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Li 2 TiO 3 -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 Li 3 TiO 3 F in the Li 2 TiO 3 –LiF system was successfully prepared by a traditional ceramic method. The synthesis process of Li 3 TiO 3 F 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 Li 3 TiO 3 F ceramic was confirmed by Rietveld refinement results. The ceramic sintered at 900 °C showed the most favorable MDP of ε r = 17.28, quality factor (Q × f) = 96,280 GHz, and τ f = −32.7 ppm/°C, obtaining a microstructure superior to that of Li 2 TiO 3. Moreover, the ceramic exhibited favorable chemical compatibility with Ag at 900 °C, indicating a great potential for the use of Li 3 TiO 3 F 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. [ABSTRACT FROM AUTHOR]

In this paper, nanocrystalline Nd[(Zn0.925Co0.075)1/2Ti1/2]O3 (NZCT75) powders were synthesized through glycine–nitrate combustion method with the intent of reducing the sintering temperature and improving the microwave dielectric properties of NZCT75 ceramics. Phase composition, structure, and morphology of the powders were analyzed by thermogravimetric analysis–differential thermal analysis (TG–DTA), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD results showed that the as-synthesized powder after rapid self-propagating combustion was highly crystallized and was mainly composed of NZCT75 phase and small amount of unknown phase. The unknown phase could be vanished through the calcination process of 600 °C. Compared to solid-state reaction route, a reduction of about 600 °C in the synthesis temperature for pure phase NZCT75 was realized. A large amount of pores with inhomogeneous distribution in size and shape was found from the SEM image of the as-synthesized powder due to the rapid combustion reaction between glycine and nitrates. The TEM study revealed that the average particle size of the calcined powder is around 31.9 nm. The bulk sample prepared by the nanosized powder could be sintered to 98.8% of the theoretical density at 1250 °C, reducing about 160 °C more than the solid-state reaction method. Meanwhile, excellent microwave dielectric properties of NZCT75 ceramics presented a dielectric constant of 37.17, a quality factor of 257,600 GHz, and a temperature coefficient of resonant frequency of – 29.48 ppm/oC. This study develops a facile approach to synthesize nanocrystalline powder for a promising application in microwave dielectric ceramics. [ABSTRACT FROM AUTHOR]