Explanation

ferroelectric materials is a kind of crystalline materials with spontaneous polarization in a certain temperature range, and the direction of spontaneous polarization can be changed by an external electric field, also known as ferroelectric body. When there is no external electric field, the spontaneous polarization exists in crystal. The small areas with the same direction are called domains, and the junction between domains is called domain walls. Because of the spontaneous polarization of the electric dipole and the existence of the electric domain, the change of the polarization strength P of ferroelectric body lags behind the change of the applied electric field E, that is, it has an electric hysteresis loop. ferroelectric body can change from phase of ferroelectrics to paraelectric phase with temperature, and its phase transformation temperature is called Curie temperature (Tc). When the temperature T is greater than the Curie temperature Tc, the ferroelectric phenomenon disappears and becomes a paraelectric phase. The polarization strength P is linear with the applied electric field E. When the temperature T is less than the Curie temperature Tc, it is a ferroelectric phase, and the polarization strength P has a hysteresis relationship with the applied electric field E. ferroelectric body have dielectric anomalies. Near the Curie temperature Tc, the dielectric constant can rapidly increase by 4-5 orders of magnitude with the increase of temperature. There are two main types of common ferroelectric materials: one is water-soluble soft iron electrics with hydrogen bond, represented by potassium dihydrogen phosphate (KH2PO4), in which the transformation from paraelectric phase to ferroelectric phase is from disorder to order; The other type is hard ferroelectrics with perovskite structure represented by barium titanate (BaTiO3), whose spontaneous polarization is caused by the relative displacement between the positive ion sublattice and the negative ion sublattice.

Classification