Enhanced reactivity of domain walls in WO3 with sodium
Department of Earth Sciences and IRC in Superconductivity,
University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK
Revised: 15 December 1999
Published online: 15 May 2000
A possible new high temperature superconducting phase was recently reported in WO3:Na. We have examined the reaction between sodium vapour and WO3, and compared the phases formed by the reaction to previously known WO3 phases. By using light microscopy and electron microprobe analysis, domain walls from the interior of the crystal are shown to have a much higher Na content than bulk material after reaction with Na vapour. This indicates preferential transport along the domain walls. The result is very similar to a reduction reaction of WO3 crystals in which twin walls lose oxygen preferentially. Oxygen deficient twin walls are superconducting with Tc≈3K.
PACS: 61.72.Mm – Grain and twin boundaries / 66.30.-h – Diffusion in solids / 81.70.Jb – Chemical composition analysis, chemical depth and dopant profiling
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2000