Impact of SrTiO3 Addition on the Microstructure and Dielectric Properties of Mg2SiO4 Ceramics for 5G/6G Applications

Title

Impact of SrTiO₃ Addition on the Microstructure and Dielectric Properties of Mg₂SiO₄ Ceramics for 5G/6G Applications

Research Background

With the rapid deployment of 5G and the arrival of 6G, there is an increasing demand for microwave dielectric ceramics that are stable at high frequencies and exhibit low loss. Such materials need to have a low dielectric constant (ε_r ≤ 12) to reduce signal delay, a high quality factor (Q×f ≥ 50,000 GHz) to minimize energy loss, and a near-zero temperature coefficient of resonant frequency (τ_f) to ensure thermal stability. Magnesium silicate (Mg₂SiO₄, MSO) has attracted attention due to its low ε_r (≈6-7) and extremely high Q×f value (≈240,000 GHz), but its strong negative τ_f (approximately -67 ppm/°C) and high sintering temperature limit its practical applications. Previous attempts to adjust τ_f through doping or adding TiO₂ often resulted in performance degradation due to the formation of secondary phases from chemical reactions, thus necessitating the search for new effective compensating agents.

Research Content

① A solid-state reaction method was successfully used to prepare (1-x)Mg₂SiO₄-x wt% SrTiO₃ (x = 0-0.07) composite ceramics, and the effect of STO addition on the phase composition and microstructure of the materials was systematically studied.

② Characterization techniques such as XRD, FESEM, and Raman spectroscopy confirmed the coexistence of MSO and STO phases in the composite material without the formation of secondary phases, and the addition of STO promoted abnormal grain growth and densification.

③ The microwave dielectric properties (ε_r, Q×f, τ_f) of ceramics with different STO contents were measured in detail, revealing that as STO increased, ε_r and τ_f increased while Q×f decreased, and τ_f was precisely controlled through linear mixing rules.

Innovations

① For the first time, SrTiO₃ with a large positive τ_f (≈+1640 ppm/°C) was introduced into the Mg₂SiO₄ system, effectively compensating for the negative τ_f of MSO through a simple physical blending method rather than chemical doping, avoiding lattice distortion and performance degradation caused by ionic substitution.

② Utilizing the significant differences in crystal structure and ionic radius mismatch between MSO and STO, the mutual reactions and secondary phase formation during the sintering process were successfully suppressed, resulting in a stable two-phase composite structure that ensures predictability and stability of performance.

③ While achieving a near-zero τ_f, a low dielectric constant (ε_r < 8) was maintained, meeting the requirements for low signal delay in 5G/6G applications, providing a new approach for developing high-frequency thermally stable microwave dielectric materials.

Paper Summary

This study successfully developed a low-loss, temperature-stable microwave dielectric ceramic suitable for 5G/6G communication base station resonators by adding SrTiO₃ to Mg₂SiO₄. The results indicate that the addition of STO not only effectively adjusts the negative τ_f value of MSO but also promotes the densification of the ceramics during sintering. When the STO addition is 7 wt%, the optimal ceramic performance is achieved after sintering at 1450°C for 5 hours: relative density reaches 95.9%, dielectric constant (ε_r) is 7.46, quality factor (Q×f) is 94,300 GHz, and the temperature coefficient of resonant frequency (τ_f) is close to zero at -3.27 ppm/°C. This composite material achieves a balance of performance through phase separation mechanisms, avoiding the complexity of chemical reactions, and shows great potential in high-frequency wireless communication applications. Although the Q×f value decreases due to the intrinsic low Q and interfacial losses of STO, its overall performance surpasses many reported magnesium silicate systems doped or aided by low-melting-point glass, providing promising material candidates for next-generation wireless communication technologies.

Original Article

https://doi.org/10.1016/j.jeurceramsoc.2025.117986