Synergistic Dual‐Phase and Microstructure Engineering toward Temperature‐Stable, Ultra‐Low Loss Li <sub>2</sub> TiO <sub>3</sub> ‐Based Microwave Dielectric Ceramic
Zuwei Wang, H. X. Guo, Yuanyuan Huang, Yueming Li
Abstract
Abstract High‐performance microwave dielectric ceramics are the essential materials for next‐generation 6G communication devices. However, simultaneously achieving temperature stability and ultra‐low loss remains a formidable challenge. To address this, a monoclinic‐cubic dual‐phase structure is engineered in Li 2 Ti 0.95 (Ga 1/2 Ta 1/2 ) 0.05 O 3 ceramic through LiF‐triggered dual‐phase formation. This unique structure effectively balances the opposing temperature coefficient of resonance frequency (TCF) between the monoclinic (positive TCF) and cubic (negative TCF) phases, thereby achieving a near‐zero TCF. Furthermore, ultra‐low dielectric loss is attained through the intrinsic suppression of oxygen vacancies via charge‐compensated substitution, coupled with LiF‐assisted liquid‐phase sintering that simultaneously promoted a dense microstructure. Benefiting from the synergistic effect, the optimized Li 2 Ti 0.95 (Ga 1/2 Ta 1/2 ) 0.05 O 3 ‐2 wt.% LiF (LTGT‐2LF) ceramic exhibits superior comprehensive properties, featuring an ultra‐high Q × f value of 126,760 GHz, a near‐zero TCF of +9.7 ppm/°C, and robust mechanical strength (flexural strength = 151.7 MPa). To demonstrate its potential for practical applications, a cylindrical dielectric resonator antenna (CDRA) based on LTGT‐2LF ceramic is designed and fabricated, exhibiting a high gain (4.6‐5.3 dBi) and radiation efficiency (> 80%). This work establishes a viable strategy for designing high‐performance microwave dielectric ceramics by synergistic engineering of phase structure, defect chemistry, and microstructure.