Mixed ionic electronic conductors (MIECs) are a group of materials that have been widely used in various applications including Solid Oxide Fuel Cells, gas separation membranes, memristors, electrostrictive actuators, chemical sensors and catalytic converters. The functionality of these materials are based on their large, quickly-changeable point defect concentrations, which also produces a mechanical response in the material. Unfortunately, considerable disagreement over the ionic point defect concentrations, surface exchange coefficients, and mechanical properties of even the most widely-used MIECs exists in the literature.This dissertation demonstrates that the Young's modulus, thermo-chemical expansion coefficient, oxygen nonstoichiometry, oxygen surface exchange coefficient, oxygen surface exchange resistance and stress state of MIEC thin films can all be obtained as a function of temperature and/or oxygen partial pressure using an in-situ, non-contact, current-collector-free wafer curvature measurement platform. The validity of this wafer curvature technique was evaluated by experiments on identically-prepared SrTi0.65Fe0.35O3-x films which showed that nearly identical oxygen surface exchange coefficients could be obtained from optical relaxation (another current-collector-free technique), and experiments on a single Pr0.1Ce0.9O1.95-x film which showed that nearly identical Young's Moduli could be obtained from more traditional X-ray diffraction based techniques. Wafer curvature experiments performed on Pr0.1Ce0.9O1.95-x films with Si surface impurities showed that Si can reduce the oxygen surface exchange coefficient of Pr0.1Ce0.9O1.95-x by several orders of magnitude, suggesting that Pr0.1Ce0.9O1.95-x may not be suitable for real-word Solid Oxide Fuel Cell operation in dusty conditions. Additionally, experiments performed on Pr0.1Ce0.9O1.95-x films with intentionally-added Pt surface impurities showed that the precious metal current collectors used to measure oxygen surface exchange coefficient via traditional techniques (such as electrical conductivity relaxation, electrical impedance spectroscopy, etc.) artificially enhance the Pr0.1Ce0.9O1.95-x oxygen surface exchange coefficient, and hence likely contribute to the large oxygen surface exchange coefficient discrepancies observed in the literature.
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