The Key Role of Piezoelectric Ceramics in Ultrasonic Transducers and Ultrasonic Motors

1. Introduction
2. Piezoelectric Ceramics Used in Ultrasonic Transducers
3. Precision Driving in Ultrasonic Motors
4. Industry Trends
5. Conclusion

Introduction
Every ultrasonic device requires means by which we can convert electrical energy to mechanical motion. Piezoelectric Ceramics do just that. When voltage is applied they vibrate. When you put pressure on them they generate voltage. This two way energy conversion is at the heart of present modern acoustical technology.
The variety of applications based on this principle is wide and still expanding. Early applications were in the field of industrial measurement and detection. Today, piezoelectric ceramics are used to energize medical imaging equipment, precision motor drives, cleaning equipments and surgical instruments. The material has become a must-have in industries requiring mechanically sound and high frequency applications.
Bestarsensor as a manufacturer of high-performance acoustic components, Bestarsensor supplies manufacturers for industrial, medical and consumer electronics all over the world. Its strength is in being able to combine material knowledge with application-specific engineering support to take customers from material polled to working system efficiently.

Piezoelectric Ceramics Used in Ultrasonic Transducers
A transducer is used to convert one form of energy into another. In ultrasonic applications, piezoelectric ceramics are used as the active element to cause this conversion to take place. When an electrical signal with alternating current is applied, the piezo ceramic element will expand and contract at the same frequency, emitting ultrasonic waves. When these waves make their way back as echoes the ceramic turns the mechanical pressure back into an electrical signal. This dual function makes it both the transmitter and receiver in one up to date compact component.
Material quality is directly related to system performance. The piezoelectric constant of a ceramic determines the efficiency of the conversion of energy in both directions. Higher values for the constant represent stronger output for a given amount of input power input, and a higher sensitivity when receiving signals. Thermal and mechanical stability are also of great importance. A specific case of use is a transducer for industrial purposes and other medical equipment where a consistent performance is required regardless of changing temperatures and under long operating cycles. Materials that drift or degrade over time results in lower accuracy of measurements, and the shorter product life.
Industrial Non Destructive Testing
Not all of these techniques employ ultrasonic transducers, but non-destructive testing (NDT) is a way of inspecting material without inferring a selection of its internal structure without way of damaging it. A transducer is used to send a pulse into a metal component, or into a composite structure. If there is a crack, void or inclusion inside, there is a timing and amplitude change of the reflected echo. Technicians use this data to locate and evaluate defects to a high level of precision. This method is commonly applied to aerospace, pipeline inspection, pressure vessel manufacturing and rail infrastructure. The ceramic element within the transducer determines the range of frequencies, resolution and depth of penetration available to the inspector.
Ultrasonic Cleaning and Welding
High frequency vibration finds tools outside sensing. In ultrasonic cleaning systems, piezoelectric transducers are used to force a bath of liquid into rapid oscillation. This creates microscopic bubbles that crash with sufficient force to loose contaminants from surfaces including recessed spots that brush cannot access. The process is applied to cleaning of optical lenses, electronic circuit boards, medical instruments and precision mechanic parts.
Ultrasonic welding is based upon a similar principle. Vibration is introduced directly to the interface between two materials. The energy produces localized heat via friction that melts and bonds the surfaces together. And the joint is formed in milliseconds: no adhesives and no fasteners. This technique is common with assembly in automobiles and parts, medical device assembly and plastic packaging.
Medical Diagnostic Imaging
Ultrasound Imaging System adopts arrays of piezoelectric ceramic elements to generate images of the internal anatomy on a real time basis. Each element in the probe fires in sequence building up a picture from the reflected echo data. The frequency used by the ceramic determines the resolution level of the images along with penetration capacity. Higher frequencies are used for making sharper images of shallow structures. Lower frequencies go less in detail to greater depths. Medical probes demand ceramics that have tight dimensional tolerances as well as consistent electrical characteristics from each element in the array. Variation between elements reduces image quality and causes problems with calibration.
Bestarsensor helps transducer manufacturers with piezo ceramic materials that are optimized for high frequency consistency. Its custom formulation abilities enable customers to have the material properties matched to their application requirements, whether it's a medical probe in which they want to maximize sensitivity, or an industrial cleaner in which they want to generate as much output power as possible.

Precision Driving in Ultrasonic Motors
Ultrasonic motors make fundamental use of piezoelectric ceramics in a very different construction. Instead of transmitting/receiving acoustic signals the ceramics produce mechanical movement which is used to drive a rotor or a linear stage. The working principle is based on standing or travelling waves which are established in a resonant structure. As the ceramic vibrates at ultrasonic frequencies, tiny elliptical movements are implied at a surface of the stator. By way of friction, these movements propel the rotor and cause the smooth rotation (or linear displacement) of the rotor.
The motion thus produced is very controlled. Displacement controls are controllable to the micrometer, and thus ultrasonic motors can perform tasks where other conventional electromagnetic motors are too imprecise. The response time is fast. There is no cogging or backlash. When the power is removed the motor maintains its position without a brake mechanism as the friction interface locks the rotor in position. This self-locking behavior is especially otherwise useful in applications that are battery powered or that critically require safety.
Ultrasonic motors do not produce any electromagnetic field. This makes them compatible with environments where magnetic interference is a problem, such as inside of MRI machines or near sensitive electronic sensors.
Optical Lens Control
Autofocus systems in camera lens are based on fast, quiet and accurate actuators. Ultrasonic motors satisfy these three requirements. They smoothly move the lens elements and without the noise involved with gear-linked systems. High-income level interchangeable lenses, drone camera gimbal and smartphone camera module all use different variants of this drive technology. The ceramic ring or disc that is at the heart of these motors must be produced with tight geometric tolerances, of course, so as the wave propagation can be seen to be consistent across the cycles, and the concentric operation is smooth over millions of cycles.
Accurate Medical Instrument
Surgical robots need actuators that are compact, accurate and free from electromagnetic interference. Ultrasonic motors are good fits to these requirements. They are applied in robotic surgical tools to control fine tessels at the tip of the tool. Infusion pumps and micro-dosing systems also incorporate piezoelectric drives which precisely control the fluid delivery with the help of piezoelectric drives. In these environments, there is no room for negotiation when it comes to reliability. Component failure has direct patient safety implications.
Bestarsensor manufactures piezoelectric ceramics to the circumscription of ring, disc and plate geometries for the structural assignments of various motor designs. Customers that need to work on custom motor architectures can specify dimensions and material grade, as well as electrode configuration to fit their drive frequency and torque needs.

Industry Trends
Traditional piezoelectric ceramics are based on lead zirconate titanate (PZT) which contains lead. Environmental regulations such as RoHS and REACH limit or discourage the use of lead in electronic products and electrical products. Research into lead free alternatives such as barium titanate and potassium sodium niobate compositions has taken off. Performance gaps exist in certain high-power applications, not least the stepped rate of progress and intensifyinguanity pressure from regulators.
The second trend is a reduction in device size. Consumer electronics, wearable health sensors and smaller industrial sensors all require smaller parts without losing performance. Piezoelectric ceramic elements are being produced to finer scales, making it possible to build into devices where space is measured in millimeters. Thin film and multilayer ceramic structures are pushing ever outward the limits of the micro scale.
The third trend is towards changing from single components to pre-assembled acoustic modules. Rather than providing a ceramic disc and allowing integration to be designed on the customer side, suppliers are now increasingly providing complete sub-assemblies. These modules contain ceramic element, backing material, matched layer, housing and electrical connections in the tested and ready-to-install form. This offers engineering relief to the customer and shorter product development times.

Bestarsensor: Worldwide Partner
Bestarsensor is a "technical partner" instead of a catalogue supplier in relation to customer relations. From initial material selection to the system integration, the company offers engineering consultation at every stage of the product development.
The combination of material know-how, application familiarity and supply chain ability make Bestarsensor an asset to manufacturers who are struggling to deal with both the short-term production requirements and the long-term technology transitions.

Conclusion
Piezoelectric ceramics occupy a unique place in the modern technology. They are easy in theory but difficult in practice. The performance of the ceramic element dictates the ability of the entire system built around it whether it be a medical imaging probe, an industrial inspection transducer or a precision motor inside a camera lens.
In the continued development of ultrasonic technology, there will be an increased need for higher performance, more consistent and environmentally responsible piezoelectric materials. Applications will be more sophisticated. Integration is going to become ever tighter. Component tolerances will increase in demand.
Bestarsensor is in a position to grow in line with such demands. Through investment in the development of materials, the precision of manufacture and global supply infrastructure, the company enables acoustic technology innovation for the same on the component level. For engineers and manufacturers engaged at the cutting edge of ultrasonic technology, that type of partnership is not a convenience. It is a competitive advantage.