10.
In this work, ultra-low loss Li
2MgTi
0.7(Mg
1/3Nb
2/3)
0.3O
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
1/3Nb
2/3)
4+ ions substituted ceramics. The addition of (Mg
1/3Nb
2/3)
4+ ions enhances the bond energy in unit cell without changing the crystal structure of Li
2MgTiO
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
2MgTi
0.7(Mg
1/3Nb
2/3)
0.3O
4 ceramics sintered at 1400?°C can achieve an excellent combination of microwave dielectric properties:
εr =?16.19,
Q·f?=?160,000?GHz and
τf =??3.14?ppm/°C. In addition, a certain amount of LiF can effectively lower the sintering temperature of the matrix, and the Li
2MgTi
0.7(Mg
1/3Nb
2/3)
0.3O
4-3?wt% LiF ceramics sintered at 1100?°C possess balanced properties with
εr?=?16.32,
Q·f?=?145,384?GHz and
τf =??16.33?ppm/°C.
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