Abstract/Details

Indium tin oxide thin film strain gages for use at elevated temperatures


2001 2001

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Abstract (summary)

A robust ceramic thin film strain gage based on indium-tin-oxide (ITO) has been developed for static and dynamic strain measurements in advanced propulsion systems at temperatures up to 1400°C. These thin film sensors are ideally suited for in-situ strain measurement in harsh environments such as those encountered in the hot sections of gas turbine engines.

A novel self-compensation scheme was developed using thin film platinum resistors placed in series with the active strain element (ITO) to minimize the thermal effect of strain or apparent strain. A mathematical model as well as design rules were developed for the self-compensated circuitry using this approach and close agreement between the model and actual static strain results has been achieved.

High frequency dynamic strain tests were performed at temperatures up to 500°C and at frequencies up to 2000Hz to simulate conditions that would be encountered during engine vibration fatigue. The results indicated that the sensors could survive extreme test conditions while maintaining sensitivity.

A reversible change in sign of the piezoresistive response from −G to +G was observed in the vicinity of 950°C, suggesting that the change carrier responsible for conduction in the ITO gage had been converted from a net “n-carrier” to a net “p-carrier” semiconductor.

Electron spectroscopy for chemical analysis (ESCA) of the ITO films suggested they experienced an interfacial reaction with the Al2O3 substrate at 1400°C. It is likely that oxygen uptake from the substrate is responsible for stabilizing the ITO films to elevated temperatures through the interfacial reaction.

Thermo gravimetric analysis of ITO films on alumina at elevated temperatures showed no sublimation of ITO films at temperature up to 1400°C. The surface morphology of ITO films heated to 800, 1200 and 1400°C were also evaluated by atomic force microscopy (AFM).

A linear current-voltage (I–V) characteristic indicated that the contact interface between the ITO and platinum was ohmic in nature. The small specific contact resistivities were determined in the range of 10−3 to 10−1 Ωcm2 from room temperature up to 1400°C using a transmission line model (TLM).

Indexing (details)


Subject
Materials science
Classification
0794: Materials science
Identifier / keyword
Applied sciences; Indium tin oxide; Strain gages; Thin films
Title
Indium tin oxide thin film strain gages for use at elevated temperatures
Author
Luo, Qing
Number of pages
146
Publication year
2001
Degree date
2001
School code
0186
Source
DAI-B 62/09, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
0493372202, 9780493372204
Advisor
Gregory, Otto J.
University/institution
University of Rhode Island
University location
United States -- Rhode Island
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3025561
ProQuest document ID
276304893
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/276304893
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