Core–shell structural engineering for efficient τf regulation in low-loss MgF2-based microwave dielectric ceramics

Achieving a near-zero temperature coefficient of resonant frequency ( τ f ) while maintaining high quality factor ( Q ), typically reported as Q × f ( Qf ), in microwave dielectric ceramics is a significant challenge. In this work, a core-shell structural engineering strategy is proposed for efficient τ f regulation in MgF 2 –0.5 wt% LiF (MFL0.5) ceramics, which exhibit excellent microwave dielectric performance ( ε r = 5.09, Qf = 100,733 GHz) but suffer from a large negative τ f (−67.4 ppm/°C). Instead of dispersing temperature-compensation phases throughout the matrix, a pre-densified TiO 2 ceramic with positive τ f is introduced as a compact core embedded within the MFL0.5 shell, forming an integrated core-shell architecture. Experimental results show that a near-zero τ f of −1.97 ppm/°C can be achieved with only ∼1.27 wt% TiO 2 , while retaining a high Qf value of 50,302 GHz. In contrast, conventional MFL0.5–TiO 2 composite ceramics require 20 wt% TiO 2 to achieve similar τ f compensation, resulting in a significant decrease in Qf to 25,933 GHz. Electric-field distribution simulations highlight the enhanced electric filling factor of the TiO 2 core, which plays a key role in efficient τ f regulation. This core-shell architecture provides a highly effective strategy for regulating τ f with minimal dielectric loss penalty, offering a promising pathway for the development of high-performance, low- ε r microwave dielectric ceramics for advanced communication systems.