Synthesis of ErFeAsO-based superconductors by the hydrogen doping method

¹ National Institute of Advanced Industrial Science and Technology - Tsukuba, Ibaraki 305-8568, Japan
² Department of Applied Electronics, Tokyo University of Science - Noda, Chiba 275-8510, Japan
³ JST, Transformative Research-Project on Iron Pnictides (TRIP) - 5, Sanbancho, Chiyoda, Tokyo 102-0075, Japan

^a paras-shirage@aist.go.jp
^b iyo-akira@aist.go.jp

Received: 21 September 2010
Accepted: 19 November 2010

Abstract

Here we demonstrate the technique to stabilize the ErFeAsO-based superconductor with the smallest lattice constants in LnFeAsO_1−y (Ln = lanthanide) series using the hydrogen doping method. Polycrystalline samples were synthesized by heating pellets with nominal compositions of ErFeAsO_1−y (1−y = 0.75–0.95) sandwiched between pellets of LaFeAsO_0.8H_0.8 compositions at 1100 ^°C under a pressure of 5.0–5.5 GP. The sample with lattice constants, a = 3.8219 Å and c = 8.2807 Å, shows the highest superconducting critical temperatures (T_c), 44.5 K and 41.0 K, determined by onset transitions of resistivity and susceptibility, respectively. We discuss the phase diagram of the Ln-dependence of T_c in LnFeAsO-based superconductors.