Novel low loss, low permittivity (1 − x)SiO 2 − xTiO 2 + ywt% H 3 BO 3 microwave dielectric ceramics for LTCC applications

Abstract

Abstract Novel microwave dielectric material of (1 − x)SiO2 − xTiO2 for low-temperature cofired ceramic (LTCC) application was investigated in this paper. TiO2 coated SiO2 powder prepared by a sol-gel method under solvothermal conditions (SGS) revealed an adsorption of fine TiO2 particles on the SiO2 surface. TiO2 coated SiO2 improved the microwave properties of SiO2 ceramics. As the TiO2 content x increased in the (1 − x)SiO2 − xTiO2 (0.1 ≦ x ≦0.3) system, dielectric constant (er) and temperature coefficient of resonance frequency (τƒ) of the material were increased due to the mixing effect of TiO2 phase. The 0.85SiO2 − 0.15TiO2 and 0.9SiO2 − 0.1TiO2 ceramics sintered at 1200 °C showed er = 5.4 and 4.6, quality factor (Q·ƒ) = 40,500 and 36,300 GHz, and τƒ = 2.5 and −0.5 ppm/°C. The sintering temperature of 0.9SiO2 − 0.1TiO2 ceramic is lowered from 1200 °C/3 h to 950°C/6 h by the addition of H3BO3. 0.9SiO2 − 0.1TiO2 ceramics with 10 wt% H3BO3 sintered at 950 °C/6 h possesses excellent microwave dielectric properties of er ∼ 4.67, Q·ƒ ∼ 78,000 GHz and τƒ ∼ −0.7 ppm/°C. From the X-ray diffraction and EDS analysis of cofired ceramics, the H3BO3 added 0.9SiO2 − 0.1TiO2 ceramic does not react with Ag at 950 °C. The attractive advantages such as low dielectric constant, low sintering temperature, high-performing microwave dielectric properties, chemical compatibility with Ag metal electrodes, no toxicity, and abundant raw materials source and low cost constituents make the SiO2 ceramic as potential candidates for substrate and LTCC devices.