Achieving Near‐Zero TCF and High Quality Factor in Li ₂ TiO ₃ ‐Based Dual‐Phase Ceramics via Synergistic Phase and Microstructure Engineering

ABSTRACT Next‐generation communication systems urgently demand microwave dielectric ceramics that combine ultra‐low dielectric loss with exceptional thermal stability. However, overcoming the persistent trade‐off between a high quality factor ( Q ) and a near‐zero temperature coefficient of resonant frequency (TCF) remains a formidable challenge. Here, we report a synergistic design strategy that integrates (Ga _1/2 Nb _1/2 ) ⁴⁺ substitution with LiF‐assisted microstructural engineering to resolve this dilemma in Li ₂ TiO ₃ ceramics. The synergistic interaction drives a phase evolution from the monoclinic phase (positive TCF) toward the cubic phase (negative TCF), constructing a dual‐phase structure that achieves near‐zero TCF through self‐compensation. Simultaneously, LiF‐assisted liquid‐phase sintering promotes densification at lower temperatures, thereby significantly reducing dielectric loss. Remarkably, the optimized Li ₂ Ti _0.95 (Ga _1/2 Nb _1/2 ) _0.05 O ₃ – 2 wt.% LiF ceramic demonstrates exceptional microwave dielectric properties, featuring a high Q × f value of 129 390 GHz (at 7.3 GHz) and a near‐zero TCF of +8.5 ppm/°C. The proposed synergistic strategy provides a robust pathway for developing high‐performance microwave dielectric ceramics for wireless communication applications.