Atmospheric plasma spraying is attractive for manufacturing solid oxide fuel cells (SOFCs) because it allows functional layers to be built rapidly with controlled microstructures.  The technique allows SOFCs that operate at low temperatures (500 to 700°C) to be fabricated by spraying directly onto robust and inexpensive metallic supports.  However, standard cathode materials used in commercial SOFCs exhibit high polarization resistances at low operating temperatures. Therefore, alternative cathode materials with high performance at low temperatures are essential to facilitate the use of metallic supports.

Coatings of materials for low temperature cathodes (including lanthanum strontium cobalt ferrite (LSCF), samaria-doped ceria (SDC) and strontium samarium cobaltite (SSC)) were fabricated on steel substrates using axial-injection atmospheric plasma spraying.  The coating layers were evaluated in terms of thickness, deposition efficiency and adhesion.  X-ray diffraction (XRD) analysis was performed on coatings to detect material decomposition and the formation of undesired phases in the plasma.  These results determined the envelope of plasma spray parameters in which coatings of each material can be manufactured, and the intersection of those envelopes defined the range of conditions in which composite cathode coatings could be manufactured.  The microstructures of the cathode coatings were evaluated by scanning electron microscopy (SEM), and the relative deposition efficiency was determined from energy-dispersive x-ray spectroscopy (EDX) measurements.