Thermomechanical properties and performance of microfabricated solid oxide fuel cell ([mu]SOFC) structures

The mechanical properties of a ceramic electrolyte, sputtered yttria-stabilized zirconia (YSZ), in thin film (<1Clm) form were studied in order to design and fabricate thermomechanically stable microfabricated SOFCs (SOFCs) at high operation temperature. YSZ films of 70-600nm thickness were deposited at either room temperature or high temperature (500/600°C) on substrates of either silicon, or silicon nitride. The residual film stresses varied from -700 to -100MPa as-deposited, and exhibited tensile hysteresis reaching stresses of -300 to +400MPa with post-deposition annealing to 500°C. Mechanisms controlling the residual stress trends include tensile stress evolution with grain growth and compressive stresses due to "atomic peening". Young's modulus was obtained by center deflection measurement of square membranes for films in mild compression, and from bulge tests for films in tension. The modulus (24-105GPa) was found to be highly dependent on deposition conditions, and was less than half the bulk value (200GPa). Meanwhile, CTEs ( 10.5 x 10-6/oC) extracted from wafer curvature measurement during thermal cycling were independent of deposition conditions. Based on these properties, maximum in-plane stresses in the films were assessed with nonlinear plate theory, and used for uSOFC design.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Aeronautics and Astronautics

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2006

Author dc:creator

• Yamamoto, Namiko

Advisor dc:contributor.advisor

• Brian L. Wardle.

• Aeronautics and Astronautics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/37950

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/37950