Effect of Dopant Species on the Dissolving Site of the Protons in La2Zr2 O 7-Doped with Alkaline-Earth Ions

Abstract

Infrared (IR) absorption spectra for O-H and O-D stretching vibration regions of and proton conductors were recorded. The spectra consisted of three to six bands at 3200-3600 cm−1. The bands were positioned at higher wavenumbers and were sharper than the case for the well-known high-temperature proton conductors with perovskite and related structures. The three to six bands observed were attributable to different sites of protons dissolved in the crystal. The dissolving sites of protons were discussed in terms of the dopant alkaline-earth species. The observed bands were reasonably interpreted assuming that six sites for protons exist in -based proton conductors. The dissolving site of protons itself did not depend on the dopant species, but the population of protons in each site did depend on the dopant species. The protons preferred the site corresponding to the at the lower wavenumber, i.e., the site with strong hydrogen bonding strength. This tendency was discussed from the viewpoint of the basicity of the oxygen near the dopant and structural distortion and relaxation introduced by doping. Because the population of protons in each site strongly depended on the dopant species despite the very small concentration of ∼1 atom %, it was shown that the protons dissolved at the nearest neighbor of the alkaline-earth dopant, at least near room temperature at which the IR spectra were recorded. © 2003 The Electrochemical Society. All rights reserved.