Within the scope of this research, Li 2 Mg 6 TiO 9 -based ceramics were prepared by a traditional solid-state sintering technique. The research analyzed the influence of lithium (Li) volatilization during the sintering process, on the phase composition, and resultant microwave dielectric performances (MIDP) of the Li 2 Mg 6 TiO 9 -based ceramics, employing advanced analytical techniques. X-ray diffraction and Raman spectroscopy analyses indicated the emergence of a second phase Mg 2 TiO 4 within the sample when the sintering temperature attained 1550 °C due to Li volatilization. The generated Mg 2 TiO 4 could effectively tune the MIDP of the ceramics. Optimal MIDP of Li 2 Mg 6 TiO 9 -based ceramics were derived from a sintering temperature of 1650 °C: dielectric constant ( ε r ) = 12.78, quality factor ( Q × f ) = 129,010 GHz, temperature coefficient of resonant frequency ( τ f ) = − 46.2 ppm/°C. Low ε r and ultrahigh Q × f indicate that the current ceramics have potential application prospects in millimeter wave communication as substrate materials.
Development of low-temperature co-fired ceramics (LTCC) is a worldwide focus due to high integration, energy saving, and environmental friendliness. Herein, a beneficial attempt was made to decrease the sintering temperature of the Li2Mg6TiO9 (L2M6T) ceramic via doping LiF for LTCC applications. Furthermore, the phase structure, microstructure, and microwave dielectric properties of the doped ceramics were investigated in detail. The densification temperature of L2M6T was significantly reduced from 1450 to 1025 °C after LiF doping, which was conducive to energy saving. A small amount of LiF doping resulted in the formation of a MgO-type solid solution. The increase in molecular polarizability led to an increase in the dielectric constant (εr). An appropriate amount of LiF doping reduced the lattice vibration damping behavior, which in reverse improved the quality factor (Q × f). The substitution of F– ion for the O2– ion increased the bond energy of the total chemical bond, optimizing the temperature coefficient of resonant frequency (τf). The L2M6T ceramic-doped 3 wt % LiF presented the best microwave dielectric properties of εr = 12.37, Q × f = 112,400 GHz, and τf = −29.5 ppm/°C. In addition, the ceramic sintered at 950 °C exhibited great chemical compatibility with silver electrodes, indicating that it is potentially valuable for LTCC applications.
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