Effect of Nb5+ content on the high temperature properties of the mixed conductors system La1−xBaxCo1−yNbyO3−δ with 0.6≤x≤1.0 and 0≤y≤0.4

• Published in: Solid state ionics 2017-02, Vol.300, p.140-148
• Main Authors: Setevich, C., Toscani, L., Larrondo, S., Prado, F., Caneiro, A.
• Format: Article
• Language: English
• Subjects: Cobaltites; Crystal structure stability; Nb-doping; Oxide mixed conductors; Perovskites; Thermal expansion, impedance spectroscopy
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2016.12.016

The replacement of Co by Nb in the La1−xBaxCo1−yNbyO3−δ (0.6≤x≤1.0) system and its effects on phase stability and high temperature properties of the cubic perovskite phase were investigated by X-ray diffraction, dilatometry, electrical conductivity, oxygen permeation and electrochemical impedance spectroscopy. The incorporation of Nb in the B site stabilizes the cubic perovskite in the as prepared samples. The Nb solubility increases from y=0.1, for the sample with Ba content x=0.6, to y=0.4 for 0.8≤x≤1.0. However, after a heat treatment at 750°C during 10days small amounts of secondary phases were detected for samples with x=0.9 and 1.0. The linear expansion of the cubic phases decreases with the Nb content as well as with the Ba content. The minimum value, α=12.9×10−6K−1, was obtained for La0.2Ba0.8Co0.6Nb0.4O3−δ. The behavior of electrical conductivity and oxygen permeation data with Nb content is explained from variations in the oxygen vacancy concentration, which is controlled by Nb5+ and Ba2+ contents. The minimum polarization resistance value, Rp=0.08Ωcm2, was obtained at 600°C for La0.2Ba0.8Co0.9Nb0.1O3−δ. The low Rp value of this compound and the crystal structure stability of various compositions in the system La1−xBaxCo1−yNbyO3−δ with x≥0.7 and y≥0.1 make these materials of interest as mixed conductors. •The replacement of Co by Nb in the La1−xBaxCo1−yNbyO3−δ (0.6≤x≤1.0) system stabilizes the cubic perovskite.•For a fixed Ba content, the incorporation of Nb5+ depress the oxygen permeation flux, ORR, σ and the TEC values.•The minimum polarization resistance value was 0.08Ωcm2, at 600°C, in air, for La0.2Ba0.8Co0.9Nb0.1O3−δ.