MTL Annual Report

Solid oxide fuel cells (SOFCs) directly convert chemical to electrical energy with high efficiency and can operate using a wide variety of fuels from hydrogen and  kerosene to gasified coal.  Many of the more advanced materials in SOFCs experience significant changes in oxygen content, or oxygen stoichiometry, during operation, resulting in changes in volume and elastic properties termed chemomechanics.  This chemical expansion, analogous to temperature-induced thermal expansion, is oxygen nonstoichiometry-induced and can have a negative impact on SOFC performance. In this project, we are studying the chemical expansion coefficient, elastic properties, and oxygen stoichiometry of thin-film and bulk SOFC materials. Thin films are of particular interest since they allow for control of strain and increase the surface-to-volume ratio, particularly important for electrode performance.  The chemomechanical properties are being investigated using high temperature, atmosphere-controlled nanoindentation, high-resolution x-ray diffraction, dilatometry, impedance spectroscopy, and thermo-gravimetry techniques.