Low-firing BaMg₂V₂O₈-based composites featuring novel ultra-low permittivity and low loss for dual-band 6G antenna applications

Abstract

The BaMg₂V₂O₈-based ceramic composites provide a high-performance, industrially viable solution, bridging the gap between polymer and ceramic dielectrics. While polymer-dielectrics are favored in flexible electronics for their low permittivity (ε_r) and compatibility with low-temperature processing, they fall short in thermal stability, mechanical strength, and long-term reliability that ceramics excel in. Our newly developed ceramic composites address these limitations by featuring an ultra-low ε_r, which is essential for 6G communication. Significant efforts have been directed towards optimizing the microwave dielectric properties of the composites by manipulating lattice structures and polarization mechanisms. This has led to the successful development of Ba₀.₈₅Sr₀.₁₅Mg₁.₉₈Zn₀.₀₂V₂O₈–xwt.%Li₂CO₃ ceramic composites within the composition range of 0.0 ≤ x ≤ 1.75. This tailored composition results in a solid solution that coexists with both tetragonal (T-phase: ε_r = 13.03, Q × f = 55,356 GHz at f ≥ 9 GHz, τ_f = −5.3 ppm/°C at x = 0.75) and orthorhombic phases (O-phase: ε_r = 3.96, Q × f = 73,775 GHz at f ≥ 17 GHz, τ_f ∼ −6.1 ppm/°C at x = 0.75), achieving an ultra-low ε_r with balanced Q × f values and a temperature coefficient of resonance frequency after sintering at approximately 840 °C/4h. The variation in ε_r and Q × f-values is attributed to the distortion and deformation of Ba-O₈ polyhedra, as well as the full width at half maximum (FWHM) values of the Eg_(Ba) and A_1g Raman modes. The phase coexistence enables tunability of dual-frequency band antennas, providing flexible solutions for advanced communication.