5.4.7 Applications of Piezoelectric Ceramics

Piezoelectric ceramics are used in a variety of applications utilizing either direct or converse piezoelectric effect.  The following are some applications of the piezoelectric ceramics:

5.4.7.1 Power Generation

• Gas Lighter

Piezoelectric material can ignite the gases by generating a spark via an electric current. This requires two piezoelectrics with opposite polarization states which are brought close to each other so those polarization vectors are in the opposite directions i.e. faces containing similar charges are together. The piezoelectric are placed in a circuit with a spark gap.

Now, application of a mechanical stress or force will induce change in the polarization. The force brings together these two pieces which then gives rise to creation of charges. The charges flow from the end faces and the middle (pressed) faces through the circuit giving rise to a spark in the spark gap which can be used to ignite a gas.

One must apply the force quickly otherwise the voltage generated disappears because the charges leaks away through the piezoceramic, across its surfaces and via the apparatus.

• Power Transformer

A piezoelectric transformer works like an AC voltage multiplier. While conventional transformers utilize magnetic coupling between input and output, the piezoelectric transformer exploits the acoustic coupling utilizing inverse piezoelectric effect. Piezo transformers can be quite compact high voltage sources.

An input smaller voltage across the thickness of a piezoceramic creates an alternating stress in the bar by the inverse piezoelectric effect. This causes the bar to vibrate with vibration frequency chosen to be the resonant  frequency of the block, typically in the 100 kHz to 1 MHz range. This generates a higher output voltage in the other section of the bar by the direct piezoelectric effect. One can achieve the step-up ratios of more than 1000:1 using this technique.