Effect Of Mg Doping Research Articles

Mg shallow doping effects on the ac magnetic self-heating characteristics of γ-Fe2O3 superparamagnetic nanoparticles for highly efficient hyperthermia

The effects of Mg doping on the magnetic and AC self-heating temperature rising characteristics of γ-Fe2O3 superparamagnetic nanoparticles (SPNPs) were investigated for hyperthermia applications in biomedicine. The doping concentration of nonmagnetic Mg2+ cation was systematically controlled from 0 to 0.15 at. % in Mgx-γFe2O3 SPNPs during chemically and thermally modified one-pot thermal decomposition synthesis under bubbling O2/Ar gas mixture. It was empirically observed that the saturation magnetization (Ms) and the out-of-phase magnetic susceptibility (χm″) of Mgx-γFe2O3 SPNPs were increased by increasing the Mg2+ cation doping concentration from 0.05 to 0.13 at. %. Correspondingly, the AC magnetically induced self-heating temperature (Tac,max) in solid state and the intrinsic loss power in water were increased up to 184 °C and 14.2 nH m2 kg−1 (Mgx-γFe2O3, x = 0.13), respectively, at the biologically and physiologically safe range of AC magnetic field (Happl × fappl = 1.2 × 109 A m−1 s−1). All the chemically and physically analyzed results confirmed that the dramatically improved AC magnetic induction heating characteristics and the magnetic properties of Mgx-γFe2O3 SPNPs (x = 0.13) are primarily due to the significantly enhanced magnetic susceptibility (particularly, χm″) and the improved AC/DC magnetic softness (lower AC/DC magnetic anisotropy) resulting from the systematically controlled nonmagnetic Mg2+ cation concentrations and distributions (occupation ratio) in the Fe vacancy sites of γ-Fe2O3 (approximately 12% vacancy), instead of typically well-known Fe3O4 (no vacancy) SPNPs. The cell viability and biocompatibility with U87 MG cell lines demonstrated that Mgx-γFe2O3 SPNPs (x = 0.13) has promising bio-feasibility for hyperthermia agent applications.

Effects of Mg-doping on characteristics of semi-polar [formula omitted] plane p-AlGaN films

The effects of Mg-doping on the characteristics of semi-polar (112¯2) plane Al0.15Ga0.85N films grown on (101¯0) m-plane sapphire substrates with metal-organic chemical vapor deposition (MOCVD) technique were investigated intensively and systematically. The characterization results showed that the crystalline quality of the (112¯2) plane AlGaN films could be improved by optimizing the Mg-delta-doping process. Whereas, the surface morphology for the samples was monotonously degraded with increasing the Mg-doping level. Meanwhile, a hole concentration as high as 5.4×1017cm−3 were achieved by optimizing the Mg-doping level. Furthermore, the luminescence mechanism of the samples was investigated by photoluminescence spectra at room temperature.

Preparation of nanocrystalline Mg doped CdSe thin films and their optical, photoluminescence, electrical and structural characterization

Phosphors used are mostly rare earth doped complex structures. A simple and unique material system of CdSe:Mg nanocrystalline thin films, which efficiently absorb UV (235 nm) and emit broad spectrum of green-yellow region has been prepared by chemical bath deposition method with average particle size of 52.3 nm, measured using AFM images. The optical absorption studies found that CdSe thin film has direct optical band gap, $${E_g}$$ of 2.62 eV that shows a blue shift of 0.88 eV compared to the bulk $${E_g}$$ value. Optical, electrical, structural and morphological properties were studied by UV–Vis–NIR spectrophotometer, photoluminescence (PL) emission spectra, dc two-probe method, X-ray diffraction (XRD), and atomic force microscope (AFM). Measured electrical resistivity decreased with increase of doping concentration. Activation energy was also calculated. The results confirm that the CdSe:Mg thin films are in the pure cubic phase. The magnesium concentrations also affect the nanocrystalline nature of the CdSe thin films. The optical band gap and surface roughness of CdSe thin films mostly decrease with 5% doping of Mg. The effect of Mg doping on refractive index, extinction coefficient and other optical parameters was also investigated.

Enhanced Stability and Performance in Perovskite Nanocrystal Light‐Emitting Devices Using a ZnMgO Interfacial Layer

AbstractPerovskite has been considered to be a promising optoelectronic material due to its superior properties, yet, it are strongly sensitive to oxygen and water, especially when applied in devices. Here, a highly efficient and stable light‐emitting device (LED) is reported by applying solution‐processed Mg‐doped ZnO (MZO) nanocrystals (NCs) as an interfacial layer. The effect of Mg doping on the optical and electronic properties of NCs is investigated. This study demonstrates that the air stability of perovskite NC film is significantly enhanced because of the decreased oxygen vacancy surface sites of MZO NCs. Incorporation of a MZO layer with favorable electronic energy level to form a suitable band alignment promotes electron injection and enhances the LED performance. Compared to the device without MZO, the LED shows 3059 cd m−2 of luminance, with 1.9 times enhanced current efficiency and 2 times increased external quantum efficiency. In addition, the device with MZO also exhibits better stability. This research provides a potential strategy for realizing stable and efficient perovskite LEDs.

Low temperature NH3-SCR of NO over an unexpected Mn-based catalyst: Promotional effect of Mg doping

MnOx/TiO2 catalysts doped with Mg have been prepared with the impregnation method. Surprisingly, 7% Mg-MnOx/TiO2 catalyst containing more Mn3+ ions showed superior low-temperature SCR activity and stability. Mg doping resulted in some adverse effects on the phases, BET surface areas, reducibility, NH3 adsorption, and morphology structures. However, according to the SCR performance, these effects were thought to be rather limited in comparison with the catalytic properties of MgMn2O4 which might stem from the enhancement of NH3-SCR activity and stability. Meanwhile, based on the in situ DRIFTS tests, the NH3-SCR reaction route of MnOx/TiO2 and Mg doped MnOx/TiO2 catalysts depended on the kind of gas (NH3 or NO) pre-adsorbed on the catalyst.

Effects of Mg doping on electrical properties of Ba0.7Ca0.3TiO3 ceramics

(Ba0.7Ca0.3)Ti1-xMgxO3-x ceramics where x=0, 0.005, 0.015 and 0.02 were prepared employing a solid state sintering technique. The abrupt decrease of tetragonality was induced by doping with x≥0.015. Ti K-edge X-ray Absorption Near-Edge Structure (XANES) spectra indicated spontaneous polarization weakness of doped ceramics. The grain size was decreased due to the creation of oxygen vacancies and solute-drag effect. The reduction of the phase transition temperature, ferroelectricity and piezoelectricity was observed in correlation with the decrease in tetragonality. Dielectric properties near room temperature of the samples could be enhanced with Mg addition. The results here suggested that the electrical properties of this ceramic may be largely tunable by Mg dopant and could be an attractive material for high-dielectric response devices.

Influence of magnesium doping the structural and magnetocaloric properties of manganites oxide prepared by sol–gel method

We have investigated the effect of Mg doping on structural, magnetic and magnetocaloric properties of a novel series of La0.67Sr0.22Ba0.11Mn1−x Mg x O3 (0 ≤ x ≤ 0.2) perovskites elaborated by a sol–gel method. These oxides were characterized by neutron powder diffraction (NPD) at room temperature and magnetization measurements versus temperature and various applied magnetic fields. Rietveld refinements from NPD data indicate an orthorhombic structure (Pnma) for all the compounds (x = 0 to x = 0.2); in all the samples with x > 0, Mg is distributed at random in the Mn positions of the perovskite. Magnetization measurements show a ferromagnetic behavior for x = 0 and x = 0.1 samples, whereas the compound x = 0.2 introduces a magnetic glass state (cluster or spin glass). The magnetic entropy change \( \left( {\left| {\Delta S_{\hbox{max} } } \right|} \right) \) and the relative cooling power are, respectively, 2.46, 1.85 and 0.83 J kg−1 K−1 and 169, 101 and 116 J kg−1 at a field change of 5 T, for all compounds x = 0, 0.1 and 0.2. These results are compared with those of some other reported manganites, helping to understand the magnetic arrangement required for magnetic refrigeration.

Effect of Mg doping and sintering temperature on structural and morphological properties of samarium-doped ceria for IT-SOFC electrolyte

Samples of Sm and Mg co-doped ceria electrolyte of Ce1−xSmx−yMgyO2−δ (x = 0.2; y = 0.00, 0.05, 0.1, 0.15, and 0.175) were synthesized by sol–gel process. The prepared samples were sintered at 1100 and 1400 °C for 4 h. The bulk densities were measured by Archimedes method. XRD measurements indicate that the synthesized samples were in single-phase cubic fluorite structure (space group Fm3m). The cell parameters decrease with the concentration of Mg, and 2θ values slightly shift towards right. The particle sizes obtained were between 7.14 and 17.44 nm. The sintered sample achieved 95% of theoretical density. FTIR spectra of samples sintered at 1400 °C indicates weak interactions between 3550–3400 cm−1 and 1600–1300 cm−1 are attributed to O–H stretching modes and strong bonds 850–450 cm−1 are assigned to characteristic Ce–O vibrations. The surface morphology and chemical composition were analyzed by SEM and EDS, SEM micrographs show spherical faceted grains, and the samples were crack free, dense material with some pores on surface which are inconsistent with density results. The average grain size obtained was 0.5 μm. Particle size obtained by TEM was in agreement with that obtained by XRD. The high-density ceria co-doped ceramic can be used as electrolyte in SOFC.

Synthesis and magnetic properties of Mg doped SnO2 thin films: experimental and Ab-initio study

Mg-doped tin oxide (SnO2) thin films were deposited using spray pyrolysis technique with an aqueous solution of SnCl2 and magnesium sulfate (Mg (SO4)·7H2O) on a heated glass substrate. In this work, the effect of Mg doping on the structural, optical and electrical properties of SnO2 was investigated in some detail by X-ray diffraction, UV–Vis spectroscopy and Hall Effect measurements. The XRD diffractograms demonstrate that SnO2 crystallized in tetragonal rutile structure with preferential orientation along (110) plane. The average transmittance in the visible range was increased from 65 to 78% and the values of energy band gap were found in the range of 3.62–3.87 eV. The lowest resistivity [1.021 × 101 (Ω.cm)] was obtained for the film doped with 5 at% Mg. The electronic structure and optical properties of the rutile structure Sn1−xMgxO2 were obtained by ab initio calculations using the Korringa-Kohn-Rostoker method (KKR) combined with the Coherent Potential Approximation (CPA), as well as CPA confirms our results.

Understanding the influence of Mg doping for the stabilization of capacity and higher discharge voltage of Li- and Mn-rich cathodes for Li-ion batteries.

Although Li- and Mn-rich layered cathodes exhibit high specific capacity, the cathode materials of the general formula Li1+x[NiyMnzCow]O2 (x + y + z + w = 1) suffer from capacity fading and discharge-voltage decay during prolonged cycling, due to the layered-to-spinel transformation upon cycling to potentials higher than 4.5 V vs. Li. In this paper, we study the effect of Mg doping (by partial replacement of Mn ions) on the electrochemical performance of Li- and Mn-rich cathodes in terms of specific capacity, capacity retention and discharge voltage upon cycling. Mg-doped Li- and Mn-rich Li1.2Ni0.16Mn0.54Mg0.02Co0.08O2 and Li1.2Ni0.16Mn0.51Mg0.05Co0.08O2 cathode materials were synthesized by a self-combustion reaction (SCR), and their electrochemical performance in Li-ion batteries was tested. The replacement of a small amount of Mn ions by Mg ions in these materials results in a decrease in their specific capacity. The doping of a small amount of Mg (x = 0.02) resulted only in the stabilization of the capacity, whereas a greater amount (x = 0.05) resulted in improved capacity retention and discharge voltage upon cycling. Li1.2Ni0.16Mn0.51Mg0.05Co0.08O2 exhibits a low specific capacity of about 160 mA h g-1, which increases and then stabilizes at about 230 mA h g-1, and finally decreases to 210 mA h g-1 during 100 cycles. The substitution of Mg for Mn (x = 0.05) results in a higher discharge voltage than the other two cathode materials examined in this study. Structural analysis of the cycled electrodes suggests that Mg suppresses the activation of Li2MnO3 during the initial cycling, and hence, partially prevents layered-to-spinel transformation, resulting in a better electrochemical performance of the Mg-doped cathode material as compared to the undoped material.

The effect of Mg-doping and Cu nonstoichiometry on the photoelectrochemical response of CuFeO2

We report the tuning of CuFeO2 photoelectrodes by Mg doping and Cu deficiency to demonstrate the effects of carrier concentration on the photoresponse.

Structural and magnetic properties of Mg doped cobalt ferrite nano particles prepared by sol-gel method

Effect of Mg doping on structural and magnetic properties of nano cobalt ferrites prepared via sol-gel auto-combustion method is reported. The sintered samples (Co1-xMgxFe2O4, where x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were characterized using X-ray diffraction, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy and vibrating sample magnetometer. Rietveld refinement of X-ray diffraction spectra shows the single phase cubic structure (space group Fd3m) for the prepared samples. Raman spectroscopy reveals a doublet-like peak behavior in A1g and Eg modes arising due to different ionic radii of Co/Mg and Fe ions. Two prominent vibration frequencies in FTIR spectroscopy data also confirm the cubic spinel structure in the prepared samples. The magnetic parameters such as saturation magnetization, coercivity and remanence are studied with increasing the Mg-concentration in cobalt ferrite. Systematic changes in magnetic properties while going from x=0 to 1 are discussed.

Enhancement of multiferroic and magnetocapacitive properties in nanocrystalline Mg-doped GaFeO3

We have study the effect of Mg doping on structural, magnetic, electric and magnetocapacitive properties of nanocrystalline Ga1−xMgxFeO3 (GMFO, 0 ≤ x ≤ 0.10) prepared by a modified Pechini method. The presence of a single crystalline phase identified as the orthorhombic structure with Pc21n space in all the GMFO samples. Magnetization measurements reveal that with increasing Mg-content up to 0.10, the ferrimagnetic transition temperature (TC) increases from 302 to 325 K. It is also found that the Mg-doped GaFeO3 (GFO) samples exhibit the characteristics of ferroelectricity at room temperature. Furthermore, Mg substitution in GFO brings in the balance of structural distortion, cation distribution, and magnetic exchange interaction, which affects both ferrimagnetism and ferroelectricity. The simultaneous enhancement of magnetization, electric polarization and magnetocapacitance of Mg-doped GFO samples are prominent candidates for the applications of multiferroic devices.

Synthesis and Characterization of Mg-Doped Na0.6Ni0.3-XMgxTi0.7O2 as Anode Material for Sodium Ion Battery

Recently, sodium-ion batteries (SIB) have gained great amount of attention as a next generation rechargeable battery. The lithium-ion batteries (LIB) have been successfully commercialized and widely applied in electronic devices, vehicles, etc. due to its high energy density. Compared to LIB, SIB system is more desirable in view point of cost because the sodium source is more abundant and widely distribution. Similar to LIB, many studies about SIB cathode reported electrode materials with layered structure where Na ion can intercalate and deintercalate during electrochemical reaction. The electrodes with layered structure can also be utilized as anode. Although the theoretical capacity of layered material is generally lower than that of other materials which undergo conversion or alloying reaction, the electrode material with layered structure shows smaller volume change and better structure stability. Among many anode materials, NaxNix/2Ti1-x/2O2 has been reported to have layered structure with low operating voltage (~0.7V vs Na/Na+) and has shown promising performance. In this study, Mg and Ni was co-doped into NaTiO2 in order to study effect of Mg doping on anode performance. The Na0.6Ni0.3-xMgxTi0.7O2 was synthesized by simple solid-state synthesis method while varying Mg amount from x=0.0 to x=0.1. The structure change depending on the amount of Mg dopant was analyzed by high-resolution X-ray diffraction, scanning electron microscopy and electrochemical test were conducted to evaluate its performance.

Room temperature ammonia sensing properties of ZnO thin films grown by spray pyrolysis: Effect of Mg doping

Undoped and different molar concentrations of Mg-doped ZnO thin films were deposited on glass substrates via. spray pyrolysis process. Doping concentration was varied from 0.002 to 0.01 M in steps of 0.002 M. Structural, morphological, optical, electrical and room temperature gas sensing characteristics of undoped and Mg-doped ZnO thin films were investigated using X-Ray Diffractometer (XRD), Field Emission Scanning Electron Microscope (FE-SEM), UV–Vis Spectrophotometer and an electrometer respectively. Structural analysis revealed that all the films were polycrystalline in nature with hexagonal wurtzite crystal structure. Spherical shaped uniformly distributed grains were observed for all the films with slight change in size. The optical absorption edge shifted towards the lower wavelength with an increase in Mg-dopant concentration confirmed the blue-shift. Films with lower Mg-dopant concentration showed maximum response towards ammonia at room temperature with quick response and recovery times.

Effects of Mg doping in the quantum barriers on the efficiency droop of GaN based light emitting diodes**Project supported by the National Natural Science Foundation of China (Grant No. 41171143).

The effects of Mg doping in the quantum barriers (QBs) on the efficiency droop of GaN based light emitting diodes (LEDs) were investigated through a duel wavelength method. Barrier Mg doping would lead to the enhanced hole transportation and reduced polarization field in the quantum wells (QWs), both may reduce the efficiency droop. However, heavy Mg doping in the QBs would strongly deteriorate the crystal quality of the QWs grown after the doped QB. When increasing the injection current, the carriers would escape from the QWs between n-GaN and the doped QB and recombine non-radiatively in the QWs grown after the doped QB, leading to a serious efficiency droop.

Effect of Mg doping in ZnO buffer layer on ZnO thin film devices for electronic applications

Zinc Oxide (ZnO) thin films have been grown on p-silicon (Si) substrate using magnesium doped ZnO (Mg: ZnO) buffer layer by radio-frequency (RF) sputtering method. In this paper, we have optimized the concentration of Mg (0–5 atomic percent (at. %)) ZnO buffer layer to examine its effect on ZnO thin film based devices for electronic and optoelectronic applications. The crystalline nature, morphology and topography of the surface of the thin film have been characterized. The optical as well as electrical properties of the active ZnO film can be tailored by varying the concentration of Mg in the buffer layer. The crystallite size in the active ZnO thin film was found to increase with the Mg concentration in the buffer layer in the range of 0–3 at. % and subsequently decrease with increasing Mg atom concentration in the ZnO. The same was verified by the surface morphology and topography studies carried out with scanning electron microscope (SEM) and atomic electron microscopy (AFM) respectively. The reflectance in the visible region was measured to be less than 80% and found to decrease with increase in Mg concentration from 0 to 3 at. % in the buffer region. The optical bandgap was initially found to increase from 3.02 eV to 3.74 eV by increasing the Mg content from 0 to 3 at. % but subsequently decreases and drops down to 3.43 eV for a concentration of 5 at. %. The study of an Au:Pd/ZnO Schottky diode reveals that for optimum doping of the buffer layer the device exhibits superior rectifying behavior. The barrier height, ideality factor, rectification ratio, reverse saturation current and series resistance of the Schottky diode were extracted from the measured current voltage (I–V) characteristics.

Hollow microspheres Mg-doped ZrO2 nanoparticles: Green assisted synthesis and applications in photocatalysis and photoluminescence

The present investigation explores various morphologies and phases of Mg doped ZrO2 nanoparticles synthesized by green assisted route. The effect of Mg doping and Aloe Vera gel concentration on phase formation, morphology and optical properties of the nanoparticles were investigated. The photocatalytic performances of the photocatalysts were evaluated for the degradation of Rhodamine B under UV light. 2 mol% Mg doped ZrO2 displayed excellent photocatalytic activity with the degradation rate of 93%. The enhanced activity is attributed to UV light response, suitable monoclinic to tetragonal ratio as well as oxygen vacancies which greatly enhances the charge carrier separation. Further, the PL studies demonstrated that the present photocatalysts were highly potential for the fabrication of blue component of white light emitting diodes. The present work directs road map in designing of new phyto synthesized photocatalysts with superior activity for environmental clean-up and nanophosphors for display devices.

Mg-doped Li2FeSiO4/C as high-performance cathode material for lithium-ion battery

Mg-doped Li2FeSiO4/C is synthesized by using Fe2O3 nanoparticle as iron source. Through Rietveld refinement of X-ray diffraction data, it is confirmed that Mg-doped Li2FeSiO4 owns monoclinic P21/n structure and Mg occupies in Fe site in the lattice. Through energy dispersive X-ray measurement, it is detected that Mg element is distributed homogenously in the resulting product. The results of transmission electron microscopy measurement reveal that the effect of Mg-doping on Li2FeSiO4 crystallite size is not obvious. As a cathode material for lithium-ion battery, this Mg-doped Li2FeSiO4/C delivers high discharge capacity of 190 mAh g−1 (the capacity was with respect to the mass of Li2FeSiO4) at 0.1C and its capacity retention of 100 charge-discharge cycles reaches 96% at 0.1C. By the analysis of electrochemical impedance spectroscopy, it is concluded that Mg-doping can help to decrease the charge-transfer resistance and increase the Li+ diffusion capability.

Probing the low-energy structures of aluminum-magnesium alloy clusters: a detailed study.

The effect of Mg doping on the growth behavior and the electronic properties of aluminum clusters has been investigated theoretically using the CALYPSO (Crystal structure AnaLYsis by Particle Swarm Optimization) method in combination with density functional theory calculations. Compared to pure aluminum clusters, the structure of Mg-doped clusters shows the charming transformation with increasing atomic number. The photoelectron spectra (PES) of the global minima of anionic Aln and AlnMg (n = 3-20) clusters have been calculated based on the time-dependent density functional theory (TD-DFT) method. The reliability of our theoretical methodology is easily corroborated by the good agreement between the experimental PES and the simulated spectra. Our findings bring forth an ionic bonding with enhanced stability for the Al6Mg cluster, paired with a surprisingly large HOMO-LUMO gap, as would be expected from the magic number of 20 valence electrons.