Study of the co-firing behavior of dielectric ceramic (Zr_0.8Sn_0.2)TiO₄ and NiZn ferrite laminated composites

(Zr_0.8Sn_0.2)TiO₄ (ZST) microwave dielectric ceramic powder was synthesized by the hydrothermal-molten salt (HMS) method, and the effects of different molding methods on the physical phases, microscopic morphology, and dielectric properties of ZST ceramics were investigated. On this basis, ZST-NZ laminated composites were prepared, and the interfacial diffusion and laminated co-firing behaviors of the composites were studied more systematically. The results show that the heat-pressing process can be used to obtain high-frequency dielectric ceramics with more comprehensive performance. The dielectric properties (1 MHz) were ɛ_r = 40.5, tanδ = 1.32 × 10⁻³. ZST-NZ laminated composites have relatively tight interfacial bonding but show significant interfacial diffusion. The mutual diffusion of ZST-NZ composites follows the semi-infinite diffusion coupling model. Based on this diffusion model, the ionic concentration distribution function was established to simulate the interfacial diffusion of ions, and the diffusion coefficients and diffusion activation energies of Fe³⁺, Zn²⁺, Sn⁴⁺, and Zr⁴⁺ were calculated under different conditions. The magnitude of diffusion coefficients in the H-ZST-NZ diffusion couples was in the order of D (Fe³⁺) > D (Zn²⁺) > D (Sn⁴⁺) > D (Zr⁴⁺), and the magnitude of diffusion activation energies at 1275 °C was in the order of Q_d (Zr⁴⁺) > Q_d (Sn⁴⁺) > Q_d (Zn²⁺) > Q_d (Fe³⁺). The strong diffusion of Ti and Fe led to the decomposition of ZST and NZ ferrite, producing new TiO₂ and Fe₃O₄ phases, which resulted in the degradation of the dielectric properties of the composites.