Abstract
Abstract The tetragonal Sr0.61Ba0.39Nb2O6 solid solution belongs to the tungsten bronze structural family and has a Curie temperature of approximately 70°C. Below the Curie temperature sponaneous polarization along the c-axis gives rise to piezoelectric coupling terms d31, d33 and d15. Interdigital electrode transducers photolithographically defined on the surface are used to generate and detect surface acoustic waves. Measurement techniques and results for SAW velocities and coupling constants for propagation on the z, x and (110) cuts will be presented in this paper. Above the Curie temperature the solid solution enters the paraelectric phase where application of an external electric field is used to induce polarization and generate surface acoustic waves. Y-cut, z-propagating surface waves are launched by poling the crystal with a spatially varying electric field. The Poling procedure is to apply a dc potential to the interdigital electrodes of the SAW transducers, the remainder of the crystal is unpoled. Important differences in acoustic generation and detection in the paraelectric and ferroelectric regimes are to be discussed in detail. The most noticeable difference is in the second harmonic generation which occurs in the paraelectric regime above the Curie temperature.
Published Version
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