Characterization of the La1−xBaxCoO3−δ (0 ≤ x ≤ 1) System as Cathode Material for IT-SOFC
C. MARTINEZ SETEVICH; L. MOGNI; A. CANEIRO; F. PRADO
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
ELECTROCHEMICAL SOC INC
Año: 2012 vol. 159 p. 72 - 79
The influence of temperature and procedure on the phase relationships of LaxBa1−xCoO3−δ with 0 ≤ x ≤ 1.0, oxygen nonstoichiometry,thermal and chemical expansion contributions, in air, and the electrochemical response of electrodes formed by threeporous layers LaxBa1−xCoO3−δ /(50:50wt%)LaxBa1−xCoO3−δ+Ce0.9Gd0.1O1.95/Ce0.9Gd0.1O1.95 have been investigated. The crystalstructures of samples with 0 ≤ x ≤ 0.5 and x = 1.0 were refined satisfactorily with a single phase. The cubic perovskite could beobtained for the x = 0.5−0.7 furnace-cooled samples (∼5◦C/min). This phase was found unstable for x = 0.6 and 0.7, in air, at T≤ 1000◦C. For x = 0.8 and 0.9 a mixture of phases has been obtained. The expansion coefficient reaches a maximum of 26×10−6K−1 for x = 0.6 and a minimum of 16×10−6 K−1 for x = 0.8 and 0.9 for T = 20−900◦C. AC impedance spectroscopy measurementswere carried out in the temperature range of 400 ≤ T ≤ 700◦C. A minimum polarization resistance Rp ∼ 0.065 ? 0.075 cm2 was obtained for 0.4 ≤ x ≤ 0.7 at T = 600◦C, which compares very well with the Rp value reported for composites preparedwith cobaltites.