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Infrared reflectance, transmittance, and emittance spectra of MgO from first principles
摘要： By using density functional theory calculations we determined the influence of anharmonic effects on the infrared reflectance, transmittance, and emittance of MgO. The goal is to determine the limit of validity of a perturbative (multiphonon) approach. MgO is chosen as a test material because of the availability of different kinds of radiative properties measured experimentally. Nonanalytic terms of the three-phonon scattering coefficients are explicitly calculated and do not provide measurable effects. The agreement is overall very good to such an extent that, already at room temperature, one can clearly identify regions in which four-phonon scattering processes are dominant with respect to the three-phonon ones. The influence of isotopic disorder at cryogenic temperatures is also settled.
关键词： emittance,transmittance,density functional theory,MgO,infrared reflectance,anharmonic effects,phonon-phonon interactions
更新于2025-09-10 09:29:36
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Complexities of atomic structure at CdO/MgO and CdO/Al 2O 3 interfaces
摘要： We report the interface structures of CdO thin films on (001)-MgO and (0001)-Al2O3 substrates. Using aberration corrected scanning transmission electron microscopy, we show that epitaxial growth of (001)-CdO||(001)-MgO occurs with a lattice misfit greater than 10%. A high density of interface misfit dislocations is found to form. In combination with molecular dynamics simulations, we show that dislocation strain fields form and overlap in very thin heterostructures of CdO and MgO (< 3 nm). On the c-Al2O3 substrate, we find that CdO grows with a surface normal of [025]. We show that three rotation variants form due to the symmetry of the sapphire surface. These results contribute insights into the epitaxial growth of these rock-salt oxides.
关键词： CdO,epitaxial growth,Al2O3,scanning transmission electron microscopy,molecular dynamics simulations,MgO,interface structures
更新于2025-09-09 09:28:46
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Tunable 3 μm optical vortex parametric oscillator
摘要： We propose a tunable millijoule-level 3-μm vortex laser formed with a 1-μm ns vortex pulse-pumped quasi-phase matching MgO-doped periodically poled lithium niobate (MgO:PPLN) optical parametric oscillator with a singly resonant plane-parallel cavity con?guration. The wavelength of the vortex output is tuned within the range of 3.360–3.677 μm merely by controlling the temperature of the MgO:PPLN crystal. The maximum vortex output energy of 2.14 mJ is obtained at the maximum pump energy of 21 mJ, and corresponds to an optical to optical conversion e?ciency of 10.2% and a photon conversion e?ciency of 33.5%. The handedness of the vortex output is controlled just by inverting the handedness of the pump vortex beam. ? 2018 The Japan Society of Applied Physics
关键词： MgO:PPLN,quasi-phase matching,tunable laser,parametric oscillator,optical vortex
更新于2025-09-09 09:28:46
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Effect of Temperature on Shape & Optical Properties of MgO/ZnO Nanocomposites
摘要： MgO/ZnO nanocomposites were synthesized by mixing magnesium acetate tetrahydrate and zinc acetate in the equimolar ratio through a simple reflux method. The refluxed sample was annealed at three different temperatures 400, 500 and 600 oC, respectively. X-ray diffraction spectra (XRD) showed wurtzite ZnO structure with cubic MgO. The HR-SEM picture showed the rod shaped morphology at 400 °C and morphology changed to spherical shape with the increase in temperature to 600 °C. Williamson-Hall plot is used to study the particle size and micro strain of the synthesized MgO/ZnO nanocomposites. The band gap and luminescent property were investigated using ultra violet-visible and photoluminescence spectra. The optical property of MgO/ZnO nanocomposites depends on the annealing temperature which is shown by the increase in the band gap as temperature increases.
关键词： MgO-ZnO nanocomposites,EDAX,Ultra violet-visible,Photoluminescence,HRSEM
更新于2025-09-09 09:28:46
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Transport Critical Current Density of Bi1.6Pb0.4Sr2Ca2Cu3O10)/Ag Superconductor Tapes with Addition of 50 and 70 nm MgO
摘要： added size 50 average particle and 70 nm were MgO nanoparticles with into Bi1.6Pb0.4Sr2Ca2Cu3O10(MgO)x/Ag superconductor tapes and sintered at 845 oC for 50 and 100 h. The effect of sintering time on the transport critical current density (Jc) was investigated. Jc of the tapes were measured in zero-field between 30 and 77 K and under magnetic fields at 77 K. The phase and microstructure of the tapes were examined by X-ray diffraction method and scanning electron microscopy, respectively. All tapes showed plate-like grains and a larger plate-like grain was observed in the tapes sintered for 100 h. Jc of the MgO added tapes was higher than those of the non-added tapes. Jc of the non-added tape sintered for 100 h was 10820 A/cm2 at 30 K and 1262 A/cm2 at 77 K. Jc of the tapes sintered for 100 h was higher than the tapes sintered for 50 h. The 50 nm MgO added tapes showed a higher Jc than the 70 nm MgO added tapes. Jc for the 100 h sintered MgO (50 nm) added tape was 22710 and 3070 A/cm2 at 30 and 77 K, respectively which are higher than that of the 100 h sintered MgO (70 nm) added tape. The improved Jc was attributed to the increase in flux pinning potential and improvement in the microstructure due to the addition of nano-sized MgO. This work showed the importance of the size of the added nanoparticles to the transport current properties of these superconductors.
关键词： flux pinning,transport critical current density,nano MgO,size effect
更新于2025-09-04 15:30:14
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Molecular beam epitaxy growth of Mn4?Ni N thin films on MgO(0?0?1) substrates and their magnetic properties
摘要： We grew Mn4?xNixN epitaxial thin ?lms on MgO(0 0 1) by molecular beam epitaxy, as well as studied their crystalline qualities and magnetic properties. The ?lms were decomposed into Ni8N or Mn-Ni alloys when x ≥ 2, as con?rmed by X-ray di?raction and re?ection high-energy electron di?raction, but this decomposition was mitigated by reducing the substrate growth temperature. The lattice constants decreased with increased Ni substitution except when the Mn ratio was high, while the crystal orientation tended to degrade. The magnetic properties were measured via vibrating sample magnetometer, and it was found that the saturation magneti- zation (MS) and perpendicular magnetic anisotropy (PMA) diminished with a small amount of Ni substitution. Speci?cally, the MS value was remarkably decreased from 86.3 ± 1.1 emu/cm3 (Mn4N) to 19.0 ± 0.5 emu/cm3 (Mn3.85Ni0.25N), and the magnetic anisotropy constant was decreased from approximately 0.94–0.027 Merg/ cm3, respectively. The PMA vanished with further Ni substitution. Ultimately, a small MS and a PMA were simultaneously achieved with a small amount of Ni substitution. These properties support spin transfer torque, which can be applied to the emerging non-volatile memory devices using domain wall motion.
关键词： A3. Molecular beam epitaxy,A1. Crystal structure,B1. Mn4N,B2. Magnetic materials,B1. MgO,B1. Ni4N
更新于2025-09-04 15:30:14
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Surface treeing and segmented worm model of tracking behavior in MgO/Epoxy nanocomposites
摘要： Surface tracking experiments were conducted on MgO/epoxy nanocomposites according to IEC60112. Treeing phenomenon, which was commonly observed in bulk insulators, was detected on the surface of tracked samples via optical microscopy. Tree branches were further found to be segmented tracking channels by scanning electron microscopy, which consisted of a series of ablation holes along electric field, i.e. wormholes. According to distribution of surface trees, tracking area was divided into three typical regions. Region A, close to electrodes, was barely ablated. Region B, which directly connects electrodes, exhibited paralleled tracking channels. Region C, which is the outer annular ablated region, is full of crossed tracking channels. At the beginning, the initial tracking channels were demonstrated to appear at the triple junction of Region A, B and C, where electric field was supposed to be the highest. Then tracking regions spread from the junction to Region B and Region C with tracking channels segmentally growing longer and wider, indicating a segmented energy accumulation process. Tracking trees were finally formed connecting two electrodes, leading to sample failure. With addition of nano-MgO particles, wide and deep channels turned into slight but dense ones. Correspondingly, comparative tracking index (CTI) increased from 400 to 475 V with increasing nano-MgO from 0 to 10 wt%. Improved tracking resistance was obtained in nanocomposites while reduced thermal conductivity and pyrolysis characteristics were observed. Combining with results above, a segmented worm model was thus proposed to explain surface tracking performance in MgO/epoxy nanocomposites.
关键词： epoxy nanocomposites,nano-MgO,surface tracking,surface treeing
更新于2025-09-04 15:30:14
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<i>In situ </i>soft x-ray absorption spectroscopic study of polycrystalline Fe/MgO interfaces
摘要： In situ soft x-ray absorption spectroscopic study of polycrystalline Fe/MgO interfaces. It is found that at the interface of iron and MgO film, about two monolayers of Fe3O4 is formed. Fe3O4 being the oxide of iron with the highest heat of formation, the reaction appears to be controlled thermodynamically. On the other hand, on the interface with MgO (001) surface, FeO is formed, suggesting that the reaction is limited by the availability of oxygen atoms. Magnetic behavior of the FeO layer gets modified significantly due to proximity effect of the bulk ferromagnetic iron layer.
关键词： FeO,soft x-ray absorption spectroscopy,Fe/MgO interfaces,Fe3O4,magnetic behavior
更新于2025-09-04 15:30:14
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Green engineered nano MgO and ZnO doped with Sm3+: Synthesis and a comparison study on their characterization, PC activity and electrochemical properties
摘要： Structural, photocatalytic, photoluminescence and electrochemical activities of rare earth (RE) metal ions (Samarium (Sm3+)) doped Magnesium oxide (MgO) and Zinc oxide (ZnO) nanoparticles (NPs) prepared by using Cicer artinum powder as a fuel via green solution combustion method were discussed in detail. The synthesized NPs were found to have an average crystal size of around 25 nm as established by powder X-ray diffraction (PXRD). The semiconductor behavior has been confirmed by the study of energy band gap via diffuse reflectance spectroscopy (DRS). The conductivity of the samples was studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was observed that on 378 and 398 nm excitation of both the samples, it emits yellow and white radiation resonating with the ideal white light. The Rare Earth (RE) doped NPs have been applied as a novel photocatalyst for removal of rodhamin-B (rh-B) and malachite green (MG) dyes. The release of OH radicals played a crucial role in dye degradation; its extent depending on the chemical structure and photocatalyst dosage. The photocatalytic activity (PCA) was found to be maximum for MgO:Sm3+ (0.1mol %) under UV light and ZnO:Sm3+ (1 mol %) under sunlight.
关键词： Cicer arietinum,MgO NPs,malachite green (MG),ZnO NPs,rhodamin-B (rh-B)
更新于2025-09-04 15:30:14