Ionic materials, particularly oxides, are often used in energy conversion and storage applications such as solid oxide fuel cells or batteries, and as a support material for high temperature catalysis. In many of these applications, high surface areas and high densities of interfacial contact points are desirable to speed overall reaction rates, and thus these ionic materials are less than one micrometer thick in at least one dimension. Recent observations by our group and others have found that point defect concentrations can differ from the bulk at the nanoscale, thus altering both electrochemical and mechanical properties. In this presentation, we examine the coupling between point defects, interfacial transport, and mechanical properties (electrochemomechanics) of model ionically conductive oxides including (Pr,Ce)O_2-δ and Pr₂CuO_4-δ. In particular, we employ in situ methods including high temperature nanoindentation, x-ray diffraction, wafer curvature, and impedance spectroscopy to elucidate correlations among elastic modulus, chemically driven dilation (chemical expansion), and oxygen transport across interfaces as a function of point defect chemistry.