Effects of adding B 2 O 3 on microwave dielectric properties of 0.9625MgTiO 3 ‐0.0375(Ca 0.5 Sr 0.5 )TiO 3 composite ceramics

A series of 0.9625MgTiO 3 ‐0.0375(Ca 0.5 Sr 0.5 )TiO 3 composite ceramics added with different amounts of B 2 O 3 (1‐5 wt%) were prepared via the solid state sintering method using the pre‐synthesized raw MgTiO 3 and (Ca 0.5 Sr 0.5 )TiO 3 powders by molten‐salt reaction. The sintering temperature of 0.9625MgTiO 3 ‐0.0375(Ca 0.5 Sr 0.5 )TiO 3 composite ceramics can be reduced from 1275°C to 1175°C due to the liquid phase sintering effect of B 2 O 3 . When the adding amount of B 2 O 3 was more than 2 wt%, a new phase MgTi 2 O 5 could be detected by X‐ray diffraction, which would substantially degrade the dielectric properties of the obtained ceramics. Resultantly, the quality factor ( Q · f ) and dielectric constant ( ε r ) of the samples increase first and decrease later with increasing addition amount of B 2 O 3 . In addition, the temperature coefficient of resonant frequency ( τ f ) progressively increases with increasing content of B 2 O 3 . By sintering at 1175°C for 4 hours, the obtained 0.9625MgTiO 3 ‐0.0375Ca 0.5 Sr 0.5 TiO 3 composite ceramics with 2 wt% B 2 O 3 possess the optimal microwave dielectric properties of ε r  = 18.9, Q·f  = 57 000 GHz and τ f  = −1.2 ppm/°C.