High temperature properties of the n = 2 Ruddlesden Popper phases (La,Sr)3(Fe,Ni)2O7-d

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

SOLID STATE IONICS

Elsevier B. V.

Año: 2006 vol. 177 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-d with 0 £ x £ 0.3 and 0 £ y £1.0 have been studied at high temperature.  High temperature X-ray diffraction and thermogravimetric measurements of the equilibrium pO2  (10-5 £ pO2 £ 1 atm) in the temperature range 400 £ T £ 1000 °C indicate that the Sr3FeNiO7-d phase is able to accommodate a large oxygen non-stoichiometry  (d ~ 1.5) without structural transformations. The electrical conductivity and oxygen permeability increase with the substitution of Ni for Fe in the range 550 £ T £ 1000 °C. The electrical transport of the Sr3FeNiO7-d phase is thermally activated and the activation energy decreases with the substitution of Ni for Fe for a given oxygen content. The increase in the oxygen permeation flux with increasing Ni content is due to an increasing oxygen non-stoichiometry and a lower activation energy for permeation.