Muon diffusion and trapping in proton conducting oxides

Trapping as a main feature of proton diffusion in proton conducting oxides was investigated by means of muon spin relaxation measurements, with the positive muon as tracer. In Sc-doped SrZrO3, a system with representative physicochemical properties and favourable nuclear magnetic moments, the muons are trapped at single Sc ions at a distance of 2.49 Angstrom with a binding energy of 0.2 eV, in accordance with previous proton results. The muons form muoxide ions which are directed along the bisector of two oxygen-oxygen connection lines. The mu SR spectra could quantitatively be described in terms of a two-state model for the muon diffusion comprising random sequences of trapping events and free diffusion periods. (C) 1998 Elsevier Science B.V. All rights reserved.