Doping Of Mg Research Articles

Replacement behavior of Ti and Mg and selective separation of MgxTi3-xO5(x=1, 0.9, 0.75, 0.6) from Ti-bearing electric furnace smelting slag via super-gravity

Ti-bearing electric furnace smelting slag produced from direct reduction and electric furnace smelting process of vanadium titanomagnetite ore, contains a high TiO2 content of 40–55 wt%. While a mass of Mg, Al, Ca and Si are closely mixed with Ti in the slag, which greatly limits the recovery of Ti resource from the slag. In this work, the replacement behavior of Ti and Mg in MgxTi3-xO5 was studied, and selective separation of various MgxTi3-xO5 phases from Ti-bearing electric furnace smelting slag was conducted via super-gravity. It was found that Mg could replace Ti in Ti3O5 and form the MgxTi3-xO5, and increasing of cooling rate greatly limited the doping of Mg into MgxTi3-xO5, the MgxTi3-xO5 was transformed from (MgTi2)O5 to (Mg0.9Ti2.1)O5, (Mg0.75Ti2.25)O5 and (Mg0.6Ti2.4)O5 respectively. On this basis, various MgxTi3-xO5(x = 1, 0.9, 0.75, 0.6) phases were selectively separated from the smelting slag via super-gravity, where the mass fraction of TiO2 was increased from 78.69 to 90.32 wt% while that of MgO was decreased from 13.56 to 6.98 wt% with the increase of Ti/Mg ratio in MgxTi3-xO5. Moreover, the replacement mechanism of Mg and Ti was confirmed from characterization of crystal structure and lattice parameter of various separated high-purity MgxTi3-xO5 crystals.

Tungsten Infused Grain Boundaries Enabling Universal Performance Enhancement of Co-Free Ni-Rich Cathode Materials

Ni-rich cathode materials suffer from poor capacity retention due to micro-cracking and interfacial reactivity with electrolyte. Addition of tungsten (W) to some Ni-rich materials can improve capacity retention. Here, a WO3 surface coating is applied on Ni-rich hydroxide precursors before heating with lithium hydroxide. After heating in oxygen, Ni-rich materials with any of the commonly used dopants (magnesium, aluminum, manganese, etc.) show a “universal” improvement in capacity retention. Experimental characterization and theoretical modelling showed W was concentrated in the grain boundaries between the primary grains of secondary particles of the layered oxides, and W is incorporated in amorphous LixWyOz phases rather than as a substituent in the LiNiO2 lattice. This self-infusion of W in the grain boundaries during synthesis also significantly restricts primary crystallite grain growth. Along with smaller primary grain size, the LixWyOz phases in the grain boundaries lead to improved resistance to microcracking and reduced surface or interfacial reactivity. Improving the intrinsic properties of primary grains through doping of Mg, Al, or Mn and reinforcing the secondary particle structure mechanically and chemically using W or a similar element, M, that forms LixMOy phases and does not substitute into LiNiO2 is a universal strategy to improve polycrystalline Ni-rich materials.

Defects, dopants and lithium incorporation in LiPON electrolyte

Lithium phosphorus oxy-nitride (LiPON) is a candidate solid electrolyte material for potential use in rechargeable lithium-ion batteries. The use of density functional theory simulations has allowed us to gain atomic-scale insight into the defect properties, solution of dopants and incorporation of lithium in LiPON. The Li2O Schottky is the most favourable disorder process in this material ensuring the formation of Li and O vacancies which are in turn required for vacancy mediated self-diffusion. The Na, As and S are the promising isovalent dopants that can be substituted on the Li, P and O sites respectively. The doping of Mg on the Li site leads to the formation of Li vacancies in LiPON. The promising dopant on the P site to create Li interstitials and oxygen vacancies is the Ge. The stability of the crystal structure upon Li incorporation (up to four Li) was considered. The incorporation confirmed the formation of Li+ ions and expanded the volume of the lattice. Incorporation of multiple Li atoms is more favourable than a single Li incorporation. The band gap of this material decreases upon of Li incorporation without changing its insulating character.

(Invited) Selective Area Etching and Doping of GaN for High-Power Applications

Selective-area doping techniques of GaN have been studied intensively for high-power applications. Diffusion or implantation of dopants is a very mature approach in Si and SiC, but it is still under investigation for GaN. Selective area epitaxy and doping is an alternative method to overcome the barrier and is reported by many groups. Two aspects will be discussed, including selective-area etching and non-uniform Mg doping in non-planar regrown trenches.Dry etching has been commonly applied to create high-aspect ratio and smooth trenches, but has also been reported to generate serious optical and electronic defects and impurities on the treated surface. Here, we report using an in-situ etchant, tertiarybutylchloride (TBCl), to replace the dry etching process. In order to demonstrate the effectiveness of TBCl etching, planar PN diodes were grown and fabricated, including continuous, dry-etched, and TBCl-etched and regrown ones. TBCl-etched and regrown device demonstrates electrical properties approach that of the continuous grown diode in the forward and reverse biased conditions.On the other hand, non-uniform doping of Mg was observed in the non-planar regrowth by several groups. With nanoscale characterization technique, atom probe tomography (APT), we identified the origin of the non-uniformity. The Mg concentration is approximately inversely proportional to the growth rate beginning ~20 nm from the regrowth interface. It indicates that the existence of semi-polar facets together with the anisotropy in the growth rate are the origin of non-uniformity. Furthermore, the evolving shape of semi-polar facets could be explained by the kinetic Wulff theorem.

Morphological, structural, thermal and optical properties of Zn/Mg-doped TiO2 nanostructures for optoelectronic applications

The advanced research of new optoelectronic materials opens avenues for improved energy devices. In the present research, the facile synthesis of TiO2 nanoparticles and ZnO/Mg-doped TiO2 nanoparticles were carried out by sol–gel technique. The synthesized samples were characterized for morphological, structural, optical, and thermal properties. Scanning Electron Microscope (SEM) indicated that a distinct increase in the size of TiO2 nanoparticles due to ZnO/Mg-doping in the form of clusters. The crystalline nature of anatase TiO2 and doping of Mg and ZnO is corroborated by XRD patterns and Raman data. Moreover, ZnO and Mg doping affirm a clear shift in energy gap values confirmed by UV–Vis spectroscopic analysis and the surface plasmonic effects observed by photoluminescence analysis. TGA analysis indicates the remarkable results on the thermal stability of newly synthesized samples. It shows the maximum weight retention in the case of ZnO doped TiO2 nanostructures. Thus, these optimized materials can be recommended for future optoelectronic devices.

Taming the Redox Property of A0.5Co2.5O4 (A = Mg, Ca, Sr, Ba) toward High Catalytic Activity for N2O Decomposition

Nitrous oxide (N2O) originating from the combustion of fossil fuels causes serious environmental issues. The design and construction of a catalyst with high performance for the removal of N2O remains challenging. Herein, a series of alkaline-earth metal-modified A0.5Co2.5O4 (A = Mg, Ca, Sr, Ba) catalysts were initiated by a hydrothermal protocol, and their catalytic activities for N2O decomposition were systematically investigated by experimental and density functional theory calculation. The results reveal that the doping of alkaline-earth metals significantly affects the morphology, structure, active oxygen species, oxygen vacancy, and redox property and thereafter the catalytic activity of A0.5Co2.5O4 for N2O catalytic decomposition. The introduction of alkaline-earth metals (A = Ca, Sr, Ba) considerably promoted the reduction of Co3+ to Co2+, thereby improving the electron-donating ability and oxygen vacancy number and thereafter weakening the Co–O bond. As a result, the catalytic activity of N2O decomposition distinctively enhanced. Among them, Ba0.5Co2.5O4 shows optimal N2O decomposition performance by virtue of its outstanding active oxygen species and excellent redox property. However, the doping of Mg suppresses the electron-donating ability of Mg0.5Co2.5O4 and thereafter the catalytic activity for N2O decomposition. Therefore, this work may shine light on the understanding of N2O decomposition over alkaline-earth metal-modified Co-based oxides.

Electrochemical performances of LiNi0.83Co0.12Mn0.05O2 by dual doping of Mg and Ti

LiNi0.83Co0.12Mn0.05O2 (NCM83) is considered as a potential cathode material owing to its high energy density and low cost, yet the discharge capacity decays rapidly with the cycles. Dual doping of Mg and Ti is used to improve electrochemical stability. MgxTixMn1-2x(OH)2+x is uniformly coated on the surface of precursor particles by co-precipitation method, and MgxTixMn1-2x diffuses evenly during the sintering process. Mg and Ti successfully enter into the crystal lattice of NCM83. The cells are cycled in 2.8–4.5 V at 1C for 200 cycles. The specific capacity of NCM83 is 192.1 mAh g−1, and the capacity retention is 61.8% after 200 cycles. The cyclability can be significantly enhanced by dual doping of Mg and Ti, which can maintain 84.3% capacity under the same condition.

Role of Zn and Mg substitutions on the mechanical behaviour of biomimetic hydroxyapatite and insight of the emergence of hydroxyapatite-ZnO nanocomposite

A simple and inexpensive biomimetic method is attempted to produce hydroxyapatite (HAp), Mg-/Zn-doped HAp and HAp-ZnO nanocomposite. An aqueous calcium solution with and without precursors of Mg2+ or Zn2+ and a carbonate containing phosphate solution are prepared at a temperature of 37 °C with pH of 7.4 and mixed in equal volumes to obtain the calcifying solution, which has similar ionic constituents as that of human blood plasma. At a temperature of 37 °C, reactions drive the calcifying solution to supersaturation for the crystallization of carbonated HAp, Mg-/Zn-doped HAp, and HAp-ZnO nanocomposite. The microstructural and morphological analyses reveal that the carbonated HAp can sustain low doping of Mg and Zn substituting at Ca sites, wherein Zn is likely to replace screw axis Ca preferentially. Significant lattice distortion leads to the transformation of nanophase HAp to amorphous calcium phosphate when Mg content in the calcium solution is increased to 40% of (Ca + Mg) solute concentration. The role of Zn is more intriguing – Ca-vacancy mediated substitution is favourable when Zn content is below 15% of (Ca + Zn) solute concentration and subsequent increase leads to the emergence of spherical ZnO nanocrystals coexisting with needle-like HAp nanocrystals. The present work describes a new way of synthesizing HAp-ZnO nanocomposite – a potential candidate for the orthopaedic and the prosthodontic applications. Simply increasing Zn content in the calcium solution and without using additional precursors, reaction pathways lead to the precipitation of HAp-ZnO nanocomposite. Field emission transmission electron microscopy reveals that when Zn/(Ca + Zn) molar ratio in the calcifying solution is set at 40%, the resulting nanocomposite is characterized by 5 nm average diameter needle shaped HAp with 15–30 nm spherical ZnO particles as an intimate mixture of two nanophase systems. The mechanical properties of HAp evaluated using the X-ray elastic constants and the modified Williamson-Hall analyses suggest a clear decreasing trend of the apparent domain size with increasing Mg and Zn incorporations while microstrain, isotropic stress, and uniform deformation energy density of nanophase HAp rise only with increasing Mg substitutions.

Characteristics of MgIn2O4 Thin Film Transistors Enhanced by Introducing an MgO Buffer Layer

In this work, an MgIn2O4 (MIO) thin film transistor (TFT) with a bottom gate structure was fabricated. The MIO channel layer was deposited by RF sputtering using a single MgIn2O4 target. The performance of MIO TFT was highly related to oxygen vacancies. As-deposited MIO TFT showed a low field-effect mobility due to doping of Mg. An MgO buffer layer was introduced to enhance the mobility of MIO TFT due to improvement of the interface with the channel layer. In addition, oxygen vacancies in the MIO channel were suppressed because of oxygen diffusion from the buffer layer. MIO TFT with a 5 nm MgO buffer layer showed an on/off current ratio of 9.68 × 103, a field-effect mobility of 4.81 cm2/V∙s, which was increased more than an order of magnitude compared with the device without a buffer layer, a threshold voltage of 2.01 V, and a subthreshold swing of 0.76 V/decade, which was improved more than 20% compared with the as-deposited one.

Mg acceptor doping in MOCVD (010) β -Ga2O3

In this Letter, in situ Mg doping in β-Ga2O3 was demonstrated via metalorganic chemical vapor deposition (MOCVD) epitaxy. The electrical insulating property of the Mg acceptors in β-Ga2O3 was found to be intrinsically activated in the as-grown Mg-doped β-Ga2O3 thin films. Growth conditions for MOCVD β-Ga2O3 were further explored and optimized at a lower growth temperature regime, leading to a better confinement of the Mg-doping profile. Detailed analysis of Mg diffusion characteristics revealed a diffusion barrier energy Ebarrier ∼ 0.9 eV for Mg in MOCVD β-Ga2O3, which is likely related to an interstitial-assisted process. Surface morphologies and electron transport were characterized on samples grown with different growth temperatures and Mg doping levels. The MOCVD growth method demonstrated its feasibility to grow semi-insulating Mg-doped β-Ga2O3 epilayers with controllable Mg incorporation while maintaining good material quality and smooth surface morphology. From capacitance-voltage charge profiling, it is verified that the Mg-doped buffer layer grown at the substrate-epilayer interface could effectively compensate the charge accumulation at the interface. The in situ acceptor doping of Mg in MOCVD β-Ga2O3 will provide versatility for designing β-Ga2O3 power devices.

New synthetic methodology to enhance Mg doping in SnS2: structural characterization and photocatalytic activity

A new modified synthetic methodology was developed to effectively introduce more amount of Mg in the structure of SnS2. The amount of Mg that is doped in the structure of SnS2 was obtained from the changes in the structural parameter (lattice parameter and occupancy, as observed through Rietveld refinement) and inductively coupled plasma mass spectrometry studies, giving conclusive evidence of doping of Mg in SnS2. We observed that, with the methodology adopted, the doping could be increased up to 11.4%. The effect of doping on optical and photocatalytic properties was demonstrated.

Tailoring Bandgap and Electrical Properties of Magnesium-Doped Aluminum Zinc Oxide Films Deposited by Reactive Sputtering Using Metallic Mg and Al–Zn Targets

Bandgap enlarged Mg-doped aluminum zinc oxide (Mg-doped AZO) film is a potential transparent conducting oxide for applications in photonics devices. The oxide film normally deposited by sputtering, particularly using ceramic targets, while maintaining its pristine property for the film deposited using metallic targets is rarely addressed. This study investigated the optical and electrical properties of Mg-doped AZO films that were performed by a magnetron reactive co-sputtering method using metallic Mg and Al–Zn targets. Doping of Mg in the AZO significantly affects the electrical resistivity and optical transmission of the films because Mg tends to replace part of Zn lattice sites. The 1.2 at.% Mg-doped AZO film had an electrical resistivity of 7.9 × 10−4 Ω·cm, an optical transmittance of 92.6% in the visible light range, and a bandgap of 3.66 eV when the film was post-annealed at 600 °C. The Mg doping widens the bandgap and, thus, increases the transmittance of the AZO film. Because of the superior electrical and optical characteristics, the Mg-doped AZO films prepared using the metallic targets can be a reliable transparent conducting oxide for applications.

Ferroelectric and Electrical Properties Optimization of Mg-doped BiFeO3 Flexible Multiferroic Films

Bi1-xMgxFeO3 (BMFO, x = 0, 0.02, 0.04, 0.06 and 0.08) multiferroic films were directly synthesized on flexible stainless steel (FSS), save the bottom electrode process, by means of sol–gel spin-coating technology. The effects of different bending conditions on ferroelectric, dielectric and leakage-current properties of BMFO films were investigated. The leakage-current densities of BiFeO3 (BFO, x = 0) and BMFO (x = 0.06) films were 5.86 × 10−4 and 3.73 × 10−7 A/cm2, which shows that the BMFO (x = 0.06) has more than three orders of magnitude lower than that of BFO film. The residual polarization (2 Pr) can be enhanced from 120 to 140 μC/cm2. The proper doping of Mg in BiFeO3 film could provide an effective method for reducing the leakage-current values as well as boosting the ferroelectric properties. In this study, the leakage-current mechanism of low electric field and high electric field of BMFO film is analyzed and established. In addition, the flexible BMFO film maintains practical ferroelectric and leakage-current properties at retention time of 106 s under different symmetry bending conditions. These results indicate that the BFMO film will be very practical in opto-electronic and storage device applications.

Effect of Mg(II) and Na(I) Doping on the Electronic Structure and Mechanical Properties of Kaolinite

Because kaolinite has multiple defects, it is very important to study the effect of different doped cations on the electronic structure and mechanical properties of kaolinite (Al4Si4O18H8) from the microscopic point of view with the first-principle calculation method. The results exhibited that the doping of Mg(II) and Na(I) makes the ion bond and layer spacing of kaolinite crystal change, and the bond length of the chemical bond between the doped and O atom is positively related to the atomic radius of the doped cations. Compared with undoped kaolinite crystal, the band gap width of the Mg-doped and Na-doped kaolinite crystal was larger, but the typical insulator characteristics were still maintained. Compared with undoped kaolinite crystal, Mg-doped and Na-doped kaolinite crystal had more electron transfer to O, while the Mg–O bond and Na–O bond had more ionic bond properties and less covalent bond composition than the Al–O bond. Finally, the elastic properties of undoped, Mg-doped, and Na-doped kaolinite crystal were further analyzed by calculating the elastic constant matrix. The influence of doping Mg(II) and Na(I) on C11 and C22 was greater than that on C33, indicating that doping had a greater influence on the stiffness in the direction of the parallel crystal plane. The doping of Mg(II) and Na(I) weakened the rigidity of kaolinite crystal materials and improved the plasticity and ductility of the materials. The atom-scale information provided a basis for explaining the mechanical behavior of kaolinite and is expected to provide guidance for solving the deformation problems in soft rock roadways.

Probing phase transition in VO2 with the novel observation of low-frequency collective spin excitation

VO2 is well known for its first order, reversible, metal-to-insulator transition (MIT) along with a simultaneous structural phase transition (SPT) from a high-temperature metallic rutile tetragonal (R) to an insulating low-temperature monoclinic (M1) phase via two other insulating metastable phases of monoclinic M2 and triclinic T. At the same time, VO2 gains tremendous attention because of the half-a-century-old controversy over its origin, whether electron-electron correlation or electron-phonon coupling trigger the phase transition. In this regard, V1-xMgxO2 samples were grown in stable phases of VO2 (M1, M2, and T) by controlled doping of Mg. We have observed a new collective mode in the low-frequency Raman spectra of all three insulating M1, M2 and T phases. We identify this mode with the breather (singlet spin excitation) mode about a spin-Pierls dimerized one dimensional spin ½ Heisenberg chain. The measured frequencies of these collective modes are phenomenologically consistent with the superexchange coupling strength between V spin ½ moments in all three phases. The significant deviation of Stokes to anti-Stokes intensity ratio of this low-frequency Raman mode from the usual thermal factor exp(hʋ/KBT) for phonons, and the orthogonal dependency of the phonon and spinon vibration in the polarized Raman study confirm its origin as spin excitations. The shift in the frequency of spin-wave and simultaneous increase in the transition temperature in the absence of any structural change confirms that SPT does not prompt MIT in VO2. On the other hand, the presence of spin-wave confirms the perturbation due to spin-Peierls dimerization leading to SPT. Thus, the observation of spin-excitations resulting from 1-D Heisenberg spin-½ chain can finally resolve the years-long debate in VO2 and can be extended to oxide-based multiferroics, which are useful for various potential device applications.

Influences of Mg and Mn doping on structure, B-site ordering and microwave dielectric properties of Ba(Co1/3Nb2/3)O3 ceramics

Influence of Mg and Mn doping on structure and microwave dielectric properties of Ba(Co1/3Nb2/3)O3 (BCN) ceramics with complex perovskite structure is investigated systematically. X-ray diffraction and Raman spectrum investigations show that doping Mg and Mn into BCN ceramics is helpful for improving the quality factor (Q · f value) resulted from enhanced B-site 1:2 ordering degree. Mg- doped samples show higher ordering degrees and larger Q · f values than Mn- doped counterparts. The sintering density, grain size, 1:2 B-site ordering structure and microwave dielectric properties of BCN ceramics show a strong dependence on Mg and Mn doping content. The sintering density of BCN ceramics can be increased significantly by doping a small amount of Mg and Mn. However, further increase in doping content results in the decrease of sintering density. τf value of BCN ceramics can be tailored by doping of Mg into Co sites. The near-zero τf value (∼0.64 ppm °C−1) is obtained when the Mg doping content is at x = 0.1. The ordering degree and Q · f value of Mg- and Mn- doped BCN ceramics increase significantly with increasing annealing time.

Implementation of magnesium doping in SrTiO3 for correlating electronic, structural and optical properties: A DFT study

In present work the structural, electronic and optical properties of Pure and Mg-doped SrTiO3 perovskites are calculated via implementing density functional theory calculation. To explore these properties, ultra-soft pseudo-potential (USP) and generalized gradient approximation (GGA) is used. The inclusion of Mg at the Sr site in SrTiO3 not only affects the electronic band structure through generating new gamma points but also band gap increases from 1.788 eV to 1.866 eV. The introduction of Mg is well explained by the partial and total density of states which is affected by incorporating dopant in pure SrTiO3. Optical properties also affected by doping. The absorption edge shifted towards lower value from 0.37 eV to 0.06 eV as Mg-doped in the pure SrTiO3 that represented a red shift. The refractive index increases by doping as of 2.49 to 2.52.The doping of Mg in SrTiO3 affects positively in electronic and optical properties and makes this material a very interesting candidate for optical devices.

Synthesis and Characterization of Mg Doped ZnO and Importance of Secondary Phases

Magnesium (Mg) doped zinc oxide (ZnO) is synthesized by nitriding method at 300 °C. XRD studies shows that crystallite size at 300 °C is 27.3 nm. The secondary phase shows the disruption of the hexagonal structure of the ZnO. EDAX confirms the presence of Zn, Mg and O and hence the sample is pure. FTIR studies confirm the presence of ZnO and MgO. Optoelectronic studies are also conducted and it has been confirmed that due to the doping of Mg and also which is present in secondary phase, the PL spectra shows a broad red shift from 633 nm to 651 nm, which shows the significance of the secondary phases.

Effect of magnesium doping on band gap and optical properties of SrZrO3 perovskite: A first-principles study

In this paper we present the First-principles calculations, established on the density functional theory (DFT) by using generalized gradient approximation (GGA) and ultra-soft pseudo-potential (USP), study to investigate Magnesium (Mg) doping outcome on the different properties of SrZrO3. The impacts on electronic structure and hence optical properties from Mg-doping have been explored and are reviewed in detail by implementing the conception of TDOS and PDOS. Replacement of Strontium (Sr) atom by Mg tunes the electronic band structure quite significantly with the emergence of new states at Gamma point. Due to this SrZrO3 indirect band gap is transformed to the direct one for Mg-doped SrZrO3. The density of states for Mg-doped in SrZrO3 relocate themselves at slightly lower energies and there is strong interaction between Mg-atom and its surrounding atoms is observed. Furthermore, at the conduction band bottom and partial density of states of SrZrO3 change appreciably and hence we conclude that the electronic band structure is affected by Mg-doping. The optical properties of the un-doped and doped SrZrO3 are investigated and are correlated with electronic structure. The enormous variation in optical properties and band gap (i.e indirect to direct) by doping of Mg declares this material as attractive contender for optoelectronic materials.

Correlation between electrical resistivity and optical transmittance of Mg- and Ga-doped ZnO window layers in NIR-IR region and its effect on current density of kesterite solar cells

The doping of Mg and Ga into ZnO is a method for obtaining excellent optical and electrical properties for a window layer in an inorganic solar cell. Because a tradeoff exists between the electrical and optical properties in the window layer, balancing them is important for enhancing the performance of the solar cells. From this viewpoint, the thickness change of the window layer affects the transmittance and the conductivity. In particular, it affects the transmittance in the NIR-IR region significantly, which can enhance the current collection but lead to poor conductivity when the transmittance of the window layer is increased. We examine the thickness effect of MGZO films for CZTSSe solar cells in order to determine the optimal conversion efficiency. The enhanced transmittance in the NIR-IR region with a thin MGZO layer contributed to a high current density, although the electrical resistivity was relatively high. An enhanced conversion efficiency of 7.54% was eventually recorded for an optimal thickness of the MGZO layer with an improved current density over 7 mA/cm2.