Enhanced structure and microwave dielectric properties of low-temperature sintering Li2Mg1 − xCaxSiO4 ceramics by Ca2+ ion substitution

Abstract

In this paper, the Ca²⁺ ion was chosen to substitute the Mg²⁺ ion of Li₂MgSiO₄ ceramics. Li₂Mg_1 − xCa_xSiO₄ (x = 0.0, 0.03, 0.06, 0.09, 0.12) ceramics materials were prepared by solid state reaction at low temperature (925 °C) with 2.5wt% Bi₂O₃ sintering aid. X-ray diffraction (XRD) results showed the ceramics presented the standard Lithium Magnesium Silicate phase formation, and no secondary phases appeared. Scanning electron microscopy (SEM) suggested that Ca²⁺ ions affected the densification of the prepared ceramics. Ca²⁺ ion substitution resulted in increasing relative density, enhancing microwave properties. Ca²⁺ ion substituted Mg²⁺ ion and formed a CaO4 structure, which affected microwave dielectric properties. With the substituted amount increase, the values of dielectric constant ε’ and quality factor Q×f gradually increased, and τ_f values increased from negative to positive values. When x = 0.09 and sintered at 925 °C, Ca²⁺ ion substitution gave ceramics excellent microwave properties: bulk density ρ = 2.479 g/cm³, relative density was 98.68%, dielectric constant ε’=6.59, dielectric loss tanδ_ε = 0.0018, quality factor Q×f = 8976.9 GHz and temperature coefficient τ_f = 1.9 ppm/°C. This ceramic material has excellent microwave dielectric properties and holds a potential for use in integrated antenna and other electronic devices.