Effects of sintering aids on densification behavior and microwave dielectric properties of CaO-SiO2 ceramic

Microwave dielectric ceramics are essential components in high-frequency communication systems, serving as filters, resonators, antennas, and substrates. CaO-SiO 2 -based ceramics are attractive candidates for such applications due to their low permittivity (ε r ) and cost-effectiveness. Nevertheless, the high sintering temperature (~ 1400 °C) constrains their practical application. In this work, the effects of Li 2 CO 3 , Na 2 CO 3 , Li 2 CO 3 -B 2 O 3 , and ZnO as sintering aids on the CaSiO 3 matrix are systematically investigated. The effects on phase evolution, crystal structure, densification behavior, and microwave dielectric properties are examined to elucidate the structure–property relationships. Analysis reveals that the CaO-SiO 2 -0.02Li 2 CO 3 ceramic develops a highly ordered crystalline structures and uniform microstructures, delivering optimal dielectric properties (ε r ~ 6.13, Q×f ~ 38,600 GHz, TCF ~ -36.62 ppm/℃ @1100 °C). Incorporation of B 2 O 3 enhances the fluxing effect, strengthening the Li 2 CO 3 -B 2 O 3 -assisted sintering effect and further lowering the sintering temperature (~1000 °C), although its Q×f decreases slightly (33,500 GHz). This study advances the theory of low-temperature sintering for CaO-SiO 2 -based ceramics, underpinning their application in high-frequency devices like satellite communication resonators.