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SAW gas sensor piezoelectric material properties
Posted 22 feb 2021, 12:02 GMT-5 3 Replies
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Hi,
In the example "saw gas sensor" present in the comsol application library, the piezoelectric material is a YZ lithium niobate. The material properties are taken from (https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1426375)
I have few questions:
1) For example c33 = 242 GPa but why in the matrix (see file attached pag4) is in the position of c11 value. I don't understand the order.
2) Why in the piezoelectric material interface, under coordinate systems, "Material XZ plane system" is selected? If the properties are already related to the YZ LiNbO3, I think that "global coordinates" has to selected, or I am wrong?
3) Why "Material XZ plane system" and not "Material YZ plane system" is selected?
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Interesting question. It appears that the posted model uses a custom set of parameters for lithium niobate. If you look at the Comsol built-in parameters for lithium niobate you will see that c11 = c22 < c33 as expected.
This helps explain the choice of the plane system.
By the way, when using the built-in LiNbO3 parameters, I think you want to use the ZY plane system to get what you want (YZ means Y-face, Z-propagating). You can sort this out by looking at the definitions of the coordinate systems and it is advisable to verify that you get the right velocities.
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Thanks for the help.
I want to model SAW device for acoustophoresis and the piezoelectric material is YZ lithium niobate. I notice that because the "saw gas sensor model" and the article (from which I have to reproduced the example) take the material properties from the same reference that I indicated in the first post.
So I use the same setup present in the "saw gas sensor model", and I don't think that I can use the built-in comsol parameters for lithium niobate. I thought to use "global coordinates" under the coordinate selection section, but maybe I am wrong.
How I can verify that I get the right velocity?
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The Eigenfrequency calculation gives you the frequency corresponding to a particular wavelength, so c = f*lambda.
Working out the orientations for anisotropic materials gets tricky. There's no alternative to thinking carefully about what you are doing and checking...twice...or more. It gets worse for multiply rotated orientations.