First-principles study of protonic conduction in In-doped AZrO 3 ( A=Ca, Sr, Ba)

Abstract

The first-principles calculations based on the density functional theory were carried out to investigate the effects of A-cations on the protonic conductivity of AZrO 3 ( A=Ca, Sr, Ba). The local geometries around proton and dopant ion, formation energies of interstitial proton and activation energies for proton transfer were simulated in the In-doped CaZrO 3, SrZrO 3 and BaZrO 3. The results showed that the crystallographic feature of AZrO 3 ( A=Ca, Sr, Ba) is an important factor to control the protonic conduction. In the In-doped CaZrO 3 or SrZrO 3 with the orthorhombic structure, there is a unique stabilized proton site located between two adjacent octahedra. But in the In-doped BaZrO 3 with the cubic structure, there exists a certain region of stable sites between them. As the ionic radii of A-cations decrease, the crystal symmetry changes from cubic to orthorhombic, resulting in the rotation of ZrO 6 (or InO 6) octahedra, which causes the increase of activation energies for proton transfer in the oxides.