Novel low-εr MGa2O4 (M = Ca, Sr) microwave dielectric ceramics for 5 G antenna applications at the Sub-6 GHz band

Two novel low- ε r gallates MGa 2 O 4 (M = Ca, Sr) have been synthesized via a standard solid-state reaction method. According to the X-ray diffraction results, CaGa 2 O 4 crystallizes in space group Pna2 1 with an orthorhombic symmetry, while SrGa 2 O 4 belongs to the monoclinic P2 1 / c system. Both ceramics show ever-improving microstructures with the increasing sintering temperature . The optimal microwave dielectric properties ( ε r = 9.2, Qf = 66,000 GHz, τ f =–85 ppm/°C for SrGa 2 O 4 and ε r = 10.6, Qf = 15,400 GHz, τ f =–58 ppm/°C for CaGa 2 O 4 ) are obtained when sintered at 1275 °C. A patch antenna is fabricated using SrGa 2 O 4 ceramics as the substrate, which realizes a return loss of –19.94 dB and total efficiency of –1.38 dB (72.8 % in power ratio) at 4.84 GHz. The exceptional performances indicate that SrGa 2 O 4 ceramics are promising candidates for antenna applications at the Sub-6 GHz band.