Effect of ion diffusion on dielectric properties of ferroelectric-dielectric composite ceramics

•The effect of pre-sintering temperature on material activity makes the degree of ion diffusion different.•The ferroelectric-dielectric material exhibits obvious compound effect at high pre-sintering temperature.•The dielectric properties will be significantly improved as the ion diffusivity decreases. In order to explore the influence of ion diffusion on the phase composition, microstructure and dielectric properties of ferroelectric-dielectric composite ceramics. Ba0.5Sr0.5TiO3 (BST) ceramics were firstly pre-sintered at different temperatures and then composited with CuGa2O4 (CG) were investigated. The ion diffusion between BST and CG phase was suppressed and the composite effect became dominant with the pre-sintering temperature of BST rising. This phenomenon induced the dielectric permittivity firstly firstly increasing and then decreasing with pre-sintering temperature. In the meantime, the Curie temperature was found to gradually move to higher temperature, which further lead to the increase in tunability at room temperature. In particular, as the pre-sintering temperature achieved to 1400 °C, as-prepared BST-CG composites exhibited enhanced dielectric properties with good tunability up to 22.4 % and a high Q value of 41.5.