Enhanced microwave dielectric properties of Co_1.1Zn_0.9-xBa_xTiO₄ ceramics via Ba²⁺ ion substitution

This study modified the Co_1.1Zn_0.9TiO₄ ceramic system through Ba²⁺ ion doping to enhance the quality factor (Q×f) and adjust the τ_f value. Ceramic samples were prepared via the solid-state reaction method at sintering temperatures of 1125–1200°C. XRD revealed that at low Ba doping concentrations (x = 0–0.01), Ba²⁺ could partially substitute Zn²⁺, maintaining the cubic spinel main phase (Co₂TiO₄) structure; when x ≥ 0.02, the larger ionic radius of Ba²⁺ induced phase separation and the formation of a secondary BaTiO₃ phase, with the secondary-phase peak intensity increasing with doping concentration. The coexistence of main and secondary phases in the Co_1.1Zn₀.87Ba₀.03TiO₄ ceramic was confirmed by Rietveld refinement. SEM demonstrated that appropriate Ba doping (x = 0.01–0.03) promoted grain growth, while excessive Ba doping (x = 0.04) led to microstructural deterioration. The Q×f value of the Co_1.1Zn₀.87Ba₀.03TiO₄ ceramic increased to 66,943.2 GHz, while the τ_f value was adjusted to −17.13 ppm/°C, effectively reducing dielectric loss and enhancing temperature stability.