What Are Ferroelectric Ceramics?

Ferroelectric ceramics, ceramic materials whose main crystal phase is ferroelectric. Common ferroelectric ceramics are mostly perovskite-type structures, such as barium titanate ceramics and their solid solutions. There are also tungsten bronze types, bismuth-containing layered compounds, and pyrochlore types. The principle of determining the formula of ferroelectric ceramics: move first and then develop, with some emphasis; consider it separately and make comprehensive adjustments. ^[1]

Ferroelectric ceramics. Spontaneous polarization at Curie temperatures. There are many electrical domains in ceramics. The important feature of ferroelectric ceramics is that their polarization intensity does not have a linear relationship with the applied voltage and has a significant hysteresis effect. Because the electrical properties of these ceramics are similar to the magnetic properties of ferromagnetic materials, they are called ferroelectric ceramics. Iron is not necessarily the main ingredient. ^[2]

Some dielectrics can be spontaneously polarized. The phenomenon of spontaneous polarization reorientation under the action of an external electric field is called a ferroelectric effect. Ceramics with this property are called ferroelectric ceramics. Ferroelectric ceramics have hysteresis loops and Curie temperatures. At the Curie temperature point, the crystal changes from a ferroelectric phase to a non-ferroelectric phase, and its electrical, optical, elastic, and thermal properties have anomalous phenomena, such as a maximum dielectric constant. In 1941, the United States first made barium titanate ferroelectric ceramics with a dielectric constant of up to 1100.

Common ferroelectric materials are mostly perovskite-type structures, such as BaTiO ₃ , PbTiO ₃ , SrTiO ₃ and so on. In addition, tungsten bronze structural materials include PbNb ₂ O ₆ , Sr _1-x Ba _x Nb ₂ O ₆ , Ba ₂ NaNb ₅ O ₁₅ and the like. The pyrochlore structure material includes Cd ₂ Ta ₂ O ₇ , Pb ₂ Nb ₂ O ₇ , Cd ₂ Nb ₂ O ₇ and the like. Layered bismuth oxide structural materials include Bi ₄ Ti ₃ O ₁₂ , PbBi ₂ Nb ₂ O ₉ and the like. More than a thousand ferroelectric oxide ceramics have been obtained through solid solution, ion substitution and doping modification. Non-oxide ferroelectric ceramics are developing. It can be used to generate capacitance, piezoelectric, thermal, electrostrictive, electroacoustic, electro-optical and other effects, as materials for sensing, driving, storage, modulation and other devices.

Ferroelectric

Its main characteristics are:

(1) Certainly

The properties of ferroelectric ceramics determine its use. With its high dielectric constant, large-capacity capacitors, high-frequency microcapacitors, high-voltage capacitors, multilayer capacitors, and semiconductor ceramic capacitors can be manufactured, with capacitances up to 0.45 F / cm ² . Using its characteristic that the dielectric constant changes non-linearly with the external electric field, dielectric amplifiers and phase shifters can be fabricated. Using its pyroelectricity, infrared detectors can be made. In addition, there is also a transparent ferroelectric ceramic, such as lead oxide (lanthanum), zirconium oxide (titanium) series transparent ceramics, which has an electro-optical effect (that is, a change in an electric domain state accompanied by a change in optical properties). By applying an external electric field to control its electrical domain state, it generates electronically controlled birefringence, electrically controlled light scattering, electrically induced phase change, and electrically controlled surface deformation. It can be used in the manufacture of light valves, light modulators, light memories, light displays, photoelectric sensors, spectral filters, laser protective glasses and thermoelectric detectors.