Realizing excellent dielectric properties in double “core-shell” structure BaTiO3-based ceramic via (Zr4+, Ca2+) isovalent co-doping effect

In this study, Ba 0.997 Gd 0.003 TiO 3 @(Ni,Mn)Nb 2 O 6 + x wt% CaZrO 3 (x=0.2, 0.3, 0.4, 0.5, 0.6) (BGT@(N,M)NO-CZO) dielectric ceramics with excellent performance are synthesized by a simple solid-state reaction method. The lattice distortion formed by the substitution of A site in the perovskite structure by rare earth Gd 3+ ions enhances the dielectric constant of BaTiO 3 (BT) -based ceramics, while a single “core-shell” structure formed by niobate-coated (Shell-1) BGT improves the temperature stability in the low-temperature range. The dielectric constant of BGT@(N,M)NO ceramic reaches about 4500, and the temperature stability meets X7R. More importantly, for further optimize the dielectric properties, an isovalent co-dopant CaZrO 3 is added to the BGT@(N,M)NO ceramic to enhance high temperature stability. In different regions of BT matrix, Zr 4+ replaces Ti 4+ at the B site in the region between the Shell-1 and the core phase to form Shell-2, while Ca 2+ replaces Ba 2+ at the A site mainly in the core phase. Moreover, the double “core-shell” structure BGT@(N,M)NO-CZO ceramics generate internal stress and strong interionic interactions in lattice, leading to a shift in the Curie temperature toward higher temperatures, which enhances the temperature stability of BT-based ceramics between 145 °C to 155 °C range. Therefore, BGT@(N,M)NO-CZO (0.3 wt%) ceramic maintains high dielectric constant (ε r =4852) while extending temperature stability to X8R. Additionally, the dielectric loss of BGT@(N,M)NO-CZO (0.3 wt%) ceramic is reduced to 0.98%, and the room temperature resistivity and breakdown strength are reached 10 10 Ω·m and 89.1 kV/cm, respectively. The DFT calculation results further indicate that high dielectric constant and wide temperature stability correspond Gd 3+ -doped BT and (Zr 4+ , Ca 2+ ) isovalent co-doped BT. Ultimately, the double “core-shell” structure BGT@(N,M)NO-CZO ceramics with excellent dielectric properties are obtained via isovalent co-doping effect, rare earth ion doping effect and “core-shell” effect, which further expands the application of BT-based ceramics in the fields of electronic material and device.