The tubular solid oxide fuel cell (SOFC) design is the most commercially advanced SOFC technology. To assemble a multi-cell stack, the outer anode layer of one tubular cell is connected to the inner cathode layer of the next tube by the interconnect material. Plasma spraying is the most common method of fabricating the interconnects. The spraying parameters must be precisely adjusted to achieve high density in the interconnect to prevent mixing of the air and fuel gases and to obtain the desired crystalline phases to maximize electrical conductivity and assure thermodynamic stability under both reducing and oxidizing conditions. The most common material choice is doped LaCrO₃, a ceramic material with a good thermal expansion coefficient match with the other components of the cell and an acceptable electrical conductivity. This material has a high melting point (above 2400 ºC). A combination of high temperatures and high velocities during the spraying are required to obtain the required coating properties. The different thermal spray techniques cover a wide range of temperatures and velocity of the in-flight particles.

In this work three different thermal spray techniques were used to deposit La_0.9Sr_0.1CrO₃ interconnects: high velocity oxy-fuel (HVOF) using a modified nozzle, air plasma spray (APS), and supersonic air plasma spray. A substitute powder with similar physical properties to La_0.9Sr_0.1CrO₃ was used for the development and optimization of the process parameters to achieve the highest density previous to the deposition of the La_0.9Sr_0.1CrO₃ on zirconium oxide substrates. The electrical conductivity of the as-sprayed coatings was correlated with the microstructure observed by scanning electron microscopy and the phase composition of the coatings obtained from X-ray diffraction analysis. Post-deposition heat treatments were studied in order to increase the electrical conductivity.