Low-temperature synthesis/densification and properties of Si 2N 2O prepared with Li 2O additive

Abstract

Dense Si 2N 2O was successfully synthesized using 2 mol% Li 2O as an additive by a hot-pressing method at 1500 °C. Compared to other metal oxide additives, Li 2O can significantly decrease the sintering temperature of Si 2N 2O, which is ascribed to the lower melting point of Li 2O–SiO 2 and the formation of less viscous liquid phase. Increasing Li 2O content has no apparent influence on the mechanical and dielectric properties of dense Si 2N 2O, which is due to the easy evaporation of Li 2O at sintering temperature. The mechanical properties of Si 2N 2O with Li 2O additive are comparable to those of Si 2N 2O synthesized with other additives. The as-prepared bulk Si 2N 2O with 2 mol% Li 2O 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.