Explanation

Small areas in ferroelectric body with the same direction of spontaneous polarization. Those arranged in an antiparallel manner are called 180 ° domains; A 90 ° electric domain is one that is arranged 90 ° from end to end. The wall thickness of the 180 ° domain wall is about a few units, and the 90 ° domain wall is thicker than the 180 ° domain wall. The type of domain is related to the symmetry of crystal. For example, barium titanate crystal has 90 ° and 180 ° domains when it is in tetragonal crystal; In the orthogonal phase, there are 60 °, 120 °, 90 ° and 180 ° domains; There are 71 °, 109 ° and 180 ° domains in the tripartite phase. Ferroelectric crystals are usually multi domain, corresponding to lower energy states. The domain can usually be observed by transmission electron microscope, optical microscope, coating method, chemical corrosion method, thermal corrosion method, etc. Under the action of an electric field, domain walls can move. Electric domains that are basically consistent with the direction of the electric field grow forward through needle like new domains and eventually tend towards the direction of the electric field. The domain is related to spontaneous polarization, so it exists in the temperature range below the curie point. When the temperature is higher than the curie point, the domain disappears. The domain of transparent ferroelectric ceramics has "electric control characteristics", that is, the orientation state of the domain is controlled by the electric field; However, the orientation of the electric domain changes the optical i properties of materials, which can be used to make optical switches and optical memory devices.

Classification