Structure, far-infrared spectroscopy, microwave dielectric properties, and improved low-temperature sintering characteristics of tri-rutile Mg_0.5Ti_0.5TaO₄ ceramics

In this study, tri-rutile type Mg_0.5Ti_0.5TaO₄ ceramics were synthesized, where the structure–property relationship, especially the structural configuration and intrinsic dielectric origin of Mg_0.5Ti_0.5TaO₄ ceramics, and the low-firing characteristics were studied. It is found that the tri-rutile structural type is unambiguously identified through the Rietveld refinement analysis, the selected area electron diffraction (SAED), and the high-resolution transmission electron microscopy (HRTEM) along the [110] zone axis. With the increase in sintering temperature, the densification and uniformity of crystal growth play important roles in regulating the microwave dielectric properties of Mg_0.5Ti_0.5TaO₄ ceramics. Intrinsically, theoretical dielectric properties calculated by the far-infrared reflective spectra approached the experimental values, indicating the importance of structural features to dielectric properties. Furthermore, a glass additive with high matching relevance with ceramics has been developed to decrease the high sintering temperature of Mg_0.5Ti_0.5TaO₄ ceramics, where 2–4 wt% Li₂O–MgO–ZnO–B₂O₃–SiO₂ (LMZBS) glass frit was adopted to reduce the suitable temperature from 1275 to 1050 ℃ without significantly deteriorating the microwave dielectric characteristics. Specifically, Mg_0.5Ti_0.5TaO₄ ceramics containing 2 wt% glass addition sintered at 1050 ℃ for 4 h possess excellent microwave dielectric properties: dielectric constant (ε_r) = 44.3, quality factor multiplied by resonant frequency (Q×f) = 23,820 GHz (f = 6.2 GHz), and the temperature coefficient of resonant frequency (τ_f) = 123.2 ppm/℃.