Microwave dielectric properties and compatibility with silver electrode of novel low-fired Ba4CuTi11O27 ceramic

A novel low-fired microwave dielectric ceramic with composition of Ba4CuTi11O27 was prepared by a conventional solid-state reaction method. A single-phase Ba4CuTi11O27 ceramic could be well densified after sintering above 950 °C for 4 h in air. A refinement using X-ray powder diffraction data was carried out in the Rietveld method using the parameters of Ba4Ti12O27 as a starting model. Ba4CuTi11O27 ceramic sintered at 975 °C has a monoclinic structure (C12/m1) with lattice parameters of a=19.8061(4) Å, b=11.4456(2) Å, c=9.9131(2) Å, β=108.8988(15) Å, V=2126.08(8) Å3, Z=4. The Ba4CuTi11O27 ceramics exhibited a low sintering temperature (~975 °C) and good microwave dielectric properties with Q×f value of 15,040 GHz, εr of 36.3 and τf value 11.9 ppm/°C. More importantly, the Ba4CuTi11O27 dielectrics demonstrated good chemical compatibility with Ag when sintered at 950 °C, keeping excellent microwave dielectric properties with Q×f=12,130 GHz, εr=36.1, τf=12.1 ppm/°C, which indicates that Ba4CuTi11O27 ceramic is a candidate for LTCC devices.