The response of the material to the external electric field has two basic forms: electrical conductivity and electrodeization. The electrodeization is the relative deviation of the center and negative charge, which is polarizable, that is, the polarization of polarization is not zero. Polarization intensity (referred to as polarization) P is vector and: p = σpi / v = σ Qi II / V, PI is electricity torque, II is charge -QI to + Qi Vector. A substance that can be established or polarized under an electric field is referred to as a dielectric. The research content of dielectric physics mainly has two aspects: 1 microscopic mechanism and polarization process of polarization; 2 changes in polarization state under various external conditions and changes in physical properties caused. Through these studies, the process and regularization of electrodeization from the atomic and molecular levels, clarify the relationship between the macroscopic properties of the medium, to improve the performance of the dielectric, develop new dielectric materials and expand the electrical medium. The development of simple history of humanity to the electrical medium is starting from electrical insulation, and the dielectric is actually used as an electrical insulating material. With the development of electrician and electronic technology, the dielectric is widely used as a capacitor material. Adapt to these two major applications, people begin to study the electrical medium from physics, gradually forming dielectric physics based on polarization, loss, conductance, and breakdown of four parameters as basic content. Although piezoelectricity was discovered in 1880, ferroelectricity was discovered in 1920, but the emergence of new types of electric media such as ferroelectrics after the 1960s, the application of dielectric physics has made great progress. People try to clarify the microscopic mechanism of polarization (including spontaneous polarization) from a unified point of view, and the polarization state changes under various external conditions, and use various experimental means and theoretical methods, which deepens and enrich the electrical physics. The study made it break through the scope of the four major parameters. The electric capacitance and polarization rate occur in the electric field, the polarization changes is the most basic characteristic of the dielectric, so the main parameter of the description of the dielectric is the capacitance (i.e., the dielectric constant) and the dielectric polarization. The electric capacitance ε is the change rate of the electric field E of the medium in the medium. In the linear dielectric of the sameby, ε = d / e = (ε0e + p) / e, where P is polarization, ε0 is a vacuum capacitor. εr = ε / ε0 called the relative capacitance. There is energy loss during polarization, in general, the capacitance should be represented by a reset: εr = ε'r-ε "r. Energy loss in units of units is proportional to TANδ = ε" r / ε'r TAN δ is called dielectric losses. The dielectric polarization rate χ is proportional to the change rate of the polarization to the electric field: χ = p / (ε0e), obviously εr = 1 + χ. The generation and change of polarization is the result of the relative shift of the positive and negative charge in the atom or molecule, from the micro-description polarization to introduce the atomic polarization or molecular polarization rate α, α = p / e1, and E1 is acting The electric field of the atom or molecule, P is the electrode torque caused by the electric field. The electric field in the electric field dielectric in the medium is the sum of the electric fields generated by the external electric field and the polarized dielectric. A microscopically macro-small test charge is called a macro electric field than the power of the power in the electric field. The electric field in macro-nature parameters (such as the capacitance and dielectric precipitation rate, etc.) is a macro electric field. The macro electric field in the dielectric is equal to the sum of the external electric field and the dental field, and the latter is the contribution of the dielectric. The polarized dielectric occurs on its surface, which is always opposite the electric field generated inside the medium to the polarization direction, so the name retreating field. When the dielectric (eg, the atomic polarization rate or molecular polarization rate) is written, it is necessary to know the effective electric field for a polarization of a certain atom or molecule. It is characterized by microscopic scales, usually significantly different from the position considered. This is a micro-field. In order to emphasize it differently, it is often known as a dielectric local field. The polarized dielectric is composed of a plurality of diphesis because each polarized atom or molecule is a dipole. These diphes will have an electric field in consideration. The local field is equal to the electric field produced in this point in this point in the medium or molecular medium except for the three electric fields. In order to calculate the latter, H.A. Lorenz proposed a method. It is envisaged to dig a macroscopically smart spherical cavity in the medium. The sphere is truly considering the arrangement of atom or molecules, and the pockets of the ball are calculated from the electric field produced by the considered point. Outside the ball is treated as a continuous medium. The calculation shows that if the arrangement of the dipole has a cubic symmetry or is completely random, the ball internally pole is zero in the considered electric field, the local field is equal to the external electric field, and the fell and P / ( The sum of the macro field and P / (3ε0). However, the electric pods here are electrically induced, and the results of Lorentz are not applicable to the polar media of the molecule having an intrinsic electrocouple torque. Totally, the local field problem has not been solved so far. The polarization of the polarization mechanism dielectric has three main mechanisms, namely electronic polarization, ionized polarization, and dipole steering polarization. Electronic polarization is a polarization mechanism that is generally existed in all materials. The electron is offset under the electric field, so that the negative charge of the electronic cloud is not coincident with the positive charge center of the atomic core to form an electric dipper. The electronic quality is very small, and the electron movement can still be in response to the optical electric field, so electronic polarization is present in DC to the optical frequency range. In fact, the optical electric field is the only polarization mechanism of electron polarization. The polarization characteristics of dielectric optical frequency are represented by refractive index n. The refractive index of the non-magnetic dielectric is equal to the square root of the relative capacitance: n = (εr) 1/2. Ion polarization is that the positive and negative ions in the ion crystals are deviated from the balanced position at the electric field. This polarization can be considered instantaneously in the low frequency electric field, but the frequency is raised to the infrared zone, and the ion movement has not changed the electric field, so this polarization in an electric field in infrared and higher frequencies no longer exists. Some substances (such as water, etc.) have an inherent dipole due to the asymmetry of the molecular structure. The electrocouple electrodes in the electric field are turned to a torque to go to the direction parallel to the electric field. In addition to the dipole caused by this molecular structure itself, the so-called "defective dipole" is more common. It is formed from a dot defect in the electricity, and a steering motion occurs under an electric field. The steering motion of the dipole in the electric field is a thermal activation process, so the response is slow. The response time depends on activation and temperature, usually from 10-8 to 10-3 seconds or longer. The above three polarizations appear under the action of electric field. There are some dielectric, such as barium titanate (BatiO3) and pelvic dihydrogen (KH2PO4), etc., there is no need to have spontaneous polarization in its respective feature temperatures, but it has spontaneous polarization, and spontaneous polarization can change under electric field. direction. Such dielectrics are referred to as ferroelectrics. The electricity capacitance of the ferroelectric is much larger than that of the ordinary dielectric, and the polarization is electrically stagnant to the electric field at a strong electric field. In-depth clarity of the mechanism of polarization, especially the cause of spontaneous polarization is a major aspect of dielectric physics. Functional effects have a variety of external conditions, and the polarization state of the dielectric changes, resulting in its performance change and some new properties, which is the functional effect of the dielectric. The medium is polarized under an electric field and the polarization changes, and the medium is isolated from DC power, but the alternating current can be passed through the induction. The greater the capacitance, the more charges appear in the surface of the electrode, the more energy stored in the medium. According to this characteristic dielectric, it is used to use a large amount as a capacitor material. The state of spontaneous polarization orientation in the ferrule is two stable states. A sufficiently strong alternating electric field can cause spontaneous polarization to reverse, thereby alternately with a positive and negative charge of equal quantity on the electrode. This positive and negative charge and bistable correspondence can be used to store information. This is the basis of currently widely studied non-volatile ferroelectric memory. Some dielectrics do not have symmetric centers, such as α-quartz crystals, all ferrics, and the electrical field can be induced and proportional, and the stress can be induced and proportional, which is the piezoelectric effect (see pressure) Electricity). Many sensors and transducers have been developed using a piezoelectric effect to account for an important role in high-tech. The electric field in any dielectric can result in a strain corresponding to its square formation, called an electrostrictive effect. Some dielectrics are quite large in some relaxation ferroelectrics, and thereby developing electrolatured materials, which have been developed, and a precision displacement is made. Self-polarization of dielectric is a function of temperature. The change in polarization when the temperature changes will cause the charge release and absorption in the outer circuit connected to the dielectric, referred to as thermoelectric effects (see thermal electricity). The thermoelectric material is important in infrared detection and thermoelectric imaging. The electret is a class of dielectric materials having long-term storage chargeability, and the functional effects such as piezoelectric and thermoelectric and thermoelectric and electroacoustic sensors and electrostatic photocopying techniques have been widely used. The polarization process of the electrical electric field under the electrical electric field is manifested as the optical vibration of the electron with respect to the nuclear nuclear vibration, and the polarized substance is an emission source of electromagnetic waves (optical wave). If the incident optical electric field is strong, it will cause nonlinear polarization, i.e., twice or more than the incident optical frequency in the transmitted optical wave. This is the performance of nonlinear optical effects. Nonlinear optical effects are the basis for techniques such as laser multiplier. The evolution of the optical range polarization is represented by a refractive index, equal to the square root of the optical relative capacitance. The refractive index can vary depending on the various fields. Changes in refractive index under DC or low frequency strong electric fields are called electro-optical effects. Changes in refractive index under stress action are called sound light effects. The change in refractive index under optical strong electric field is referred to as light transformation effects. Based on these effects, electro-optic materials, sound light materials, and light-transforming materials are developed, respectively. They have important applications in optical and optical electronic technology. Dielectric breakdown electrical insulation characteristics are different from the above various properties, referring to the resistance of dielectric on strong electric fields, the main indicator is the breakdown strength, that is, the largest electric field that is not broken through. Breeding is a large number of stimulation, strong transfer, and cause structural destruction. Although the electrical insulating material is related to the polarization limits of binding charges under strong electric field, it is mainly not a polarization problem. The historical medium and the insulator are almost synonymous. At that time, the dielectric was applied as an insulating material. Later, a variety of functional effects were found in the dielectric, which greatly expanded the application range of the dielectric. However, due to the use of electrical use inventory, it is indispensable for electrically insulating materials in the past, or in the future, the electrical insulation characteristics are also research contents of dielectric physics. The breakdown of the solid electrical medium has three types of electric shock, hot shot and chemical breakdown. Electric shock and wear is called this. There is always a small amount of conduction electrons in the medium, which is accelerated in the strong electric field, and the resulting energy exceeds its energy loss with the lattice, which can cause collision ionization in the medium, and the resulting electrical conductive rises sharply. Result in breakdown. When the heat generated by the conductance and dielectric loss exceeds the calorim of the sample, the heat balance in the sample is destroyed by conducting, convection, and radiation, the temperature of the sample is destroyed, and the temperature is constantly rising, which is the hotteath. . Chemical breakdown originated from electrochemical reactions. The current generated by strong electric field in the medium can cause electrochemical reactions under high temperature and so on, such as electrolysis, reduction or the like. The separated substance constitutes a conductive path between the two electrodes, or the gas bubble discharges in the medium forms carbon monoxide and the wall contact, so that the local electrical conductivity increases the local breakdown, and finally expands to complete breakdown. The breakdown of dielectric involves the structure, impurity, defects, electronics and phonics and electronics and electrons interaction, although it has been working hard, but still has not been well solved. Recommended Book Each Lights. Beijing: Science Press, 1996. Xia Zhongfu. Eramy. Beijing: Science Press, 2001. Yin Zhi, Fang Junxin. Dielectric Physics. Beijing: Science Press, 2003. P>
