Enhanced microwave dielectric properties of Co1.1Zn0.9-xBaxTiO4 ceramics via Ba2+ ion substitution

This study modified the Co 1.1 Zn 0.9 TiO 4 ceramic system through Ba 2 ⁺ 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), Ba 2 ⁺ could partially substitute Zn 2 ⁺, maintaining the cubic spinel main phase (Co 2 TiO 4 ) structure; when x ≥ 0.02, the larger ionic radius of Ba 2 ⁺ induced phase separation and the formation of a secondary BaTiO 3 phase, with the secondary-phase peak intensity increasing with doping concentration. The coexistence of main and secondary phases in the Co 1.1 Zn 0 .87Ba 0 .03TiO 4 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 1.1 Zn 0 .87Ba 0 .03TiO 4 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.