PVDF-300 desktop piezoelectric thin film polarization device is a device that applies Piezotech polymer molding voltage polarization, the output voltage is arbitrarily adjustable, the output is stable, the effect is high, the effect is good, the digital design is adopted, it can be heated, and silicone oil can be added, a combination of various polarization methods, that is, polarization is tested, with the ZJ-3 precision D33 tester of the Chinese Academy of Sciences, real-time data of the measured samples is provided.
First, the main features of the product:
1. One-button operation, digital display, can polarize all kinds of PVDF films and piezoelectric ceramics (polymers are made of vinylidene fluoride (VDF), trifluoroethylene (TRFE, 1-chlorofluoroethylene (CFE) and or chlorotrifluoroethylene (CTFE)).
2. The output voltage is up to 2kV, and the output power is 2W
3. Ignition protection and short-circuit protection, automatically cut off the voltage.
4. Low temperature coefficient 0001% per degree Celsius.
5. Full digital operation, high efficiency and good effect.
6. Multiple polarization methods (air, silicone oil, heating).
7. External potentiometer or external control voltage is given.
8. Small size, printed circuit board mounting.
9. Positive polarity or negative polarity output.
Main technical parameters:
1. PVDF polymer film samples and PZT piezoelectric ceramic materials.
2. Regional surface polarization, polarization size: 0-50mm, 3. D33 test: 0-8000pc n
3. The voltage is not less than 30kV DC negative pressure polarization, air polarization at room temperature, silicone oil, and heating methods.
4. Digital display of winding speed and winding length, winding line speed is constant and adjustable.
5. Removal of ozone after surface charge polarization.
7. Working power supply: AC220V 50 60Hz Rated power: 20kw
10. Piezoelectric material polarization or withstand voltage test: DC: 0-30kV (5 continuously adjustable two words).
11. Total current: 10mA
12. Cut-off current of each channel: 05ma
13. Timing: 1-99min 5 arbitrary setting.
14. Heating element: high-quality resistance wire.
16. Temperature: good temperature control method.
17. Dimensions: width 1350, height 1450, depth 1150mm
18. Configure ZJ-3 and ZJ-6 piezoelectric testers.
1. Basic knowledge of PVDF film materials:
PVDF (polyvinylidene fluoride) is a polymer material with good weather resistance, chemical resistance and mechanical properties, and is widely used.
It is widely used in coatings, films, plates, fibers and other fields.
2. The difference between PVDF thin film materials and piezoelectric ceramics.
There are two main crystal forms of PVDF film, namely type and type, the type crystal does not have piezoelectric properties, but after the PVDF film is rolled and stretched, the original type crystal in the film becomes a type crystal structure. When the stretch-polarized PVDF film is subjected to external force or deformation in a certain direction, the polarization surface of the material will produce a certain charge, that is, the piezoelectric effect.
Compared with piezoelectric ceramics and piezoelectric crystals, piezoelectric films have the following main advantages:
1) Light weight, its density is only a quarter of the commonly used piezoelectric ceramic PZT, pasted on the measured object has almost no impact on the original structure, high elastic flexibility, can be processed into a specific shape can be completely fitted with any measured surface, high mechanical strength, impact resistance;
2) High voltage output, under the same force conditions, the output voltage is 10 times higher than that of piezoelectric ceramics;
3) High dielectric strength, can withstand the action of strong electric field (75V um), at this time most of the piezoelectric ceramics have been depolarized;
4) The acoustic impedance is low, only one-tenth of that of piezoelectric ceramic PZT, which is close to water, human tissue and viscose
5) Wide frequency response, from 10-3Hz to 109, can convert electromechanical effects, and the vibration mode is simple.
3. Performance of piezoelectric film materials.
1. Dielectric constant.
Although piezoelectric films are monocrystalline or preferentially oriented polycrystalline films, the atoms in them are not as compact and orderly as in crystals, so the dielectric constant values of piezoelectric films are different from those of crystals. In addition, there are also large residual internal stresses that are common in thin films and measurement reasons, which also cause the dielectric constant value of the film to be different from the corresponding value of the crystal.
Previous studies have shown that the dielectric constant of piezoelectric films is not only related to the crystal orientation, but also depends on the test conditions. The dielectric constant of piezoelectric films has a considerable dispersion due to the difference in the composition of the seamark film from the chemical formula stoimetric ratio and the thickness of the film, in addition to the difference in the magnitude of internal stress and the test conditionsIt is generally believed that the dielectric constant of a thin film decreases with thinning. In addition, the dielectric constant of piezoelectric films also changes significantly with temperature and frequency.
2. Volume resistivity.
In terms of reducing the dielectric losses and relaxation frequency of the piezoelectric film, it is desirable that it has a high resistivity, at least v 108 cm. The resistivity of ALN films is 2 1014 1 1015 cm, which is much higher than 108 cm, so ALN is a very good film in this regard. In addition, the electrical conductivity of ALN piezoelectric films with temperature also obeys the law of 1N 1 t.
None of the piezoelectric crystals have a center of symmetry, so their electron mobility is also anisotropic and their electrical conductivity is also different. The conductivity of ALN piezoelectric films along the C-axis is different from that in the direction of the perpendicular C-axis, which is about 1 2 orders of magnitude smaller.
3. The loss angle is tangent.
The dielectric loss angle tangent of the ALN piezoelectric film is Tanδ=0003～0.005, the tanδ of the zno film is larger, which is 0005～0.01。The reason why the tanδ of these films is so large is that there is a significant relaxation phenomenon in these films in addition to the conductivity process.
Similar to dielectric films, the tanδ of piezoelectric thick films increases with increasing temperature and frequency, as well as increasing humidity. In addition, when the thickness of the film decreases, the tanδ tends to increase. Obviously, the increase of tanδ with temperature is due to the increase of conductance and the increase of relaxation particles, and it increases with frequency because of the increase in the number of relaxations in time.
4. Breakdown strength.
Because the breakdown field strength of the dielectric is a strength parameter, and it is inevitable that there are various defects in the film, the breakdown field strength of the piezoelectric film has considerable dispersionAccording to the breakdown theory of ampandrons, for intact films, the breakdown field strength should gradually increase with the decrease of film thickness. However, in fact, because the film contains many defects, the lower the thickness, the more significant the effect of the defects, so when the thickness is reduced to a certain value, the breakdown field strength of the film decreases sharply. In addition to the film itself, the breakdown field strength of the film is also affected by the edge of the electrode during the test. Since the thicker the film, the more uneven the electric field at the edge of the electrode, the breakdown field strength gradually decreases as the thickness of the film increases.
In addition to several factors, the breakdown field strength of the dielectric film also depends on the film structure. For piezoelectric films, the breakdown field strength also follows the direction of the electric field, i.e., it is also anisotropic in terms of breakdown field strength. Due to the grain boundaries of polycrystalline films, their breakdown field strength is lower than that of amorphous filmsFor similar reasons, the breakdown field strength of preferentially oriented piezoelectric films in the grain orientation direction is lower than that in the perpendicular direction.
Like other dielectric films, the breakdown field strength of piezoelectric films is dependent on external factors such as voltage waveform, frequency, temperature, and electrodes. Because the breakdown field strength of piezoelectric films is related to a variety of factors, for the same kind of film, the breakdown field strength values reported in various relevant literature are often inconsistent, or even quite different, for example, the breakdown field strength of Zno film is 001～0.4mV cm, ALN film is 05～6.0mv/cm。
5. Bulk acoustic performance.
The most important characteristic parameters of bulk acoustic wave piezoelectric converters are resonant frequency f0, acoustic impedance ZA and electromechanical coupling coefficient k, so the sound velocity and temperature coefficient, acoustic impedance and electromechanical coupling coefficient of piezoelectric films are particularly strict. These properties of the film not only depend on the elastic, dielectric, piezoelectric and thermal properties of the grains in the film, but also closely related to the structure of the piezoelectric film, such as the degree of grain packing tightness and the degree of preferential orientation. In piezoelectric films, the physical constants of the films are a little different from the crystal values because there are many defects and strains in the grains, so they are not intact single crystals.
Because the microstructure of piezoelectric films is closely related to the preparation process, the performance values reported in various literatures are often inconsistent even for the same piezoelectric film. Among all inorganic non-ferrous piezoelectric films, ALN films are most suitable for ultra-high frequency and microwave devices due to their large elastic constant, low density and maximum sound velocity.
6. Sonic performance.
When the surface acoustic wave propagates in the piezoelectric medium, the displacement amplitude of the particle point decreases rapidly with the increase of the distance from the surface of the medium, so the surface acoustic wave energy is mainly concentrated in the range of the next two wavelengths of the surface.
The surface acoustic properties of thin film materials can be expressed as a function of the following:
Table acoustic wave properties = f (raw material, substrate, thin film structure, wave mode, propagation direction, interdigitive electrode form, thickness wave number product).
Therefore, no single value can be used to represent any of the acoustic wave performance parameters of piezoelectric films. Another acoustic performance of piezoelectric films is transmission loss. Because the piezoelectric film is often used as a sound transmission medium in surface wave devices, the transmission loss is mainly the scattering of sound waves in the piezoelectric film and substrate.