Properties Of MgB2 Research Articles

Superconductive MgB2 Intercalated Muscovite with Dynamically Tunable Stress.

In this study, we utilized a stress-sensitive superconductor MgB2 in combination with a flexible muscovite, a layered silicate, to demonstrate that materials in a reduced-dimension environment could be influenced by external strain. MgB2 nanocrystals were inserted into the muscovite interlayers using gas phase intercalation, creating a two-dimensional cavity-like structure. Several experiments confirmed that the cavity-induced static pressure from the intercalation effect and the external dynamic bending effect can affect the physical properties of MgB2. The results of analyzing the changes in superconducting critical temperature (T c) indicate that the dynamic bending effect corresponds to an applied pressure of approximately 1.2 GPa. This method demonstrates that muscovite intercalation serves as a versatile platform for evaluating the stress effects on functional materials in reduced dimensions under ambient conditions.

Impact of doping on MgB2 superconductors: A comprehensive review

This review introduces fresh insights into the ongoing discussion on doping in the MgB2 superconductor compound, enriching the comparative analysis with previous reviews. Its primary objective is to succinctly summarize and enhance comprehension regarding the influence of doping on the superconducting properties of MgB2. It delves into various aspects, including the impact on the superconducting transition temperature (Tc) and the critical current density (Jc) of the doped samples, while also shedding light on the diverse synthesis methodologies employed by different research laboratories. Throughout the review, the doping agents under scrutiny encompass a wide array, ranging from Li and Be to Bi and Pb. The properties are compared with those undoped samples crafted by the authors of each publication. This review catalogs a range of cited doping agents, including H, Li, Be, C, C15H12O2, diamond, graphene oxide, NaCl, Na2CO3, Mg, Al, Si, K2CO3, CaH2, CaCO3, Sc, Ti, Ni, Cu, Zn, MgGa, GeO2, Se, Rb2CO3, Rh, Pd, Ag, In, Sn, Sb2O3, Te, Cs2CO3, LaB6, La2O3, CeO2, Pr6O11, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Tb4O7, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Lu2O3, Os, Ir, Pt, Hg, Pb, and Bi. Notably, doping with Be, Na2CO3, C, Al, Rb2CO3, Cs2CO3, Hg and Pb impacts mesh parameters through either Mg or B substitution. Conversely doping with Li, CaH2, Cu, Ag, La2O3, CeO2, Pr6O11, Nd2O3, Gd2O3, Tb4O7, Dy2O3, Ho2O3, Er2O3, Tm2O3, Lu2O3, GeO2, Rh, In, Sb2O3, and Pt exhibits minimal impact on Tc. Moreover, Jc can be substantially enhanced by adding C, Zn, Ag, or Sb2O3. Remarkably, the incorporation of Pd or Pt has shown a substantial increase in Jc with a remarkable improvement of +328 % and +614 % respectively observed at 2 T and 20 K. Doping with rare earth elements such as La2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, and Ho2O3 resulted in extraordinary improvement in the value of the critical current density at 20 K under specific conditions, within a range of 0–4 T.

Comparison of electronic structures, thermodynamic, optical and mechanical properties of MgB2 and MgMB4(M=Al, Pb, W) based on first-principles

As an important superconducting material, MgB2 has a wide range of applications in electronics and communication fields. The optimization of its properties has been a hot research topic. In this paper, it uses first-principles calculations to delve into the impact of doping Type-I superconducting elements M (M = Al, Pb, W) on the properties of MgB2. The main focus is on exploring improvements in thermodynamic, optical and mechanical properties in conjunction with the analysis of electronic properties. For thermodynamic properties, MgPbB4 demonstrates significant variation in entropy and free energy as temperature increases, reaching 356.84 KJ/mol and −411.46 KJ/mol, respectively, at 2000 K. Regarding optical properties, the absorption band edge disappears and the range widens with the introduction of M elements. Specifically, MgWB4 exhibits the highest reflectivity R (0) and static dielectric constant ε1 (0) in the [001] direction, measured at 0.49 and 32.2, respectively. In terms of mechanical properties, the elastic modulus of MgAlB4 and MgWB4 enhances notably with B/G ratios less than 1.75, indicating their brittleness. MgWB4, in particular, stands out with the highest elastic modulus and the weakest elastic anisotropy AU (0.703), exhibiting a spatial distribution nearer to spherical. Conversely, MgPbB4 transforms the material into a ductile one, with reduced elastic modulus and the strongest anisotropy AU (4.963). This study can provide a more comprehensive perspective for the future design of MgB2-based materials.

Amorphous B coated Mg nanopowder induces low angle grain boundaries and enhances J c of MgB2 wire

In this work, amorphous B coated Mg nanopowder (BCMN) is synthesized and transport property of MgB2 superconducting wire is significantly enhanced with different contents of BCMN. BCMN has high reactivity since it contains nanoscale Mg and amorphous B. It allows to obtain MgB2 nanocrystals at only 400 °C with the compression of a lattice parameter and expansion of c lattice parameter compared to MgB2 formed by micron-sized Mg mixed with amorphous B (Mg + B) powders. These MgB2 nanocrystals serve as crystal nuclei and promote the crystallization and growth of MgB2. The mismatch of different lattice parameters prepared using BCMN and M + B powders induces low angle grain boundaries (LAGBs) embedded in MgB2 grains. LAGBs act as plane defects, leading to a dominant surface pinning mechanism and an enhancement in the critical current density on the magnetic field (J c(H)). At 4.2 K in 6 T, transport critical current density (J ct) of wire with 20 wt.% BCMN is 6.7 × 104 A·cm−2, approximately 1.8 times wire with 0 wt.% BCMN.

Single-photon detection using large-scale high-temperature MgB2 sensors at 20 K

Ultra-fast single-photon detectors with high current density and operating temperature can benefit space and ground applications, including quantum optical communication systems, lightweight cryogenics for space crafts, and medical use. Here we demonstrate magnesium diboride (MgB2) thin-film superconducting microwires capable of single-photon detection at 1.55 μm optical wavelength. We used helium ions to alter the properties of MgB2, resulting in microwire-based detectors exhibiting single-photon sensitivity across a broad temperature range of up to 20 K, and detection efficiency saturation for 1 μm wide microwires at 3.7 K. Linearity of detection rate vs incident power was preserved up to at least 100 Mcps. Despite the large active area of up to 400 × 400 μm2, the reset time was found to be as low as ~ 1 ns. Our research provides possibilities for breaking the operating temperature limit and maximum single-pixel count rate, expanding the detector area, and raises inquiries about the fundamental mechanisms of single-photon detection in high-critical-temperature superconductors.

The Influence of Electroluminescent Inhomogeneous Phase Addition on Enhancing MgB2 Superconducting Performance and Magnetic Flux Pinning.

As a highly regarded superconducting material with a concise layered structure, MgB2 has attracted significant scientific attention and holds vast potential for applications. However, its limited current-carrying capacity under high magnetic fields has greatly hindered its practical use. To address this issue, we have enhanced the superconducting performance of MgB2 by incorporating inhomogeneous phase nanostructures of p-n junctions with electroluminescent properties. Through temperature-dependent measurements of magnetization, electronic specific heat, and Hall coefficient under various magnetic fields, we have confirmed the crucial role of inhomogeneous phase electroluminescent nanostructures in improving the properties of MgB2. Experimental results demonstrate that the introduction of electroluminescent inhomogeneous phases effectively enhances the superconducting performance of MgB2. Moreover, by controlling the size of the electroluminescent inhomogeneous phases and optimizing grain connectivity, density, and microstructural uniformity, we can further improve the critical temperature (TC) and flux-pinning capability of MgB2 superconducting materials. Comprehensive studies on the physical properties of MgB2 superconducting structures added with p-n junction electroluminescent inhomogeneous phases also confirm the general effectiveness of electroluminescent inhomogeneous phases in enhancing the performance of superconducting materials.

Impact of hair-derived carbon substitution on structural and superconducting properties of MgB2

This study presents a comprehensive analysis of the effects resulting from the substitution of biowaste-derived carbon-dot (CD) from human hair on structural and superconducting properties of MgB2. Syntheses of polycrystalline samples were accomplished through a standard solid-state reaction route. X-ray powder diffraction results confirm the formation of MgB2 as a primary phase in all samples and show the successful substitution of carbon for boron in MgB2. The critical current density, determined at 20 K and 4.5 T, for carbon-substituted MgB2 synthesized at 850 °C was enhanced by more than four times compared with unsubstituted MgB2. The observed improvement is due to the formation of efficient pinning centers resulting from the incorporation of carbon substituting for boron in MgB2. Furthermore, x-ray photoelectron spectroscopy (XPS) confirmed the presence of carbon bonding to boron in MgB2 synthesized with biowaste-derived CDs, indicating successful incorporation into the structure. Ultraviolet photoelectron spectroscopy (UPS) results show that the carbon-substituted MgB2 can lead to changes in the electronic band structure and values of work function. These changes significantly impact the properties of MgB2 materials, including superconducting transition temperature, upper critical field, and critical current density. The XPS and UPS experimental results are in good agreement with density functional theory calculations for MgB2 with and without carbon substitution.

The effect of AlB2 addition on MgB2 superconducting bulks

Optimization of intrinsic and extrinsic properties of MgB2 superconducting material is extremely important for practical application in cables, wires, and tapes. The main mechanisms used to obtain this optimization are through the synthesis process, improvement in the grain connectivity, densification, pinning, doping, and limiting MgO formation. Many groups around the world use elements such as Ti, Zr, Hf, Al, Mn, Si and others, as dopants. Defects or any other inhomogeneity in the superconducting matrix can improve the flux pinning behavior and, hence, the transport properties. In this work MgB2 superconducting bulks with additions of AlB2 powder were prepared and analyzed in an attempt to enhance the critical current density of MgB2 and to understand the effect of this addition on the intrinsic and extrinsic characteristics of the material. Crystallographic, microstructural, optical, and superconducting characterization were performed and analyzed. AlB2 additions modified the superconducting properties of MgB2 increasing its critical current density and irreversibility field compared to pure MgB2 prepared using the same procedures.

Review of synthesis of high volumetric density, low gravimetric density MgB2 bulk for potential magnetic field applications

This review paper summarizes and analyses the current literature on the synthesis of dense MgB2 bulk with high density and by both the modified solid reaction method and the Mg infiltration method. MgB2 bulk shows Telsa-level magnetic field-trapping ability in small volumes (1–5 cm3) at 15–20 K, which is beneficial for multiple applications, particularly where light weighting is beneficial. The review also compares the properties of MgB2 to rare earth barium cuprate bulk magnets and NbTi solenoid magnets and discuess potential applications such as magnetic lenses, compact NMR, and magnetic shielding.

Biaxial strain engineering on the superconducting properties of MgB2 monolayer

The effect of biaxial strain on the superconducting properties of MgB2 monolayer was studied by first-principles calculations. The stability analyses by phonon dispersions show that a biaxial strain of as much as 7% can be applied onto MgB2 without inducing any imaginary frequency. The superconducting property calculations based on the frame of Migdal-Eliashberg theory successfully reproduce the two-gap superconductivity of MgB2. The results show that the tensile biaxial strain can increase the critical temperature of MgB2 by as much as ∼20% while the compressive biaxial strain would decrease the critical temperature by ∼29%. The detailed microscopic mechanism of the biaxial strain effect on the superconducting properties was studied by calculations of electronic structures and phonon dispersions. The increased Tc is a combining result of the increased electron density at the Fermi level and the in-plane boron phonon softening. By means of high-throughput screening of proper substrates, it is found that most of the substrates would result in tensile strain in MgB2 film, some of which can result in tensile strain of higher than 10%, consistent with many experimental works that the MgB2 thin film has increased Tc. The results in this work provide a detailed understanding of the biaxial strain engineering mechanism and demonstrate that biaxial strain engineering can be an effective way of tuning the superconducting properties of MgB2 and other similar materials.

Correlation between Tc and local structure of MgB2 with ZnO buffer layer: X-ray absorption fine structure study

In practical application, it is necessary to preserve the superconducting properties, including the critical temperature (Tc) of MgB2 in the form of tapes and wires that bond to a metallic substrate with a buffer layer. In this work, we investigate the relationship between the Tc and local structure of MgB2 films on ZnO buffered-Hastelloy substrate with various thicknesses using X-ray absorption fine structure. X-ray absorption near edge structure spectra reveal fluctuation of the boron σ-band near the Fermi level indicating an existence of lattice distortion inside the MgB2 films. Variations in the bond lengths of Mg–B and Mg–Mg from the extended X-ray absorption fine structure prove that the distortion in the MgB2 lattice is owing to the ZnO buffer layer. Besides the bond length, the Mg–B bond ordering was found to significantly affect the Tc behavior, which was attributed to the inter-plane strain caused by the ZnO buffer layer. Understanding the effect of the ZnO buffer layer on the local structure of MgB2 may help in determining the optimal conditions for enhancing the superconducting properties of MgB2 for power applications.

Novel efficient alloys for ionizing radiation shielding applications: A theoretical investigation

This work investigates the radiation shielding properties of MgB2, CrAs0.45Sb0.55, and FeAs polycrystalline alloys synthesized by a conventional solid-state reaction method. The structural properties of the prepared alloys were reported by X-ray diffraction using the Rietveld refinement available in Match 3 software. The densities for the prepared alloys were measured experimentally to explore the radiation shielding properties. The mass attenuation coefficient (MAC) and different radiation shielding were determined using Phy-X software for each studied sample in the energy range of 0.015–15 MeV. The XRD results manifested P 6 2 space group for the MgB2 sample, P 6c 2c for CrAs0.45Sb0.55 sample, and P 2c 2 ab for the FeAs sample. The density values for MgB2, CrAs0.45Sb0.55 and FeAs are 1.9041, 3.9482, and 5.6934 g/cm3. The MAC values at 0.015 are 3.59 cm2/g for MgB2 sample, 44.04 cm2/g for the CrAs0.45Sb0.55 sample, and 80.84 cm2/g for the FeAs sample. The results revealed that the FeAs sample has the best ionizing radiation shielding properties among all investigated samples. These findings suggest that this alloy can be used in ionizing radiation shielding applications.

Evaluation of superconducting features and gap coefficients for electron–phonon couplings properties of MgB2 with multi-walled carbon nanotube addition

Evaluation of superconducting features and gap coefficients for electron–phonon couplings properties of MgB2 with multi-walled carbon nanotube addition

Study on the relationship between uniaxial strain and critical transition temperature of MgB2 based on first-principles

It has been indicated the critical transition temperature (T c) of MgB2 decreases with the increase of hydrostatic pressure, but this is a comprehensive T c change after the multiaxial strain, and the influence of strain on T c is not fully understood. In this paper, based on the McMillan superconducting calculation formula and the first-principles density functional theory, the T c change and the properties of MgB2 such as energy band, Fermi surface, differential charge density, and phonon dispersion under uniaxial strain were studied, and the relationship between uniaxial strain and these properties was analyzed. The calculated T c of MgB2 at zero strain was 38.35 K, which is in good agreement with the experimental value of 39 K. When the a-axis strain was 1%, the T c value could increase to 49.7 K, and there was a further improvement trend. When the a-axis compression strain was −1%, T c decreases to 31.52 K. When the c-axis tension–compression strain was applied, the change of T c value was small. Further analysis showed that the impact of a-axis strain on the differential charge density, electronic band structure, phonon dispersion, and other properties of MgB2 was significantly greater than that of c-axis strain, and the influence of these properties on T c was discussed. The work in this paper has certain theoretical and guiding significance for preparing MgB2 with higher T c and the study of the effect of uniaxial strain on T c of superconducting materials.

The influence of LiH and TiH2 on hydrogen storage in MgB2 II. XPS study of surface and near-surface phenomena

Mg(BH4)2 is a promising solid-state hydrogen storage material, releasing 14.9 wt% hydrogen upon conversion to MgB2. The rehydrogenation of MgB2 is particularly challenging, requiring prolonged exposure to high pressures of hydrogen at high temperature. Here we report an XPS study probing the influence of LiH and TiH2 on the hydrogen storage properties of MgB2 in the surface and near-surface regions, as a complementary investigation to a preceding study of the bulk properties. Surface and near-surface properties are important considerations for nanoscale and bulk hydrogen storage materials. If there are reactions occurring at the surface that modify the chemical composition in the near-surface region, species diffusion can alter the chemical composition even deep into the bulk of the material. For LiH/MgB2, metastable LiH–B and LiH–Mg species are produced that are more reactive than Bulk MgB2. With prolonged glovebox storage, the LiH/MgB2 material shows increased reactivity towards O and C and enriched levels of Li and B in the near-surface region. In addition, Li induces the growth of Li2CO3 in the surface and near surface regions. Exposing LiH/MgB2 to hydrogen at 700 bar and 280 °C for 24 h produces borohydride at a temperature 100 °C below the threshold for bulk MgB2 hydrogenation. In a specifically surface process with macroscopic implications, the hydrogenation conditions also cause Li2CO3 to react with boron hydroxide in the sample to form a Li-deficient glassy lithium borate melt at the interfaces of the particles, bonding them together. Subsequent heating to 380 °C dehydrogenates the borohydride and eliminates the Li-deficient glassy lithium borate. The LiH/MgB2 material is not reversible because desorption does not lead back to LiH/MgB2, but rather to elemental B and Mg metal in the near-surface region. In contrast to LiH, TiH2 does not react with MgB2, despite the favorable thermodynamics for destabilization via TiB2 formation. Furthermore, high pressure hydrogenation yields only unreacted TiH2 and MgB2 in the surface and near-surface regions. Thus, added TiH2 provides no benefit to MgB2 hydrogenation, in agreement with the findings of the preceding bulk study.

CVD Yöntemi ile Karbon Katkılanmış Bor Kullanılarak Üretilen MgB2 Süperiletkeninin Yapısal ve Manyetiksel Özelliklerine Sıcaklık Etkisinin İncelenmesi

Carbon, which is known to play a improvement role on the superconductivity properties of MgB2, was doped into MgB2 by CVD (chemical vapor deposition) method, and the change of structural and magnetic properties observed in MgB2 in relation to the change of sintering temperature was investigated. In this context, in the sample preparation step, amorphous nano boron powders with carbon added by chemical vapor deposition method were mixed with magnesium powders at certain mass ratios and sintered at four different temperatures (700-800-900-1000 0C) with the classical solid state reaction method and converted into carbon-added MgB2 samples. SEM photographs of amorphous nano-boron powders with carbon added were taken and subjected to elemental analysis. The structural and magnetic properties of the samples obtained were examined. X-ray diffraction graph, magnetization values and Magnetic Field-Magnetic Moment (M-H) graphs of the samples obtained by XRD method and the critical current density values with Bean Method were found and Magnetic Field-Critical Current Density (Jc-H) graph was created. It was determined that, in all the samples obtained, the MgB2 superconductor structure was formed and the carbon structures included in the structure caused changes in the lattice parameters due to the ion radius difference, that fracture occurred in the magnetization curve of the sample prepared by sintered at 1000 0C due to the intense impurities caused by the phase transitions due to the high temperature, in samples prepared at low temperatures, and that magnetization curves that could not expand sufficiently were observed, flux jumping occurs in the magnetization curve and this also affected the critical current density. In addition, the change in the critical current density value from 7.0×10^3 A/cm2 to 2.8×10^4 A/cm2 showed that the reaction temperature was an effective parameter on the experimental results. As a result of the examinations, when compared between the 4 different sintering temperature values used, it was found that the sintering temperature of 900 0C was the temperature at which the best physical results were obtained in MgB2.

Investigation of microhardness properties of the multi-walled carbon nanotube additive MgB2 structure by using the vickers method

In this study, the effect of multi-walled carbon nanotube doping to MgB2 compound on microhardness properties of MgB2 was investigated by using solid-state reaction method. The amount of multi-walled carbon nanotubes was chosen as 0, 1, 2, 3 and 4% by weight of total MgB2. All samples were obtained by sintered at 650 °C temperatures. The microhardness properties of the samples obtained were examined using the Vickers method. At the same time, the samples obtained were analyzed according to Meyer’s Law, proportional sample resistance (PSR) model, Hays-Kendall (HK) approach and elastic/plastic deformation (EPD) model. Samples were found to exhibit indentation size effect (ISE) behavior. It was understood that the multi-walled carbon nanotubes doped to the samples made MgB2 softer by reducing the intergranular bonding of the MgB2 structure. In addition, it was found that the force applied to the samples caused both plastic and elastic deformation on the samples.

Effect of Thermomechanical Treatment Conditions on the Structure and Properties of MgB2

The effect of pressure-assisted sintering and preliminary densification by hydrostatic pressure of commercial powder on the microstructure and superconducting properties of MgB2 ceramics is studied in this work. Various thermomechanical actions are shown to result in the formation of different structural defects, which can be considered probable centers of magnetic flux pinning.

Electron-phonon coupling behavior in MgB2 films with various thicknesses of ZnO buffer layer on metallic substrates

In order to investigate the effect of buffer layer on the superconducting properties of MgB2, behaviors of electron-phonon coupling (EPC) in MgB2 thin films with various thicknesses of ZnO buffer layer on two different substrates Al2O3 and Hastelloy were studied. As the ZnO thickness increases, the values of Tc of MgB2 films on two substrates show opposite behaviors. Sharply decreased and then saturated Tc of ~38K is observed on Al2O3 substrates while an abrupt increase of Tc with no tendency of decrease is obtained on Hastelloy substrates. These Tc behaviors are closely related to the E2g phonon hardening/softening inside MgB2 which may be induced from a lattice distortion caused by an introduction of ZnO buffer layer. The electron-E2g coupling provides a dominant contribution to EPC from all phonon modes, however, it shows a very weak dependence on ZnO thickness to explain the Tc behavior of our samples. Therefore, in order to establish a mechanism of ZnO buffer layer influencing Tc of MgB2 films, contribution from other phonon modes needs to be considered. Understanding the effect of ZnO buffer layer on the EPC and the Tc behavior opens a possibility to obtain an optimal condition for ZnO buffer layer of MgB2 for the field of application.

Improvement of critical current density of MgB2 bulk superconductor processed by Spark Plasma Sintering

AbstractSpark Plasma Sintering (SPS) is a promising rapid consolidation technique that allows a better understanding and optimization of the sintering kinetics and therefore makes it possible to obtain MgB2 bulk superconductor with tailored microstructures consisting of grains with either spherical or elongated morphology. In this contribution, the role of the precursor powders on the superconducting properties of MgB2 is investigated. Three sets of bulk MgB2 material were processed from: (i) a commercially available MgB2 powder; (ii) a mixture of Mg metal and amorphous B using a single‐step solid‐state reaction process and (iii) a mixture of amorphous boron coated with carbon and Mg metal. The samples were prepared in the same SPS processing conditions. The microstructure of the samples was investigated by X‐ray diffraction, SEM and TEM and correlated to their superconducting properties. The critical current density of the best sample at 20K was Jc = 500 kA/cm2 in self‐field, which is one of the highest critical current density reported for MgB2 bulk superconductors.