5G microstrip patch antenna and microwave dielectric properties of 4 mol%LiF–MgO–xwt%MTiO3 (M = Ca, Sr) composite ceramics

The combination of low dielectric constant ( ε r ) and a high-quality factor ( Q × f ) in MgO ceramics makes them attractive for 5G applications. However, the large negative temperature coefficient of resonance frequency ( τ f ) impedes these applications. In this paper, the composite ceramics of MgO– x MTiO 3 (M = Ca, Sr; x = 0, 2.5, 5, 7.5, 10 wt%) with the addition of 4 mol% LiF as a sintering aid were fabricated by the traditional solid-state reaction method. The coexistence both MgO and MT phases can be observed in XRD and SEM in the 4 mol% LiF–MgO–wt%MTiO 3 systems under the high-temperature sintering process. With the addition of MT, the grain size of MgO decreased, the ε r value improved with τ f value gradually increasing from negative to positive value. Optimized microwave dielectric properties were achieved for 4 mol%LiF–MgO–10wt%SrTiO 3 ceramics sintered at 1300 °C for 6 h, yielding ε r = 11.2, Q × f = 46, 815 GHz, and τ f = + 3.51 ppm/°C. Based on it, a prototype of microstrip patch antenna was designed and fabricated with a center frequency at 5.64 GHz for 5G–Sub6GHz communication applications.