Piezo-ceramics for Power Converters

Piezo-ceramic Transducers for Sonar and High-power Ultrasonic Applications

Power conversion composite transducers, also referred to as Langevin-Bolt transducers (LBT), are made from specially developed piezo-ceramics characterized by low dielectric loss and high mechanical Q-factors.

Piezo-ceramics for Power Converters

Worth knowing:

Applications for Piezo-ceramic Transducers

  • Surgical knives
  • Echo sounders
  • Fish finders
  • Level senors
  • Hydroacoustics
  • Lithotripters
  • Sonar technology
  • Ultrasonic material processing
  • Ultrasonic cleaning
  • Ultrasonic welding
  • Underwater object recognition
  • Plaque removal
  • Non-destructive material testing

CeramTec offers the material types SONOX® P4 and SONOX® P8 with different property profiles.

SONOX® P4 is suitable for ultrasonic cleaning and non-destructive testing transducers. Its high coupling factors, medium-range Q-factors, and excellent mechanical stability permit high oscillation amplitudes at resonance. The achievable active power output in transducer configurations (emitting unilaterally in water) varies between approximately 7 and 10 W/cm2. The maximum operating temperature of the ceramic is 125°C. Its compressive strength depends on the mounting conditions (homogeneous load distribution) with 70 maximum MPa in continuous mode.

“CeramTec materials for power transducers are ideal for high-power ultrasonic app­lications in the 20 kHz to several MHz range.”

SONOX® P8 is designed for power transducers handling maximum loads per unit area. This material combines high mechanical Q-values with high coupling factors and low dielectric loss. Since it also features a high depolarization resistance, SONOX® P8 is particularly suitable for high-power transducers.

Applications for Piezo-ceramic Transducers

Surgical Knives

A composite transducer consisting of several small piezo-ceramic rings oscillates in resonance at frequencies between 20 kHz and 80 kHz. This causes a small scalpel blade in a medical tool to vibrate, allowing the surgeon to perform minutely small, very precise cuts using substantially less cutting force and without damaging surrounding tissue.

Design: Ring
Materials: SONOX® P 4, SONOX® P 8

Echo Sounders and Fish Finders

The applications for sonar systems range from single small transducers for pleasure craft to professional systems in large ships that detect water depth and schools of fish. Piezo-ceramic transmitters with varying geometries that cover a frequency range of 5 kHz to 10 MHz are used in the different systems. Some systems use the same piezo-ceramic transducers for transmitting and receiving. Others use different ceramic transducers for transmitting and receiving, such as in towed array sonar systems which can work over long distances. Large ships use transducer arrays, which consist of a high number of individual piezo-ceramic elements. These elements can be controlled separately and electronically delayed. This makes it possible to use electronic beam deflection.

 

Designs: Round disc, cylinder, rectangular plate, circular segment, spherical segment and other special designs
Materials: SONOX® P 4, SONOX® P 5, SONOX® P 8

Level Sensors – Propagation Time Measurement

Level sensors are typically divided into two different measuring systems. Immersed transducer measurement using piezo-ceramic sensors and propagation time measurement using piezo-ceramic transducers. Here, level measurement takes place using propagation time measurement of an airborne ultrasonic signal that is transmitted and then reflected by the substance being measured. One key advantage of this system is that it operates on a “non-contact” basis, meaning that is also possible to measure the level of solids in silos, for example. A disadvantage is that the accuracy of the measurement depends on the reflection properties of the respective substance. For the piezo-ceramic transducer to measure accurately, a certain amount of the wave it emits must be reflected. If the wave front is scattered too much or absorbed by the stored materials, no useful measurement is possible.

Designs: Round disc, perforated rings other special forms
Material: SONOX® P 4

Lithotripters

A large number of piezo-ceramic elements are attached to the inner side of a concave shell. A high-voltage pulse is applied simultaneously to all of these ceramics to produce a mechanical ultrasonic shock wave. Due to the concave form of the shell, this is concentrated at one point. The high energy in the focus of this shock wave shatters kidney stones and the fragments can leave the body naturally via the ureter. This makes it possible to remove painful kidney or gall stones without any anesthesia and or surgical intervention in a manner that is relatively painless.

 

Design: Cylinder
Materials: SONOX® P 4, SONOX® P 5, SONOX® P 53

Sonar Technology and Hydroacoustics

Components made from SONOX® P4 are used for recognition, location and navigation in a wide range of underwater applications such as echo sounders for pleasure craft to detect obstacles or transmitter arrays for large ships to check water depth, monitor trawl nets and locate schools of fish.

Material: SONOX® P 4

Ultrasonic Material Processing

The design layout and the generation of ultrasonic waves is identical to ultrasonic welding, except that a tool for machining the material is coupled to the end of the sonotrode and an additional suspension is used which acts like an abrasive. The tool is excited to produce ultrasonic vibrations in the feed direction, which also make the abrasive particles in the water suspension vibrate. For a fraction of a vibration cycle the particles are frictionally engaged with the workpiece and tool. The workpiece is microscopically cut during these impacts. This process makes it possible to machine almost any material, from glass to hard metal. The advantage of this machining method is its great precision and the high-quality surface finish of the machined part.

Design: Perforated ring
Material: SONOX® P 8

Ultrasonic Cleaning

End device cleaning is a topic that covers a very wide range of designs from small eyeglass cleaning baths for opticians all the way to 20m-long industrial cleaning plants with automatic conveyor systems. Ultrasonic cleaning works by creating cavitation in a cleaning liquid by means of high-power ultrasonic waves. Cavitation is the formation (due to pressure differences in the fluid) of tiny local gas bubbles, which implode again after a very short period of time. The cavitation intensively cleans the contaminated surface of the substance, even with complicated shapes. The ultrasonic energy is transmitted into the fluid via the bottom and the walls of the cleaning tank, or via immersed transducers. The piezo composite transducers that generate the ultrasonic waves usually consist of at least two piezo-ceramic perforated rings mechanically preloaded with metallic end pieces. In very small cleaning baths, a single piezo-ceramic round plate is glued to the bottom of the tank.

Designs: Round disc, perforated ring
Materials: SONOX® P 4, SONOX® P 8

Ultrasonic Welding

Ultrasonic welding takes advantage of the friction energy generated by the ultrasound at the boundary surfaces. When two preforms are pressed together at their connecting surfaces and excited using high-frequency ultrasound, the surfaces of the two parts generate so much energy that their connecting surfaces fuse together. This works with both metal and plastic parts. The ultrasonic energy is fed to the parts to be joined via a sonotrode, which amplifies the ultrasound generated by the piezo composite transducer. The piezo composite transducer consists of two or more piezo-ceramic perforated rings that are mechanically pre-stressed using two metallic end pieces. Ultrasonic welding has established itself in industry as a very fast, cost-effective and reliable joining technology.

Design: Perforated ring
Material: SONOX® P 8

Underwater Object Recognition (Sonar Technology)

The name “sonar” stands for “sound navigation and ranging”. What is meant are systems used for detection, locating and navigation under water. The applications for sonar systems range from single small transducers for pleasure craft for locating fish or obstacles to professional systems in large ships that detect water depth and schools of fish. Piezo-ceramic transmitters with varying geometries that cover a frequency range of 5 kHz to 10 MHz are used in the different systems. Some systems use the same piezo-ceramic transducers for transmitting and receiving. Others use different ceramic transducers for transmitting and receiving, such as in towed array sonar systems which can work over long distances. Large ships use transducer arrays, which consist of a high number of individual piezo-ceramic elements. These elements can be controlled separately and electronically delayed. This makes it possible to use electronic beam deflection.

Designs:  Round disc, cylinder, rectangular plate, circular segment, spherical segment and other special designs
Materials: SONOX® P 4, SONOX® P 5, SONOX® P 8

Plaque Removal

A composite transducer consisting of two to eight small piezo-ceramic rings oscillates in resonance at frequencies between 20 kHz and 80 kHz and drives a dental medical tool in the form of a small scraper. The tip is cooled with water or special liquids. The high oscillating frequency of the tool at very small amplitudes (in the µm range) makes it possible to thoroughly remove plaque without damaging the tooth.

Design: Ring
Materials: SONOX® P 4, SONOX® P 8

Non-destructive Material Testing

In mechanical, plant and tool engineering, the maxim for many years has been to produce maximum load resistance with a minimum of material. The precondition for this is that the materials or semi-finished products used are free of defects or inhomogeneities. Non-destructive material testing allows for comprehensive quality assurance in the production process. Of all the testing methods used in industry, the reflection technique is the most widespread. In this method, a piezo-ceramic transmitter is connected either directly or via a liquid or solid coupling medium to the workpiece to be tested. The piezo-ceramic transducer radiates an ultrasonic wave package into the test piece where it is either reflected if there are defects or inhomogeneities, or passes through the test piece without hindrance. Reflected sound waves are received again by the same piezo transducer and detect defects in the material.

Designs: Round disc, rectangular plate, square plate
Materials: SONOX® P 4

Recommended Contacts

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