The piezoelectric crystal is used in transducers in ultrasound medical imaging. The crystal vibrates when an electric field is applied to it, the oscillations of the crystal vibrating occurs at very high frequencies beyond the threshold of human hearing.
Like this: (piezoelectric-crystal)
The sound,or sound waves, with frequency higher then human hearing span are called ultrasound. The healthy human ear can usualy hear up to 20kHz. Ultrasound is produced and detected using an ultrasound transducer. Ultrasound transducers are capable of sending an ultrasound and then the same transducer can detect the sound and convert it to an electrical signal to be diagnosed. To produce an ultrasound, a piezoelectric crystal has an alternating current applied across it. The piezoelectric crystal grows and shrinks depending on the voltage run through it. Running an alternating current through it causes it to vibrate at a high speed and to produce an ultrasound. This conversion of electrical energy to mechanical energy is known as the piezoelectric effect. The sound then bounces back off the object under investigation. The sound hits the piezoelectric crystal and then has the reverse effect - causing the mechanical energy produced from the sound vibrating the crystal to be converted into electrical energy. By measuring the time between when the sound was sent and received, the amplitude of the sound and the pitch of the sound, a computer can produce images, calculate depths and calculate speeds.
this is not how they are made naturally but how they are made for diagnostic uses: ultrasound waves are made by applying a current that is similar to the natural frequency of the piezoelectric quartz crystal, when this is applied to the crystal they produce ultrasonic waves! ADDED: As a point of detail, quartz is rarely if ever used now, replaced by much more sensitive, artificial, piezoelectric ceramics.
When you squeeze a piezoelectric crystal, electricity forms. This is helpful in products such as watches, microphones, computers, and gas grills.
When an electric current is passed through a piezoelectric crystal, it will cause the crystal to deform or vibrate due to the inverse piezoelectric effect. This effect converts electrical energy into mechanical movement, causing the crystal to physically change shape. This property is utilized in devices such as piezoelectric sensors, actuators, and transducers.
To make a piezoelectric crystal, you need to start with a material that exhibits piezoelectric properties, such as quartz or certain ceramics. These materials can be shaped into a crystal form through processes like cutting, grinding, and polishing. Once the crystal is formed, electrodes can be attached to it to allow for the generation of an electric charge when mechanical stress is applied. This process requires precision and expertise to ensure the crystal functions effectively as a piezoelectric device.
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When an electric current is passed through a piezoelectric crystal, the crystal experiences mechanical deformation or vibrations due to the inverse piezoelectric effect. This effect causes the crystal to change shape or generate vibrations in response to the electrical input. Conversely, when the crystal is mechanically stressed, it generates an electric charge along its surface due to the direct piezoelectric effect. This dual behavior allows piezoelectric crystals to convert electrical energy into mechanical motion and vice versa.
All the (pairs of ) surfaces of a piezoelectric crystal do not have the same piezo properties. And the temperature coefficient also alters at different angles through the crystal. So commonly, the 'BT' cut is the one with the lowest temperature coefficient.
When a piezoelectric crystal is mechanically deformed, it generates an electric voltage. This is due to the conversion of mechanical energy into electrical energy within the crystal lattice structure. The crystal can then be used to convert mechanical vibrations or pressure changes into electrical energy or vice versa.
A commonly chosen direction to cut piezoelectric crystals is perpendicular to the polar axis of the crystal. This direction optimizes the piezoelectric properties and enhances the performance of the crystal. Additionally, the orientation of the crystal lattice should also be considered when deciding the cutting direction to achieve the desired functionality.