Sintering behavior, structural evolution, and dielectric properties of Li3Mg3NbO7 + x wt% LiF microwave dielectric ceramics

In this paper, x wt% LiF (1 ≤ x ≤ 10) is utilized to decrease sintering temperature, improve microstructure and enhance Q × f of Li 3 Mg 3 NbO 7 ceramics. Remarkably, the appropriate addition of LiF leads to the dramatic reduction in sintering temperature (reduced by 300 °C) and the significant improvement in Q × f (increase ratio: 26 %). The addition of LiF causes the generation of cubic oxyfluoride solid solution, which is confirmed by XRD, SEM and TEM. When x ≤ 8, both orthorhombic oxide and cubic oxyfluoride solid solution exist in ceramics. When x = 10, the ceramic is composed of cubic oxyfluoride solid solution and LiF. It is confirmed that the maximum mass percentage of LiF required to fully form a cubic solid solution is between 8 wt% and 10 wt%. The significant improvement in Q × f is mainly attributed to increase in relative density and orthorhombic-cubic phase transition. In this system, Li 3 Mg 3 NbO 7 + 8 wt% LiF ceramics sintered at 900 °C possess the optimal dielectric properties: ε r = 14.10, Q × f = 152,510 GHz and τ f = −43.5 ppm/°C. The Li 3 Mg 3 NbO 7 + 8 wt% LiF ceramics show an outstanding combination of low ε r , high Q × f and low sintering temperature, surpassing the performance of most low-temperature dielectric materials. The excellent chemical compatibility with Ag electrodes suggests that the Li 3 Mg 3 NbO 7 + 8 wt% LiF ceramics are particularly promising for LTCC applications.