Phase evolution and microwave dielectric properties of ceramics with nominal composition Li2x(Zn0.95Co0.05)2- xSiO4 for LTCC applications

Abstract

Li2x(Zn0.95Co0.05)2-xSiO4 (0 ≤ x ≤ 1) ceramics were prepared through the conventional solid-state route. A fixed amount of Li2O-MgO-ZnO-B2O3-SiO2 (LMZBS) glass was used as a sintering aid to help lower the sintering temperature to around 900 °C. The effects of part lithium-ion substitution on the phase formation, sintering behaviour, microstructures and microwave dielectric properties of the ceramics were systematically investigated. When x = 0.25, the sample achieved a dense microstructure and exhibited excellent microwave dielectric properties of ϵr = 6.47, Q × f = 131 579 GHz and τf = -27.12 ppm °C-1. For its practical application in low-temperature co-fired ceramics (LTCC), large positive τf of CaTiO3 was used to adjust the τf value of the composite ceramic to nearly zero. The composite ceramic of 0.975Li0.5(Zn0.95Co0.05)1.75SiO4-0.025CaTiO3 sintered at 900 °C also presented good microwave dielectric properties of ϵr = 6.773, Q × f = 69 177 GHz and τf = -2.45 ppm °C-1.