Fabrication of multilayer electronic magnetic window material by Si2N2O decomposition

•Two types of sandwich structures were obtained by adjusting the Si2N2O decomposition.•Outer layers were pure β-Si3N4, while the inner layer is Si2N2O.•Layer thickness is tunable by controlling the decomposition temperature.•The mechanical and dielectric properties can be tailored.

Silicon oxynitride (Si2N2O) based wave transparent material with multilayer structures was fabricated by a two step sintering route. Influences of temperature and atmosphere on microstructure and properties of the materials were investigated. Results showed that the decomposition of Si2N2O is the reason of such multilayer structure. Thickness of the β-Si3N4 outer layers and the Si2N2O inner layer could be tailored by adjusting the decomposing temperature. The flexural strength of the material was decreased after decomposed at 1600 °C–1700 °C, while decomposition occurred at 1800 °C strengthened the ceramic bodies. Materials with such structures showed good mechanical properties (flexural strength δ = 210–236 MPa) and suitable dielectric properties (dielectric constant ε < 4.8, loss tangent tanδ < 0.0044). This simple process allows the gas pressure sintered Si3N4/Si2N2O/Si3N4 ceramic composites to be widely used as the radome material for military and commercial applications.

Graphical abstractThe decomposition of Si2N2O is the reason for the formation such multi-layer structure. The outer layers are β-Si3N4, while the inner layer is Si2N2O.Figure optionsDownload full-size imageDownload as PowerPoint slide