Last Updated on March 1, 2023 by You Ling
Piezoelectric ceramics are complex materials, we share some experiences to make it easier for everyone to understand piezoelectric ceramics
1、What is Piezoelectric ceramics
Piezoelectric ceramics refer to ferroelectric ceramics which are formed by mixing oxides (zirconia, lead oxide, titanium oxide, etc.) at high temperature and sintered at high temperature and undergoing solid-state reaction, and have a piezoelectric effect through DC high-voltage polarization treatment. collectively.
Piezoelectric ceramics are a unique class of materials that have the ability to convert mechanical energy into electrical energy, and vice versa. This property makes them valuable in a wide range of technological applications, including sensors, transducers, actuators, and many other types of devices. In this essay, we will explore the properties of piezoelectric ceramics, their applications, and their potential future uses.
2、How piezoelectric ceramics work
Piezoelectricity is a phenomenon in which certain materials can generate an electric charge in response to mechanical stress, such as pressure or vibration. Conversely, these materials can also deform in response to an electric field, creating mechanical motion. This phenomenon was first discovered in 1880 by Pierre and Jacques Curie, who found that applying pressure to certain crystals, such as quartz, generated an electrical charge across their surfaces.
3、History of piezoelectric ceramics
The word “piezo” (piezoelectric) is derived from the Greek word for “pressure”. In 1880, Jacques Paul Curie and Pierre Curie discovered that the application of pressure can generate charges in various crystals such as quartz and tourmaline, which they called the “piezoelectric effect”. Later, they discovered that electric fields can deform piezoelectric materials. This effect is called “inverse piezoelectric effect” (inverse piezoelectric effect).
In 1942, people discovered the piezoelectricity of BaTiO3. Due to its high dielectric constant, it was quickly applied and developed. It is still used to make vibrators for sonar devices, acoustic measurement devices, and filters. However, due to the existence of stable frequency and temperature Problems such as poor sex.
In 1954, researchers in the United States discovered that lead zirconate titanate (PZT) ceramics had good piezoelectric properties, and its electromechanical coupling coefficient was nearly twice that of BaTiO3. In the next 30 years, PZT became the most widely used piezoelectric material due to its strong and stable piezoelectric properties. The emergence of this material expanded piezoelectric devices from traditional transducers and filters to ignition and detonation devices, Voltage transformers and piezoelectric generators, etc. If BaTiO3 is used as a representative of unit piezoelectric ceramics, then PZT can be used as a representative of binary piezoelectric ceramics. Due to its diversity of performance parameters, research and development and utilization of vibration modes, and progress in device manufacturing technology, PZT piezoelectric ceramics have developed rapidly in the past ten years and their applications have become increasingly widespread.
4、Working principle and characteristics of piezoelectric ceramics
The working principle of piezoelectric ceramics is: a ceramic material has a piezoelectric effect, that is, the material itself will accumulate charges after being subjected to the external pressure, that is, the phenomenon of charges generated by pressure is called the piezoelectric effect. Therefore, the change of pressure can be sensed by the change of charge. The most common application is B-ultrasound, sonar, etc.
In addition, piezoelectric ceramics also have an inverse piezoelectric effect, that is, under the action of an external electric field, their own materials will produce small deformations. Therefore, through this characteristic, piezoelectric ceramics are also made into micro-displacement brakes to achieve precise control of small displacements.
Properties of Piezoelectric Ceramics
Dielectricity: The dielectricity of piezoelectric ceramics reflects the response of ceramic materials to external electric fields, and is usually expressed by the dielectric constant ε0.
Elasticity: The elastic coefficient of piezoelectric ceramics is a parameter reflecting the relationship between the deformation and force of ceramics.
Piezoelectricity: The biggest feature of piezoelectric ceramics is piezoelectricity, including positive piezoelectricity and inverse piezoelectricity. Positive piezoelectricity refers to the relative displacement of the positive and negative charge centers in some dielectrics under the action of external force, resulting in polarization, which leads to the appearance of bound charges with opposite signs on the surface of the dielectric.
5、Types of piezoelectric ceramics
Piezoelectric ceramic materials are classified according to their chemical composition,
Lead Zirconate Titanate (PZT)
The latter, PZT, is the most widely used and is a mixture of lead zirconate and lead titanate. PZT has higher piezoelectric sensitivity and higher high-temperature stability than other materials. In addition, the piezoelectric properties of PZT can be formulated to be rigid or soft. All of these properties have led to the widespread adoption of PZT despite environmental concerns over the use of lead.
On the other hand, it is classified according to specific application conditions
soft piezoelectric material
Ideal for piezoelectric actuators and sensors
Ferroelectric soft piezoelectric ceramic materials can be polarized fairly easily even at relatively low field strengths. This is due to their typical relatively high domain mobility. The advantages of soft PZT materials are a large piezoelectric charge coefficient, moderate dielectric constant, and high coupling coefficient.
Important areas of application for soft piezoelectric ceramics are Actuators for micropositioning and nanopositioning, sensors such as conventional vibration detectors, ultrasonic transmitters, and receivers, e.g. for flow or level measurement, object recognition or Monitoring, and electroacoustic applications as sound transducers and microphones, but also as pickups on musical instruments.
hard piezoelectric material
High-performance materials for ultrasonic transducers
Ferroelectric hard PZT materials are subject to high electrical and mechanical stress. Their properties show little change under these conditions.
The advantages of these materials are moderate dielectric constants, high piezoelectric coupling coefficients, high mechanical properties, and very good stability under high mechanical loads and operating fields. Low dielectric loss facilitates their continuous use in resonant mode with little inherent heating of the components.
Especially high-power acoustic applications benefit from the properties of hard piezoelectric materials. Their areas of application include ultrasonic cleaning (usually in the kHz frequency range), material processing (ultrasonic welding, bonding, drilling, etc.), ultrasonic processors (e.g. dispersing liquid media), medical fields (ultrasonic tartar removal, surgical instruments, etc.) and sonar technology.
Lead-Free Piezoelectric Materials
These materials are based on sodium bismuth titanate (BNT) and exhibit very similar properties to barium titanate materials. These materials are suitable for ultrasonic transducers in the MHz range as well as for sonar and hydrophone applications.
6、Application Fields of Piezoelectric Ceramics
In recent years, piezoelectric ceramics have been applied in the following aspects including but not limited to:
medical diagnosis and treatment
Ultrasonic processing and joining
Technology (welding, drilling)
In conclusion, piezoelectric ceramics are a class of materials with unique electrical and mechanical properties. Their ability to convert mechanical energy into electrical energy, and vice versa, has made them valuable in a wide range of technological applications, including sensors, transducers, and actuators. As research into these materials continues, they may find even more exciting applications in the future, from energy harvesting to new forms of biomedical sensing and treatment.