Dielectric ceramics are also called dielectric ceramics. A functional ceramic that has polarization ability under the action of an electric field and can establish an electric field in the body for a long time. They can be divided into electrical insulation, capacitors, piezoelectric, pyroelectric and ferroelectric ceramics according to their use and performance. It has the characteristics of high insulation resistivity, small dielectric constant, small dielectric loss, good thermal conductivity, small expansion coefficient, good thermal stability and chemical stability. It is used to install, fix, and protect electronic components, as an insulating support for current-carrying conductors, and as a ceramic material for various circuit substrates.
The main materials are alumina, corundum, mullite, forsterite, magnesia, zirconia, zircon, boron nitride, aluminum nitride, beryllium oxide, hectorite, and various glass ceramics.
There are many types of capacitor ceramic dielectric materials, including low-frequency BaTiO3 series ceramics, high-frequency MgTiO3 and CaTiO3 series ceramics, high-voltage and large-capacity SrTiO3 series ceramics, and low-frequency high-medium monolithic capacitors Pb (Mg, Nb) O3 series porcelain and so on.
There are also many types of microwave dielectric ceramics. Currently, there are (Mg, Ca) TiO3 series (ε≃20) and BaO · 4TiO2 series, 2BaO · TiO2 series, Pb (Mg, Nb) O3 series, Pb (Zn, Nb) O3 series, Ba (Zn, Nb) O3 series, Ba (Sr, Ta) O3 series (their ε are between 30-40), BaO-Nd2O3-TiO2, BaO-Sm2O3-TiO2 rare earth mixed crystal system (ε = 70-90), etc.
This type of ceramic has low dielectric loss and high mechanical strength, and has been widely used in substrate materials. The biggest advantage of beryllium oxide is its high thermal conductivity, but its manufacturing process is complicated, its cost is high, and its toxicity is high, which limits its use. The thermal conductivity of silicon carbide is better than that of alumina. Some people have adopted the hot pressing method and have made high-performance substrates. The performance can still meet the practical requirements when working to about 200 ° C. However, due to the toxicity of the additives, the hot pressing sintering process is complicated. Limited its development