Riza Dervisolgu
From Grey Lab Page
e-mail: riza.dervisoglu..at..gmail.com
web page: http://greymatter.chem.sunysb.edu/index.php?title=Riza_Dervisolgu
Solid Oxide Fuel Cells (SOFCs) offer a clean, low emission, quiet, reliable, fuel adaptable, transportable and highly efficient way to obtain electricity. SOFC's work by conducting oxygen ions through a solid electrolyte which is between cathode and anode, and combining oxygen and fuel (H2 and/or H2-derived) forming H2O, CO2 and energy. Brownmillerite structured oxides (A2B2O5) are promising fast oxygen ion conductors because of large number of oxygen vacancies in the structure. In Brownmillerite structure oxygen vacancies are ordered, at higher temperatures material goes into face transformation from Orthorombic to Tetragonal and at last becomes Disordered Cubic. Ordered oxygen vacancies do not supply good ion conductivity whereas the Disordered Cubic structure is a fast solid ionic conductor.
Local structural changes, short range order (SRO) and coordination numbers of specific atoms can be investigated by methods like High Energy X-Ray diffraction Pair Distribution Function (PDF) analysis and Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR). In order to get good insight of materials and compare probable structures, Ab-Initio calculations, Cluster Expansion and Monte Carlo simulation are required.
I work on Ba2In2O5 which is a Brownmillerite type material that is a promising mid-range temperature SOFC electrolyte material when doped. In order to decrease working temperature of Ba2In2O5, A side and B side doping with La and Ga is applied at various concentrations. My aim is to determine the mechanisms of high oxygen ion conductivity at high temperatures and design a way to reproduce this high oxygen conductivity at mid-range temperatures (700°C).
Orthorhomic Brownmillerite Structure
Distorted Cubic Structure
Presentations:
