Sintering characteristics, phase transitions, and microwave dielectric properties of low-firing [(Na <sub>0.5</sub>Bi <sub>0.5</sub>) <sub> <i>x</i> </sub>Bi <sub>1− <i>x</i> </sub>](W <sub> <i>x</i> </sub>V <sub>1− <i>x</i> </sub>)O <sub>4</sub> solid solution ceramics
Xian Xue, Xiaomeng Li, Changli Fu, Yan Zhang, Jing Guo, Hong Wang
Abstract
A series of high-k [(Na<sub>0.5</sub>Bi<sub>0.5</sub>)<em><sub>x</sub></em>Bi<sub>1−<em>x</em></sub>](W<em><sub>x</sub></em>V<sub>1−<em>x</em></sub>)O<sub>4</sub> solid solution ceramics with a scheelite-like structure are synthesized by a modified solid-state reaction method at a temperature range of 680-760 °C. The monoclinic (0 ≤ <em>x</em> < 0.09) to tetragonal scheelite (0.09 ≤ <em>x</em> ≤ 1.0) structural phase transition is confirmed by XRD, Raman and IR analyses. The effect of structural deformation and order-disorder caused by Na<sup>+</sup>/Bi<sup>3+</sup>/W<sup>6+</sup> complex substitution on microwave dielectric properties is investigated in detail. The compositional series possess a wide range of variable relative permittivities (24.8 ~ 80) and TCF values (-271.9 ~ 188.9 ppm/°C). The maximum permittivity of 80 and a high <em>Q</em> × <em>f</em> value of ~10,000 GHz are obtained near the phase boundary at <em>x</em> = 0.09. Furthermore, a temperature stable dielectric ceramic sintered at 680 °C with excellent microwave dielectric properties of = 80.7, <em>Q</em> × <em>f</em> = 9,400 GHz (at 4.1 GHz) and TCF value = -3.8 ppm/°C is designed by mixing the <em>x</em> = 0.07 and <em>x</em> = 0.08 components. In summary, the similar sinterability and structural compatibility of scheelite-like solid solution systems make it potential for the LTCC applications.