Mg₂SiO₄–TiO₂ composite ceramics prepared using a liquid phase deposition process

Forsterite (Mg₂SiO₄) indicates a high quality factor (Q·f) of 270,000 GHz and a low dielectric constant ɛ _r of 6.8, which are applicable for microwave and millimeter-wave dielectric devices. However, a large negative temperature coefficient of resonant frequency (τ _f) of −73 ppm/°C hinders stability. Actually, Mg₂SiO₄–TiO₂ composite ceramics prepared by ordinary solid state reaction showed improved τ _f to 0 ppm/°C. However, Q·f of the composite ceramics decreased because other phases such as MgTi₂O₅, MgTiO₃ and MgSiO₃ were created in the reaction between TiO₂ and Mg₂SiO₄ during sintering. This study uses a different process to prepare the Mg₂SiO₄–TiO₂ composite ceramics to prevent the production of the secondary phase. Porous Mg₂SiO₄ ceramics were prepared by sintering Mg₂SiO₄ with pore-forming agents. Then, TiO₂ was inserted into the pores using liquid phase deposition (LPD). Deposited TiO₂ in the pores was anatase form. The increase of the inserted anatase TiO₂ amount contributed to improvement of τ _f.