Free standing yttria-doped zirconia membranes: Geometrical effects on stability
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Professor Arthur Nowick made seminal contributions to the areas of ionic conduction mechanisms in crystalline and disordered systems. An area of emerging interest in the solid state ionics community is investigating conduction in the mesoscopic regime. With free standing membranes, one can probe low-dimensional effects such as confinement without interference from substrates. Membranes have potential relevance to solid state devices that benefit from reduced ionic resistance, for example sensors and solid oxide fuel cells. Membranes with varying lateral dimensions have been previously reported in literature; however, understanding of stress interactions in suspended oxide structures is in early stages. In this paper, we demonstrate self-supported, i.e. in the absence of any additional mechanical support layers, square and circular membranes of 100 nm thick yttria-doped zirconia (YDZ) having side length and diameters of 0.15–2 mm. The buckled membrane shape is intimately linked to the fabrication processes arising from dry versus wet etching protocols. Geometrical considerations associated with buckling and stability are discussed. Thin film solid oxide fuel cells utilizing circular membranes are fabricated, exhibiting open circuit voltages between 0.8 and 1 V that correlate with membrane size and exhibit a total power output on the order of several mW. These results contribute to advancing experimental techniques to fabricate free standing oxide membranes for fundamental and applied studies pertaining to ionic and electronic conduction.
KeywordsYttria doped zirconia Ultrathin membrane Thin film solid oxide fuel cell Geometric stability Thin film stress
S.X. acknowledges Harvard School of Engineering and Applied Science (SEAS) for financial support. K.K. was supported by the Department of Defense through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.
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