Sintering characteristics, phase transitions, and microwave dielectric properties of low-firing [(Na0.5Bi0.5)xBi1-x](WxV1-x)O4 solid solution ceramics

A series of high-k [(Na0.5Bi0.5)xBi(1-x)](WxV1-x)O-4 (abbreviated as NBWV(x value)) solid solution ceramics with a scheelite-like structure are synthesized by a modified solid-state reaction method at the temperature range of 680-760.. A monoclinic (0 <= x < 0.09) to tetragonal scheelite (0.09 <= x <= 1.0) structural phase transition is confirmed by X-ray diffraction (XRD), Raman, and infrared (IR) analyses. The effect of structural deformation and order-disorder caused by Na+/Bi3+/W6+ complex substitution on microwave dielectric properties is investigated in detail. The compositional series possess a wide range of variable relative permittivity (epsilon(r) = 24.8-80) and temperature coefficient of resonant frequency (TCF value, -271.9-188.9 ppm/ degrees C). The maximum permittivity of 80 and a high Qxf value of similar to 10,000 GHz are obtained near the phase boundary at x = 0.09. Furthermore, the temperature-stable dielectric ceramics sintered at 680 degrees C with excellent microwave dielectric properties of epsilon(r) = 80.7, Qxf = 9400 GHz (at 4.1 GHz), and TCF value = -3.8 ppm/degrees C are designed by mixing the components of x = 0.07 and 0.08. In summary, similar sinterability and structural compatibility of scheelite-like solid solution systems make it potential for low-temperature co-fired ceramic ( LTCC) applications.