Journal of Materials Research

Articles

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

Chelsey D. Baertscha1 p1, Klavs F. Jensena1 c1, Joshua L. Hertza2, Harry L. Tullera2, Srikar T. Vengallatorea3 p2, S. Mark Spearinga3 and Martin A. Schmidta4

a1 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

a2 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

a3 Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

a4 Microsystems Technology Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

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).

(Received March 23 2004)

(Accepted May 14 2004)

Key Words:

  • Thin film;
  • Physical vapor deposition (PVD);
  • Microelectrical mechanical (MEMS)

Correspondence:

c1 Address all correspondence to this author. e-mail: kfjensen@mit.edu

p1 Present address: School of Chemical Engineering, Purdue University, West Lafayette, IN 47907

p2 Present address: Department of Mechanical Engineering, McGill University, Quebec, Canada H3A 2K6

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