Effect of heating rate on ion diffusion and dielectric properties of ferroelectric-dielectric composite ceramics

The ion diffusion phenomenon in ferroelectric-dielectric composite ceramics will deteriorate its dielectric properties. In this paper, Ba_0.5Sr_0.5TiO₃-CuGa₂O₄ composite ceramics were prepared at different sintering heating rates. The phase composition, microstructure and dielectric properties were tested and analyzed. The effects of grain growth and the different degrees of ion diffusion on the properties of ferroelectric-dielectric composite ceramics at various heating rates were studied. The results show two crystal phases including perovskite structure BST and spinel structure GuGa₂O₄ in the composite ceramics. With the increase of the heating rate, the dielectric permittivity decreased, the tunability showed a decreasing trend, and the Q value also appeared to decrease after a slight increase. The inhomogeneity of grain size is apparent when the heating rate is higher. Moreover, as the grain size heterogeneity increases, the density decreases, adversely affecting the dielectric property of the samples.