A new perspective on ductile high-Tcsuperconductors under ambient pressure: few-hydrogen metal-bonded hydrides

Superconducting materials have garnered widespread attention due to their zero-resistance characteristic and complete diamagnetism. After more than 100 years of exploration, various high-temperature superconducting materials including cuprates, nickelates, iron-based compounds, and ultra-high pressure multi-hydrides have been discovered. However, the practical application of these materials is severely hindered by their poor ductility and/or the need for high-pressure conditions to maintain structural stability. To address these challenges, we first provide a new thought to build high-temperature superconducting materials based on few-hydrogen metal-bonded hydrides under ambient pressure. We then review the related research efforts in this article. Moreover, based on the bonding type of atoms, we classify the existing important superconducting materials and propose the new concepts of pseudo-metal and quasi-metal superconductivity, which are expected to be helpful for the design of new high-temperature superconducting materials in the future.

Crystal structures and hydrogenation properties of palladium-rich compounds with elements from groups 12–16

We report on crystal structure data and hydrogenation properties of 24 palladium-rich intermetallic compounds with elements from groups 12–16 of the Periodic Table. Refined crystal structures based on X-ray powder diffraction data are presented for Pd3As (Fe3P type structure) and several members of the Pd5TlAs type structure family. Hydrogenation was studiedin situby differential scanning calorimetry (DSC) under 5.0 MPa hydrogen pressure up to 430 °C. Pd0.75Zn0.25, PdCd, PdHg, Pd2Sn, Pd5Pb3, Pd13Pb9, Pd3As, Pd20Sb7, Pd8Sb3, Pd5Sb2, PdSb, Pd5Bi2, Pd17Se15, Pd4Se, Pd5TlAs, Pd5CdSe, Pd5CdAs, Pd5HgSe, Pd5InAs, Pd8In2Se and Pd3Bi2Se2do not show any sign of hydrogen uptake according to DSC and X-ray diffraction. For Pd3Sn and Pd3Pb a significant hydrogen uptake with unit cell volume increases of 0.4 and 0.6 %, respectively, with a retained structure type of the parent intermetallic was observed. Hydrogenation of Pd5InSe yields Pd3InH≈0.9and a mixture of palladium selenides. Thermal analysis experiments in helium and in hydrogen atmosphere show that this is a multistep reaction with a decomposition of Pd5InSe to Pd3In and a liquid phase and subsequent hydrogenation of Pd3In.