Microstructure Sensitive Design and Processing in Solid Oxide Electrolyzer Cell

Abstract

SUMMARYThe aim of this study was to develop an inexpensive manufacturing process for deposition of functionally graded thin films of LSM oxides with porosity graded microstructures for use as IT-SOFCs cathode. The spray pyrolysis method was chosen as a low-temperature processing technique for deposition of porous LSM films onto dense YSZ substrates. The effort was directed toward the optimization of the processing conditions for deposition of high quality LSM films with variety of morphologies in the range of dense to porous microstructures. Results of optimization studies of spray parameters revealed that the substrate surface temperature is the most critical parameter influencing the roughness and morphology, porosity, cracking and crystallinity of the film. Physical and chemical properties of deposited thin films such as porosity, morphology, phase crystallinity and compositional homogeneity have shown to be extensively dependent on the preparation conditions. Detailed analysis of the film formation mechanisms have been discussed in this work. It is suggested that using volatile metal-organic precursors as in CVD would alter the film formation mechanism to MOCVD process in which films of high quality can be processed. Novel electrode microstructures currently include a graded microstructure wherein the large pores are made close to the surface in outer layers for maximum mass transport into the electrode structure and smaller pores and particles close to the electrolyte interface would create maximum number of active reaction sites. Taking the advantage of simplicity of spray pyrolysis technique combined with using metal-organic compounds, the conventional ultrasonic spray system was upgraded to a novel system whereby highly crystalline multiMicrostructure Sensitive Design for Materials in Solid Oxide Electrolyzer Cell, Garmestani vi layered porosity graded LSM cathode with columnar morphology with good electrical conductivity in the range of 500-700 °C was fabricated through a multi-step spray and via optimizing spray parameters. This achievement for the current graded LSM cathode would allow its use in IT-SOFCs.Microstructure Sensitive Design for Materials in Solid Oxide Electrolyzer Cell, Garmestani 7