Precise measurements of BAW and SAW properties of Langasite in the temperature range from 25°C to 1000°C

J. Bardong, M. Schulz, M. Schmitt, I. Shrena, D. Eisele, E. Mayer, L.M. Reindl, H. Fritze

    Research output: Conference proceeding/Chapter in Book/Report/Conference Paperpeer-review

    Abstract

    There is a high demand for wireless sensing devices
    in harsh environments for industrial applications. For temperatures above 250○C, silicon-based sensors cannot be used. In
    contrast, bulk acoustic wave (BAW) and surface acoustic wave
    (SAW) devices are still suitable for this purpose. Further high temperature applications include thermogravimetry on small
    volumes and gas sensing based on stoichiometry change of
    thin sensor films. Langasite (La3Ga5SiO14) is a piezoelectric
    single crystal that preserves its piezoelectric properties and is
    chemically stable up to its melting point at 1470○C without any
    phase transition and, therefore, is a promising material for high temperature devices.
    Using a resonance-antiresonance method based on bulk oscillations, all components of elastic and piezoelectric tensors of
    langasite have been determined at temperatures up to 900○C. Resonance spectra of several langasite samples have been measured
    and fitted with the impedance calculated from a one-dimensional
    physical model of piezoelectric bodies vibrating in several modes.
    In order to extract the electromechanical parameters, different
    resonator geometries and orientations are used.
    Also, the results of measurements are presented for SAW
    devices on langasite at temperatures from 25 to 750○C. Two
    cuts with Euler angles (0°, 138.5°, 26.6°) and (0°, 30.1°, 26.6°)
    have been studied. The devices were fabricated with a platinum
    (Pt) layer with different heights on a zirconium (Zr) adhesion
    layer. The main material parameters relevant for SAW devices
    such as phase velocity vp, propagation loss α and coupling
    coefficient k² have been obtained. The measured SAW phase
    velocities compare well with those calculated with the elastic and
    piezoelectric tensors obtained by bulk-oscillation measurements.
    Original languageEnglish
    Title of host publication2008 IEEE International Frequency Control Symposium
    Pages326-331
    Number of pages6
    DOIs
    Publication statusPublished - 2008

    Keywords

    • Langasite
    • high temperature
    • measurements

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