Microwave dielectric properties of Na⁺-substituted CaMg_0.9Li_0.2Si₂O₆ ceramics

¹ State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
² Yangtze River Delta Research Institute of UESTC (Huzhou), Huzhou, 313000, China

^* Corresponding author: fangyi_huang@163.com

Abstract

Ceramics with low dielectric constant are widely used in high frequency substrates. The low temperature sintered CaMg_0.9-xNa_2xLi_0.2Si₂O₆(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 ε_r were relevant to bulk density and the second phase. The τ_f 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: ε_r = 7.03, Q × f = 17,956 GHz, and τ_f= −79 ppm/°C.