Effect of La0.8Sr0.2MnO3 powder addition in the precursor solution on the properties of cathode films deposited by spray pyrolysis

Resumo

Films of lanthanum strontium manganite, LSM (La0.8Sr0.2MnO3) were deposited on yttria stabilized zirconia
(YSZ) substrates by different methods aiming to establish the most suitable route to prepare cathodes for
solid oxide fuel cells (SOFC). Samples were obtained by using a solution of lanthanum, strontium and
manganese nitrates or a dispersion of the LSM powder in this solution. Both commercial and synthetized
LSM powders were used, the last one obtained by amorphous citrate method. The films were deposited by
spray pyrolysis on YSZ substrates prepared by uniaxial and isostatic pressing. Samples were characterized by
scanning electron microscopy, confocal laser scanning microscopy, X-ray diffraction and two-probe
conductivity measurements. The area specific resistance and relaxation to cathodic activation were measured
by electrochemical impedance spectroscopy. The substrate obtained by uniaxial pressing and the commercial
LSM produced films with the highest amount of surface cracks. The film obtained from the suspension
showed area specific resistance and activation energy lower than the other produced from the solution. For
both samples, the cathodic activation process resulted in an initial reduction of the total resistance of around
20%, the sample produced from the suspension being more resistant to relaxation. Therefore, the LSM
suspension is more suitable than the salts solution for preparing films by spray pyrolysis on YSZ substrates to
obtain efficient cathodes for SOFC.