MICROWAVE PROCESSING OF DIELECTRICS FOR HIGH POWER MICROWAVE APPLICATIONS

摘要

While most electronic applications are moving rapidly towards solid-state devices, high power microwave communication devices still utilize vacuum tube technology to achieve the required power density. Traditionally BeO and BeO composites were used as support and tuning dielectrics. However, AlN based materials are now desirable due to the health effects of BeO. Dielectric constant and thermal conductivity are the key properties for high power communications. Even with liquid phase sintering it is not easy to achieve high thermal conductivity in AlN materials using conventional firing. Microwave firing promotes rapid development of thermal conductivity. With microwave firing, thermal conductivities above 200 W/mK. in pure AlN can be achieved in four hours. In addition, thermal conductivities of 100-150 W/mK can be achieved in tailored dielectric constant AlN-TiB2 and AlN-SiC tuning dielectric composites in 1-2 hours. Our approach is applicable to other applications for AlN and its composites.