It was found that the proton was strongly absorbed in heavily Sc-doped material. Neutron diffraction studies were made of single crystals, and the O-H distance was found to be about 0.12nm. The proton concentration was estimated to be about 2mol% in the case of SrTi0.98Sc0.02O3. Protonic conduction was determined, in Sc-doped material, by performing alternating-current conductivity measurements in wet air. The hole conductivity was estimated by making measurements in dry air. The conductivities in water vapor were always higher than those in heavy-water vapor. The conductivity ratios of the proton and the deuteron were approximately proportional to the inverse of the mass ratio. The conductivities in water vapor, at temperatures below 200C, became larger than those in dry air (figure 7). In this temperature region, it was clear that protons migrated by hopping from site to site. At temperatures above 400C, the conductivities were almost the same for the 3 atmospheres. The conductivity was a little higher in dry air, at temperatures between 300 and 400C, than in water plus heavy-water vapor. At temperatures above 400C, the electrical conduction was attributed mainly to holes or O vacancies, rather than protons or deuterons. According to neutron diffraction data, the proton was situated at a site, between O-O ions which made up an O octahedron, as if it constituted a H bond. It was proposed that the protonic conductivity increased when the strength of the O-H bond weakened due to H-bonding effects. This was suggested to be responsible for the high protonic conductivity in this material.

N.Sata, K.Hiramoto, M.Ishigame, S.Hosoya, N.Niimura, S.Shin: Physical Review B, 1996, 54[22], 15795-9