Applications of rare earth doped complex oxides in potentiometric sensors, solid oxide full cells, and thermoelectrics

Rare-earth doped complex oxide materials have a number of interesting applications in the clean energy economy. By tailoring the materials composition, the electronic, thermal, and ionic transport properties can be tuned for the intended application. In this study, three examples of such applications are considered. First, a crystal structure known as sodium super ionic conductors (Na1+3xZr2(P1-xSixO4)3 ) was modified to synthesize a cerium super ion conductor [Ce.1Zr.9)40/39Nb(PO4)3]. Tuning the composition resulted in a complex oxide that has been shown to have selective cerium ion conductivity, making it a candidate as a solid electrolyte in a real time rare earth ion sensor. These sensors were successfully applied to demonstrate real time monitoring of cerium concentrations in aqueous solutions and could potentially be modified to detect other rare earth elements, eliminating the time intensive chemical assay testing currently used in rare earth recycling and refining. Another application of complex oxides includes the use of lanthanum doped strontium manganese oxide (La.8Sr.2MnO3) as an electronically conductive diffusion barrier. This material was applied to 2205 stainless steel to test its potential as an interconnect in solid oxide fuel cells (SOFCs). These barrier layers can reduce high temperature oxidation and spallation in SOFCs interconnects, potentially increasing the lifetime of SOFC stacks, and allowing for cheaper ferrous alloys to be used in operating conditions up to 800°C, further lowering the overall cost of SOFCs. Lastly, gadolinium doped strontium titanate (Gd.08Sr.92TiO3) is considered as a thermoelectric material. Specifically the addition of a second phase of gadolinium doped cerium oxide (Gd.2Ce.8O3-δ) was used to achieve enhancements in the thermoelectric properties.2016-10-27T00:00:00

Electrical conduction and magnetic properties of nanoconstrictions and nanowires created by focused electron/ion beam and of Fe3O4 thin films

La tesis se centra en la fabricación y estudio de las propiedades eléctricas y magnéticas de nanoestructuras con aplicaciones potenciales en nanoelectrónica. Se estudian las propiedades de magnetotransporte de películas epitaxiales de Fe3O4. Se desarrolla un método para fabricar constricciones de tamaño atómico en metales usando un haz focalizado de iones. Y se examinan diferentes tipos de nanohílos fabricados mediante deposición usando un haz focalizado de electrones/iones: los de Pt presentan una transición metal-aislante, los de W son superconductores por debajo de 5 K y los de Co son fuertemente magnético