A transducer is a device that convert one form of energy into another. Ultrasound transducers are used to convert an electric signal into ultrasonic energy that can be transmitted into tissue, and to convert ultrasonic energy reflected back from tissue into an electric energy back.
Piezoelectric crystal:
The most important part of any ultrasound transducer is a thin piezoelectric crystal. Its thick is usually in the range of 0.5 mm and is always located near the face of the transducer. When electric supply is given to crystal by two electrodes coated with a thin conducting film, it shows deformity which is called strain of the crystal.
Quartz:
Some naturally occurring materials posses piezoelectric properties, one of them is quartz. But most of the crystals used in medical field are man-made. The group of artificial piezoelectric materials is known as ferroelectrics. Barium titanate was the first of the ceramic ferroelectrics to be discovered. But now it is largely replaced with Zirconate titanate, which most commonly known as PZT. Where PZT is a registered trade name of PZT materials from the Clevite Corporation. There is a big advantage of artificial crystals is that, they can easily be converted to the shape and/or size required in any specific application. Moreover they can vibrate in any of its dimension. Mostly in medical field we use them in thickness vibration.
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