Show simple item record

dc.contributor.authorCetin, Denizen_US
dc.date.accessioned2016-12-02T18:38:02Z
dc.date.available2016-12-02T18:38:02Z
dc.date.issued2016
dc.identifier.urihttps://hdl.handle.net/2144/19501
dc.description.abstractThe need for cleaner and more efficient alternative energy sources is becoming urgent as concerns mount about climate change wrought by greenhouse gas emissions. Solid oxide fuel cells (SOFCs) are one of the most efficient options if the goal is to reduce emissions while still operating on fossil energy resources. One of the foremost problems in SOFCs that causes efficiency loss is the polarization resistance associated with the oxygen reduction reaction(ORR) at the cathodes. Hence, improving the cathode design will greatly enhance the overall performance of SOFCs. Lanthanum nickelate, La2NiO4+δ (LNO), is a mixed ionic and electronic conductor that has competitive surface oxygen exchange and transport properties and excellent electrical conductivity compared to perovskite-type oxides. This makes it an excellent candidate for solid oxide fuel cell (SOFC) applications. It has been previously shown that composites of LNO with Sm0.2Ce0.8O2-δ (SDC20) as cathode materials lead to higher performance than standalone LNO. However, in contact with lanthanide-doped ceria, LNO decomposes resulting in free NiO and ceria with higher lanthanide dopant concentration. In this study, the aforementioned instability of LNO has been addressed by compositional tailoring of LNO: lanthanide doped ceria (LnxCe1-xO2,LnDC)composite. By increasing the lanthanide dopant concentration in the ceria phase close to its solubility limit, the LNO phase has been stabilized in the LNO:LnDC composites. Electrical conductivity of the composites as a function of LNO volume fraction and temperature has been measured, and analyzed using a resistive network model which allows the identification of a percolation threshold for the LNO phase. The thermomechanical compatibility of these composites has been investigated with SOFC systems through measurement of the coefficients of thermal expansion. LNO:LDC40 composites containing LNO lower than 50 vol%and higher than 40 vol% were identified as being suitable to incorporate into full button cell configuration from the standpoint of thermomechanical stability and adequate electrical conductivity. Proof-of-concept performance comparison for SOFC button cells manufactured using LNO: La0.4Ce0.6O2-δ composite to the conventional composite cathode materials has also been provided. This thermodynamics-based phase stabilization strategy can be applied to a wider range of materials in the same crystallographic family, thus providing the SOFC community with alternate material options for high performance devices.en_US
dc.language.isoen_US
dc.subjectCathodeen_US
dc.subjectFuel cellen_US
dc.subjectLanthanum nickelateen_US
dc.subjectThermodynamic stabilityen_US
dc.subjectMaterials scienceen_US
dc.titleThermodynamic stability of perovskite and lanthanum nickelate-type cathode materials for solid oxide fuel cellsen_US
dc.typeThesis/Dissertationen_US
dc.date.updated2016-11-05T01:07:54Z
etd.degree.nameDoctor of Philosophyen_US
etd.degree.leveldoctoralen_US
etd.degree.disciplineMaterials Science & Engineeringen_US
etd.degree.grantorBoston Universityen_US


This item appears in the following Collection(s)

Show simple item record