Low-temperature synthesis/densification and properties of Si2N2O prepared with Li2O additive

Dense Si2N2O was successfully synthesized using 2 mol% Li2O as an additive by a hot-pressing method at 1500 °C. Compared to other metal oxide additives, Li2O can significantly decrease the sintering temperature of Si2N2O, which is ascribed to the lower melting point of Li2O–SiO2 and the formation of less viscous liquid phase. Increasing Li2O content has no apparent influence on the mechanical and dielectric properties of dense Si2N2O, which is due to the easy evaporation of Li2O at sintering temperature. The mechanical properties of Si2N2O with Li2O additive are comparable to those of Si2N2O synthesized with other additives. The as-prepared bulk Si2N2O with 2 mol% Li2O additive exhibits both low dielectric constant (6.17 at 1 MHz) and loss tangent (0.0008 at 1 MHz) and combines good mechanical performance, indicating it is a potential high-temperature structural/functional material.