High thermal conductivity aluminum nitride ceramics for high power microwave tubes

Sienna Technologies, Inc., has successfully developed a family of high thermal conductivity aluminum nitride (AlN) based dielectrics as an alternative to BeO and BeO-SiC composites in microwave tubes. A pressureless sintering process was developed to fabricate high thermal conductivity (185-200 W/m-K), low loss (tan /spl delta/ = 0.0007 at 9 GHz), pure AlN for collector rods and rf windows. The collector rods were successfully tested in two different tube designs. The thermal performance of our ST-180 grade AlN collector rods is illustrated.