A new microwave ceramic with low-permittivity for LTCC applications

摘要

A new low-temperature microwave dielectric ceramic with low-permittivity was found and investigated in the CaO-MgO-SiO_2-TiO_2 system. Phase constitutes and dielectric properties of (Ca_(1-x), Mg_x)SiO_3 (x = 0.1-0.5) ceramics were studied with different x contents, and CaTiO_3 demonstrated an effective compensation in (Ca_(1-x), Mg_x)SiO_3 tau_f value. The 0.88CaMgSi_2O_6-0.12CaTiO_3 compositions show a relatively low-permittivity (approx 9.42), high Q X fvalues up to 52,800 GHz, and near-zero temperature coefficients (5.6 ppm/deg C), which were obtained via sintering at 1300 deg C. The addition of <=2.0 wt percent Li_2CO_3-V_2O_5 was very effective in lowering the sintering temperature (T_s), and dense ceramics could be obtained at T_s < = 900 deg C. The addition of Li_2CO_3-V_2O_5 does not induce apparent degradation in the microwave properties. The specimens with 1 wt percent Li_2CO_3-V_2O_5 sintered at 880 deg C for 2 h shows excellent dielectric properties: epsilion_r = 9.23, Q X f= 46,200 GHz, and tau_f = 1.3 ppm/deg 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.