What is the Ferroelectric Effect?
The ferroelectric effect is the property of certain dielectric materials to exhibit spontaneous electric polarization, which can be reversed by applying an external electric field. Ferroelectrics retain polarization even without a field and show a characteristic hysteresis loop in a Polarization vs. Electric Field graph, similar to ferromagnets with magnetization.
How is the Ferroelectric Effect Produced?
- Occurs in crystals with non-centrosymmetric structures.
- Produces separated centers of positive and negative charge, resulting in electric dipoles.
- When cooled below the Curie temperature (Tc), dipoles spontaneously align to create domains of polarization.
- The polarization direction can be switched by a strong external electric field.
- Examples of ferroelectric materials include Barium titanate (BaTiO3) and Rochelle salt.
Uses of Ferroelectric Materials
- Non-volatile Memory (FeRAM): Stores binary data with remnant polarization, retaining information without power.
- Sensors and Actuators: All ferroelectrics are piezoelectric, used in microphones, ultrasound, and transducers.
- Capacitors: Used in tunable and high-permittivity capacitors due to a high dielectric constant.
- Electro-optic Devices: For optical switches and modulators, as their polarization modulates light.
- Pyroelectric Detectors: Sensitive to temperature changes, applied in infrared and thermal sensors.