LiGaSiO4: An ultra-low permittivity dielectric material enabling application in patch antenna

Abstract

A low permittivity microwave dielectric ceramic, Li-containing silicate (LiGaSiO4), was synthesized using the standard solid-state reaction method. The nominal LiGaSiO4 ceramic exhibited a relative permittivity of approximately 4.4. The effects of nonstoichiometric Li on the microstructure, sintering behavior, and microwave dielectric properties of LiGaSiO4 were comprehensively investigated. Excess Li content (6 mol%) significantly improved the relative density (96.1 %) and microwave dielectric properties (εr∼5.34, Q × f ∼55,600 GHz, and τf ∼ -48.6 ppm/°C), while reducing the optimum sintering temperature from 1070 °C to ∼1010 °C. Additionally, the incorporation of 2 wt% LiF further reduced densification temperature (∼940 °C). The regulation of the τf was achieved through the addition of CaTiO3 ceramic, and a patch antenna was designed and fabricated using a modified Li1.06GaSiO4-LiF-CaTiO3 composite ceramic. The resulting patch antenna resonates at 5.87 GHz with an impressive bandwidth of 83.1 MHz, while both simulated and measured results demonstrate excellent agreement.