Stabilization of ErFeAsO-based superconductor by hydrogen doping under high pressure

► Discovery of New Superconductor. ► A novel method for synthesis of ErFeAsO-based superconductor by hydrogen doping using high-pressure (HP) synthesis technique. ► Lattice constants are smallest among the Ln-1111series. ► Superconducting critical temperatures (Tc) shows at 44.5 K determined by onsets of resistive transitions. Here we report on the successful synthesis of ErFeAsO-based superconductor by hydrogen doping using high-pressure (HP) synthesis technique. The ErFeAsO1−y target pellets were sandwiched between LaFeAsO0.8H0.8 pellets, which act as a hydrogen source. Hydrogen released from the hydrogen source soaks into the target pellets during HP synthesis and the target pellets crystallizes with the tetragonal crystal structure with the lattice constants a=3.8219 Å and c=8.2807 Å. The hydrogen doped sample ErFeAsO1−y(H) thus obtained shows superconducting critical temperatures (Tc) of 44.5K and 42.5K determined by onsets of resistive and diamagnetic transitions, respectively.