Fabrication of gradient porous LSM cathode by optimizing deposition parameters in ultrasonic spray pyrolysis

Multiple-step ultrasonic spray pyrolysis was developed to produce a gradient porous lanthanum strontium manganite (LSM) cathode on yttria-stabilized zirconia (YSZ) electrolyte for use in intermediate temperature solid oxide fuel cells (IT-SOFCs). The effect of solvent and precursor type on the morphology and compositional homogeneity of the LSM film was first identified. The LSM film prepared from organometallic precursor and organic solvent showed a homogeneous crack-free microstructure before and after hear treatment as opposed to aqueous solution. With respect to the effect of processing parameters, increasing the temperature and solution flow rate in the specific range of 520-580 degrees C leads to change the microstructure from a dense to a highly porous structure. Using a dilute organic solution a nanocrystal line thin layer was first deposited at 520 degrees C and Solution flow rate of 0.73 ml/min on YSZ surface: then, three gradient porous layers were sprayed from concentrated Solution at higher temperatures (540-580 degrees C) and Solution flow rates (1.13-1.58 ml/min) to form a gradient porous LSM cathode film with similar to 30 mu m thickness. The microstructure, phase crystallinity and compositional homogeneity or the fabricated films were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive analysis of X-ray (EDX). Results showed that the spray pyrolized gradient film fabricated in the temperature range of 520-580 degrees C is composed of highly crystalline LSM phase which can remove the need for subsequent hear treatment. (C) 2008 Elsevier B.V. All rights reserved.