Application Cases

Experiment Title: Study on the Properties of Ferroelectric Materials Under Force-Electric Coupling

Testing Equipment: High Voltage Amplifier, Signal Generator, A/D Acquisition Card, Strain Gauge, Piezoelectric Ceramic, etc.

Experiment Process:

Figure 1: Force-Electric Coupling Test Device

The loading and testing units involved in this experiment are shown in Figure 1. The high voltage electric field E is generated by the D/A signal generator card through the high voltage amplifier, which can provide a maximum voltage of 10kV. To prevent high voltage breakdown of air, the experiment is conducted in silicone oil. During the experiment, the electric field strength is output by the monitor channel of the high voltage amplifier, and the electric polarization strength is measured through the Sawyer-Tower circuit [121]. Two sets of strain gauges, which are vertically arranged and attached to the surface of the sample, are used to measure the strain in the polarization direction and the strain perpendicular to it. The three sets of physical quantities are read into the computer via the acquisition card.

Figure 2: Loading Direction of Load and Electric Field and Sample Treatment

The sample used in the test is a PZT-5 piezoelectric ceramic, a cube with dimensions of 8×4×4 (length×width×height, in mm), with two opposite 4×4 surfaces being silvered. BX120-2AA type strain gauges are used to measure material deformation. The strain gauges come with 20cm insulated wires, ensuring the insulation of the strain gauges within the electric field. The strain gauges are attached to the polished PZT ceramic surface using 502 quick-drying glue. To avoid corona discharge in the high voltage electric field, it is necessary to apply silicone rubber on the surface for insulation. Since silicone rubber dissolves in silicone oil, an additional layer of sealing silicone should be applied on the outermost layer for oil protection. The treatment of the sample is shown in Figure 2.

As shown in Figure 2, a load is applied along the x-axis on the two surfaces of the PZT-5 ceramic. Two strain gauges measure the electrostrictive strain λP33 in the same direction as the load and the strain λP31 perpendicular to the load. The electric field is applied along the z-axis, and during the experiment, both the compressive load and the two strain signals are collected simultaneously.

Experimental Results:

Figure 3: Initial Linear Segment of PZT-5 Electrostrictive Curves Under Different External Loads

The experimental results are shown in Figure 3. The λP-E curves in both directions are linear, with the slope of the curve representing the piezoelectric coefficients of the material in the x and z directions, denoted as dP33 and dP31, respectively. Due to the polarization process being constrained by the external load, the piezoelectric coefficients in both directions decrease with increasing external load. However, the piezoelectric coefficient dP31 perpendicular to the polarization direction shows a more pronounced downward trend. Under a compressive stress of 50MPa, the piezoelectric coefficient drops by 53%, while the piezoelectric coefficient dP33 in the polarization direction only decreases by 12.8%.

High Voltage Amplifier Recommendation: ATA-7050

Figure: Specifications of the ATA-7050 High Voltage Amplifier

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