Investigation of Sputtered Ba0.5Sr0.5Co0.8Fe0.2O3-?? Electrodes With Impedance Spectroscopy

Joshua HertzSolid oxide fuel cells (SOFCs) are energy conversion devices that rely upon the oxidation of a hydrogen-based fuel to generate electricity. They are extremely attractive for use in automotive and stationary power because of their high efficiency compared to combustion engines and broad range of fuels which can be used. Currently, performance of SOFCs is hindered by one or more rate-limiting steps at the cathode of the fuel cell. By replacing traditional porous, electron conducting cathode materials with those capable of mixed ionic/electronic conduction (known as MIECs), efficiency can be greatly increased. This work focused on the synthesis and characterization of the MIEC known as BSCF. This material was synthesized in the bulk using traditional solid state ceramic processing methods and its crystal structure was verified using x-ray diffraction. Sputtering deposition rates were then performed under a variety of processing parameters and optical interferometry was used to measure the thickness of the resulting films. It was shown that optimal film growth occurred at a sputtering power of 75 W with a pressure of 5 mTorr and an Ar:O2 ratio of 8:2. BSCF was then deposited into 200 nm thick, circular electrodes ranging from 1 to 5 mm in diameter on a yttria-stabilized zirconia (YSZ) substrate (the industry standard for SOFC electrolytes). Initial impedance spectroscopy measurements were taken on this system to quantify its performance in an SOFC system. Based on the results, it is proposed that one or more factors caused inconsistencies in the data. Therefore, multiple methods are proposed to improve the electrode processing method as well as impedance spectroscopy techniques.Mechanical Engineerin