Low‐Temperature Sintering and Microwave Dielectric Properties of Li₂MgSiO₄ Ceramics

Abstract

Development of a low-temperature sintered dielectric material derived from Li 2 MgSiO 4 (LMS) for low-temperature cofired ceramic (LTCC) application is discussed in this paper. The LMS ceramics were prepared by the solid-state ceramic route. The calcination and sintering temperatures of LMS were optimized at 8501C/4 h and 12501C/2 h, respectively, for the best density and dielectric properties. The crystal structure and microstructure of the ceramic were studied by the X-ray diffraction and scanning electron microscopic methods. The microwave dielectric properties of the ceramic were measured by the cavity perturbation method. The LMS sintered at 12501C/2 h had e r 5 5.1 and tan d 5 5.2 Â 10 À4 at 8 GHz. The sintering temperature of LMS is lowered from 12501C/2 h to 8501C/2 h by the addition of both lithium borosilicate (LBS) and lithium magnesium zinc borosilicate (LMZBS) glasses. LMS mixed with 1 wt% LBS sintered at 9251C/2 h had e r 5 5.5 and tan d 5 7 Â 10 À5 at 8 GHz. Two weight percent LMZBS mixed with LMS sintered at 8751C/2 h had e r 5 5.9 and tan d 5 6.7 Â 10 À5 at 8 GHz.

Influence of B₂O₃ on sintering behavior and the dielectric properties of Li₂MgSiO₄ ceramics

“…There is a negligible influence of B 2 O 3 content on the ). For comparison purposes, the dielectric properties of other LMS ceramics reported in an earlier study 9) are also presented in …”

“…On the contrary, in the SEM images in Ref. 9), the presence of the glassy phases seems to cause more pronounced changes in the microstructure of the sintered LMS ceramics. Consequently, in this study, all this effort to improve sintering was significantly simplified (since there is no need to prepare first the glasses, but just to add B 2 O 3 powder directly in the precursor powder mixture).…”

“…Moreover, the resultant ceramics had excellent microwave dielectric properties of ¾ r = 5.5 and tan ¤ = 7.0 © 10 ¹5 at 8 GHz. 9) Nevertheless, preparation of LBS glass is timeconsuming, which increases the production cost.…”

“…For comparison purposes, pellets of B 2 O 3 -free LMS were also produced in a similar way but sintered at 1250°C. This temperature was chosen because an earlier study 9) has reported that sintering of pure LMS at 1250°C is optimal for achieving maximum densification.…”

“…The values of ¾ r and tan ¤ were calculated from the resonant frequency and the geometric dimensions using the HakkiColeman dielectric resonator method and the relevant (HakkiColeman) program (details for the cavity perturbation technique are provided in Ref. 9). All measurements were conducted at room temperature.…”