Principles, design, structure and properties of ceramics for microwave absorption or transmission at high-temperatures

The multifunctional metastable SiBOCN system ceramics (including SiBN, SiCN, SiON, SiBC, SiBCN, SiBON, SiBOCN, etc.) are a new type of advanced structure–function integrated materials with unique structure and adjustable dielectric properties for high-temperature applications in thermal protection, communications, precise guidance, and microwave-absorption stealthy. These metastable materials generally require the rational co-design of multiscale structure and chemical composition to achieve desirable dielectric properties which induce interaction with incident electromagnetic wave. Herein, this review presents the latest development of metastable SiBOCN system ceramics, with the intent of summarising key findings, uncovering major trends and providing guidance for future efforts. Major themes in this assessment focus on the main processing routes, basic mechanisms for microwave transmission and absorption, scientific basis for material selection in specific background, principles for multiscale structure design and chemistry optimisation, tunable microwave transparent or absorbing properties, and future challenges and prospects in this active research filed.