金属水素化物PdD(x)の超伝導相における格子欠陥の役割

Abstract

The interactions of hydrogen with the lattice defects in palladium have attracted much attention because macroscopic properties such as hydrogen storage and metal embrittlement are markedly affected by H (D)-defect interactions. In this paper we report the inhomogeneous superconducting state in PdD(x )and the hydrogen absorption/desorption processes on annealed and unannealed Pd wires. Deuterium was loaded simultaneously with unannealed Pd wire in the ''as received'' condition and annealed Pd wire by electrolysis in 0.1M LiOD in D2O at room temperature. A superconducting (SC) state, however, is induced only for the unannealed Pd wire and is robust against time. Since the easier insertion and stronger trapping of D atoms is realized at the vacancies and dislocation cores, an SC region (relatively D-rich region) may be formed around the lattice defects and a nonSC region may be formed around the regions away from the dislocation cores and vacancies. In addition, we find that the reduction of x estimated from T(sub c) is much smaller than reduction of x estimated from T(sub a), indicating the slower escape of D atoms in the SC region than in the nonSC region. This result suggests occurrence of the SC state is associated with the formation of a dense Cottrell cloud of D atoms at around lattice defects.