PiezoceramicsThe special ceramics can expand and shrink by applying voltage
Piezoelectric ceramics is a polycrystalline ceramics that is made by sintering high pure powder like titanium oxide and barium oxide. When piezoelectric ceramics is exerted forcefully (mechanical energy is applied), it generates electric voltage (the direct piezoelectric effect). Conversely, when piezoelectric ceramics is applied with voltage, it expands or shrinks depending on the polarity of voltage (the reverse piezoelectric effect). In this manner, piezoelectric ceramics can convert electric energy to mechanical energy, and vice versa (Piezoelectric effect). By applying polarization treatment (a DC high voltage is applied on ceramics under a high temperature to orientating the spontaneous polarization), ceramics has piezoelectric effect.
Direct piezoelectric effect and reverse piezoelectric effect
Emitting ultrasound using piezoelectric ceramics
Applying alternating voltage on a piezoelectric ceramics.....
By installing electrodes on a piezoelectric ceramics and applying an alternating voltage, the ceramics vibrates to emit sound due to the piezoelectric effect.
A vibration using a resonance frequency can generate ultrasound having a larger amplitude. As a resonant frequency depends on the shape of ceramics, a piezoelectric ceramics is made in a suitable shape for obtaining a necessary frequency.