Physical and microwave dielectric properties of the MgO-SiO₂ system

Unreported dielectrics based on the binary system of MgO-SiO₂ were investigated as potential candidates for microwave dielectric applications, particularly those demanding a high fired density and high quality factors. Extensive dielectric compositions having different molar ratios of MgO to SiO₂, such as 2:1, 3:1, 4:1, and 5:1, were prepared by conventional solid state reactions between MgO and SiO₂. 1 mol% of V₂O₅ was added to aid sintering for improved densification. The dielectric compositions were found to consist of two distinguishable phases of Mg₂SiO₄ and MgO beyond the 2:1 compositional ratio, which determined the final physical and dielectric properties of the corresponding composite samples. The increase of the ratio of MgO to SiO₂ tended to improve fired density and quality factor (Q) without increasing grain size. As a promising composition, the 5MgO.SiO₂ sample sintered at 1400 °C exhibited a low dielectric constant of 7.9 and a high Q × f (frequency) value of ~99,600 at 13.7 GHz.