Abstract: The development of microwave dielectric ceramics with excellent comprehensive performance is an important research direction in the field of wireless communications. In this work, we have tailored disordered phase LiZn_0.5TiO₃ (LZT, Fd-3m) with ordered spinel Li₂MgTi₃O₈ (LMT, P4332) to prepare high-entropy ceramics (1-x)LZT-xLMT (1/4 ≤ x ≤ 3/4, P4332). As the LMT content increases, lattice defects increase, and dislocations are observed in the corrugated lattice fringes. The reduced entropy and increased lattice strain collectively affect the dielectric loss characteristic. Additionally, the rattling effect of cations in octahedral positions and the pinning effect of the defective dipoles cause the permittivity (ε_r) to deviate from classical theoretical predictions, while maintaining a low dielectric loss. And the temperature coefficient of permittivity (τ_ε) transitions from positive to negative, resulting in the temperature coefficient of resonance frequency (τ_f) tending toward zero (-4.09 ppm/°C). Notably, a positive correlation is observed between ε_r and τ_f. Based on these findings, 1/4LZT-3/4LMT ceramics (εᵣ = 26.9, Q × f = 52,976 GHz) with a near-zero τ_f were selected as the substrate material for a novel circularly polarized dielectric resonance antenna (CPDRA) designed for communication systems. This antenna exhibits an impedance bandwidth (42.4%) covering multiple communication bands, a 3 dB axial ratio bandwidth of 29.45%, and excellent circular polarization characteristics in the 5 G WiFi band. These features make it highly effective in suppressing multipath interference. In summary, these excellent characteristics highlight the exceptional potential of the developed high-entropy ceramic in communication systems.

Key words: Microwave dielectric ceramics, Dislocations, defective dipole, Near-zero τ_f, Circularly polarized dielectric resonance antenna