Last Updated on March 17, 2023 by You Ling
Real and professional answers to common questions about piezoelectric ceramics
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Correct. Piezoelectric ceramics generate an electric current when subjected to mechanical stress, but this current is typically a direct current (DC) rather than an alternating current (AC).
2、How much voltage can a piezoelectric produce?
Yes, that is correct. The voltage generated by piezoelectric ceramics is typically in the range of microvolts to millivolts, and the current generated is also in the microamp range. Piezoelectric ceramics are mainly used as sensors or actuators in various applications, including medical devices, industrial control systems, and ultrasonic imaging systems.
3、What is the most powerful piezoelectric material?
Yes, that’s correct. PMN-PT (lead magnesium niobate-lead titanate) and PZN-PT (lead zinc niobate-lead titanate) are indeed high-performance piezoelectric materials, but they also have some limitations such as higher sensitivity to temperature changes, higher susceptibility to fatigue, and more complex production processes compared to PZT. As a result, PZT remains the most commonly used piezoelectric material in energy harvesting applications due to its high piezoelectric activity, good mechanical stability, and relatively low cost of production.
4、Is quartz A piezoelectric?
That’s correct. Natural quartz crystals can be piezoelectric and so can synthetic piezoelectric ceramics which are made to have similar properties as quartz. Both types of materials can convert mechanical stress into an electrical charge and vice versa, which makes them useful in various electronic devices such as quartz clocks, microphones, and piezoelectric sensors.
An acceptor dopant in a ceramic formulation creates oxygen (anion) vacancies in the crystal structure. Hard ceramics have characteristics generally opposite those of soft ceramics, including Curie points above 300°C, small piezoelectric charge constants, large electromechanical coupling factors, and large mechanical quality factors. They also are more difficult to polarize or depolarize. Although hard ceramics generally are more stable than soft ceramics, they cannot produce the same large displacements. Hard ceramics are compatible with high mechanical loads and high voltages.
soft ceramics – are characterized by large electromechanical coupling factors, large piezoelectric constants, high permittivity, large dielectric constants, high dielectric losses, low mechanical quality factors, and poor linearity. Soft ceramics produce larger displacements and wider signal bandwidths, relative to hard ceramics, but they exhibit greater hysteresis and are more susceptible to depolarization or other deterioration. Lower Curie points (generally below 300°C) dictate that soft ceramics be used at lower temperatures. Generally, large values for permittivity and dielectric dissipation factor restrict or eliminate soft ceramics from applications requiring combinations of high-frequency inputs and high electric fields. Consequently, soft ceramics are used primarily in sensing applications, rather than in power applications.
The Curie temperature of piezoelectric ceramics is the temperature at which the material transitions from a ferroelectric phase to a paraelectric phase. Below the Curie temperature, the material is in a polarized and ordered state, while above it the material experiences a depolarization phenomenon and the dipole moment becomes disordered.
piezoelectric materials can be used to generate electrical energy, which can then be stored in a battery. The mechanical strain caused by pressure or force applied to the piezoelectric material creates a voltage difference across its surfaces, which can be harvested and stored in a battery for later use. However, the amount of energy generated by piezoelectric materials is typically small, so it is typically used for low-power applications such as powering sensors or generating backup power.
It depends on the type of coating and its properties. In general, adding a coating to a piezo can affect its displacement if the coating changes its mechanical or electrical properties. If the coating is too thick or stiff, it can decrease the overall displacement of the piezo. On the other hand, if the coating is flexible, it may not affect the displacement significantly. It is important to consider the specific properties of the coating and how they will interact with the piezo material before applying the coating.
Yes, oil can be used to cool piezo ceramics. The oil helps to transfer heat away from the piezo, reducing its temperature and preventing overheating. However, it is important to use an oil that is compatible with the piezo material and does not react with it. Additionally, the oil should have high thermal conductivity and low viscosity to effectively dissipate heat.
It’s also worth noting that other cooling methods, such as air or water cooling, may also be used depending on the specific application and requirements. It’s important to carefully consider the cooling solution and ensure that it meets the requirements for your piezo application.
Yes, it’s important to note that applying torsion force to piezoelectric ceramics can be risky and should be avoided, as it can lead to damage to the adhesive layer and potentially cause fracture of the piezoelectric ceramic itself. When applying a preload force to the piezoelectric ceramic, it is crucial to ensure that the preloaded tightening torque is not transmitted to the ceramic, as the shear force greater than 1 MPa can cause significant damage. It is important to carefully consider the mechanical loading conditions and design the system accordingly to prevent any adverse effects on the piezoelectric ceramic.
Yes, it is recommended that piezoelectric ceramics work under a preload force of 0-80 MPa, with a typical range of 10-20 MPa. It’s crucial to design the preload within this range and ensure that it stays within this range under all conditions, as a preload force that is too high or too low can result in damage to the piezo and impact its performance. Careful consideration and proper design of the preload are essential to ensure the reliable and optimal operation of the piezoelectric ceramic.
The amount of preload that can be applied to a piezo depends on several factors, including the type and size of the piezo, the material properties of the piezo and any coatings or adhesives used, and the specific application requirements.
In general, the maximum preload that can be applied to a piezo is determined by its mechanical strength, which can be influenced by factors such as temperature, humidity, and the presence of any external loads. A preload that is too high can cause damage to the piezo, including cracking or permanent deformation.
It is recommended to consult the manufacturer’s specifications or guidelines for the specific piezo being used to determine the recommended preload range. Additionally, testing and experimentation may be necessary to determine the appropriate preload for a specific application.
The displacement of piezoelectric ceramics can be increased under negative pressure, but this needs to be done within the limits set by the manufacturer to avoid depolarization and other potential damage. Applying an electric field that exceeds the limit could lead to depolarization, which reduces the piezoelectric effect and the performance of the piezoelectric ceramic. It is important to operate the piezoelectric ceramic within its specified limits to ensure its reliability and performance.
The resonant frequencies listed in the parameters are usually defined for the cantilever configuration with no added mass or clamping. When a load is added or the piezoelectric ceramic is clamped, the resonant frequency will be affected, and it will usually be lower than the resonant frequency in the absence of these factors. The effect of clamping and loading on the resonant frequency can be significant and should be taken into consideration when designing and using piezoelectric ceramic systems. Additionally, the resonant frequency of a piezoelectric ceramic system may also depend on other factors such as temperature, humidity, and material properties, so it is important to consider these factors as well when evaluating the performance of a piezoelectric ceramic system.
The exposed internal electrodes of multilayer piezoelectric ceramics can be dealt with in several ways, depending on the specific application and requirements. Some common methods are:
Encapsulation: The internal electrodes can be encapsulated with a protective material such as epoxy or silicone to prevent electrical shorting and physical damage.
Surface Coating: The internal electrodes can be coated with a thin layer of protective material, such as gold or silver, to improve their durability and reduce the risk of corrosion.
Electrical Isolation: The internal electrodes can be electrically isolated from each other to prevent electrical shorting and ensure safe and reliable operation.
Circuit Design: The internal electrodes can be incorporated into a circuit design that minimizes their exposure and reduces the risk of electrical shorting or damage.
In any case, it is important to follow the manufacturer’s recommendations and to ensure that the appropriate measures are taken to protect the internal electrodes and ensure the safe and reliable operation of the multilayer piezoelectric ceramic.
While other factors such as physical stress, temperature, duty cycle, etc. also affect depolarization, for SOFT PZT components, the safe voltage range is 5-7 volts/mil (200-280 V/mm) thickness, while for HARD PZT components, the safe voltage range is 20 volts/mil (600-800 V/mm).
Soft PZT, such as PZT-5H material.
Soft PZT components, such as PZT-5H / PZT-5A / PZT-5J materials, are very suitable for sensing applications.
If you want a safety margin, a good estimate is half of the material’s Curie temperature (Tc). Other stresses such as duty cycle, applied voltage, and physical stress also affect the material and maximum safe working temperature. The materials we provide can be used in environments up to 240°C.
Yes, they do. The aging rate of PZT materials depends on the composition and is measured in percentage (loss or gain) per decade (1 day, 10 days, 100 days, 1000 days, etc.). Additionally, the aging rate of each material characteristic is different.
The characteristics of PZT materials decrease at low temperatures. Therefore, users need to determine the suitability of various materials for each application at the temperatures of interest.
Piezoelectric ceramic shear slices are typically tested under a pressure of 3.5 MPa. Piezoelectric ceramics can withstand higher compressive forces (>50 MPa), but in practical use, we recommend that the axial load on piezoelectric ceramic shear slices not exceed 5 MPa. This is because even small defects on the contact surface can lead to stress concentration and damage to the piezoelectric ceramic. If high pressure is required, we recommend using contact surfaces with higher flatness (including the surface of the piezoelectric shear slice and the contact surface on the structure).