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

In this paper, the Ca2+ ion was chosen to substitute the Mg2+ ion of Li2MgSiO4 ceramics. Li2Mg1 - xCaxSiO4 (x = 0.0, 0.03, 0.06, 0.09, 0.12) ceramics materials were prepared by solid state reaction at low temperature (925 degrees 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 epsilon' and quality factor Qxf gradually increased, and tau(f) values increased from negative to positive values. When x = 0.09 and sintered at 925 degrees C, Ca2+ ion substitution gave ceramics excellent microwave properties: bulk density rho = 2.479 g/cm(3), relative density was 98.68%, dielectric constant epsilon'=6.59, dielectric loss tan delta(epsilon) = 0.0018, quality factor Qxf = 8976.9 GHz and temperature coefficient tau(f) = 1.9 ppm/degrees C. This ceramic material has excellent microwave dielectric properties and holds a potential for use in integrated antenna and other electronic devices.