Low-firing of CaAl2B2O7 ceramics with Li2O–B2O3–SiO2 and LiF additions

Lithium borosilicate (LBS) and lithium fluoride (LiF) are verified to be effective sintering aids for CaAl 2 B 2 O 7 microwave dielectric ceramic to reduce the sintering temperature and lower the activation energies . Benefiting from the liquid phase sintering , low-firing, low permittivity and low-loss CaAl 2 B 2 O 7 microwave dielectric composite has been successfully obtained. Typically, CaAl 2 B 2 O 7 assembled with 1 wt % LBS composite possesses desirable properties of ε r  = 5.91, Q × f = 39,443 GHz, τ f  = −23.51 ppm/°C (@16.53 GHz). For composite ceramics with 0.5 wt % LiF, the optimal microwave dielectric properties are ε r  = 6.08, Q × f = 37,295 GHz, τ f  = −22.39 ppm/°C (@15.78 GHz). The two kinds of composite are densified at 875 °C, with co-existed CaB 2 O 4 and liquid phase. The mechanism underlying the low temperature sintering is revealed by well-matched wettability and lower activation energy of composite ceramics with additions.