High temperature properties of the n=2 Ruddlesden?Popper phases

L. MOGNI; F.PRADO; A. MANTHIRAM; A. CANEIRO

SOLID STATE IONICS

Elsevier

Año: 2006 vol. 176 p. 1807 - 1810

0167-2738

The crystal chemistry and mixed conductor properties of the n=2 member of the Ruddlesden?Popper (R?P) phases Sr3−xLaxFe2−yNiyO7−δwith 0≤x≤0.3 and 0≤y≤1.0 have been studied at high temperature. High-temperature X-ray diffraction and thermogravimetric measurementsof the equilibrium pO2 (10−5≤pO2≤1 atm) in the temperature range 400≤T≤1000 °C indicate that the Sr3FeNiO7−δ phase is able toaccommodate a large oxygen non-stoichiometry (δ∼1.5) without structural transformations. The electrical conductivity and oxygen permeabilityincrease with the substitution of Ni for Fe in the range 550≤T≤1000 °C. The electrical transport of the Sr3FeNiO7−δ phase is thermally activatedand the activation energy decreases with the substitution of Ni for Fe for a given oxygen content. The increase in the oxygen permeation flux withincreasing Ni content is due to an increasing oxygen non-stoichiometry and a lower activation energy for permeation.© 2006 Elsevier B.V. All rights reserved.