Preparation and microwave dielectric properties of Li₂O-Al₂O₃-SiO₂ glass-ceramic used as an impedance transfer layer of microwave absorbing materials

The low thermal expansion coefficient and the moderate permittivity of Li₂O-Al₂O₃-SiO₂ glass-ceramic make it possible to be used as an impedance transfer layer of radar wave absorbing materials to increase the microwave absorbing efficiency and expand absorbing bands. But a series of accurate permittivities of impedance transfer are needed to meet the impedance matching design. Therefore, the relationship between the permittivity of the glass-ceramic and sintering conditions was studied. The results show that the real and imaginary parts of the permittivity of the glass-ceramic increase with the sintering densities, and no frequency dependency of the permittivity was found. The reflectivity-frequency curves illustrate that the attachment of the glass-ceramic to the microwave absorbing materials greatly reduces the materials' reflectivity to microwave and a little change of the permittivity of the glass-ceramic can also exert a remarkable influence on microwave absorbing materials. So an expected permittivity of the glass-ceramic is needed and can be obtained by varying sintering conditions of the glass-ceramic.