Structural evolution, Raman spectra, and microwave dielectric properties of Zr-substituted ZnTiTa₂O₈ ceramics

A series of Zn(Ti_1−xZr_x)Ta₂O₈ (x = 0, 0.2, 0.4, 0.6, 0.8, 1) ceramics samples were synthesized by conventional solid-state reaction route. The sintering behavior, crystal structure, Raman spectroscopy, microstructure, and microwave dielectric properties were studied. The crystal structure, lattice parameters, and bonding of the ceramics were analyzed using X-ray powder diffraction and Raman spectroscopy. As Zr⁴⁺ content increasing, the structural transition followed the sequence: tri-rutile → coexistence of tri-rutile and columbite → columbite → wolframite. The microwave dielectric properties of ceramics were considerably affected by the structural transition. Compared with pure phase ZnTiTa₂O₈ ceramics, a small amount of Zr-substitution (x = 0.2) could significantly improve the Q × f values (from 19,852 to 44,048 GHz) and τ_f values (from 77.1 to − 11.9 ppm/°C) of ceramics. Typically, ZnTi_0.8Zr_0.2Ta₂O₈ (x = 0.2) ceramics exhibited an excellent microwave dielectric property of ε_r ~ 29.9, Q × f ~ 44,048 GHz, and τ_f ~ − 11.9 ppm/°C as the sintering temperature was 1300 °C.