Our paper is now available from the Journal of Materials Chemistry A site:
- S.C. Middleburgh, I. Karatchevtseva, B.J. Kennedy, P.A. Burr, Z. Zhang, E. Reynolds Grimes, R.W. Grimes and G.R. Lumpkin, “Peroxide defect formation in zirconate perovskites”, Journal of Materials Chemistry A, (2014) doi:10.1039/C4TA02558J
In this paper we find a novel method for the accomodation of excess oxygen in ternary perovskite oxides. These materials are of high interest due to their proton conductivity and high temperature stability. For these properties, it is crucial to understand if the material may accomodate deviation from stoichiometry and what is the underlying mechanism. A peroxide substitution defects (i.e. two tightly bonded oxygen atoms replacing a single lattice oxigen) was predicted to be more favourable than conventional oxygen defects at low electron chemical potentials, as these can be accomodated without the need for a charge compensating species. In particular, for BeZrO3 this has important implicaitons as it reduces the solution energy of excess oxygen down to near 0 eV. These predictions were confirmed by Raman spectroscopy of BaZrO3 and SrZrO3 that were treated with H2O2.
Atomic scale modelling suggests that excess oxygen can be accommodated in the group II perovskite zirconates by the formation of peroxide ion defects. This is unprecedented given the lack of charge compensating defects required for standard excess oxygen accommodation. The solution energy of O2 was predicted to be close to zero for BaZrO3, accommodating the peroxide ion defect more easily than in SrZrO3 or CaZrO3. This was experimentally examined by exposing SrZrO3 and BaZrO3 to hydrogen peroxide solution and then carrying out Raman spectroscopy measurements to look for a peak indicative of peroxide ions. A peak was observed at 1000 cm-1 in both compositions, suggesting the theoretically predicted peroxide ion is present