Millimeter-wave Dielectric Ceramics of Alumina and Forsterite with High Quality factor and Low Dielectric Constant

Abstract

Millimeter-wave dielectric ceramics have been used like applications for ultrahigh speed wireless LAN because it reduces the resources of electromagnetic wave, and Intelligent Transport System (ITS) because of straight propagation wave. For millimeter-wave, the dielectric ceramics with high quality factor (Q·f), low dielectric constant(e r ), and nearly zero temperature coefficient of resonant frequency (τ f ) are needed. No microwave dielectric ceramics with these three properties exist except Ba(Mg 1/3 Ta 2/3 )O₃ (BMT), which has a little high τ f . In this paper, alumina (Al₂O₃) and forsterite (Mg₂SiO₄), candidates for millimeter-wave applications, were studied with an objective to get high Q·f and early zero τ f . For alumina ceramics, Q·f more than 680,000 GHz was obtained but it was difficult to obtain nearly zero τ f . On the other hand, for forsterite ceramics, Q·f was achieved from 10,000 GHz of commercial forsterite to 240,000 GHz of highly purified MgO and SiO₂ raw materials, and τ f was reduced a few by adding TiO₂ with high positive τ f .