Dodecahedron lattice of rattling phenomenon, and microwave dielectric properties of yttrium aluminum garnet ceramics and its application verification for Wifi6E/7 patch and 6G resonant antennas

Abstract

In garnet phase ceramics Y2.9M0.1Al4.9Si0.1O12 (M = Mg2+, Co2+, Zn2+, Mn2+, Ca2+, Sr2+, Ba2+), rattling effects occur when M = Mg2+, Co2+, Zn2+, Mn2+ ions with smaller ionic radius (<1Å) occupy the dodecahedron lattice lattices. This results in an abnormally high dielectric constant, in contrast to the larger ionic radius (>1 Å) of M = Ca2+, Sr2+ and Ba2+, which deviate from the theoretical values calculated using the Clausius-Mosotti formula according to each ion’s polarizability. The optimal microwave dielectric properties for Y2.9Mg0.1Al4.9Si0.1O12 was obtained by sintering at 1575 °C for 5 h (Q×f = 51,382 GHz, εr = 9.74, and τf = −30.12 ppm/°C). Additionally, a thermal stable Y2.9Mg0.1Al4.9Si0.1O12-6 wt%TiO2 composite ceramic was developed. Based on this composite, a Wifi6E/7 patch antenna operating at 6.3 GHz and a millimeter-wave resonant antenna functioning at 27.1 GHz were designed and validated. This indicates the potential application prospects of garnet ceramics in 5G/6G radio communication technologies.