Application Cases

Experiment Name: Design and Construction of a Comprehensive Performance Testing Device for Piezoelectric Materials

Testing Equipment: High-voltage amplifier, ferroelectric analyzer, oscilloscope, capacitive displacement sensor, etc.

Figure 1: Piezoelectric Test Chamber

Experiment Process:

A piezoelectric test chamber was designed and fabricated as shown in Figure 1. A comprehensive performance testing device for piezoelectric materials was then set up. During the testing process, the piezoelectric material's domain reversal requires an electric field as high as 40 kV/mm. The high-voltage amplifier can reach a maximum voltage of 10000 V, which meets the testing requirements. The signal generator can set alternating signals with different frequencies, amplitudes, and waveforms. These signals are amplified by the high-voltage amplifier to apply electric field excitation to the samples within the piezoelectric test chamber. The oscilloscope collects the voltage signal from the signal generator. The ferroelectric analyzer is used to obtain the polarization strength of the piezoelectric samples. The displacement of the samples, obtained by the capacitive displacement sensor, can be used to calculate the strain of the material. The oscilloscope collects the aforementioned signals to obtain the hysteresis loops and butterfly curves of the piezoelectric samples.

First, prepare 5mm×5mm×0.3mm PZT and BNT sheet samples. Utilize the self-built comprehensive performance testing device for piezoelectric materials to conduct the tests. The testing process mainly consists of three parts.

First: Preparation of the piezoelectric test chamber. Since the samples are fragile piezoelectric ceramics, they need to be gently placed between the upper and lower fixtures of the test chamber. To prevent high-voltage breakdown of the samples, silicone oil is placed inside the piezoelectric test chamber.

Second: Calibration of the capacitive displacement sensor. First, connect all components of the capacitive displacement sensor and fix the displacement probe on the sensor base. Manually rotate the screw frame to adjust the rough position relationship between the probe and the measuring plate. Then, use a micro-motion stage to precisely adjust the contact between the probe and the measuring plate. At this point, observe the voltage signal output from the capacitive displacement sensor to the oscilloscope to ensure that the material's displacement changes are within the measuring range.

Third: Configuration of the control system. Input the sample parameters, including thickness and area, into the control system. The electric field is set to two cycles of triangular waves, with each triangular wave having a frequency of 1 Hz. Turn on the ferroelectric analyzer and the high-voltage amplifier, and connect the monitor voltage output of the high-voltage amplifier to the oscilloscope. The oscilloscope remains in the rolling acquisition mode as the system begins testing.

Hysteresis loops and butterfly curves of PZT and BNT are obtained in this way.

Experimental Results:

(1) The obtained P-E curves are as follows:

As shown in Figure 2-13 and Figure 2-14, due to the different inherent properties of PZT and BNT materials, PZT chose an external electric field strength E with a maximum of 14 kV/cm to 20 kV/cm, while BNT's maximum external electric field was 30 kV/cm to 42 kV/cm. Polarization saturation of PZT and BNT occurred at 20 kV/cm and 42 kV/cm, respectively.

(2) The obtained butterfly curves are as follows:

As shown in Figure 2-15, the curve is for PZT, with four double-cycle triangular wave electric field excitations, and the maximum electric fields are 14 kV/cm, 16 kV/cm, 18 kV/cm, and 20 kV/cm, respectively. It can be seen from the figure that PZT has good breakdown voltage resistance, with a breakdown electric field of 20 kV/mm, which fully demonstrates that the surface treatment of the PZT sample is good and that there are fewer defects inside the PZT sample.

As shown in Figure 2-16, the curve is for BNT, using double-cycle triangular wave electric field excitation, with maximum electric fields of 30 kV/cm, 32 kV/cm, 34 kV/cm, and 40 kV/cm, respectively. It can be seen from the figure that BNT has superior breakdown voltage resistance, with a breakdown electric field as high as 42 kV/cm, which is twice that of PZT.

The fluctuations in the butterfly curves are caused by the friction damping between the loading column and the sliding bearing in the piezoelectric test chamber, as well as the weight of the loading column itself. Therefore, during the strain rising stage, the strain direction is opposite to the direction of gravity, and it is necessary to overcome the weight of the loading column connection and the friction damping to transmit the strain to the displacement sensor. The perturbation is relatively large at this time, which is specifically reflected in the larger fluctuations in the strain rising stage of the butterfly curve. In the strain falling stage, the strain direction is the same as the direction of gravity, and it is only necessary to overcome the friction damping between the loading column and the sliding bearing. This is also the reason why the curve in the strain falling stage of the butterfly curve is smoother.

Voltage Amplifier Recommendation: ATA-7050

Figure: Specification Parameters of the ATA-7050 High-Voltage Amplifier

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