Structure Of MgO Research Articles

Study of the influence of nitrogen doping on magnetic anisotropy in CoFe/MgO thin films with different deposition sequences

Abstract The ferromagnetic (FM)/MgO structure multilayers with perpendicular magnetic anisotropy (PMA) play a crucial role in magnetic random-access memory. It is essential to explore the methods for modulating magnetic anisotropy and to clarify the underlying mechanisms. We study the regulation of the magnetic anisotropy with nitrogen (N) doping concentration (CN) in two samples: Ta/CoFe(N)/MgO/Ta (S1) and Ta/MgO/CoFe(N)/Ta (S2) with different deposition sequences. The S1 sample exhibits in-plane magnetic anisotropy (IMA) without N doping. And the sample presents PMA when CN = 15%. The S2 sample shows weak PMA without N doping, and the sample converts to IMA when CN = 15%. X-ray photoelectron spectroscopy is performed to evaluate the oxidation level of Fe at the CoFe/MgO interface by the peak area ratio of Fe oxide to Fe (ϵ). It is believed that excessively high and low ϵ values correspond to over-oxidation and under-oxidation of Fe, respectively. For films deposited in different sequences, both over-oxidation and under-oxidation lead to IMA, while moderate oxidation facilitates the formation of PMA. The microstructure analysis reveals that the N doping does not affect the crystallization of the films, indicating that magnetocrystalline anisotropy has a minor influence on the changes of K eff.

Green synthesis of magnesium oxide nanoparticles using Hyphaene thebaica extract and their photocatalytic activities

Magnesium oxide nanoparticles (MgO NPs) represent an interesting inorganic material widely utilized across various fields including sensing, antimicrobial applications, optical coatings, water purification, fuel additives, absorbents, and catalysis, owing to their exceptional broad energy band gap, surface affinity, and strong chemical and thermal durability. In this investigation, MgO NPs were successfully synthesized through a green approach employing fruit extract from the gingerbread tree (Hyphaene thebaica). Analysis via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed their agglomerated quasi-spherical shape with a size range of 20–60 nm. The X-ray diffraction (XRD) pattern exhibited prominent peaks at planes (200) and (220), indicating the high crystallinity of MgO NPs with a crystallite size of 32.6 ± 5 nm while Energy-dispersive X-ray spectroscopy (EDS) analysis highlighted the composition comprises 40.47% Magnesium and 48.64% Oxygen by weight. Fourier transform infrared spectroscopy (FT-IR) revealed characteristic Mg-O bonds through peaks at 560 cm−1 and 866 cm−1, while Raman spectroscopy affirmed the cubic structure of MgO. Subsequently, the photocatalytic performance of MgO NPs under visible light irradiation was evaluated. Remarkably, the addition of 1 g/L of MgO nano-catalyst resulted in a degradation efficiency of 98% after 110 min on methylene blue dye, showcasing the high catalytic activity of MgO NPs. This remarkable photocatalytic efficiency emphasizes the potential of MgO NPs in environmental remediation.

In-situ synthesis of samarium activated MgO–LaAlO3 nanocomposite for enhanced and prolonged phosphorescence

A series of MgO–La1-xAlO3:xSm (x = 0–5 mol.%) nanocomposite phosphors have been synthesized in-situ using Pechini sol-gel method. The rhombohedral and face-centered crystal structures of LaAlO3 and MgO, respectively, were corroborated utilizing X-Ray Diffractograms and their Rietveld refinement. The optical band gaps of these nanocomposites have been observed in the range of 5.20–5.63 eV. Upon excitation by n-UV 405 nm radiation, the emission characteristics of these phosphors spanning 450–750 nm have been thoroughly investigated. The most notable emission occurred at 599 nm in the orange region, confirmed by CIE-1931 chromaticity coordinates. The MgO–La1-xAlO3:xSm (x = 2 mol.%) is found to be the optimum concentration exhibiting maximum luminescence with a high color purity of 90 %. Insights from Riesfeld's theory pointed towards d-q multipolar interactions as the underlying mechanism behind concentration quenching observed beyond this optimum concentration. Bi-exponential decay behavior was observed via Time-Resolved Photoluminescence (TRPL) technique, with an Internal Quantum Efficiency of 63 % calculated utilizing Auzel's formalism. The study extensively explored the impact of MgO addition on the crystallite size, band-gap, luminescence, and life-time properties, attributing the enhanced and prolonged luminescence behavior to the MgO–La1-xAlO3:xSm (x = 2 mol.%) nanocomposite. Assessment of additional parameters such as CCT (Correlated Color Temperature) and energy transfer efficiencies further reinforced the suitability of these orange emissive phosphors for potential applications in photonics and forensics, underlining their promising prospects in various technological domains.

Understanding the multiplet fine structures of MgO: Cr3+ with combination method of first−principles calculations and ligand field theory

The interpretative and predictive capabilities on the energy fine structures of transition metal ions in solids are explored by integrating the first -principles calculations with ligand-field (LF) theory. The charge-compensated site of MgO: Cr3+ is chosen as a case and the aim is to determine the energy-level fine structure and EPR g factor g// and g⊥. The approach involves initially computing all the required parameters for LF theory through first-principles calculations, and these parameters are subsequently fed into the LF model Hamiltonian, which fully incorporates interactions between different spectrum terms through the LF operator, spin-orbit coupling (SOC) operator and other relevant factors. The calculated zero-field splitting parameter D and g factors of the ground term A24(t23) are reasonably good agreement with the experimental observations. However, the energy levels of excited states are slightly underestimated compared to experimental values due to the underestimation of Racah parameters in the first-principles calculations, except the T24[t22(T13)e] term which is insensitive to Racah parameters for it is equal to 10Dq relative to ground term A24(t23) with possible minor corrections due to perturbations.

Enhancing the comprehensive performance of MgO–MgAlON composite refractories synthesized from natural minerals

Developing and designing carbon-free refractory materials is an effective alternative to MgO–C refractory materials to produce large-scale, high-quality, low-carbon special steels. Therefore, in this work, excessive MgO is introduced into MgAlON to prepare a series of MgO–MgAlON composite refractories. The enhancement mechanism of comprehensive performance is systematically evaluated, where MgO as a reinforcer features intergranular phase strengthening and grain boundary purification effects. Besides, the pore structure of MgO–MgAlON composite refractories is also optimized to regulate the molten slag wetting behavior. The results demonstrated that MgO–MgAlON composite refractories have apparent porosity of 13.86%–15.84 %, bulk density of 2.78–2.97 mg cm−3, and compressive strength of 204.17–253.97 MPa. When 42.8 % MgO is introduced, the sample strength retention ratio after thermal shock measurement and slag corrosion experiments are 64 % and 75 %, respectively. Consequently, a cost-effective and feasible reinforcement strategy for MgO–MgAlON composite refractories is proposed, paving the way for.

Synthesis, Characterization, and Photocatalytic Activity of Cu-Doped MgO Nanoparticles on Degradation of Methyl Orange (MO)

The purpose of this study is to synthesize Cu-doped MgO nanoparticles and test the performance of photocatalytic degradation of methyl orange (MO). Mg(NO3)2, CuCl2, NaOH, and fresh Calotropis procera leaf extract were used as precursors. The prepared nanoparticles were characterized by using FT-IR, XRD, SEM, and UV-Vis spectrometer to study the functional group, crystal structure, surface morphology, and absorption edge, respectively. The wide band above 3000 cm−1 from the FT-IR spectrum corresponds to the stretching vibrations of flavonoids and phenolic compounds of Calotropis procera leaf extract. Furthermore, the Mg-O bonding of undoped MgO and Cu-doped MgO NPs is represented by new peaks which appeared at 831 and 835 cm−1, respectively. The crystal size of undoped MgO and Cu-doped MgO nanoparticles is 13.04 nm and 12.08 nm, respectively. The SEM microstructure of pure MgO showed higher agglomeration than the Cu-doped MgO nanoparticles. The degradation efficiency of the Cu-doped MgO NPs was compared with that of the MgO NPs, and the photocatalytic activity of these NPs was evaluated using the photocatalytic degradation rates of MO dye. Cu-doped MgO NPs showed higher degradation efficiency than pure MgO NPs. The insertion of Cu in the MgO structure improved the photocatalytic efficiency of the MgO NPs under optimal conditions. Therefore, Cu-doped MgO exhibits high photocatalytic activity compared with undoped MgO nanoparticles under sunlight irradiation.

Characterisation of the ground X+ 2ΠΩ and first excited A+ 2Σ+ electronic states of MgO+ by high-resolution photoelectron spectroscopy.

Despite the importance of MgO+ for understanding the electronic structure and chemical bonds in alkaline-earth metal oxides and its potential astrophysical relevance, hardly any spectroscopic information is available on this molecular cation. We report on a high-resolution photoelectron spectroscopic study of MgO using a resonant (1 + 1') two-photon excitation scheme in combination with PFI-ZEKE photoelectron spectroscopy. By carrying out the resonant excitation via selected rotational levels of several intermediate states of different electronic configurations, total electronic spins, and internuclear distances, a broad range of vibrational levels of the X+ 2ΠΩ (Ω = 3/2, 1/2) ground and A+ 2Σ+ first excited states of MgO+ were observed for the first time. The new data provide a full characterisation of the rovibronic level structure of MgO+ up to 2 eV (16 000 cm-1) of internal energy. A full set of vibrational, rotational and spin-orbit-coupling molecular constants were extracted for these two electronic states. The adiabatic ionisation energy and the singlet-triplet interval of 24Mg16O were determined to be 64 577.65(20) cm-1 and 2492.4(3) cm-1, respectively.

Improved Thermophysical and Mechanical Properties in LiNaSO4 Composites for Thermal Energy Storage.

Solid-solid phase-change materials have great potential for developing compact and low-cost thermal storage systems. The solid-state nature of these materials enables the design of systems analogous to those based on natural rocks but with an extraordinarily higher energy density. In this scenario, the evaluation and improvement of the mechanical and thermophysical properties of these solid-solid PCMs are key to exploiting their full potential. In this study, LiNaSO4-based composites, comprising porous MgO and expanded graphite (EG) as the dispersed phases and LiNaSO4 as the matrix, have been prepared with the aim of enhancing the thermophysical and mechanical properties of LiNaSO4. The characteristic structure of MgO and the high degree of crystallinity of the EG600 confer on the LiNaSO4 sample mechanical stability, which leads to an increase in the Young's modulus (almost three times higher) compared to the pure LiNaSO4 sample. These materials are proposed as a suitable candidate for thermal energy storage applications at high temperatures (400-550 °C). The addition of 5 wt.% of MgO or 5% of EG had a minor influence on the solid-solid phase change temperature and enthalpy; however, other thermal properties such as thermal conductivity or specific heat capacity were increased, extending the scope of PCMs use.

Novel MgO and Ag/MgO nanoparticles green-synthesis for antibacterial and photocatalytic applications: A kinetics-mechanism & recyclability

The present study identifies the novel nano production of MgO nanoparticles as well as the Ag decoration of MgO nanoparticles using Morinda tinctoria plant extract. Green compounds are used to reduce zero valent atoms and to decorate metal oxide surfaces. X-ray Diffractometer analysis (XRD) was used to examine the cubic structure of MgO (28 nm) and Ag/MgO (21 nm) nanoparticles. Fourier transform infrared spectroscopy (FTIR) analysis was used to determine the reactive functional groups, metal–oxygen bonding, and OH molecules. Ultra-Violet Diffuse Reflectance Spectroscopy (UV-DRS) analysis revealed the optical entity and their orbital electron shift. Using the Kubelka-Munk relation, the optical defect of MgO (4.68 eV) and Ag/MgO (3.18 eV) nanoparticles was calculated. Scanning Electron Microscope (SEM) indicated surface decorations and their pure MgO nanoparticles rod-like shape, and Energy-Dispersive X-Ray Spectroscopy (EDX) identified their elements. TEM analysis confirmed the poly-dispersive nature of the Ag decorations on the MgO surface. X-Ray Photoelectron Spectroscopy (XPS) was used to determine the valency of metal (Ag-3d) and metal oxide (Mg-2 s&O-1 s). MgO and Ag/MgO were used in visible light photocatalytic dye degradation of Rh-B dye. The biological properties were tested against S.aureus and E.coli. The plasmonic decoration on the MgO surface accelerated photodegradation and increased biological susceptibility. The innovative characteristics of this work squeeze the green synthesis of Ag/MgO nanoparticles, their improved photocatalytic and antibacterial performance, and their potential applications in water remediation and biomedicine.

Drug kinetics and antimicrobial properties of quaternary bioactive glasses 81S(81SiO2-(16-x)CaO-2P2O5-1Na2O-xMgO); an in-vitro study

Bioactive glasses have recently been attracted to meet the challenge in bone tissue regeneration, repair, healing, dental implants, etc. Among the conventional bio-glasses, a novel quaternary mesoporous nano bio-glass with composition 81S(81SiO2-(16-x)CaO-2P2O5-1Na2O-xMgO) (x = 0, 1.6, 2.4, 4 and 8 mol%) employing Stober's method has been explored for examining the above potential application through in-vitro SBF assay, MTT assay, antimicrobial activity and drug loading and release ability. With increasing the MgO concentration up to 4 mol%, from in-vitro SBF assay, we observe that HAp layer develops on the surface of the nBGs confirmed from XRD, FTIR and FESEM. MTT assay using MG-63 cells confirms the biocompatibility of the nBGs having cell viability >225 % for MGO_4 after 72 h which is more than the clinically used 45S5 bio-glass. We have observed cell viability of >125 % even after 168 h. Moreover, MGO_4 is found to restrict the growth of E. coli by 65 % while S. aureus by 75 %, confirming the antimicrobial activity. Despite an increase in the concentration of magnesium, nBGs are found to be non-toxic towards the RBCs up to 4 mol% of MgO while for 8 %, the hemolysis percentage is >6 % which is toxic. Being confirmed MGO_4 nBG as a bioactive material, various concentrations of drug (Dexamethasone (DEX)) loading and release kinetics are examined. We show that 80 % of loading in case of 10 mg-ml−1 and 70 % of cumulative release in 100 h. The mesoporous structure of MGO_4 having an average pore diameter of 5 nm and surface area of 216 m2 g−1 confirmed from BET supports the loading and release kinetics. We conclude that the quaternary MGO_4 nBG may be employed effectively for bone tissue regeneration due to its high biocompatibility, excellent in-vitro cell viability, antimicrobial response and protracted drug release.

Compositional Effect on the Structure and Properties of MgO–Al2O3–SiO2 Ternary Glasses

Compositional Effect on the Structure and Properties of MgO–Al2O3–SiO2 Ternary Glasses

Effects of alkali-metal nitrate salts on hydrotalcite-based sorbents for enhanced cyclic CO2 capture at high temperatures

CO2 capture using solid-based adsorbents at high temperatures has been in the spotlight as a CO2 capture and storage (CCS) technology for solving global warming and climate change problems. Hydrotalcite is an anionic clay that is widely used as a CO2 sorbent at temperatures of 200–400 °C. In various methods to improve the relatively low CO2 uptake of hydrotalcite, the hydrotalcites with a high Mg/Al molar ratio achieved significantly increased CO2 sorption uptake. This was because the preparation method allowed incorporation of NaNO3 in the hydrotalcite structure; the maximum CO2 sorption uptake was measured as 28.4 wt% when the Mg/Al molar ratio was 30. The different degrees of NaNO3 melting, depending on the sorption temperature, led to different CO2 sorption kinetics and uptakes at 250, 275, and 300 °C. Over the repeated sorption-desorption cycles, the CO2 cyclic capacity continuously decreased under sorption at 250 and 275 °C, whereas it increased at 300 °C, regardless of the Mg/Al molar ratio. The partial melting of NaNO3 at 250 and 275 °C, below its melting temperature, provided insufficient rearrangement of molten NaNO3. This further caused sintering of the MgO structure, which also increased its crystallite size. Conversely, the accelerated rearrangement of molten NaNO3 at 300 °C, near its melting temperature, and the low CO2 uptake at the initial step inhibited sintering. Different changes in the strength of CO2 sorption on the hydrotalcite-based sorbents also appeared as the cycle number increased.

Crystal structure and phase formation of MgO–MoO3‐based ceramics with ultralow dielectric loss: A comprehensive study

AbstractThe MgO‐MoO3 system shows significant potential for applications in microwave dielectric ceramics. However, the formation mechanism, crystal structures, and microwave dielectric properties of this system have not been systematically investigated. This work aims to comprehensively study the crystal structures, phase transitions, and microwave dielectric properties of compounds in the MgO‐MoO3 system. In particular, the research delves into the unexplored transformation mechanism from β‐MgMo2O7 to α‐MgMo2O7 and MgMoO4. As a result, the three compounds exhibiting favorable microwave dielectric properties have been successfully fabricated. These compounds can be effectively sintered at temperatures ranging from 685 to 900°C and exhibited dielectric constants (εr) ranging from 5.41 to 6.89, as well as Qf values ranging from 100 000 to 130 000 GHz. Additionally, prototype microstrip antennas are designed and fabricated using β‐MgMo2O7 and MgMoO4 ceramics as substrates. The obtained antenna's performance is excellent, with S11 values below −30 dB and a gain exceeding 6 dB at 5.8 GHz, highlighting the potential of the developed ceramics for practical applications in microwave devices.

Study of vibrational modes of MeV Ni ion implanted MgO crystal

The control over various vacancy and substitutional defects by ion implantation provides many interesting properties for the modulation of materials. In this report, we studied the effect of defects and anionic vacancies produced by MeV Ni ion implanted single crystal MgO on different vibrational active modes. The breathing mode of D bands is observed for most of the Raman peaks, and simultaneously, the overlapping of D and G bands is confirmed from Raman spectra. The Fourier Transform Infrared spectra identified the stretching and bending vibrations of Mg, O, and Ni atoms and compared them with pristine. The presence of atmospheric constituents and their role in affecting the vibrational modes are well justified. The phonon band and density of states calculation in the framework of density functional theory confirms the presence of T1u and T2u Raman active mode that arises due to vibration from different vacancy and substitutional defect associated in MgO structures, agrees well with experimental results. The tunable anionic vacancies produced in MgO by ion implantation can be beneficial to form the filament in valance charge memory-based resistive random-access memory (RRAM).

Effect of Ti/P ratio on structure, crystallization behaviour and photocatalytic activity of MgO–TiO2–P2O5–Al2O3–SiO2 glass-ceramics

In the present work, MgO–TiO2–P2O5–Al2O3–SiO2 glasses with different Ti/P ratios were prepared by the melt-quenching method, and Mg0.5Ti2(PO4)3 glass-ceramics were obtained by controllable crystallization. The effects of the Ti/P ratio on the structure, crystallization behaviour, and properties of the glasses and glass-ceramics were studied by FTIR, DSC, XRD, EDS, UV–Vis DRS, and so on. The results show that with the increase of the Ti/P ratio, the content of the [TiO6] group and Ti–O–P bond in the glass network increases, which strengthens the cross-linking of the glass network. However, the decrease of glass former P2O5 reduces the thermal stability of the glass. The appropriate Ti/P ratio is beneficial to the formation of single-phase glass-ceramics, and the band gap width of glass-ceramics containing single Mg0.5Ti2(PO4)3 crystal phase is 3.0 eV. With the irradiation of a high-pressure mercury lamp for 120 min, the glass-ceramics after crystallization at 850 °C for 4 h can effectively degrade MB dye solution (41%∼75%). The potential application prospect of the prepared glass-ceramics in the field of water purification of organic dyes was confirmed.

Enhancement in Interfacial Dzyaloshinskii–Moriya Interaction in Pt/CoFe(B)/MgO Structures by Suppression of FePt Interface Phases with the Addition of Boron

Enhancement in Interfacial Dzyaloshinskii–Moriya Interaction in Pt/CoFe(B)/MgO Structures by Suppression of FePt Interface Phases with the Addition of Boron

Solid-State Reaction Synthesis of MgAl2O4 Spinel from MgO-Al2O3 Composite Particles Prepared via Electrostatic Adsorption.

This paper presents the formation of magnesium aluminate spinel using composite particles prepared via electrostatic adsorption (ESA). Scanning electron microscopy (SEM) images confirmed the presence of Al2O3-MgO composite particles. A mixture of Al2O3 and MgO raw materials was also prepared by using the conventional bead-milling method for comparison. The samples sintered at elevated temperatures were characterized through X-ray diffraction, SEM, and relative density measurements. Additionally, the lattice parameter and strain of the samples were determined using the Nelson-Riley function and the Williamson-Hall equation. A pure spinel phase formed in the ESA-derived sample sintered at 1400 °C, while the MgO structure remained in the conventionally prepared sample sintered at 1600 °C. The densities of samples sintered at 1450 °C or higher exceeded 90%. The lattice strain of the prepared samples was inversely proportional to the sintering temperature, attributed to the formation of large grains at higher temperatures. However, the sample sintered at 1600 °C for 8 h exhibited the highest strain of 0.0074 because the crystals grew in a certain direction.

Voltage-gated field-free spin–orbit torque switching in Pt/Co/Ir/MgO wedged structures

The ability to efficiently manipulate magnetization is of great significance for practical applications of spin–orbit torque (SOT) devices. In this study, we report the voltage-controlled, field-free SOT switching in perpendicular magnetized Pt/Co/Ir/MgO structures with wedge iridium interlayers. The insertion of a thin iridium interlayer at ferromagnet/oxide can significantly reduce the perpendicular magnetic anisotropy depending on the Ir thickness. The wedging of the iridium layer breaks lateral structural symmetry, resulting in deterministic switching without the assistance of in-plane magnetic fields. In such a structure, the SOT critical switching currents are remarkably decreased by 29% when a positive 6 V gate voltage is applied. Further quantitative analysis shows that multiple factors contribute to the decrease in switching currents, including a 23% reduction in magnetic anisotropy energy, a reduction in nucleation field, and a minor enhancement in damping-like torque under gate voltage. Moreover, the probabilistic hindrance that gate voltage poses to field-free switching is revealed by the decrease in current-induced perpendicular effective fields from symmetry-breaking. Our research shows that energy-efficient SOT switching can be controlled by gating and offers insight into the mechanism behind voltage-gated SOT switching.

Effect of Li2CO3–Bi2O3 doping on the low-temperature sintering, structure, and dielectric and mechanical properties of MgO–TiO2(w) ceramics

Dense MgO–12% TiO2(w) ceramics containing 12 wt% TiO2, which were doped with Li2CO3–Bi2O3 composite sintering aids, were prepared at a low sintering temperature of 950 °C in this study. The effects of sintering additives on the sintering characteristics, phase composition, microstructure, and dielectric and mechanical properties of the ceramic samples were systematically investigated, and the influences of their phase composition and microstructure on the dielectric and mechanical properties were examined. The introduction of sintering aids produced a new Bi4Ti3O12 phase in the sample structure, while the residual Bi2O3 mixed with the newly formed Mg2TiO4 and Bi4Ti3O12 phases distributed at MgO grain boundaries formed a structure surrounding MgO grains. This structure filled the pores in the ceramic sample, which increased its density and enhanced the mechanical properties. At a Li2CO3–Bi2O3 content of 15 wt%, the density, flexural strength, and Vickers hardness of the ceramic samples reached their maximum values of 3.4 g/cm3, 218.9 MPa, and 778.7 HV, respectively. However, the further increase in the Li2CO3–Bi2O3 content deteriorated their dielectric properties although the dielectric constant and dielectric loss remained below 13.4 and 2.1 × 10−3, respectively. The findings of this work indicate that Li2CO3–Bi2O3 sintering aids can significantly lower the sintering temperature of MgO–12% TiO2(w) ceramics and control their dielectric and mechanical properties through microstructural changes.

Study the structural and mechanical properties of HAP-MgO NPs-PMMA nano-composite

Polymer composite of heat cure acrylic (PMMA) matrix reinforced with different weight of nanoparticles Hydroxyapatite and Magnesium Oxide (1, 5 and 10% wt.) were prepared by hand molding technique. The Magnesium oxide nanoparticles were synthesized by Simple Chemical Method (Co-precipitation). The structure and morphology properties of MgO examined by X-ray diffraction (XRD), Field Emission Scanning electron microscopy (FESEM) and EDX. Lattice constant is a= 4.19