Effect of percolation characteristics and ion diffusion on dielectric properties of ferroelectric-dielectric composite ceramics

Abstract The ferroelectric-dielectric composite ceramics of (1-x)Ba0.4Sr0.6TiO3-xZnGa2O4 (x = 10, 30, 50 and 70 wt%) were prepared via a solid-state sintering process. The relationships between phase structure, connectivity structure and dielectric properties were investigated. The tunability of the composites gradually enhanced compared to that of pure BST40, with the Curie temperature shifting towards higher temperature with the increase of ZnGa2O4 content. Tunability and dielectric permittivity demonstrated significantly change above the percolation threshold, which was attributed to the connectivity evolving from 0-3 to 3-3. The permittivity and the tunability of 30 wt% ZnGa2O4 sample were 616 and 22% respectively, while those of 70 wt% ZnGa2O4 sample dropped significantly to 70 and 11.5% respectively. The composites possessed decent dielectric properties. High tunability of 21.8% (at 30 kV/cm), decent Q value of 348 (at 3.335 GHz) and appropriate permittivity of 142 were available simultaneously at x = 50 wt%.