Ferroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field.[1][2] All ferroelectrics are pyroelectric, with the additional property that their natural electrical polarization is reversible. The term is used in analogy to ferromagnetism, in which a material exhibits a permanent magnetic moment. Ferromagnetism was already known when ferroelectricity was discovered in 1920 in Rochelle salt by Valasek.[3] Thus, the prefix ferro, meaning iron, was used to describe the property despite the fact that most ferroelectric materials do not contain iron. Materials that are both ferroelectric and ferromagnetic are known as multiferroics.
https://en.wikipedia.org/wiki/Ferroelectricity
Paraelectricity is the nominal behavior of dielectrics when the dielectric permittivity tensor is a diagonal matrix, i.e., an applied electric field causes polarization and/or alignment of dipoles only parallel (and opposite) to the applied electric field. Contrary to the analogy with a paramagnetic material, no permanent electric dipole needs to exist in a paraelectric material. Removal of the fields results in the polarization returning to zero.[12] The mechanisms that causes paraelectric behaviour are distortion of individual ions(displacement of the electron cloud from the nucleus) and polarization of molecules or combinations of ions or defects.
Paraelectricity can occur in crystal phases where electric dipoles are unaligned and thus have the potential to align in an external electric field and weaken it.
Most dielectric materials are paraelectrics. A specific example of a paraelectric material of high dielectric constant is strontium titanate.
The LiNbO3 crystal is ferroelectric below 1430 K, and above this temperature it transforms into a disordered paraelectric phase. Similarly, other perovskites also exhibit paraelectricity at high temperatures.
Paraelectricity has been explored as a possible refrigeration mechanism; polarizing a paraelectric by applying an electric field under adiabatic process conditions raises the temperature, while removing the field lowers the temperature.[13] A heat pump that operates by polarizing the paraelectric, allowing it to return to ambient temperature (by dissipating the extra heat), bringing it into contact with the object to be cooled, and finally depolarizing it, would result in refrigeration.
https://en.wikipedia.org/wiki/Dielectric#Paraelectricity
In electromagnetism, a dielectric (or dielectric material) is an electrical insulator that can be polarized by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor, but instead only slightly shift from their average equilibrium positions, causing dielectric polarization. Because of dielectric polarization, positive charges are displaced in the direction of the field and negative charges shift in the direction opposite to the field (for example, if the field is moving parallel to the positive x axis, the negative charges will shift in the negative x direction). This creates an internal electric field that reduces the overall field within the dielectric itself.[1] If a dielectric is composed of weakly bonded molecules, those molecules not only become polarized, but also reorient so that their symmetry axes align to the field.[1]
The study of dielectric properties concerns storage and dissipation of electric and magnetic energy in materials.[2][3][4] Dielectrics are important for explaining various phenomena in electronics, optics, solid-state physics, and cell biophysics.[5][6]
https://en.wikipedia.org/wiki/Dielectric
Ferroelectric and Antiferroelectric Liquid CrystalsBy Sven T. Lagerwall
https://books.google.com/books?id=pHOLlDUogDMC&pg=PA421&lpg=PA421&dq=Helielectricity&source=bl&ots=wE-Qm744BZ&sig=ACfU3U3DLovY6Z4ggBMu7Z0ajjJ0_umCIw&hl=en&sa=X&ved=2ahUKEwiXsq3U_P3yAhWqc98KHRUUB1MQ6AF6BAgLEAM#v=onepage&q=Helielectricity&f=false
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