Views: 8 Author: Site Editor Publish Time: 2020-02-24 Origin: Site
When customers inquire about the use temperature of piezoelectric ceramics, we often encounter various problems. Can piezoelectric ceramics withstand high temperatures? Can low temperature environmental ceramics be used? Does temperature have a big effect on piezoelectric ceramics? Today, let's talk about the effect of temperature on piezoelectric ceramics.
The performance of piezo transducer material depends on temperature. Changes in temperature will greatly change the performance of piezoelectric ceramics. For example, the capacitance and loss factor will increase with increasing temperature, while excessive temperature will reduce performance and service life. Therefore, temperature is a very important factor affecting the experimental results. It is recommended that users consider the temperature factor during the experiment in different application environments.
An increase in temperature will cause a significant change in the dielectric constant of the piezoelectric ceramic, that is, the capacitance of the piezoelectric ceramic will change, and the capacitance of the piezoelectric ceramic will increase by about 40% from room temperature to 80 ° C.
Application temperature range of piezoelectric ceramics?
This depends on the Curie temperature of the piezoelectric ceramic material. The stacking piezoelectric ceramic PST 150 series we usually use has a Curie temperature of 155 ° C. The recommended safe use temperature is-25 to 80 ° C. For high-voltage piezoelectric ceramic hs / ht materials, The Curie temperature is 340 ° C. The recommended safe use temperature is about 175 ° C. The low temperature and high temperature piezoelectric ceramics can withstand temperatures of 200 ° C.
Storage temperature range of piezoelectric ceramics?
The recommended storage temperature is-5 to 40 ° C and the relative humidity is less than 40%. Selection of dynamic operation controller: When the piezoelectric ceramic is dynamically operated, due to the internal friction during the expansion and contraction of the piezoelectric ceramic, about 5-20% of the driving power is converted into the heat generated by the piezoelectric ceramic. When piezoelectric ceramics work dynamically, heat is generated and the temperature rises. At this time, the electrostatic capacity of the piezoelectric ceramic will increase accordingly. Therefore, when selecting a matching controller, you cannot simply calculate the required current based on the capacitance measured at room temperature in the parameter table.
Curie temperature
The Curie temperature of the piezoelectric ceramic is the temperature of the magnetic transition. When the piezoelectric ceramic reaches the Curie temperature point, the closer the piezoelectric ceramic will be to the Curie temperature of the piezoelectric ceramic, the more the performance of the piezoelectric ceramic changes. Therefore, in the process of using piezoelectric ceramics, it must be far below the Curie temperature, and zui is not higher than half of the Curie temperature. The Curie temperature point of piezoelectric ceramics of different materials is different. Generally, the Curie temperature point of low-voltage laminated piezoelectric ceramics is about 150-200 ° C, and the station temperature point of low-voltage and high-temperature piezoelectric ceramics is about 340 ° C. The temperature inside is about 215-340 ° C.
What is the thermal expansion coefficient?
The axial linear expansion coefficient of low-temperature laminated co-fired piezoelectric ceramics (in the range of -40 ~ 120 ° C) is negative-5 ppm / ° C, and the axial linear expansion coefficient of high-pressure piezoelectric ceramics is + 2 ppm / ° C.
5.Does the piezoelectric strain capacity change?
The strain capacity e displacement / voltage of piezoelectric ceramic transducer is expressed by the d33 coefficient in the material parameter table. Compared with room temperature operation, when the temperature decreases, the strain capacity decreases accordingly. When working at ultra-low temperatures, the piezoelectric effect is greatly reduced. The effect of temperature rise on d33 depends on the Curie temperature of the piezoelectric ceramic material used. The piezoelectric efficiency of soft materials decreases slightly. When the temperature rises to 80 ° C, when the working voltage is 0-150 v, the displacement of the stacked piezoelectric ceramic PST 150 / 5x 5/20 is about 19 μm. It is 20 μm. High-temperature piezoelectric ceramic materials are mainly hs / ht. When the temperature rises to 100 ° C, the piezoelectric efficiency increases by about 5%.
6.What about operating piezoelectric ceramics in high temperature environments?
Many applications can operate in high temperature environments. At this time, standard piezoelectric ceramics can no longer meet the needs of users. Only high temperature piezoelectric ceramics with special materials can be selected. The core can provide stacked NAC 6024 series or xmt series mechanical packaging piezoelectric ceramics. Tomorrow's high temperature 200 ℃ environment, and can be used in 150 ℃ environment.
7.Requires high dynamic operation of piezoelectric ceramics
In some applications that require high-frequency vibration, such as precision machining and active vibration control, how to control the temperature rise caused by high-frequency internal friction of piezoelectric ceramics? Our usual method is mainly tomorrow's external air cooling or core thermal stability and heat sinks The device's fast heat conduction reduces the risk of damage to piezoelectric ceramics caused by high-frequency heating. Choosing a core thermal stabilizer tomorrow can more than triple the dynamic power of piezoelectric ceramics.
8. Can piezoelectric ceramics resist low temperatures?
The core can be supplied with piezoelectric plate crystal for low temperatures of -273 ° C tomorrow. However, what you need to know is that the piezoelectric effect of piezoelectric ceramics below room temperature will be reduced, and the output and displacement of piezoelectric ceramics will be greatly reduced. At low temperature <260 K, the loss is about 0 / K in liquid. Under nitrogen, the displacement of piezoelectric ceramics is about 10% of room temperature.
The piezoelectric ceramic sheet we usually use is a semi-bipolar piezoelectric ceramic, that is, the negative pressure that the piezoelectric ceramic can withstand is 20% of the maximum positive voltage. Due to the sharp resistance of the ceramic material to depolarization in a low temperature environment Increased, it is possible to drive a piezoelectric ceramic bipolar in an ultra-low temperature environment, thereby achieving double displacement. For example, PST 150 reduces its strain capacity to 20% of room temperature at a low temperature of 77k, but 40% of the room temperature unipolar displacement can be obtained by the bipolar method. In the ultra-low temperature environment, it is necessary to choose a manganese copper wire with a lower thermal conductivity to keep the low-temperature environment unaffected.
