While measuring D33 coefficient on piezoelectric ceramic pellets, that have been polled in DC electric field and silver electrode platted by D33 meter, a positive D33 coefficient is observed every time, no change of sign of coefficient occurs upon changing side of pellets. So my question is, should the sign of d33 coefficient be changed when reversing pellet or it is always positive? If not, then what might be reasons for this?
As you reverse the poled pellet, the d33 value would present the reverse value. This is due to changing the direction of polarization. Thus. the induced space charge correspondingly would have the oppite representation as compared with your original polarization direction of not reversing the poled pellet. If no change of sign of coefficient occurs upon changing side of pellets, you should inspect the d33 meter.
Base on my experience while using the d33 meter, YES, the sign of the d33 coefficient will change due to the changing of the polarization. May I ask? Before you use the d33 meter, have you test it with the standard sample (usually PZT which came together with the d33 meter) ? If yes, you will notice that the sign of the d33 coefficient will change once we change the direction of the standard sample. We always test it during the calibration process before we proceed to use the d33 meter. If no, I suggest to you to do this. If there are still problem, it might have problem with your d33 meter. Thank you.
It is always a good practice to check the d33 measurements on both sides.
your measured d33 values should be approximately the same, but opposite in sign, this indicates effective poling treatment given to your samples.
K. Sreenivas
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