Introduction to Piezoelectricity and Piezoelectric Ceramics

Introduction to Piezoelectricity and Piezoelectric Ceramics

Piezoelectricity is the creation of electric potential in certain materials when they are under mechanical stress, such as bending, stretching, or compressing. Physicists refer to this phenomenon as the piezoelectric effect. The materials that exhibit these characteristics are called piezoelectric materials.

The piezoelectric effect happens when the electric charge domains in the piezoelectric material are displaced under stress. Piezoelectric materials also exhibit the reverse property – called inverse piezoelectric effect – of changing shape in an electric field. The inverse property is due to the external electric field pushing the positive and negative charge crystals inside the material away from each other.

Piezoelectric materials are used for making many household items such as inkjet printers and quartz watches, as well as industrial devices like sound generators and detectors.

Quartz and topaz are examples of naturally occurring piezoelectric materials. There are many other natural piezoelectric materials, but synthetic ferroelectric ceramics exhibit stronger piezoelectric effects and are far more affordable. Hence, ceramic piezoelectric materials have been widely adopted by the industry.

What Are Piezoelectric Ceramics

Ceramics, in general, are made up of electrically charged crystals. In most ceramics, except ferroelectric ceramics, the electrical charges of the crystals balance out. Ferroelectric ceramics are electrically polarized and hence possess piezoelectric properties.

Right after they are made, however, they do not exhibit piezoelectric effects due to the random distribution of electrical charge bearing crystals. The crystals need to be aligned by applying a high DC voltage, thus polarizing the ceramic to make it piezoelectric. Once they are polarized, piezoelectric ceramics retain polarization even when the DC voltage is removed.

Piezoelectric ceramics include:

  • Barium Titanate
  • Potassium Niobate
  • Sodium Tungstate
  • Lead Zirconate Titanate (PZT)

The latter, PZT, is the most widely used and is a mix of lead zirconate and lead titanate. PZT has higher piezoelectric sensitivity and greater stability at high temperatures than other materials. In addition, the piezoelectric properties of PZT can be formulated to be hard or soft. All these characteristics have led to the wide adoption of PZT, despite environmental concerns about the use of lead.

Soft vs Hard Piezoelectric Materials

Softness or hardness of a piezoelectric material refers to how easily they are polarized. Soft piezoelectric materials are easily polarized while hard ones are not.

Soft piezoelectric materials have a high coupling coefficient, which means that they have greater sensitivity to electric fields. They also have a high piezoelectric charge coefficient, a high dielectric constant and a noise-free response to the stimulus. Their common applications include:

  • Sound sensors
  • Microphones
  • Microbalances
  • Ultrasonic transducers
  • Equipment for non-destructive inspection and testing in the automotive and aeronautical industries

Hard piezoelectric materials require a high DC voltage for polarization. They are very stable and operate well in environments with high mechanical or electric stress. So they are used in ultrasonic cleaners and sonar devices that call for high electrical power and mechanical strength.

Piezoelectric Ceramics from Kadco

Piezoelectric ceramics are used in a wide range of household products and industrial applications. It is important that you work with the right vendor to select the appropriate ceramic material and shape it to your specifications.

Kadco Ceramics can help you choose piezoelectric ceramics with the right characteristics for your application. We also offer a variety of machining services for your prototyping or production needs.

Our piezoelectric machining capabilities can produce the complex geometries required for varied ultrasonic applications ranging from submarine detection to non-invasive neurological surgery for Parkinson’s disease.

Kadco uses its precise diamond milling, grinding, ID slicing and dicing capabilities for many other hard materials.

These commonly include:

  • alumina,
  • quartz,
  • glass,
  • sapphire,
  • silicon,
  • zirconia and
  • ferrites.

We are always interested in working with new and unusual materials

Please contact us today for all your piezoelectric ceramic machining needs.

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