Crystal structure and microwave dielectric properties of an ultralow-temperature-fired (AgBi)_0.5WO₄ ceramic

A new microwave dielectric (AgBi)_0.5WO₄ ceramic with an ultralow firing temperature was prepared by the solid-state reaction method. (AgBi)_0.5WO₄ can be obtained as a dense single-phase bulk material with a calcination temperature of 500 °C and sintering temperatures of ca. 580 °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/°C at 7.5 GHz. The crystal structure of (AgBi)_0.5WO ₄ 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) Å, b = 11.0013(0) Å, c = 7.2756(4) Å, and β = 127.712(3)°. From an X-ray diffraction analysis, the (Ag _0.5Bi_0.5)WO₄ ceramic reacts with silver after heat treatment at 560 °C to form new compounds, namely, Bi ₂WO₆ and Ag₂WO₄. However, the (AgBi)_0.5WO₄ ceramic is chemically compatible with aluminum powder at 600 °C as an alternative cofired electrode material. All the results suggest that (AgBi)_0.5WO₄ ceramic is a promising new candidate material for ultralow-temperature cofired ceramic (ULTCC) technology. (AgBi)_0.5WO₄ can be obtained as a dense single-phase bulk material with sintering temperatures of ca. 580 °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/°C at 7.5 GHz. It is chemically compatible with aluminum powder at 600 °C as an alternative cofired electrode material.