Premium
Microwave Dielectric Properties of Low Firing Temperature Bi 2 W 2 O 9 Ceramics
Author(s) -
Feteira Antonio,
Sinclair Derek C.
Publication year - 2008
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2008.02272.x
Subject(s) - materials science , temperature coefficient , ceramic , orthorhombic crystal system , analytical chemistry (journal) , relative permittivity , permittivity , dielectric , electrode , ferroelectricity , mineralogy , crystal structure , crystallography , chemistry , composite material , optoelectronics , chromatography
Phase stability, sinterability, and microwave dielectric properties of Bi 2 W 2 O 9 ceramics and their cofireability with Ag, Cu, and Au electrodes have been investigated. Single‐phase Bi 2 W 2 O 9 powder was synthesized by solid‐state reaction in air at 800°C for 3 days. X‐ray powder diffraction data show Bi 2 W 2 O 9 to have an orthorhombic crystal structure described by the noncentrosymmetric space group Pna 2 1 , with lattice parameters a =5.4401(8), b =5.4191(8), c =23.713(4) Å. Ceramics fired at temperatures up to 865°C remain single‐phase but above this temperature ferroelectric Bi 2 WO 6 appears as a secondary phase. The measured relative permittivity of Bi 2 W 2 O 9 ceramics increases continuously from 28.6 to 40.7 for compacts fired between 860° and 885°C. The bulk relative permittivity of Bi 2 W 2 O 9 corrected for porosity was calculated as 41.3. Bi 2 W 2 O 9 ceramics fired up to 875°C exhibit moderate quality factors, Q × f r , ∼7500–7700 GHz and negative temperature coefficient of resonant frequency, ∼−54 to −63 ppm/°C. Chemical compatibility experiments show Bi 2 W 2 O 9 ceramics to react with both Ag and Cu electrodes, but to form good contacts with Au electrodes.