Samples of pure, 5%Yb- and 5%Nd-doped material were investigated by using extended X-ray absorption fine-structure spectroscopy and computer simulation techniques. The former results revealed that Yb3+ behaved as an acceptor dopant and replaced Zr4+, while the larger Nd3+ dopant behaved like a donor-dopant and replaced Ca2+. The extended X-ray absorption fine-structure spectroscopic results were confirmed by atomistic modelling data; according to which small lanthanide dopants were expected to be incorporated at Zr4+ sites (with an O-vacancy compensation that was essential for proton incorporation). Larger lanthanide dopants were incorporated at the Ca2+ site. A decrease in proton conductivity, which was caused by the larger lanthanides, was suggested to be related to the reduced O-vacancy concentration which arose from dopant-site selectivity.

Cation Dopant Sites in the CaZrO3 Proton Conductor: a Combined EXAFS and Computer Simulation Study. R.A.Davies, M.S.Islam, A.V.Chadwick, G.E.Rush: Solid State Ionics, 2000, 130[1-2], 115-22