A new microwave ceramic with low-permittivity for LTCC applications

A new low-temperature microwave dielectric ceramic with low-permittivity was found and investigated in the CaO–MgO–SiO2–TiO2 system. Phase constitutes and dielectric properties of (Ca1−x,Mgx)SiO3 (x = 0.1–0.5) ceramics were studied with different x contents, and CaTiO3 demonstrated an effective compensation in (Ca1−x,Mgx)SiO3τf value. The 0.88CaMgSi2O6–0.12CaTiO3 compositions show a relatively low-permittivity (∼9.42), high Q × f values up to 52,800 GHz, and near-zero temperature coefficients (5.6 ppm/°C), which were obtained via sintering at 1300 °C. The addition of ≤2.0 wt% Li2CO3–V2O5 was very effective in lowering the sintering temperature (Ts), and dense ceramics could be obtained at Ts ≤ 900 °C. The addition of Li2CO3–V2O5 does not induce apparent degradation in the microwave properties. The specimens with 1 wt% Li2CO3–V2O5 sintered at 880 °C for 2 h shows excellent dielectric properties: ɛr = 9.23, Q × f = 46,200 GHz, and τf = 1.3 ppm/°C. The low-temperature sintering ceramics powders were suitable for the tape casting process. Also, the material is compatible with Ag electrodes, and therefore, is suitable for LTCC application.