Influence Of Mg Doping Research Articles

The Influence of Mg Doping in α-Al2O3 Crystals Investigated with First-Principles Calculations and Experiment.

The influence of Mg doping in α-Al2O3 crystals is investigated in this article by first-principles calculations and formation energies, density of states, and computed absorption spectra. Three models related to Mg2+ substituting for Al3+ doping structures were constructed, as well as spinel structure models with varying aluminum-magnesium ratios. The formation energy calculations confirmed the rationality of the MgAlVO model, which means that Mg substitutional doping incorporating oxygen vacancies is most likely to form in crystals. The combined action of magnesium and oxygen vacancies introduced new defect energy levels in the bandgap. The calculated absorption spectra of the MgAlVO and Mg-rich spinel structures exhibited various color centers. The experimental absorption spectra and thermoluminescence characteristics of α-Al2O3:Mg and alumina-magnesium (Al-Mg) spinel crystal samples were tested. The thermoluminescence peak of the Al-Mg spinel was significantly stronger than that of the α-Al2O3:Mg crystal. The consistency between the model-calculated absorption spectra and the experimental results confirmed the theoretical predictions. Based on the experimental and computational results, the influence of Mg2+ substitutional doping in α-Al2O3 and the impact of the locally Mg-rich spinel on the optical and radiation performance of α-Al2O3:Mg crystals are elucidated.

Influence of Mg doping on structure and optical properties of red-emitting phosphor Li2TiO3:Mn4+

Li2TiO3:Mn4+ has been previously identified as a potential candidate to replace commercial red-emitting Eu2+-activated phosphors. Its luminescent efficiency is limited by the presence of defects and the sensitivity of Mn4+ to redox processes. A series of co-doped Li2TiO3: x Mg2+, 0.01 Mn4+ samples were prepared to gain insight on the effect of electron doping on the structure and photoluminescent properties, through characterization by powder X-ray diffraction, elemental analysis, and optical spectroscopy. As Mg2+ substitutes for Li+, the ordered arrangement of cations within the honeycomb layers in the parent structure (Li2SnO3-type, an ordered derivative of rocksalt) gradually transforms to a more disordered arrangement. The increased cation site disorder leads to less intense and broader emission peaks as well as lower quantum yields.

Development of enduring interstitial defects in Mg-doped CuO thin films.

Doping is one of the easiest methods to enhance the properties of semiconducting thin films. This work presents a systematic study of the influence of Mg doping on the optoelectronic properties of copper oxide (CuO) thin films prepared by spray pyrolysis. The pristine and doped films were prepared on glass substrates at an optimized temperature of 350 °C and a precursor solution concentration of 0.15 M while the Mg doping concentration was varied between 2 and 10 at%. The properties of the prepared films were studied in detail by using various characterization techniques such as X-ray diffraction, field emission scanning electron microscopy, Raman and photoluminescence, X-ray photoelectron spectroscopy and Hall measurement. The results suggest that oxygen interstitial (Oi) defects were enhanced upon doping which has influenced the properties of the film. The size of the crystallites reduced, and the band gap widened after doping. In addition, comprehensive density functional theory analyses have been conducted to gain a thorough understanding of the impact of impurity (i.e., doping/interstitial) atoms on the optical and electrical characteristics of CuO. This study shows that Oi defects improved the conductivity and enhanced the carrier concentration leading to an improvement in the electrical properties of the films.

Effect of Mg doping at Fe/Cr site on magnetic and optical properties of Gd2FeCrO6 double perovskite

The influence of Mg doping on structural, magnetic and optical characteristics of Gd2FeCrO6, Gd2Fe0.75Mg0.25CrO6 and Gd2FeCr0.75Mg0.25O6 double perovskites has been systematically investigated. The monoclinic crystal structure with the P21/n space group is confirmed by powder X-ray diffraction data. From the scanning electron microscopy graphs, we noticed few nearly spherical and dumbbell-shaped grains for all compounds with an average grain size of about 76 - 85 nm. The magnetic studies demonstrated the presence of a weak ferromagnetic transition with antiferromagnetic background at low temperatures for all the samples. A decrement in the transition temperature of Gd2FeCrO6 (TC = 8.14 K) is observed on Mg doping, which is due to the smaller ionic radii of Mg at the Fe/Cr site in Gd2Fe0.75Mg0.25CrO6 and Gd2FeCr0.75Mg0.25O6 double perovskites. By analyzing the UV–visible spectroscopic absorption data, direct band gaps around 3 eV are concluded for pure and Mg doped Gd2FeCrO6 double perovskites, validating their application in wastewater photocatalysis.

Influence of Mg Doping on the Structure and Mechanical Properties of Al2Cu Precipitated Phase by First-Principles Calculations.

Al-Cu-Mg high-strength alloys are widely used in industrial production because of their excellent mechanical performance and good machining properties. In this study, first-principles calculations based on density functional theory were carried out to investigate the influence of Mg doping on the structural stability and mechanical properties of the Al2Cu (θ) precipitated phase in Al-Cu-Mg alloys. The results show that the structural stability, electronic structure, bulk modulus, mechanical anisotropy, and thermodynamic properties of the precipitated Al2CuMgX phase change with the concentration of Mg doping (X = 2, 4, 6, and 8). The cohesive energy calculation and electronic structure analysis show that Al2CuMg6 has a high structural stability. The criterion based on elastic constants indicates that Al2CuMg2, Al2CuMg4, and Al2CuMg8 have a brittle tendency and show strong anisotropy of mechanical properties, while Al2CuMg6 shows better comprehensive mechanical properties. The thermodynamic analysis results based on the quasi-harmonic Debye model show that the Al2CuMg6 precipitated phase has good stability at high temperatures and pressure.

Enhanced magnetoelectric coupling effect in Mg-doped Y-type hexaferrite BaSrCo2-xMgxFe11.1Al0.9O22 ceramics

The influences of Mg doping on the magnetic order structure and magnetoelectric (ME) effect were investigated in Y-type hexaferrite BaSrCo2-xMgxFe11.1Al0.9O22 (x = 0.00, 0.25, 0.50, 0.75, 1.00) ceramics. The results revealed that the Mg doping could increase the magnetic phase transition temperature. The optimal magnetic-driven electric polarization could be obtained at x = 0.25 ceramic, exhibiting a maximum electric polarization of 16.22 μC/m2 and a ME coefficient of 203 ps/m at 100 K. The stability of reversible electric polarization was demonstrated via the measurement of continuous magnetic field cycles. Moreover, the ME phase diagram was established by measuring the magnetic dielectric properties. Finally, a possible Mg-tune magnetic structure was proposed to explain the enhanced ME effect.

Influence of Mg doping on the structural and optical properties of manganese oxide (Mn2O3) nanoparticles

The work presents here the synthesis of pristine manganese oxide (Mn2O3) nanoparticles and magnesium (Mg) doped Mn2O3nanoparticles with the help of the chemical co-precipitation method. We have investigated the influence of Mg doping (9 wt%, 12 wt%, and 15 wt%) on the optical and structural properties of Mn2O3. The structural properties of undoped and doped Mn2O3 nanoparticles have been studied using X-ray Diffraction Spectroscopy (XRD). The numerous physiochemical bondings present within the prepared nanoparticles have been examined using Fourier Transform Infrared Spectroscopy (FTIR). Both photoluminescence (PL) and UV-Visible (UV-Vis) spectroscopy have been used to investigate the optical characteristics. All the measurements are done at room temperature. All of the samples’ absorption spectra have been investigated within the wavelength range of 200 to 800 nm. The UV-Vis absorption spectrum for pristine Mn2O3 nanoparticles shows a sharp peak at 289 nm. We have further determined the band gap of the prepared samples using Tauc’s equation. The pristine Mn2O3 exhibits a direct bandgap of 4.04eV. At an excitation wavelength of 320 nm, the prepared samples’ emission spectra have also been recorded.

A comprehensive study on the influence of Mg doping on structural, AC conductivity, and dielectric behavior of ZnONPs

In this research magnesium (Mg) doped zinc oxide nanoparticles (Zn1-x MgxO, where x = 0 for pure ZnO) were synthesized using a simple chemical route. Their structure and morphology was characterized using different methods, such as X-ray diffraction, scanning electron microscopy, Fourier Transform spectroscopy, photoluminescence. Nanoparticles (NPs) were synthesized and analyzed for their structure, shape, chemical content, and optical and dielectric activity with Zn1-x MgxO (where x = 5,15,50 wt%). The crystalline, hexagonal ZnO was verified by X-ray diffraction, with an average grain size of 45 nm for ZnO and 28 nm for Mg doping and a more interplane spacing that ranges from 2.9 nm to 18 nm. In the nanoscale domain, with a hexagonal crystalline shape between 30 and 80 nm, Zn1-x MgxO were analyzed in scanning electron microscopy (SEM) pictures. Transmittance rises with doping, as shown by optical characterization, and UV–vis spectroscopy reveals low absorbance in the visible area. Absorption values drop dramatically for all samples in the UV region, and when magnesium content rises, the absorption peak moves to shorter wavelengths. As the Mg content increased from 5 % to 50 %, the optical absorption spectra of ZnO switched to red. The UV emission peak in PL spectra was seen between 389 and 700 nm. It revealed that up to 50 % Mg doping, the strength of the emission bands at 405 and 525 nm decreases. According to fluorescence emission, zinc oxide has interaction with porphyrin, which results in a new peak at 389 nm. This 389 nm peak is thus specific to ZnO and Zn1-x MgxO nanoparticles as a result of the electron transport between the two materials. The Zn1-x MgxO samples show low dielectric losses and high dielectric constants in the middle and high-frequency ranges. The Mg doping at 5 % concentration is particularly intriguing since it shows enormous dielectric constant across a broad frequency range. At low frequencies, all the samples suffer from a significant loss factor. In the high-frequency range, it stabilizes.

Influence of Mg doping on structural, dielectric properties and Urbach energy in ZnO ceramics

Influence of Mg doping on structural, dielectric properties and Urbach energy in ZnO ceramics

Impacts of Mg doping on the structural properties and degradation mechanisms of a Li and Mn rich layered oxide cathode for lithium-ion batteries

The Li- and Mn-rich layered oxide cathode material class is a promising cathode material type for high energy density lithium-ion batteries. However, this cathode material type suffers from layer to spinel structural transition during electrochemical cycling, resulting in energy density losses during repeated cycling. Thus, improving structural stability is an essential key for developing this cathode material family. Elemental doping is a useful strategy to improve the structural properties of cathode materials. This work examines the influences of Mg doping on the structural characteristics and degradation mechanisms of a Li1.2Mn0.4Co0.4O2 cathode material. The results reveal that the prepared cathode materials are a composite, exhibiting phase separation of the Li2MnO3 and LiCoO2 components. Li2MnO3 and LiCoO2 domain sizes decreased as Mg content increased, altering the electrochemical mechanisms of the cathode materials. Moreover, Mg doping can retard phase transition, resulting in reduced structural degradation. Li1.2Mn0.36Mg0.04Co0.4O2 with optimal Mg doping demonstrated improved electrochemical performance. The current work provides deeper understanding about the roles of Mg doping on the structural characteristics and degradation mechanisms of Li-and Mn-rich layered oxide cathode materials, which is an insightful guideline for the future development of high energy density cathode materials for lithium-ion batteries.

Microstructural and dielectric properties of Ba0.45Mg0.05Sr0.5-x CaxTiO3 high entropy ceramics

Ba0.45Mg0.05Sr0.5-xCaxTiO3 (BMSCT) high entropy ceramics were prepared using a solid-state reaction process sintered at temperatures ranging from 1250 °C to 1400 °C. A change in Ca content significantly affects the crystalline phase and dielectric properties of the BMSCT ceramics. High resolution TEM observations and the analysis of respective images reveal a large number of intragranular on the nanoscale that are massively disordered and disturbed on the atomic level. The influence of Mg doping, resulting in a shift of the Curie point to −50 °C. For Ca-substitution (up to 10 at.%), a broad phase transition is observed in the BMSCT, and the Curie point is −30 °C. Comparing the dielectric constant at 1 MHz and 1 GHz, the permittivity of the BMSCT-9182 is only slightly inferior to the on at low frequency ～6%, but the one for BST is drastically decreased ～70% at microwave frequencies.

Characterization of crystal structure, electrical and electromechanical properties of Mg-doped 0.94Na1/2Bi1/2TiO3-0.06BaTiO3

The use of lead-free piezoelectric materials in high-power applications requires a high mechanical quality factor Qm and temperature-stable ferroelectric properties. In this article, the influence of Mg-doping on the 0.94Na1/2Bi1/2TiO3-0.06BaTiO3 system is analysed with focus on the role of defects related to ferroelectric hardening. Temperature stability (depolarization temperature), electromechanical properties (piezoelectric activity, Qm), electrical properties (conductivity) and crystal structure for compositions were quantified. Compositions with similar amount of Zn-doping were analyzed for reference. A drastic increase in electrical conductivity at −0.3/−0.5 mol% Mg was associated with a concomitant increase in Qm. Similar behavior in Zn-doped compositions provides a basis for a more comprehensive mechanistic understanding of acceptor doping in these lead-free piezoceramics. The very high and almost vibration-velocity-independent Qm above 800 makes Mg-doped 0.94Na1/2Bi1/2TiO3-0.06BaTiO3 an excellent candidate for high-power application.

Influence of Mg doping on structural, optical and dielectric properties of sol–gel spin coated ZnO thin films

Influence of Mg doping on structural, optical and dielectric properties of sol–gel spin coated ZnO thin films

Influence of Mg doping on the structural, electrical and dielectric properties of Co-Zn nanoferrites

Mg-Co-Zn nanoferrites of composition MgxCo0.5Zn0.5Fe2−xO4 (x = 0.25, 0.5, 0.75 and 1.0) were successfully synthesized by using a citrate precursor method. After synthesis, the samples were examined using different techniques for structural, morphological, electrical and dielectric characterizations. All the samples were found to have single phase spinel cubic structure with Fd-3m space group in the X-ray diffraction spectroscopy (XRD) investigation. The value of average crystallite size ranged from 37 to 47 nm with the increase in Mg ion concentration from x = 0.25 to 1.0. The hopping lengths at tetrahedral and octahedral sites showed an increasing behaviour with increasing magnesium ion concentration. The presence of tensile strain in the samples was confirmed by W-H plots. The dielectric behaviour of the prepared nanoferrites was recorded at room temperature in the frequency range 10 kHz–10 MHz. The real part and imaginary part of the dielectric constant were found to be in the range 3.80–7.93 and 0.0036–0.644 at 1 MHz frequency and the value of loss tangent was 0.00095–0.081 at 1 MHz for the magnesium doped Co-Zn nanoferrites. The value of loss tangent decreased very sharply to remarkably low values at 10 MHz frequency. The dc resistivity value was found very low in the range 3.2 × 108 Ω-cm to 4.0 × 109 Ω-cm for different concentrations of Mg2+ ions in the samples. Due to such low losses at high frequency region and high value of dc resistivity, these materials can be considered as potential candidate for high frequency applications.

Influence of Mg doping on the ultrafast electron dynamics of VO2 films

Influence of Mg doping on the ultrafast electron dynamics of VO2 films

Study on the eletronic structure and effective mass of Mg–Fe co-doped GaN based on first principles

According to the first-principle method for the density functional theory (DFT), combined with the hybrid functional (HSE06), the electronic structure and effective mass of Mg-doped GaN and Mg–Fe co-doped GaN systems are calculated, and the stability of the co-doped structure is analyzed from the perspective of formation energy and phonon dispersion. The results showed that the introduction of Fe improved the characteristics of GaN:Mg system: the GaN material doped with Mg merely would cause the material’s valence band maximum to exceed the Fermi level, presenting a [Formula: see text]-type conduction; the addition of Fe increased the energy band density of the system, and the insulation of the material was enhanced due to the higher energy level of the introduced impurity. Furthermore, the influence of Mg doping on the magnetic properties of GaN-based diluted magnetic semiconductor (DMS) was considered as well, with the magnetic moment obtained from co-doping Mg–Fe slightly reduced by a comparison of that of GaN:Fe measured by our research group. The results showed that the difference in the effective mass of GaN:Mg:Fe system in different directions was smaller than that of GaN:Mg system, indicating that the anisotropy of the system was reduced by doping Fe.

Influence of Mg-doping on the characteristics of ZnO photoanodes in dye-sensitized solar cells.

Dye-sensitized solar cells (DSSCs) based on ZnO photoanodes have, despite extensive research, lagged behind cells based on TiO2, which is due to generally lower open-circuit voltages VOC and fill factors. Here, DSSCs have been prepared using Mg-doped ZnO (MZO) photoanodes based on nanoparticles, thin films or ZnO-MZO core-shell-type nanoparticles with varying Mg-concentration. The cells were studied in detailed photoelectrochemical and photoluminescence experiments. It was confirmed that VOC was significantly increased by Mg-doping. A clear influence of the Mg-concentration was also revealed on the transport and recombination of electrons in MZO, leading to a higher cell performance at low and lower cell performance at high concentrations of Mg in MZO. Nanoparticles with a pure ZnO core and an MZO shell offered a way to lower the influence of increased transport resistance in MZO and to capitalize on the significantly improved VOC.

Structural and optical characterization of sprayed Mg and Ni co-doped CdS thin films for photovoltaic applications

In the present work, Mg and Ni co-doped CdS thin films are grown on glass substrates at a temperature of 400 °C through spray pyrolysis. The influence of Mg-doping on structural, morphological and optical properties of CdS:Ni thin films are examined. Mg level is changed from 0 % to 7 % for CdS: Ni samples just as Ni concentration is fixed 2 % for all CdS thin films. It is observed from the X-ray diffraction spectra that all the samples exhibit hexagonal structure of CdS thin films. The scanning electron microscopy (SEM) images showed a dense surface structure composed of crystallites whose average size increase with increasing the Mg doping. The optical transmission curves demonstrate that CdS:Ni thin films exhibit a best optical transparency in the visible range for 1 % Mg content compared to other specimens. The energy of the optical band gap tends to decrease from 2.46 to 2.40 eV with increasing Mg concentration in CdS: Ni.

Understanding the influences of Mg doping on the physical properties of SrMoO3 perovskite

The structural, mechanical, and electronic properties of perovskite molybdates are a topic of frequent study in materials science. In this study, the influence of Mg doping on the physical metallurgy of perovskite molybdates is investigated using first-principles calculations based on density functional theory (DFT) and molecular dynamics (MD) simulation. Our calculated optimized lattice parameters (3.9945, 3.8964, 3.8634, 3.8440, and 3.7952 Å [mentioned only DFT data, MD data listed in Table 2] for x = 0, 0.1, 0.2, 0.3, and 0.4 respectively) of SrMo1−xMgxO3 are highly consistent with other experimental results (3.9762, 3.9695, and 3.9649 Å for x = 0, 0.1, and 0.2 respectively) and some available theoretical results (3.9720 Å for x = 0, no previous data available for Mg-doped systems). The calculated elastic constants satisfied the Born stability criteria, indicating that our studied materials are mechanically stable at all doping concentrations, which was also confirmed by the calculated negative values of Cohesive energy. The mechanical behaviors of perovskite, including elastic constants, elastic moduli, ductility, and elastic anisotropy, were investigated and discussed. Our computed results suggest that Mg doping can increase elastic moduli. The calculated Pugh’s ratio increased from 0.42 to 0.71 [DFT] and from 0.47 to 0.75 [MD] as well as the Poisson’s ratio decreased from 0.31 to 0.21 [DFT] and from 0.30 to 0.21 [MD] which transformed the compound from ductile to brittle due to the addition of Mg at Mo-site. The band structures, density of states, and charge density redistributions of the undoped and Mg-doped materials were predicted. Our simulation outputs clearly illustrated the importance of accounting for Mg doping’s influence in theoretical simulations of the physical properties of the presently studied perovskite material.

Influence of Mg doping on In adsorption and In incorporation in (In,Ga)N superlattices

We present a detailed investigation of the mechanisms at play for the incorporation of In and Mg on the GaN(0001) surface during plasma-assisted molecular beam epitaxy. First, we have studied the kinetics of In desorption in the presence of Mg either without or with N supply from the plasma cell by quadrupole mass spectrometry in the line of sight. Second, we have explored the effect of Mg doping at a different time along the cycle of (InN/GaN) supply repeated 10 times to form (In,Ga)N/GaN superlattices (SLs). By the complementary ex situ investigation of these SLs by x-ray diffraction and secondary ion mass spectrometry, we found that in the monolayer-thick (In,Ga)N layer, the In content was maximized when Mg was not supplied simultaneously to In, but it drastically decreased otherwise. In contrast, the Mg concentration strongly increased in the (In,Ga)N monolayers compared to the GaN barriers. We attribute this finding to the surfactant effect of In for Mg, which decreases the binding energy of Mg in GaN in the presence of N.