Superconductivity in the cobalt-doped V3Si A15 intermetallic compound

The A15 structure of superconductors is a prototypical type-II superconductor that has generated considerable interest since the early history of superconducting materials. This paper discusses the superconducting properties of previously unreported V3-xCoxSi alloys. It is found that the lattice parameter decreases with increasing cobalt-doped content and leads to an increased residual resistivity ratio (RRR) value of the V3-xCoxSi system. Meanwhile, the superconducting transition temperature (Tc) cobalt-doped content. Furthermore, the fitted data show that the increase of cobalt-doped content also reduces the lower/upper critical fields of the V3-xCoxSi system. Type-II superconductivity is demonstrated on all V3-xCoxSi samples. With higher Co-doped content, V3-xCoxSi alloys may have superconducting and structural phase transitions at low-temperature regions. As the electron/atom (e/a) ratio increases, the Tc variation trend of V3Si is as pronounced as in crystalline alloys and monotonically follows the trend observed for amorphous superconductors.Comment: 20 pages, 7 figure

Superconductivity in the high-entropy ceramics Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2Cx with possible nontrivial band topology

Topological superconductors have drawn significant interest from the scientific community due to the accompanying Majorana fermions. Here, we report the discovery of electronic structure and superconductivity in high-entropy ceramics Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2Cx (x = 1 and 0.8) combined with experiments and first-principles calculations. The Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2Cx high-entropy ceramics show bulk type-II superconductivity with Tc about 4.00 K (x = 1) and 2.65 K (x = 0.8), respectively. The specific heat jump is equal to 1.45 (x = 1) and 1.52 (x = 0.8), close to the expected value of 1.43 for the BCS superconductor in the weak coupling limit. The high-pressure resistance measurements show that a robust superconductivity against high physical pressure in Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2C, with a slight Tc variation of 0.3 K within 82.5 GPa. Furthermore, the first-principles calculations indicate that the Dirac-like point exists in the electronic band structures of Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2C, which is potentially a topological superconductor. The Dirac-like point is mainly contributed by the d orbitals of transition metals M and the p orbitals of C. The high-entropy ceramics provide an excellent platform for the fabrication of novel quantum devices, and our study may spark significant future physics investigations in this intriguing material.Comment: 28 pages, 7 figures,The manuscript with the same title will be published by Advanced Scienc

CO2-Tolerant Oxygen Permeation Membranes Containing Transition Metals as Sintering Aids with High Oxygen Permeability

Chemical doping of ceramic oxides may provide a possible route for realizing high-efficient oxygen transport membranes. Herein, we present a study of the previously unreported dual-phase mixed-conducting oxygen-permeable membranes with the compositions of 60 wt.% Ce0.85Pr0.1M0.05O2-δ-40 wt.%Pr0.6Sr0.4Fe0.8Al0.2O3-δ (M = Fe, Co, Ni, Cu) (CPM-PSFA) adding sintering aids, which is expected to not only improve the electronic conductivity of fluorite phase, but also reduce the sintering temperature and improve the sintering properties of the membranes. X-ray powder diffraction (XRD) results indicate that the CPM-PSFA contain only the fluorite and perovskite two phases, implying that they are successfully prepared with a modified Pechini method. Backscattered scanning electron microscopy (BSEM) results further confirm that two phases are evenly distributed, and the membranes are very dense after sintering at 1275 °C for 5 h, which is much lower than that (1450 °C, 5 h) of the composite 60 wt.%Ce0.9Pr0.1O2-δ-40 wt.%Pr0.6Sr0.4Fe0.8Al0.2O3-δ (CP-PSFA) without sintering aids. The results of oxygen permeability test demonstrate that the oxygen permeation flux through the CPCu-PSFA and CPCo-PSFA is higher than that of undoped CP-PSFA and can maintain stable oxygen permeability for a long time under pure CO2 operation condition. Our results imply that these composite membranes with high oxygen permeability and stability provide potential candidates for the application in oxygen separation, solid oxide fuel cell (SOFC), and oxy-fuel combustion based on carbon dioxide capture