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

Abstract 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.