Anisotropic Dielectric Properties of LiNb_(0.6)Ti_(0.5)O_3 Microwave Ceramics by Screen-Printing Templated Grain Growth

摘要

In this work, anisotropic LiNb_(0.6)Ti_(0.5)O_3 (LNT) template particles are prepared by molten salt synthesis in LiCI flux. Plate-like particles with diameters of 5-20 μm and thicknesses of 0.5-2.0 μm synthesized at 1000℃ 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 (ε_r) and the temperature coefficient of dielectric constant (τ_ε) at 1 MHz. LNT(/ /) samples exhibit lower ε_r (=55.3) than randomly oriented ceramics and a positive temperature coefficient τ_ε (75 ppm/℃), whereas, LNT(⊥) samples exhibit higher ε_r (=83.6) and a negative temperature coefficient τ_ε (= -120 ppm/℃). The textured ceramics also exhibit anisotropic and excellent properties at microwave frequency, with LNT-M(//) showing ε_T = 57.9, Q×f= 6325 GHz, τ_f = -14 ppm/℃ and LNT-M(⊥) showing ε_r = 81.8, Q ×f = 5751 GHz,⊥_f = 43 ppm/℃. By tailoring along different directions, continuously tunable dielectric constant ranging from 55 to 83 could be obtained, and ⊥_f could be changed from -14 to 43 ppm/℃. These findings can be technologically beneficial for wireless communication devices.