The role of the Co²⁺/Co³⁺ redox-pair in the properties of La_2?xSr_xCoTiO₆ (0?¡Ü?x?¡Ü?0.5) perovskites as components for solid o

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• 作者：Alejandro Gó ; mez-Pé ; rez^a ; Mercedes Yuste^a ; Juan Carlos Pé ; rez-Flores^a ; ^{jcaperez@ceu.es} ; Clemens Ritter^b ; M. Teresa Azcondo^a ; Jesú ; s Canales-Vá ; zquez^c ; Marí ; a Gá ; lvez-Sá ; nchez^c ; Khalid Boulahya^d ; Flaviano Garcí ; a-Alvarado^a ; Ulises Amador^a
• 关键词：Solid oxide fuel cells ; Doped double perovskite ; Electrochemical characterization ; Cathode ; Neutron powder diffraction ; Charge transport
• 刊名：Journal of Power Sources
• 出版年：2013
• 出版时间：1 April, 2013
• 年：2013
• 卷：227
• 期：Complete
• 页码：309-317
• 全文大小：1362 K

文摘

Substitution of La³⁺ by Sr²⁺ in the perovskite La₂CoTiO₆ yields materials of the La_2?xSr_xCoTiO₆ series. The dominant charge-compensating mechanism is oxidation of Co²⁺ if they are prepared at air. The as prepared oxides can be reduced inducing a large amount of oxygen vacancies while keeping the perovskite structure. The electrical behaviour of the La_2?xSr_xCoTiO₆ series is dominated by p-type electronic conduction in a wide pO₂ range through non-adiabatic hopping of small-polarons. The electrical conductivity increases with x, except for the x?=?0.5 material which shows an unexpectedly low conductivity due to microstructural and short-range ordering effects. The highest conductivity material, La_1.60Sr_0.40CoTiO₆, is selected to study the electrochemical properties of the series. This compound is chemically compatible with YSZ up to 1373?K, in both oxidizing and reducing atmospheres. The preliminary evaluation of the electrode performance reveals that La_1.60Sr_0.40CoTiO₆-based electrodes exhibit polarization resistances of typically 0.8?¦¸?cm² at 1073?K in oxygen, which are close to the values obtained for LSM-based cathodes. Thus, the electrochemical behaviour of this oxide as cathode is particularly encouraging since the electrode microstructure is not optimized; it is expected that an improved microstructure will perform at least similarly to the state-of-art in SOFCs materials.