Microwave dielectric properties of porous Mg2SiO4 filling with TiO2 prepared by a liquid phase deposition process

Forsterite (Mg2SiO4) possesses a high quality factor (Q·f) of 270,000 GHz and a low dielectric constant ɛr of 6.8. However, it shows a relatively large negative temperature coefficient of resonant frequency τf of −73 ppm/°C. For microwave telecommunication, a τf of nearly 0 ppm/°C is desirable to keep the frequency stability. In order to improve τf, we have tried to produce pure Mg2SiO4–TiO2 composite ceramics with no secondary phases using a liquid phase deposition (LPD) method. Porous Mg2SiO4 ceramics was prepared by sintering Mg2SiO4 with polymethyl methacrylate (PMMA) particles, and then TiO2 was filled in the pores of Mg2SiO4 by the LPD method. The porosity and microstructure of porous Mg2SiO4 was controlled by amount and particle sizes of PMMA and formation process. τf of Mg2SiO4 filled with TiO2 by LPD method was improved to −46 ppm/°C.