Research and development of microwave dielectric ceramics for wireless communications

Intense research and development of microwave and millimeterwave dielectric materials is expected for applications in the wireless communications in the ubiquitous age. There are three important directions for research and development of microwave and millimeterwave dielectric materials. We have been studying on these three directions based on the crystallography. In the first direction for miniaturization of mobile equipments, tungsten-bronze-type like Ba6-3xR8+2xTi18O54 (R = rare earth) solid solutions with high dielectric constant have been studied to improve quality factor based on the compositional ordering of cations. For the second direction for applications in mobile phone base stations, we have developed homologous A La4Ti4O15 (A = Ba, Sr and Ca) compounds with excellent dielectric properties such as high dielectric constant and high quality factor. For the third direction, dielectric ceramics of silicate compounds such as forsterite Mg2SiO4 and willemite Zn2SiO4, and alumina are expected for millimeterwave applications. The dielectric ceramics with high quality factor are obtained by using high purity raw materials. Temperature coefficients of resonant frequency tau(f) of these materials are improved adding rutile with high positive tau(f).