■ Title : Dynamic Control and in-situ Measurements of Oxygen Nonstoichiometry and Phase of Layered Cuprate-based Thin Films by Electrochemical Pumping
■ Speaker : Dr. Chang Sub Kim
■ Date and Time : 7/25 (Wed) 1:30 PM
■ Venue : Applied Engineering Buliding (W1-1) Seminar Room #2
■ H o s t : Prof. Woo Chul Jung
■ Abstract :
Three major criteria are essential for a good solid oxide fuel cell (SOFC) electrode: 1) mixed ionic and electronic conductivity, 2) electrocatalytic activity towards oxygen surface exchange reaction, and 3) chemical and chemo-mechanical stability. Conventional method of assessing these electro-chemo-mechanical properties requires doping different concentrations of aliovalent cations and/or controlling atmosphere. These, however, are constrained by solubility limits of dopants, the range of oxygen partial pressures readily experimentally achievable, and require knowledge of the applicable defect chemical model. In this study, we control and measure oxygen defect types, concentrations, and phases in promising rare earth cuprate (RE2CuO4: RE = rare earth) SOFC cathode materials by electrochemical pumping of oxygen through an yttria-stabilized zirconia supporting electrolyte. These layered perovskites can incorporate both oxygen interstitials and vacancies, as well as two different crystal structures – T and T’ – depending on the Cu-O coordination, thereby broadening the range of investigations. Oxygen nonstoichiometry values and crystal structures are determined by in-situ measurement of chemical capacitance and x-ray diffraction, respectively, and are correlated with surface kinetics, in-plane conductivities, ionic diffusivities, and chemo-mechanical properties.