Date of Award

8-2005

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Electrical and Computer Engineering

Advisor

Mauricio Pereira da Cunha

Second Committee Member

John F. Vetelino

Third Committee Member

M. Clayton Wheeler

Abstract

There is a pressing need for the research and development of sensors to operate as pressure, temperature, and gas sensors, frequency control elements, and signal processing filters, in harsh environments, at elevated temperature and pressure conditions. The applications range from gas and oil wells, automobile and aerospace combustion engines, and high power duplexers in communication systems. Surface acoustic wave (SAW) devices have been recently reconsidered for harsh environment sensing upon the introduction of the langasite (LGS) family of crystals, which can operate up to 1470°C. This thesis reports on the investigation of LGS as a high temperature (up to 750°C) SAW device and gas sensor. The investigations carried out in this research work included: high temperature LGS SAW devices design, fabrication, and test; interdigital transducer (IDT) electrode materials analysis and deposition; high temperature test chambers design and fabrication; dual oscillator sensing configuration design and implementation; and the realization of the appropriate high temperature gas sensing experimental set up. High temperature LGS SAW Pt electrode devices, WOs film devices, and original all-Pd electrode devices, which use Pd as both electrode and sensing layer, have been fabricated in this work. These SAW components have been used to sense ethylene (C2H4) and hydrogen (Hz) as a proof-of-concept effort at temperatures ranging from 250°C to 450°C.

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