV-Vis study, band gap (Eg) of the Mg-doped SnO2 is adjusted from 3.76 eV to 3.65 eV via 3 at% concentrations. Results of photovoltaic measurement for dye-sensitized solar cells (DSCs) based on Mg-doped SnO2 film as photoanode indicate that the doping of Mg ions can improve the open-circuit voltage (V oc) of the DSCs, while the electric current density (J sc) of the DSCs is almost unchanged. The cells were measured at 3 days intervals within 24 days after fabrication. Power conversion efficiency (PCE) of 3 at% Mg-doped SnO2 DSCs increases step by step and achieves 4.38% as the cell is tested after 18 days. Electrochemical impedance spectroscopy (EIS) analysis shows that Mg doping enhances light collection, increased the number of photogenerated electrons and inhibits charge recombination.

Probing the effect of Mg doping on triclinic Na2Mn3O7 transition metal oxide as cathode material for sodium-ion batteries

Triclinic Na2Mn3O7 has been identified as a promising material for high-capacity sodium-ion batteries. However, the knowledge on the effect of doping of metal ions and structural transformations of Na2Mn3O7 during dis(charge) is limited. Integration of alkali metal-ions, specially Mg2+ can enhance the electrochemical properties in transition metal oxides. Herein, a series of Mg2+ doped triclinic Na2Mn3O7 cathode materials was explored for the first time. Electrochemical analysis revealed that Mg2+ improves specific capacities, and rate capabilities. Ex situ X-ray diffraction (XRD) and Galvanostatic charge discharge cycling (GCD) showed that the triclinic phase reversibly converts into two monoclinic phases at high Na+ insertion levels. Na+ extraction at high potentials is supported by another biphasic region which converts to a major triclinic phase at the end of the charge. GCD, cyclic voltammetry (CV) and ex situ X-ray absorption spectroscopy (XAS) documented that the capacity mainly evolved through a Mn4+/3+ redox couple and a reversible O2-/n− redox reaction. CV and Galvanostatic intermittent titration techniques (GITT) showed that Mg2+ reduces the Na+-vacancy ordering and improves the Na+ diffusion. The 2 mol.% Mg-doped material exhibited a high specific capacity of 143 mAh/g after 30 cycles and a rate capability of 93 mAh/g (at 500 mA/g). GCD analysis demonstrated that O2-/n− redox is remarkably stable up to at least 90 cycles. Full cells made using the 0.5 mol.% Mg-doped material displayed a promising discharge specific capacity of 80 mAh/g. The effects of cation doping into the complex crystal structures, phase transformations during Na+ de(intercalation) and the importance of O2-/n− redox for achieving high capacities were uncovered. The findings of this work will guide the design of novel cathode materials for sodium-ion batteries.

Effects of Mg doping and annealing temperature on the performance of Mg-doped ZnO nanoparticle thin-film transistors

Mg-doped ZnO nanoparticle (NP) thin-film transistors (TFTs) were fabricated using a solution process under a range of Mg content and annealing temperature conditions. The effects of Mg doping and annealing on the electrical properties of the Mg-doped TFTs were investigated. The experimental results demonstrate that critical Mg doping and thermal annealing improve the electrical characteristics of the TFTs. It can mainly be attributed to the suppression of oxygen vacancy formation verified from X-ray photoelectron spectroscopy (XPS) analyses and Hall measurements.

High Hole Concentration and Diffusion Suppression of Heavily Mg-Doped p-GaN for Application in Enhanced-Mode GaN HEMT

The effect of Mg doping on the electrical and optical properties of the p-GaN/AlGaN structures on a Si substrate grown by metal organic chemical vapor deposition was investigated. The Hall measurement showed that the activation efficiency of the sample with a 450 sccm Cp2Mg flow rate reached a maximum value of 2.22%. No reversion of the hole concentration was observed due to the existence of stress in the designed sample structures. This is attributed to the higher Mg-to-Ga incorporation rate resulting from the restriction of self-compensation under compressive strain. In addition, by using an AlN interlayer (IL) at the interface of p-GaN/AlGaN, the activation rate can be further improved after the doping concentration reaches saturation, and the diffusion of Mg atoms can also be effectively suppressed. A high hole concentration of about 1.3 × 1018 cm−3 can be achieved in the p-GaN/AlN-IL/AlGaN structure.

Effect of Mg doping on Cu2ZnSnS4 solar cells prepared by DMF-based solution method

In this paper, magnesium was successfully introduced into CZTS using the DMF-based solution method, and CZMTS solar cell was prepared. The effects of Mg doping on the morphology, crystal structure, and electronic properties of the CZTS absorber were investigated in detail. The crystal structure of the CZMTS absorber and the chemical valence states of the other elements (Cu, Zn, Sn, and S) were not changed as shown by XRD, Raman, and XPS analyses. The results show that Mg doping can improve the electronic properties and microstructure of CZTS absorbers, thus enhancing the PCE from 2.91% to 4.10%. This performance enhancement is associated with good crystal quality, reduced cation-disordering defects, and high external quantum efficiency at the longwave region caused less recombination and open circuit voltage loss. Therefore, Mg doping has a positive effect on improving the performance of CZTS solar cells. • The feasibility of the DMF-based solution method to achieve Mg doping is demonstrated. • Mg doping can reduce recombination and open-circuit voltage loss of CZTS solar cells. • After Mg doping, the PCE of CZTS solar cells is increased from 2.91% to 4.10%.

Effect of Mg Doping on Structural, Alloying, Electronic, Optical, and Bactericidal Properties of CunAg25–n Nanoclusters: A Computational Study

Effect of Mg Doping on Structural, Alloying, Electronic, Optical, and Bactericidal Properties of Cu_<i>n</i>Ag_{25–<i>n</i>} Nanoclusters: A Computational Study

Effect of Mg-doping in tailoring d0 ferromagnetism of rutile TiO2 compounds for spintronics application

d0 ferromagnetism in non-magnetic element-doped oxide materials has caught the attention of researchers due to their promising application in spintronics devices. In a search of finding novel materials exhibiting d0 ferromagnetism, we have studied the Mg-doped TiO2, i.e., Ti1-xMgxO2 (x = 0, 0.02, 0.04, and 0.06) compounds, synthesized by solid-state reaction route method. Single phase of tetragonal rutile structure is observed by X-ray diffraction (XRD) patterns for all compounds. The samples show uniform morphology with particles size ranging from 150 to 200 nm, as per the scanning electron microscopy observations. The magnetic properties investigation by SQUID magnetometer indicates paramagnetic behavior in undoped TiO2 and 2% Mg-doped TiO2, whereas the Ti0.96Mg0.04O2 compound exhibits ferromagnetism embedded in a paramagnetic phase. However, 6% Mg-doped TiO2 exhibits ferromagnetism with a transition temperature of 180.2 K. Further, magnetization vs. temperature curves measured under zero-field, and field-cooled condition for x = 0.06 sample reveal low-temperature magnetic irreversibility, which can be ascribed to the competing antiferromagnetic and ferromagnetic phases. The hysteresis curve with a coercivity of 6515 Oe at 5 K along with domain wall pinning and zero-field-cooled exchange-bias behavior are observed for x = 0.06 sample from the M–H curves.