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Garnet-type oxide is one of the most promising solid-state electrolytes (SSEs) for solid-state lithium-metal batteries (SSLMBs). However, the Li dendrite formation in garnet oxides obstructs the further development of the SSLMBs seriously. Here, we report a high-performance garnet oxide by using AlN as a sintering additive and Li as an anode interface layer. AlN with high thermal conductivity can promote the sintering activity of the garnet oxides, resulting in larger particle size and higher relative density. Moreover, Li 3 N with high ionic conductivity formed at grain boundaries and interface can also improve Li-ion transport kinetics. As a result, the garnet oxide electrolytes with AlN show enhanced thermal conductivity, improved ionic conductivity, reduced electronic conductivity, and increased critical current density (CCD), compared with the counterpart using Al 2 O 3 sintering aid. In addition, Li symmetric cells and Li∣LiFePO 4 (Li∣LFP) half cells using the garnet electrolyte with the AlN additive exhibit good electrochemical performances. This work provides a simple and effective strategy for high-performance SSEs.

Iron-based superconductors have strong potential for magnet applications through their very high upper critical field, low anisotropy and manufacturability through the powder-in-tube (PIT) route. The engineering critical current density (Je) is a key parameter for measuring the maximum current density that superconducting materials can withstand in practical applications. It serves as a bridge between theoretical research and practical applications of superconductors and has great significance in promoting the development and application of superconducting technology. In this study, Ag sheathed Ba0.6K0.4Fe2As2 (Ba-122) iron-based superconducting tapes were prepared by using the process of drawing, flat rolling and heat treatment by hot pressing (HP). For the first time, the filling factor of the tapes increased to about 40%, leading to a reduction in the volume fraction of Ag, consequently lowering the overall cost. The optimal parameters for achieving high transport Je were obtained by comparing the effects of different HP pressures on the properties and micro-morphology of the tapes. The prepared mono-filament tapes are capable of carrying the transport Je of 4.1 × 104 A/cm2 (Ic = 350 A) at 4.2 K, 10 T, marking the highest Je reported for Ba-122 wires and tapes to date. Our results show that high transport Je can be obtained in Ba-122 superconducting tapes, and iron-based superconductors have a promising future in practical applications.

In the last decade, the self-field critical current density Jc(s.f.) in Type-II superconductors has been considered fundamentally limited by a Silsbee-like criterion of Jc(s.f.) = Hc1/λ. We show that this universal limit to self-field critical current density Jc(s.f.) is not universally valid. We present several examples for this in YBa2Cu3O7−δ-type and REBa2Cu3O7−δ thin films and one for Nb thin films and show that calculated Jc(s.f.) using the Silsbee-like criterion using thermodynamic parameters has been substantially exceeded experimentally. We also show that Jc(s.f.) can be significantly improved by incorporation of artificial pinning centers (APCs), further implying that no such universal limit to Jc(s.f.) can exist because such an upper bound, Jc(s.f.) would have to be independent of APCs. These findings call for a revision of the accepted understanding of current-carrying limits in Type-II superconductors and reveal substantial potential for improving Jc in REBCO-based coated conductors through optimization of APCs for large-scale applications, including commercial nuclear fusion.

In this study, high-density magnesium diboride (MgB2) bulk superconductors were synthesized by spark plasma sintering (SPS) under pressure to improve the field dependence of the critical current density (Jc-B) in MgB2 bulk superconductors. We investigated the relationship between sintering conditions (temperature and time) and Jc-B using two methods, ex situ (sintering MgB2 synthesized powder) and in situ (reaction sintering of Mg and B powder), respectively. As a result, we found that higher density with suppressed particle growth and suppression of the formation of coarse particles of MgB4 and MgO were found to be effective in improving the Jc-B characteristics. In the ex situ method, the degradation of MgB2 due to pyrolysis was more severe at temperatures higher than 850 °C. The sample that underwent SPS treatment for a short time at 850 °C showed higher density and less impurity phase in the bulk, which improved the Jc-B properties. In addition, the in situ method showed very minimal impurity with a corresponding improvement in density and Jc-B characteristics for the sample optimized at 750 °C. Microstructural characterization and flux pinning (fP) analysis revealed the possibility of refined MgO inclusions and MgB4 phase as new pinning centers, which greatly contributed to the Jc-B properties. The contributions of the sintering conditions on fP for both synthesis methods were analyzed.

Iron-based superconductors are under study for their potential for high-field applications due to their excellent superconducting properties such as low structural anisotropy, large upper critical fields and low field dependence of the critical current density. Between them, Fe(Se,Te) is simple to be synthesized and can be fabricated as a coated conductor through laser ablation on simple metallic templates. In order to make all the steps simple and fast, we have applied the spark plasma sintering technique to synthesize bulk Fe(Se,Te) to obtain quite dense polycrystals in a very short time. The resulting polycrystals are very well connected and show excellent superconducting properties, with a critical temperature onset of about 16 K. In addition, when used as targets for pulsed laser ablation, good thin films are obtained with a critical current density above 105 A cm−2 up to 16 T.

Rare-earth barium copper oxide (REBCO) high-temperature superconductors, owing to their ability to maintain high critical current density (Jc) under liquid-nitrogen-temperature and high-magnetic-field conditions, are widely regarded as one of the most promising material systems among all superconductors. This review systematically summarizes fabrication strategies for REBCO coated conductors, with a focus on pulsed laser deposition (PLD) for achieving high-quality epitaxial growth with precise composition control. To enhance in-field performance, strategies for introducing artificial pinning centers (APCs) are examined, including rare-earth element doping, substrate surface decoration, and nanoscale secondary phase incorporation. The mechanisms of vortex pinning from different dimensional defects and their synergistic effects are compared. Finally, we suggest potential future directions aimed at further enhancing the superconducting properties.

Nb 3 (Al 1– x Zn x ) ( x  = 0–0.05) wires were obtained after single rapid heating, quenching and low temperature transformation (single-RHQT) process. It is found that Zn element can make crystal plane diffraction peaks of Nb 3 Al phase shift to higher angle, and the interplanar crystal spacing decreases gradually, which indicates that Al atoms in Nb 3 Al lattice are replaced by Zn atoms with smaller diameters. And the addition of Zn can reduce Δ T c and make the superconducting phases purer, and magnetic performances such as critical temperature ( T c ), critical current density ( J c ), irreversible field ( B irr ) are better than that of the pure sample. Nb 3 (Al 0.99 Zn 0.01 ) wire shows the highest J c value of about 5.9 × 10 4 A/cm 2 at 4.2 K and 8 T, and the highest T c value of 16.8 K was found in Nb 3 (Al 0.98 Zn 0.02 ). The influence of multiple rapid heating, quenching and low temperature transformation (multi-RHQT) process on Nb 3 (Al 1– x Zn x ) wires was mainly explored, and 2 at% and 3 at% Zn samples were selected with relatively high Δ T c values for five times RHQT treatment. It is observed that the multi-RHQT process can further reduce Δ T c , and more homogeneous superconducting phases are discovered compared with that of single-RHQT process. The elements are also evenly distributed in the multi-RHQT-processed Nb 3 (Al 1– x Zn x ) wires, leading to the improvement of J c , B irr performances compared to single-RHQT samples. Multi-RHQT-processed Nb 3 (Al 0.98 Zn 0.02 ) and Nb 3 (Al 0.97 Zn 0.03 ) samples show the J c values of 1.7 × 10 5 A/cm 2 and 1.2 × 10 5 A/cm 2 (4.2 K, 8 T), which are nearly ten times as many as that of single-RHQT samples, and Nb 3 (Al 0.97 Zn 0.03 ) has the highest B irr values of 19.6 T (4.2 K) and 10.7 T (10 K). Flux pinning of the Nb 3 (Al 1– x Zn x ) ( x  = 0.01–0.05) wires follows the surface pinning mechanism, where grain boundary and stacking faults are considered as pinning centers.

The smart meta-superconductor MgB2 and Bi(Pb)SrCaCuO increase the superconducting transition temperature (TC), but the changes in the transport critical current density (JC) and Meissner effect are still unknown. Here, we investigated the JC and Meissner effect of smart meta-superconductor MgB2 and Bi(Pb)SrCaCuO. The use of the standard four-probe method shows that Y2O3:Eu3+ and Y2O3:Eu3++Ag inhomogeneous phase significantly increase the JC, and JC decreases to a minimum value at a higher temperature. The Meissner effect was measured by direct current magnetization. The doping of Y2O3:Eu3+ and Y2O3:Eu3++Ag luminescent inhomogeneous phase causes a Meissner effect of MgB2 and Bi(Pb)SrCaCuO at a higher temperature, while the non-luminescent dopant reduces the temperature at which samples have Meissner effect. The introduction of luminescent inhomogeneous phase in conventional MgB2 and copper oxide high-temperature Bi(Pb)SrCaCuO superconductor increases the TC and JC, and Meissner effect is exerted at higher temperature. Therefore, smart meta-superconductivity is suitable for conventional and copper oxide high-temperature superconductors.

We show that the structure of multifilament MgB2 wires made by the powder-in-tube (PIT) method can be texturized by annealing the structure under high isostatic pressure. Our results show that we obtained continuous fibers with a uniform diameter of 250 nm in all 36 filaments, a small grain size of approximately 50 nm and a high density of the superconducting material. These results contribute to a significant improvement in the critical current density in high magnetic fields, e.g., 100 A/mm2 at 14 T and 4.2 K.

In situ MgB2 superconducting samples were prepared by using the spark plasma sintering method. The density of the obtained bulks was up to 95% of the theoretical value predicted for the material. The structural and microstructural characterizations of the samples were investigated using X-ray diffraction and SEM and correlated to their superconducting properties, in particular their critical current densities, Jc, which was measured at 20 K. Extremely high critical current densities of up to 6.75 × 105 A/cm2 in the self-field and above 104 A/cm2 at 4 T were measured at 20 K, indicating that vortex pinning is very strong. This property is mainly attributed to the sample density and MgB2 nanograins in connection to the presence of MgO precipitates and areas rich in boron.