SGER: Investigation of High Temperature Resonant Gas Sensor

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The feasibility of extending the operation of highly sensitive resonant-based gas sensors to elevated temperatures will be investigated. Towards this end, the electrical, resonant and mass transport properties of langasite, a piezoelectric material stable to elevated temperatures, will be characterized as functions of temperature, oxygen partial pressure and cation composition. The defect model, to be developed and based on these results, will be used to modify langasite in order to maintain high Q values and compositional stability to elevated temperatures thereby insuring high sensitivity. Means for isolating thermal and stress cross effects will be investigated and implemented. Gas sensitive films (PrxCe1-xO2-?, and ZnO) will be deposited on langasite by pulse laser deposition with varying thickness and microstructure. Sensitivity and response time will be correlated to film stoichiometry, thickness and grain morphology. Parallel monitoring of film stoichiometry and resistivity with temperature and pO2 will provide further insights into gas-solid interactions.Bulk and surface acoustic wave resonant devices exhibit exceptional sensitivity to a wide range of chemical and biological species when coated with appropriate species-sensitive films but are typically limited to room temperature operation. In this program, the electrical and mass transport properties of langasite, a piezoelectric material stable to elevated temperatures, are modeled and investigated to elevated temperatures and in controlled atmospheres. Understanding gained from these studies, will enable the operation of this multifunctional resonant sensor platform to elevated temperatures and thereby address the need for improved sensors in the transportation, industrial process and energy industries. This proposal was submitted in response to the Dear Colleague Letter: Next Generation Chemical and Biological Sensors and Sensing Systems [nsf 02-112].