Microwave dielectric properties of low firing temperature Bi2W2O9 ceramics

作者：Feteira Antonio^*; Sinclair Derek C

来源：Journal of the American Ceramic Society, 2008, 91(4): 1338-1341.

DOI：10.1111/j.1551-2916.2008.02272.x

Phase stability, sinterability, and microwave dielectric properties of Bi2W2O9 ceramics and their cofireability with Ag, Cu, and Au electrodes have been investigated. Single-phase Bi2W2O9 powder was synthesized by solid-state reaction in air at 800 degrees C for 3 days. X-ray powder diffraction data show Bi2W2O9 to have an orthorhombic crystal structure described by the noncentrosymmetric space group Pna2(1), with lattice parameters a=5.4401(8), b=5.4191(8), c=23.713(4) angstrom. Ceramics fired at temperatures up to 865 degrees C remain single-phase but above this temperature ferroelectric Bi2WO6 appears as a secondary phase. The measured relative permittivity of Bi2W2O9 ceramics increases continuously from 28.6 to 40.7 for compacts fired between 860 degrees and 885 degrees C. The bulk relative permittivity of Bi2W2O9 corrected for porosity was calculated as 41.3. Bi2W2O9 ceramics fired up to 875 degrees C exhibit moderate quality factors, Q x f(r), similar to 7500-7700 GHz and negative temperature coefficient of resonant frequency, similar to-54 to -63 ppm/degrees C. Chemical compatibility experiments show Bi2W2O9 ceramics to react with both Ag and Cu electrodes, but to form good contacts with Au electrodes.

• 出版日期2008-4