Journal of the American Ceramic Society, Vol.94, No.12, 4364-4370, 2011
Anisotropic Dielectric Properties of LiNb0.6Ti0.5O3 Microwave Ceramics by Screen-Printing Templated Grain Growth
In this work, anisotropic LiNb0.6Ti0.5O3 (LNT) template particles are prepared by molten salt synthesis in LiCl flux. Plate-like particles with diameters of 5-20 mu m and thicknesses of 0.5-2.0 mu m synthesized at 1000 degrees C are chosen as templates. Highly textured microwave ceramics of M-phase LNT with tunable dielectric properties are fabricated by a novel screen-printing templated grain growth technique (sp-TGG), and their characteristics and dielectric properties are studied systematically. Dielectric anisotropy is observed in dielectric constant (epsilon r) and the temperature coefficient of dielectric constant (tau e) at 1 MHz. LNT(//) samples exhibit lower epsilon r (=55.3) than randomly oriented ceramics and a positive temperature coefficient tau e (75 ppm/degrees C), whereas, LNT(perpendicular to) samples exhibit higher epsilon r (=83.6) and a negative temperature coefficient tau e (= -120 ppm/degrees C). The textured ceramics also exhibit anisotropic and excellent properties at microwave frequency, with LNT-M(//) showing epsilon r = 57.9, Q x f =6325 GHz, tau f = -14 ppm/degrees C and LNT-M(//) showing epsilon r = 81.8, Q x f = 5751 GHz, tau f = 43 ppm/degrees C. By tailoring along different directions, continuously tunable dielectric constant ranging from 55 to 83 could be obtained, and tau f could be changed from -14 to 43 ppm/degrees C. These findings can be technologically beneficial for wireless communication devices.