The results of O non-stoichiometry were presented for chromite LaCr0.79Cu0.05Al0.16O3−δ with hexagonal perovskite structure at 1000C. The modelling of the defect structure of this O deficient chromite was carried out by considering also the acceptor dopant Cu on B-site. The equilibrium constants, necessary to calculate all a priori unknown equilibrium defect concentrations, were determined by fitting the derived model equation to the measured O non-stoichiometry. The three oxidation states 3+, 2+, and 1+ for Cu were considered simultaneously in Cu-doped lanthanum chromite in addition to 3+ and 4+ states for Cr in the host lattice. The results of the fitting revealed that there was no significant change of the Cr3+ oxidation state over the complete O partial pressure range investigated (−20 ≤ log(PO2/atm) ≤ 0). In contrast to this, Cu changed its oxidation state continuously from 3+ via 2+ to 1+ if the O partial pressure decreased; thereby giving rise to O vacancy formation.

Oxygen Vacancy Formation and Defect Structure of Cu-Doped Lanthanum Chromite LaCr0.79Cu0.05Al0.16O3−δ. A.Zuev, L.Singheiser, K.Hilpert: Solid State Ionics, 2005, 176[3-4], 417-21