Sintering conditions of cordierite for microwave/millimeterwave dielectrics

With the advent of ubiquitous age, the high- quality, dielectric materials have been required for the applications of wireless communications available to millimeterwave as well as microwave frequencies such as ultra-high speed local area network (LAN), electronic toll collection (ETS), and car anticollision systems on the intelligent transport system (ITS), and so on. Cordierite (Mg₂Al₄SiO₁₈), which is one of the silicates, is a good candidate for mi- crowave/millimeterwave dielectrics due to low dielectric constant epsiv_r and low loss. This study is focused on optimization of the sintering condition of cordierite. A single phase of cordierite could be obtained from the powders calcined from 1355degC to 1375degC for 3 hours, and the samples sintered from 1375degC to 1440degC for 2 hours. The highest relative density of 98.7% was obtained for the samples sintered at 1440degC for 2 hours. The dielectric constant and the quality factor of cordierite depend on the sintering temperatures. The density also was improved to 2.51 g/cm³ by a slower heating and cooling rate of 3degC/minute. The microwave dielectric properties are as follows: epsiv_r = 6.14, Q ldr f = 59682 GHz, and tau_f = -26.1 ppm/degC.