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 (εr) 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 (τf) impedes these applications. In this paper, the composite ceramics of MgO–xMTiO3 (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%MTiO3 systems under the high-temperature sintering process. With the addition of MT, the grain size of MgO decreased, the εr value improved with τf value gradually increasing from negative to positive value. Optimized microwave dielectric properties were achieved for 4 mol%LiF–MgO–10wt%SrTiO3 ceramics sintered at 1300 °C for 6 h, yielding εr = 11.2, Q × f = 46, 815 GHz, and τf =  + 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.