Application of piezoelectric thin film materials

Piezoelectric films are widely used because of their excellent performance. Piezoelectric thick films can be used to manufacture a variety of micro devices, such as micropumps, ultrasonic motors, resonators, pyroelectric thick film sensors, thick film actuators, micro-energy pickups, etc.

1. Hydrophone and sonar

General Electric Company's single-diaphragm hydrophones with a 2.5 μm thick PVD F piezoelectric film as a substrate, piezo ceramic disc can be used in medical and NDE transducers, and can be used in the range of 0.5 to 50 HZ characterization and calibration. Due to the long-term stability and repeatability of these devices, these characteristics of hydrophones have been utilized to develop a new type of multivariate instrument.underwater scanning sonar system is composed of 100 PVDF substrate hydrophones for underwater safety/rescue devices. This device was produced  a few years ago. The system uses passive mode with an operating frequency of 1 to 1 000 HZ. It can also operate in three different frequencies in active mode. It can be detected with this system small submarines up to 3 km away can also detect engines up to 600 m away, and the angle deviation is less than 5'. The recent hydrophone calculation model shows that if the PVD F element is properly designed, the hydrophone can detect signals over 10 dB in the system demonstration.

2. Antifouling

Piezo film has very broad prospects in antifouling applications. At present, the National Institute of Research and the University of Montrich have conducted research on the anti-fouling of piezoelectric films. Piezoelectric film has been proved to be more effective for measuring the vibration of the polymer in the shell. Therefore, it can be used to prevent the approach of most marine organisms that will cause pollution of ships. In addition, the Delft Scientific Research Institute in the Netherlands is extending the conclusions it has obtained to larger metal structures, such as the shells of merchant ships . At the same time, the same principle of piezo ceramic disc crystal is being studied on how to produce antifreeze surfaces on airplanes.

3. Medicine

At present, people are actively studying the application of PVDF in medicine. In many countries, many babies die of SIDS or other syndromes every year. In order to reduce the sudden death rate of infants, at least three companies in the Netherlands, and the United States are producing a respiratory monitor. A

This monitor puts a mat with PVD F piezoelectric film under the baby's body to continuously monitor the slight vibration caused by breathing and heartbeat (especially at night), when the interval of breathing or heartbeat exceeds At a pre-set length of time, say 20 s, it will trigger an alarm, which can prevent suffocation and death of the baby in time and effectively.

4. Electrodes

If the outer surface of the electrode is covered with a layer of PVDF piezoelectric polymer, it can convert information such as vibration, shock, pressure, stress and strain into electrical signals. For this type of electrode, for the quasi-static input from low frequency to high frequency, its output can always retain its frequency characteristics, and the output of the electrical signal has a linear relationship with the applied pressure. At the same time, this electrode also has good temperature stability, suitable for various environments of-40 ~ 70 ℃. The range is generally from 0.25 to 25 p C/N. By winding the narrow piezoelectric sheet into a circle, a sensitive piezoelectric electrode with a value of 40 p C/N can be obtained.

5. Aviation and Navigation

The "Portable Automatic Remote Inspection System" developed by Research, abbreviated as PAR IS, is one of the first advanced devices to enter the commodity era. This system is specially designed for in-situ inspection of large-area layered structures or composite structures.

The key element is a 200× 200 mm deformable PVDF piezoelectric film, which contains 1024 transducers. The flexibility of this film is very good, and it can completely fit the curved surface with a radius of curvature of 4. The device connected with it also has a hand-held controller, data sampler and display device.

This receiver has a total signal-to-noise ratio of 100 dB and a center frequency of 2.5 M Hz. Graphite-epoxy composites on airplanes or large structures on ships can be used for convenient testing. For aluminum and steel, satisfactory results have already been obtained in this regard. For this particular application of PVD F, it has been found that the film with biaxial polarity is more suitable than the uniaxial polarity.

6. Structural monitoring

The PVD F piezoelectric film also has certain applications in structural monitoring. A systematic study on the basic characteristics of the PVD F piezoelectric film monitoring structure was carried out. A dynamic and static response test of the PVDF piezoelectric film monitoring structure was done. At the same time, a preliminary study on the impact load of the structure using PVDF piezoelectric film was also conducted. .

As the application of piezoelectric discs transducer is more and more extensive, it will be well developed in the future. The manufacturing technology of piezoelectric thin film will also develop towards high efficiency, low cost and high quality. Because the CVD method has better coverage, it can be deposited on deep holes, steps, depressions or other complex three-dimensional shapes.In addition, the chemical vapor deposition method can also control the stoichiometric ratio of the prepared film in a wide range, which is very prominent compared with other methods.The cost and operating cost of chemical vapor deposition equipment are relatively low, suitable for both batch production and continuous production, and have good compatibility with other processing procedures. Therefore, in the future, the use of CVD method for the preparation of piezoelectric films will be well applied, and piezoelectric films will be better used.