Artificial core–shell cofired architectures for high-performance microwave dielectric ceramics

The rapid advancement of 5G/6G communication technologies imposes ever-increasing demands on microwave dielectric ceramics (MWDCs). However, it remains challenging to simultaneously achieve good temperature stability and high Q×f values. Metamaterials with artificially designed structures exhibit extraordinary properties, and metamaterialogy holds great potential for advancing conventional materials. Inspired by this paradigm, an artificial core-shell cofired architecture was designed to realize high-performance MWDCs. The architecture employed the Zn_1.01Nb₂O₆ (ZNO) matrix as the shell and positive-τ_f compensators, including TiO₂ (TO), CaTiO₃ (CTO), or SrTiO₃ (STO), in either green or pre-sintered states, as cores. The τ_f values of all the core-shell samples were effectively tuned to near zero while high Q×f values were retained. Specifically, the ZNO-TO core-shell ceramic with a 1.43 wt% pre-sintered TO core exhibited εᵣ ~ 25.32, Q×f ~ 119,100 GHz, and τ_f ~ -4.8 ppm/°C, while the temperature-stable counterparts using the CTO or STO cores retained Q×f ≥ 67,800 GHz. Furthermore, HFSS simulation of a cylindrical dielectric resonator antenna (CDRA) based on the optimized ZNO-TO core-shell ceramic predicted favorable impedance matching (VSWR ~ 1.015), radiation efficiency above 90%, and a peak realized gain of 6.13 dBi at 4.31 GHz. It preliminarily demonstrates the feasibility of CDRA applications. The artificial core-shell architecture provides a general strategy for synergistically optimizing microwave dielectric properties by tailoring the electric-field participation and confining heterogeneous interfacial reactions, which is beneficial to developing high-performance MWDCs required for next-generation communication technologies.