Effects of partial substitution at different sites on the microwave dielectric properties of K2Co2(MoO4)3 ceramic and its applications as a 5G/6G antenna array.

Novel K₂Co₂(MoO₄)₃ microwave dielectric materials were prepared and investigated for the first time. The effects of substituting Ag⁺ for K⁺ and Zn²⁺ for Co²⁺ on the ceramic structure, sintering temperature, surface microstructure, and microwave dielectric properties were studied. The X-ray diffraction results showed that the samples had a monoclinic crystal structure and belonged to the P12₁/c1 (14) space group, with a single-phase composition of K₂Co₂(MoO₄)₃. The pure phase K₂Co₂(MoO₄)₃ ceramic achieved a Q × f = 42,300 GHz, an ε_r = 7.31, and a τ_f = − 81.3 ppm/°C at a sintering temperature of 630 °C. Partial substitution in the specimen can effectively enhance its densification and reduce the dielectric loss, particularly at the K-site. This improvement is primarily attributed to the more significant variation in the cell volume of the ceramics. The K₂Co_1.9Zn_0.1(MoO₄)₃ specimen with minute substitution achieved Q × f = 57,300 GHz, ε_r = 7.82 and τ_f = − 69 ppm/°C at 630 °C, while the K_1.86Ag_0.14Co₂(MoO₄)₃ specimen showed Q × f = 61,200 GHz, ε_r = 8.73 and τ_f = − 68 ppm/°C at 540 °C. The research also exhibited that the material had outstanding chemical compatibility with aluminum electrodes during co-firing. Based on the results, these ceramics show potential as attractive candidates for ULTCC applications, such as an 8 × 8 dual-polarization antenna array used in the millimeter-wave region for 5G/6G systems. [ABSTRACT FROM AUTHOR]