Sintering behavior, microstructure and microwave dielectric properties of Li_2MgTi_3O_8 modified by LiF

摘要

Abstract Sintering behavior, microstructure and microwave dielectric properties of Li_2MgTi_3O_8 ceramics modified by LiF have been studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermal dilatometry and with a network analyzer at the frequency of about 6-10 GHz. The addition of LiF to Li_2MgTi_3O_8 led to the formation of trace amounts of MgF_2(ss), and Li_2TiO_3(ss) secondary phases, which reduced the sintering temperature to 850 ℃ without affecting its microwave dielectric properties. In contrast, the LiF-doped composition exhibited single phase solid solution with ordered spinel structure after sintering at 900℃/2 h, and MgTi_2O_5 secondary phase appeared after sintering at 1100℃/2 h. An excellent combined microwave dielectric properties with ε_r of ~27.8, Qxf of-63,000 GHz and τ_f of —4.1 ppm/℃ could be obtained for the LiF-added composition with x = 0.15 sintered at 850℃/2 h. The x = 0.15 composition was chemically compatible with Ag powders after sintering at 850 ℃ for 2 h.