High temperature nanobalance sensor based on langasite

Desirable nanobalance applications such as thermogravimetry on thin films and gas sensing based on stoichiometry change of thin films at elevated temperatures require high temperature stable piezoelectric materials. However, the application temperature of current nanobalances is limited to approximately 450 degreesC due to the intrinsic properties of standard piezoelectric materials. Materials such as langasite (La3Ga5SiO14) and related compounds are promising candidates for piezoelectric applications at high temperatures. Therefore, this material was investigated with respect to its ability to serve as a high temperature nanobalance. Langasite resonators are shown to exhibit bulk oscillations at temperatures of up to 900 degreesC. The peak frequency of the real part of the impedance spectra is chosen as the characteristic frequency. At 800 degreesC, the mass load response for a 0.78-mm thick resonator is 6.49 Hz cm(2) mug(-1). At temperatures above 900 degreesC, the bulk resistivity of the resonator devices significantly attenuates the resonance signal. Langasite is found to be insensitive to oxygen partial pressures to temperatures of up to at least 600 degreesC. Finally, the operation of a gas sensor using a langasite nanobalance with integrated TiO2 film is demonstrated at elevated temperatures for the first time. (C) 2001 Elsevier Science B.V. All rights reserved.