LiF-Doped Li2Mg6TiO9 with Improved Sintering Characteristics and Ultrahigh Quality Factor for Low-Temperature Co-Fired Ceramic Applications

Abstract

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 (ε_r). 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 O^2– ion increased the bond energy of the total chemical bond, optimizing the temperature coefficient of resonant frequency (τ_f). The L2M6T ceramic-doped 3 wt % LiF presented the best microwave dielectric properties of ε_r = 12.37, Q × f = 112,400 GHz, and τ_f = −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.