When an electric field is applied to a material in a capacitor, the electric field causes polarization in the material through electronic, ionic, and molecular polarization. The three primary contributions to the dielectric constant are electronic, ionic, and molecular polarization. Electronic polarization responds the fastest, while ionic and molecular polarization respond slower. The four primary dielectric breakdown mechanisms are thermal, avalanche, discharge, and electrolytic. The breakdown strength can be improved through using high purity materials with low defect densities. Ferroelectrics exhibit spontaneous polarization without an applied electric field and have applications in non-volatile RAM, dynamic RAM, tunable microwave devices, pyroelectric detectors, piezoelectric sensors and actuators.

4. Polarization in Insulators Positively charged species in insulators shift/rotate/align toward the negative electrode and negatively charged species shift/rotate/align towards the positive electrode; creating dipoles. The dipole moment density is termed the Polarization (P) and has the units of C/m 2 . + - Electron Cloud Electron Cloud + E Electronic polarization, occurs in all insulators - + + + - + + E Ionic polarization occurs in all ionic solids: NaCl, MgO… - - - - + - - + + - + + E Molecular polarization, occurs in all insulating molecules; oils, polymers, H 2 O… Electric Dipole Moment Polarization

5. Frequency Response (Switching Time) Electronic Polarization Ionic Polarization Molecular Polarization

12. Ferroelectrics

13. Spontaneous Polarization

14. Electrostriction and Piezoelectricity FEs possess a spontaneous strain. This is called electrostriction . The FE crystal can be deformed by the application of an electric field or it generates a potential when there is an applied stress. This is called piezoelectricity.

15. Pyroelectricity The spontaneous polarization is strongly dependent on the temperature. It dissapears completely at the phase transformation temperature T C . The variation in the polarization with respect to the temperature is called the pyroelectric effect .

17. Non-Volatile RAMs (memory)

18. Non-Volatile RAMs (memory) Smart cards use ferroelectric memories. They can hold relatively large amounts of information and do not wear out from use, as magnetic strips do, because they use contactless radio frequency input/output. These cards are the size and shape of credit cards but contain ferroelectric memory that can carry substantial information, such as its bearer's medical history for use by doctors, pharmacists and even paramedics in an emergency. Current smart cards carry about 250 kilobytes of memory.

20. Tunable Microwave Devices / Optical Waveguides Filters Phase shifters Delay lines Oscillators   ( E =0)

21. Pyroelectric Detectors/Sensors

22. Pyroelectric Detectors/Sensors

23. Piezoelectric Sensors/Actuators, MEMS

24. Piezoelectric Sensors/Actuators, MEMS