Microwave dielectric properties of ultra-low loss Li2MgTi0.7(Mg1/3Nb2/3)0.3O4 ceramics sintered at low temperature by LiF addition

In this work, ultra-low loss Li 2 MgTi 0.7 (Mg 1/3 Nb 2/3 ) 0.3 O 4 ceramics were successfully prepared via the conventional solid-state method. X-ray photoelectron spectroscopy (XPS), thermally stimulated depolarization current (TSDC) and bond energy were used to determine the distinction between intrinsic and extrinsic dielectric loss in (Mg 1/3 Nb 2/3 ) 4+ ions substituted ceramics. The addition of (Mg 1/3 Nb 2/3 ) 4+ ions enhances the bond energy in unit cell without changing the crystal structure of Li 2 MgTiO 4 , which results in high Q·f value as an intrinsic factor. The extrinsic factors such as porosity and grain size influence the dielectric loss at lower sintering temperature , while the oxygen vacancies play dominant role when the ceramics densified at 1400 °C. The Li 2 MgTi 0.7 (Mg 1/3 Nb 2/3 ) 0.3 O 4 ceramics sintered at 1400 °C can achieve an excellent combination of microwave dielectric properties : ε r =  16.19, Q·f  = 160,000 GHz and τ f = −3.14 ppm/°C. In addition, a certain amount of LiF can effectively lower the sintering temperature of the matrix, and the Li 2 MgTi 0.7 (Mg 1/3 Nb 2/3 ) 0.3 O 4 -3 wt% LiF ceramics sintered at 1100 °C possess balanced properties with ε r  =  16.32, Q·f  = 145,384 GHz and τ f = −16.33 ppm/°C.