A novel oxyfluoride ceramic in Li2TiO3–LiF system for LTCC applications

Abstract

Li2TiO3-based materials are gaining momentum in the field of microwave dielectric ceramics for their moderate dielectric constant and high-quality factor. Herein, a novel oxyfluoride ceramic Li3TiO3F in the Li2TiO3–LiF system was successfully prepared by a traditional ceramic method. The synthesis process of Li3TiO3F ceramic was optimized to obtain improved microstructure and desired microwave dielectric properties (MDP) by means of material characterization techniques, such as thermogravimetric-differential thermal analysis, X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. A cubic rock salt structure for Li3TiO3F ceramic was confirmed by Rietveld refinement results. The ceramic sintered at 900 °C showed the most favorable MDP of εr = 17.28, quality factor (Q × f) = 96,280 GHz, and τf = −32.7 ppm/°C, obtaining a microstructure superior to that of Li2TiO3. Moreover, the ceramic exhibited favorable chemical compatibility with Ag at 900 °C, indicating a great potential for the use of Li3TiO3F ceramic as substrates in low temperature cofired ceramic (LTCC) technology. More importantly, the results of this work offered the option of using low temperature firing of ceramic by forming a solid solution between the oxide and the fluoride.