In this study, tri-rutile type Mg0.5Ti0.5TaO4 ceramics were synthesized, where the structure–property relationship, especially the structural configuration and intrinsic dielectric origin of Mg0.5Ti0.5TaO4 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  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 Mg0.5Ti0.5TaO4 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 Mg0.5Ti0.5TaO4 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, Mg0.5Ti0.5TaO4 ceramics containing 2 wt% glass addition sintered at 1050 ℃ for 4 h possess excellent microwave dielectric properties: dielectric constant (εr) = 44.3, quality factor multiplied by resonant frequency (Q×f) = 23,820 GHz (f = 6.2 GHz), and the temperature coefficient of resonant frequency (τf) = 123.2 ppm/℃.
The authors acknowledge financial support from the open research fund of Songshan Lake Materials Laboratory (No. 2022SLABFN20), the Qinchuangyuan Citing High-level Innovation and Entrepreneurship Talent Projects (No. QCYRCXM-2022-40), the Natural Science Basic Research Program of Shaanxi (No. 2022JQ-390), the National Natural Science Foundation of China (No. 52102123) the National Key R & D Program of China (No. 2022YFB2807405), and the Natural Science Foundation of Sichuan Province (Nos. 22NSFSC1973 and 2022NSFSC1959). The authors would also like to thank Prof. Chuansheng Hu and Prof. Zeming Qi from the Infrared Spectroscopy and Microspectroscopy Endstation (BL01B) of NSRL for their support in the infrared spectra measurement.
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