Fabrication and structural characterization of self-supporting electrolyte membranes for a micro solid-oxide fuel cell

Baertsch, Chelsey D., Jensen, Klavs F., Hertz, Joshua L., Tuller, Harry L., Srikar T., Vengallatore, Spearing, S. Mark and Schmidt, Martin A. (2004) Fabrication and structural characterization of self-supporting electrolyte membranes for a micro solid-oxide fuel cell. Journal of Materials Research, 19 (9), 2604-2615. (doi:10.1557/JMR.2004.0350).

Abstract

Micromachined fuel cells are among a class of microscale devices being explored for portable power generation. In this paper, we report processing and geometric design criteria for the fabrication of free-standing electrolyte membranes for microscale solid-oxide fuel cells. Submicron, dense, nanocrystalline yttria-stabilized zirconia (YSZ) and gadolinium-doped ceria (GDC) films were deposited onto silicon nitride membranes using electron-beam evaporation and sputter deposition. Selective silicon nitride removal leads to free-standing, square, electrolyte membranes with side dimensions as large as 1025 µm for YSZ and 525 µm for GDC, with high processing yields for YSZ. Residual stresses are tensile (+85 to +235 MPa) and compressive (–865 to -155 MPa) in as-deposited evaporated and sputtered films, respectively. Tensile evaporated films fail via brittle fracture during annealing at temperatures below 773 K; thermal limitations are dependent on the film thickness to membrane size aspect ratio. Sputtered films with compressive residual stresses show superior mechanical and thermal stability than evaporated films. Sputtered 1025-µm membranes survive annealing at 773 K, which leads to the generation of tensile stresses and brittle fracture at elevated temperatures (923 K).

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Contributors

Author: S. Mark Spearing

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