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.