Effects of Cu substitution on microstructures and microwave dielectric properties of Li2ZnSiO4 ceramics

Herein, the influence of Cu2+ substitution on the phase composition, bulk density, microstructures, and microwave dielectric properties of Li2CuxZn1−xSiO4 (0 ≤ x ≤ 0.06) ceramics prepared by a solid-state reaction were investigated. The results of XRD and mapping showed that Cu2+ substitution can avoid the influence of secondary phase on the properties of samples. According to the analysis of bulk density, microstructure and microwave dielectric properties, a proper amount of Cu substitution not only improved the sintering characteristics of Li2CuxZn1−xSiO4 ceramics, reduced the densification temperature from 1250 °C to 950 °C, but also increased the Q×f value. Furthermore, Cu2+ substitution also improved the temperature stability of the samples. Particularly, the Li2Cu0.04Zn0.96SiO4 ceramics sintered at 950 °C for 5 h possessed excellent microwave dielectric properties: εr = 5.624, Q×f = 12,764 GHz, and τf = −77 ppm/°C, exhibiting a potential for the low temperature co-fired ceramic applications.

Microwave dielectric properties of Na+-substituted CaMg0.9Li0.2Si2O6 ceramics

Ceramics with low dielectric constant are widely used in high frequency substrates. The low temperature sintered CaMg0.9-xNa2xLi0.2Si2O6(x = 0–0.05 and 0.1) ceramics with low dielectric constant and dielectric loss were prepared by the traditional solid-state reaction method, with 0.5wt%LBSCA additive. The XRD patterns of the samples were obtained by X-ray diffraction and it was found that there were three ceramic components, CaMgSi2O6, CaSiO3 and Na2MgSiO4, which indicated that the experimental sample was a multiphase ceramic system. Through the trend of bulk density as functions of the content of substitution and the change of SEM morphology, it could be found that appropriate amount of Na+ substitution can promote the grain growing and the densification of ceramics. Results demonstrated that both the Q × f and εr were relevant to bulk density and the second phase. The τf was also affected by the second phase to some extent. In particular, the ceramics sintered at 925 °C for 3h possessed the desirable microwave dielectric properties for LTCC application: εr = 7.03, Q × f = 17,956 GHz, and τf= −79 ppm/°C.