Preparation and properties of Si2N2O/β-cristobalite composites

Bulk Si2N2O/β-cristobalite composites have been fabricated by a hot-pressing method using Si3N4, SiO2 and Li2CO3 as starting materials. β-Cristobalite in the as-sintered composites is successfully stabilized to room temperature through incorporating N and Li into its structure. The introduction of β-cristobalite significantly improves the dielectric properties. Si2N2O/62 vol.% β-cristobalite composite shows a low dielectric constant of 4.8 at 1 MHz. In addition, the density, Youngʹs and shear modulus, and strength of the composites decrease with the increase of β-cristobalite content. When the β-cristobalite content is up to 62 vol.%, the flexural strength of the composite reaches 212 MPa. The bulk Si2N2O/β-cristobalite composites show the combination of low density, excellent mechanical performance, low dielectric constant and loss tangent, indicating that they are promising high-temperature structural/functional materials.