Theoretical calculations have been performed for the temperature stability of the amorphous TeO 2 /128 Y-X LiNbO3 structure. The phase velocity, electromechanical coupling coefficient and temperature coefficient of delay (TCD) have been calculated. Amorphous TeO 2 film has been found as an attractive negative TCD over-layer that can yield a zero TCD when combined with a positive TCD material such as 128 Y-X LiNbO3. And in comparison to conventional SiO 2 over-layer, the amorphous TeO 2 film reaches the zero TCD under a much less thickness. The effect of the temperature coefficients of amorphous TeO 2 's elastic constants on the structure's TCD has also been studied. We find the temperature coefficients of amorphous TeO 2 's C 11 have a more dominant effect on TCD.
In this paper, a hybrid method, which combines the traditional concept of guided waves and the finite element method (FEM), is proposed to analyze the spurious modes of aluminum nitride (AlN) film with electrodes. First, the guided wave modes in the plated area are obtained by 1-D FEM. Second, a mode-match method is used to satisfy the boundary conditions. The vibration of the film resonator is a superposition of all of the guided modes. With respect to an AlN film resonator, which is a thicknessstretch mode resonator, we have identified three families of spurious modes: extension, thickness-stretch, and thicknessshear. The spectrum of spurious modes is calculated and the influence of the spurious modes is discussed.
The change in the resonance frequency of the thickness-shear vibration of rotated Y-cut quartz resonators using various electrode materials was studied. We used a three-dimensional finite element method to calculate the strain distribution of a circular plate and the electrodes under a pair of diametrical forces so that the anisotropy of the blank can be accurately considered. The relationship between mass-loading and force–frequency (F– f) characteristics is obtained for several types of electrode material. The results show that, for some electrode materials, the change in the F– f coefficients induced by the initial strain field distribution in the electrode through the third-order elastic constants is significant, but for others, the variations are small. We also find that the change is proportional to the thickness of the electrode. Furthermore, different materials have different effects. For most metals, such as gold, silver, copper, aluminum and nickel, with the increase in thickness, the F– f coefficient increase. However, for chromium, the increase in thickness may result in a lower F– f coefficient.
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