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A ceramic strain gage based on reactively sputtered indium-tinoxide (ITO) thin films is being developed to monitor the structural integrity of components employed in aerospace propulsion systems operating at temperatures in excess of 1500°C. The hightemperature stability and piezoresistive properties depend to a large extent on the thickness of the active ITO strain elements comprising these ceramic strain gages. Scanning electron microscopy of the thick ITO sensors revealed a partially sintered microstructure consisting of a contiguous network of submicrometer ITO particles with well-defined necks and isolated nanoporosity. It appeared that densification of the ITO particles was retarded during high-temperature exposure with nitrogen playing a key role in stabilizing the nanoporosity. Based on these preliminary results, ITO strain sensors were also prepared by reactive sputtering in various nitrogen/oxygen/argon partial pressures to incorporate more nitrogen into the films. Under these conditions, sintering and densification of the ITO particles containing these nitrogen-rich grain boundaries was retarded and a contiguous network of nanosized ITO particles was established. The influence of nitrogen in the sputtered and annealed ITO films on the microstructure and the high-temperature piezoresistive properties was investigated, and the results are presented in this paper. © 2004 The Electrochemical Society. [DOI: 10.1149/1.1767839] All rights reserved.

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© The Electrochemical Society, Inc. 2004. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed, or modified without the express permission of The Electrochemical Society (ECS).