Defects and protons in the CaZrO3 perovskite and Ba2In2O5 brownmillerite: computer modelling and EXAFS studies

Atomistic computer modelling techniques are used to investigate the substit ution of dopants in the CaZrO3 perovskite and the incorporation of protons in the Ba2In2O5 brownmillerite. The defect calculations on CaZrO3 predict t hat small trivalent cations show Zr-site selectivity with oxygen vacancy co mpensation, while larger cations show Ca-site selectivity with Ca vacancy c ompensation. EXAFS experiments on doped CaZrO3 demonstrate Yb and Nd substi tution at Zr and Ca sites, respectively, in agreement with the simulations. Finally, several water incorporation reactions in Ba2In2O5 have been exami ned, including mechanisms involving oxygen interstitial sites. (C) 2001 Els evier Science B.V. All rights reserved.