Crystal Structure and Microwave Dielectric Properties of an Ultralow-Temperature-Fired (AgBi)(0.5)WO4 Ceramic

A new microwave dielectric (AgBi)(0.5)WO4 ceramic with an ultralow firing temperature was prepared by the solid-state reaction method. (AgBi)(0.5)WO4 can be obtained as a dense single-phase bulk material with a calcination temperature of 500 degrees C and sintering temperatures of ca. 580 degrees C. The material has a microwave relative permittivity of ca. 35.9, a Qf value of ca. 13000 GHz, and a negative temperature coefficient of -69 ppm/degrees C at 7.5 GHz. The crystal structure of (AgBi)(0.5)WO4 was determined by a combination of X-ray and transmission electron microscopy (TEM) diffraction analysis. The compound crystallizes in the monoclinic C12/m1 (no. 12) space group with the lattice parameters a = 10.1330(8) angstrom, b = 11.0013(0) angstrom, c = 7.2756(4) angstrom, and = 127.712(3)degrees. From an X-ray diffraction analysis, the (Ag0.5Bi0.5)WO4 ceramic reacts with silver after heat treatment at 560 degrees C to form new compounds, namely, Bi2WO6 and Ag2WO4. However, the (AgBi)(0.5)WO4 ceramic is chemically compatible with aluminum powder at 600 degrees C as an alternative cofired electrode material. All the results suggest that (AgBi)(0.5)WO4 ceramic is a promising new candidate material for ultralow-temperature cofired ceramic (ULTCC) technology.