The coercive field for a ferroelectric material is the electric field required to switch its polarisation from remanent [PR] to zero polarisation [P = 0]. The value of Ec for a ferroelectric crystal is dependant on many parameters including thermal & electrical history, envionmental factors, as well as type and area of switching electrodes.

This is defined as the temperature at which a ferroelectric material undergoes a crystallographic phase change from an asymmetrical, non-centrosymmetric structure to a centrosymmetric crystal structure, thus losing it spontaneous polarisation. It is determined at zero applied field.

A ferroelectic material is a material that exhibits, over some range of temperature, a spontaneous electic polarisation that can be reversed or reorientated by application of an electric field [poling].

The frequency constant, N, is the product of the resonant frequency and the linear dimension governing the resonance. There are various modes of resonance including radial mode, plate length mode, cylinder length mode, thickness mode (plate, disc) and plate shear mode.

These are the piezoelectric constants that relate the electric field that can be generated from an applied mechanical stress. It is defined as the ratio of the electric field produce to the mechanical stress applied. The units for these constants are Volt.meter per Newton (V.m.N-1)

Piezoelectricity is the generation of electricity as a result of a mechanical pressure, or more precisely... "electrical polarisation produced by mechanical strain in crystals belonging to certain classes, the polarisation being proportional to the strain and changing sign with it."

Defined as the incremental change in electric displacement per unit electric field when the magnitude of the meausring field is very small compared to the coercive electric field.

Polarisation is the electric dipole moment per unit volume, and is related to electric displacement, D though the linear expression: Di= Pi+ e0Ei

Poling is the electrical process by which the myriad of randomly orientated crystallites, each containing many domains (only a few allowed orientations), in a polycrystalline ferroelectric ceramic are aligned to produce a useful electroactive material. Without this orientation the material is unlikely to exhibit any net macroscopic polarisation.

Pyroelectric materials characteristically develop an electric polarisation if their temperature is changed. All pyroelectric crystals are necessarily piezoelectric, with some also being ferroelectric .