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

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

SOLID STATE IONICS

Elsevier

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 aprox. 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.