Dopant and proton incorporation in perovskite-type zirconates

Atomistic simulation techniques are used to investigate the energetics of defect and dopants, of oxygen migration and of proton incorporation in AZrO(3) (A = Ca, Sr). In agreement with recent EXAFS studies, small lanthanide dopants are predicted to substitute on the Zr-site (with oxygen vacancy compensation necessary for proton incorporation), while larger lanthanide dopants substitute on the A-site. Proton incorporation in AZrO(3) is found to be exothermic, with increasing acceptor dopant levels causing an energetic stabilisation of the protonic defect. Our results suggest that trends in proton conductivity can be rationalised in terms of effective oxygen vacancy creation arising from dopant site selectivity, relative values of water incorporation energies, and possible proton-dopant association. (C) 1999 Elsevier Science BN. All rights reserved.