Enhanced structure and microwave dielectric properties of low-temperature sintering Li 2 Mg 1 − x Ca x SiO 4 ceramics by Ca 2+ ion substitution

In this paper, the Ca 2+ ion was chosen to substitute the Mg 2+ ion of Li 2 MgSiO 4 ceramics. Li 2 Mg 1 − x Ca x SiO 4 (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% Bi 2 O 3 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 Ca 2+ ions affected the densification of the prepared ceramics. Ca 2+ ion substitution resulted in increasing relative density, enhancing microwave properties. Ca 2+ ion substituted Mg 2+ 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, Ca 2+ ion substitution gave ceramics excellent microwave properties: bulk density ρ = 2.479 g/cm 3 , 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.