Low sintering temperature, temperature-stable scheelite structured Bi[V1−x (Fe1/3W 2/3)x]O4 microwave dielectric ceramics

Abstract

Low sintering temperature Bi[V1−x(Fe1/3W2/3)x]O4 (BVFWx) (0.02 ≤ x ≤ 0.08) ceramics have been prepared by solid-state reaction. Compositions with 0.02 ≤ x ≤ 0.08 were scheelite-structure, but distortion of [BO4] tetrahedra decreased with increase in x. Although the crystal class remained monoclinic, the phase transition temperature (TC) decreased from 255 ℃ (BV) to 51 ℃ (BVFW0.08), suggesting that higher concentrations of (Fe1/3W2/3) would result in the stabilization of tetragonal scheelite at room temperature. The decrease in the [BO4] distortion additionally resulted in a large reduction in the magnitude of the temperature coefficient of resonant frequency (TCF) with near-zero values obtained by sintering BVFW0.08:2BVFW0.06 at 780 °C to give TCF ≈ −5.9 ppm / °C, relative permittivity εr ≈ 77.4, and microwave quality factor, Q × f ≈ 8100 GHz (@ ~ 4.3 GHz). These promising microwave dielectric properties coupled with the low sintering temperature suggest that BVFWx ceramics are of interest in low-temperature cofired ceramic (LTCC) technology, and for monolithic resonator and filter applications.