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 temperature coefficient of resonant frequency (τ_f) compensators, including TiO₂ (TO), CaTiO₃ (CTO), or SrTiO₃ (STO), in either green or presintered 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% presintered TO core exhibited ε_r ≈ 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, high frequency structure simulator (HFSS) simulation of a cylindrical dielectric resonator antenna (CDRA) based on the optimized ZNO–TO core–shell ceramic predicted favorable impedance matching (voltage standing wave ratio (VSWR) ≈ 1.015), radiation efficiency above 90%, and a peak realized gain of 6.13 dBi at 4.31 GHz. This 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 for developing the high-performance MWDCs required for next-generation communication technologies.