- An effect exhibited by certain quartz crystals (such as lead zirconate titanates) known as ‘piezoelectric crystals’:
- Also exhibited by certain ceramics and biological materials such as collagen and DNA
- The piezoelectric crystal will change shape when an electrical potential is applied across it:
- Dimensions change slightly depending upon the polarity of the applied voltage
- Change in shape causes local changes in pressure, leading to mechanical waves (ultrasonic radiation) being generated at the exact frequency of the applied voltage
- The converse effect occurs when pressure is applied to a piezoelectric crystal:
- Compressive stress causes a change in dimensions of the crystal
- Generates an output voltage at the frequency of the compressive waves
- Allows piezoelectric crystals to act as transducers:
- Direct effect converts mechanical energy into electrical energy
- Converse effect converts electrical energy into mechanical energy
