Effects of Zn²⁺ substitution on the sintering behaviour and dielectric properties of Li₂Mg_1−xZn_xSiO₄ ceramics

Abstract

Silicates, the basis on which low-temperature-fired dielectric materials widely studied for applications in the fields of microwave integrated circuits, have been develo** vigorously owing to their low dielectric constants and tangent loss values. In this work, Zn²⁺ was gradually substituted to Mg²⁺ to make the sintering temperature decreased and enhance the microwave dielectric properties of Li₂MgSiO₄. Li₂Mg_1−xZn_xSiO₄ (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) powders were prepared through solid-state reaction. Aiming to decrease the sintering temperature to approximately 900 °C, 3 wt% Li₂O–B₂O₃–SiO₂–CaO–Al₂O₃ glass was used as a sintering aid. The XRD patterns made it clear that the major crystalline phase of the materials was Li₂(Mg,Zn)SiO₄. A new unexpected crystalline phase of Zn_xSiO₄ appeared when the amount of Zn²⁺ substituted increased to more than 0.4. SEM micrographs demonstrated that when x = 0.4, the most homogeneous microstructure appeared. Meanwhile, the Q × f value and the relative density also reached to their peaks when x = 0.4, respectively. Moreover, 3 wt% LBSCA-doped Li₂Mg_0.6Zn_0.4SiO₄ ceramics exhibited excellent dielectric properties of ε_r = 5.89, Q × f = 44,787 GHz and τ_f = − 71.65 ppm/°C when sintered at 900 °C. The material exhibited low relative permittivity and low dielectric loss and could thus be a potential candidate for LTCC device applications.