Search

(La{sub 1-x}Sr{sub x}){sub y}Fe{sub 1-z}Ni{sub z}O{sub 3-{delta}} perovskites have been proposed as alternative cathode materials. In this communication the electrochemical characterisation of (La{sub 0.8}Sr{sub 0.2}){sub 0.95}Fe{sub 0.8}Ni{sub 0.2}O{sub 3-{delta}} tested on symmetrical cells are compared to full cell tests. Significant differences between the test procedures are observed. Area specific resistances below 0.5 {omega} cm{sup 2} at 800 C indicate a potential of LSFN for SOFC applications. However, the initial performance and long-term stability are found to be inferior to state-of-art La-Sr Co-Fe perovskite cathodes. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

Note: Times Cited: 10Si Reference EPFL-ARTICLE-206060doi:10.1002/fuce.200800116View record in Web of Science URL: ://WOS:000273394400015 Record created on 2015-03-03, modified on 2017-05-12

BaZr0.9Y0.1O3-δ has been synthesised by three different methods: the solid-state reaction, the spray pyrolysis and the spray drying. Significantly different apparent lattice parameters (between 0.4192 nm for the sample prepared by the solid-state reaction method and sintered at 1,500 °C and 0.4206 nm for the sample prepared by the solid-state reaction method and sintered at 1,720 °C) are observed after calcination and sintering, depending on the synthesis method and the sintering temperature. The bulk conductivity values also vary over several orders of magnitude (–7.2< log σb

Journal of Applied Electrochemistry, 39 (4), ISSN:0021-891X, ISSN:1572-8838

TiO 2 , MgO, Mo, Al 2 O 3 and Bi 2 O 3 up to a few percentages in quantity were intentionally added to BaZr 0.9 Y 0.1 O 3 − δ . The selected additives do not contribute to any improvement of the sintering behaviour. The lattice parameter of BaZr 0.9 Y 0.1 O 3 − δ for the samples containing additives is smaller than for the pure material. The bulk conductivity also falls drastically with metal addition. For instance, the conductivity of the sample containing TiO 2 is 2.5 orders of magnitude lower than the sample without additive. The grain boundary conductivity is also affected by the presence of metal ions.

The influence of a high temperature annealing (∼ 2200 °C) on the microstructure and the electrical properties of BaZr 0.9 Y 0.1 O 3− δ has been examined. The high temperature annealing was achieved using an optical floating zone furnace. The obtained sample is homogeneous with an average grain size of about 5 μm. No additional phases were found in the XRD pattern and the structure was identified to be cubic. After the high temperature annealing, the grain boundary conductivity is increased by approximately two orders of magnitude, while the bulk conductivity remains the same.

Proton conducting oxides such as BaCe0.9Y0.1O3−δ have considerable promise for intermediate temperature fuel cells. Unfortunately these tend to be unstable, e.g. to attack by carbonation. Previous work has highlighted the possibility of utilising barium zirconate to provide a chemically stable electrolyte; however such materials are difficult to sinter yielding very high overall resistances. Whilst this sintering problem is soluble, there are still very significant questions about the intrinsic grain conductivity, which varies by orders of magnitude for different reports. Here we demonstrate that there are two variants of BaZr0.9Y0.1O2.95, both with the cubic perovskite structure. The α-form exhibits a slightly smaller unit cell and much lower protonic conductivity than the β-form. The α-form is observed in better equilibrated samples and neutron diffraction demonstrates that this difference originates in a small degree of cross substitution of the Y atom onto the A-sites for the β-form, suggesting a novel approach to enhance ionic conductivity by reducing defect association through A-site substitution.