Tuning sintering temperature and microwave dielectric properties of MgGa2O4 ceramics via LiF addition for LTCC applications

This study demonstrates the successful synthesis of (1- x )MgGa 2 O 4 - x LiF ( x  = 0.1–0.4, mass fraction) ceramics via solid-state reaction, achieving a significant reduction in sintering temperature from 1410 to 850 °C. The XRD and Raman testing results showed the formation of a new phase of LiGaO 2 , which affected the dielectric properties. Variations in the sintering density and ionic polarizability cause changes in the permittivity. In addition, the packing fraction analysis of MgGa 2 O 4 , which influences the crystal structure stability, elucidates the intrinsic mechanisms affecting the dielectric loss. The composite effect makes the τ f value of the ceramic shift toward the negative value, owing to the large negative frequency temperature coefficient of LiF. Finally, (1- x )MgGa 2 O 4 - x LiF ( x  = 0.3) sintered at 850 °C possesses the superior dielectric properties: ε r  = 9.45, Q × f = 32,790 GHz, τ f  = −28.5 ppm/°C (at 14 GHz). In addition, (1- x )MgGa 2 O 4 - x LiF ( x  = 0.3) ceramics exhibit good cofiring compatibility with Ag electrodes promoting the ceramic to be a suitable candidate for LTCC applications.