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Relative permittivity and coupling matrix

Posted Apr 12, 2017, 10:37 a.m. EDT Acoustics & Vibrations, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 5.2a 3 Replies

Hamed Rahimi
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Hello,

I am new to Comsol.
I want to model a piezoelectric transducer. Comsol is asking for coupling matrix and relative permittivity.
Could anyone give me some information on what are these parameters? Do these parameters depend on my problem geometry and conditions that I want to solve or they are intrinsic properties of the material?

Appreciate any help.

Thanks,
3 Replies Last Post Apr 12, 2017, 11:56 p.m. EDT
Dave Greve Certified Consultant
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Posted: 7 years ago Apr 12, 2017, 12:04 p.m. EDT
You will find a list of commonly used piezoelectric materials included with your Comsol installation. Each piezoelectric material has values for the compliance, coupling, and permittivity matrices. You only need to enter these manually if (1) you are using an unusual material or (2) you think the built-in parameters are wrong.

A common mistake is NOT making non-piezo materials linear elastic. When this is done Comsol prompts you for permittivity and coupling matrix for steel or such, which makes no sense.

D.W. Greve
DWGreve Consulting
You will find a list of commonly used piezoelectric materials included with your Comsol installation. Each piezoelectric material has values for the compliance, coupling, and permittivity matrices. You only need to enter these manually if (1) you are using an unusual material or (2) you think the built-in parameters are wrong. A common mistake is NOT making non-piezo materials linear elastic. When this is done Comsol prompts you for permittivity and coupling matrix for steel or such, which makes no sense. D.W. Greve DWGreve Consulting
Hamed Rahimi
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Posted: 7 years ago Apr 12, 2017, 2:24 p.m. EDT

You will find a list of commonly used piezoelectric materials included with your Comsol installation. Each piezoelectric material has values for the compliance, coupling, and permittivity matrices. You only need to enter these manually if (1) you are using an unusual material or (2) you think the built-in parameters are wrong.

A common mistake is NOT making non-piezo materials linear elastic. When this is done Comsol prompts you for permittivity and coupling matrix for steel or such, which makes no sense.

D.W. Greve
DWGreve Consulting


Thank you D.W. Greve for the response.
We have an ultrasound transducer and when we asked the manufacturer for piezoelectric properties, we only got density, elastic stiffness, dielectric constant, electromechanical constant, and thickness. Is there any way that I could calculate permittivity and coupling matrix from provided info?

Thanks,
[QUOTE] You will find a list of commonly used piezoelectric materials included with your Comsol installation. Each piezoelectric material has values for the compliance, coupling, and permittivity matrices. You only need to enter these manually if (1) you are using an unusual material or (2) you think the built-in parameters are wrong. A common mistake is NOT making non-piezo materials linear elastic. When this is done Comsol prompts you for permittivity and coupling matrix for steel or such, which makes no sense. D.W. Greve DWGreve Consulting [/QUOTE] Thank you D.W. Greve for the response. We have an ultrasound transducer and when we asked the manufacturer for piezoelectric properties, we only got density, elastic stiffness, dielectric constant, electromechanical constant, and thickness. Is there any way that I could calculate permittivity and coupling matrix from provided info? Thanks,
Dave Greve Certified Consultant
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Posted: 7 years ago Apr 12, 2017, 11:56 p.m. EDT
Many- maybe most- commercial transducers use some variety of PZT (Lead zirconate titanate). Different types (designated PZT-4, PZT-5A, etc.) differ in permittivity and coupling factor. You MIGHT be able to match up the permittivity with one of the types included in COMSOL. Good agreement with electromechanical coupling factor would be a further confirmation, but then you must be careful to use the right electromechanical coupling factor (it depends on direction, probably more than permittivity).

This only allows you to make a good guess and sometimes manufacturers use special mixtures or even different materials.

Details of transducer construction are regarded as proprietary by manufacturers, so you may not be able to get much more information.

DWGreve
Many- maybe most- commercial transducers use some variety of PZT (Lead zirconate titanate). Different types (designated PZT-4, PZT-5A, etc.) differ in permittivity and coupling factor. You MIGHT be able to match up the permittivity with one of the types included in COMSOL. Good agreement with electromechanical coupling factor would be a further confirmation, but then you must be careful to use the right electromechanical coupling factor (it depends on direction, probably more than permittivity). This only allows you to make a good guess and sometimes manufacturers use special mixtures or even different materials. Details of transducer construction are regarded as proprietary by manufacturers, so you may not be able to get much more information. DWGreve

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