Study on tailoring crystal structure and enhancing microwave and terahertz dielectric performance of ZnTiNb2O8 ceramics via Mg2+ and W6+ co-doping

This study systematically investigates the intricate mechanism by which Mg 2 ⁺ and W 6 ⁺ co-doping affects the crystal structure and microwave/terahertz dielectric properties of ixiolite-type ZnTiNb 2 O 8 (ZTN) ceramics. A series of doped ZTN ceramics were prepared via the solid-state reaction method, with doping concentrations ranging from 3 to 15 mol%. The incorporation of Mg 2+ and W 6+ ions into the ZTN lattice was confirmed by X-ray diffraction (XRD) analysis and subsequent Rietveld refinement, resulting in a significant expansion of the lattice parameters. The dielectric constant (ε r ) of the co-doped ceramics decreased gradually with increasing doping content, which can be attributed to the reduced ionicity of Nb–O bonds and the lower molecular polarizability caused by ion substitution. Notably, an optimal quality factor (Q × f) of approximately 39300 GHz (@6.6 GHz) was achieved at a 9 mol% doping level. At 12 mol%, the sample achieved an excellent Q × f value approaching 39050 GHz in the terahertz band (@ 0.84 THz). This enhancement is explained by the increased lattice energy and improved structural stability caused by the co-doping. Furthermore, the τ f value shifted from − 68.4 to − 47.1 ppm/°C with increasing Mg/W content, which is associated with the reduced thermal expansion coefficient and enhanced stability of the oxygen-polyhedral framework. These results provide a theoretical basis for designing high-performance microwave and terahertz dielectric materials.