Sintering behaviors and microwave dielectric properties of BaO–MgO–SiO2 ternary ceramics

In the present work, five compositions in the BaO–MgO–SiO₂ ternary system were chosen, and ceramics were prepared using the solid-state reaction method. Single phases were formed easily for the first four compositions, and BaMgSi₃O₈ ceramics were found to be a mixture of both BaSi₂O₅ and MgSiO₃, according to X-ray diffraction results. Among all the compositions, Ba₂MgSi₂O₇ ceramic sintered at 1225°C possesses the highest Qf (Q = 1/dielectric loss = 1/tanδ, f = resonant frequency) value ∼55 010 GHz along with relative permittivity ∼8.0 and temperature coefficient of resonant frequency (TCF) ∼−57.5 ppm/°C. With 3 wt.% BCB (BaO–B₂O₃–CuO) additions, Ba₂MgSi₂O₇ ceramic was well densified at 950°C with a relative permittivity ∼8.1, Qf value ∼28 920 GHz (at 12.37 GHz) and TCF value ∼‒56.6 ppm/°C. These series ceramics with low relative permittivity values might be good candidates for low-temperature co-fire ceramic technology substrate applications.