Enhancing densification and mechanical performance of B₄C ceramics using Y₃Si₂C₂ as a novel sintering additive

Boron carbide (B₄C) is a highly strong covalent ceramic material with a low surface diffusion coefficient, making it extremely difficult to consolidate at low temperature. Therefore, the development of effective sintering additives that enable low-temperature, high-density consolidation while maintaining excellent mechanical properties remains a critical challenge for the scalable application of B₄C. In this study, Y₃Si₂C₂ was employed as a novel sintering additive to enhance the densification and mechanical performance of B₄C ceramics for the first time. B₄C ceramics containing 0–10 wt% Y₃Si₂C₂ were fabricated using the spark plasma sintering (SPS) technique at temperatures ranging from 1700 to 1900 °C. The effects of the Y₃Si₂C₂ sintering additive content and sintering temperature on the densification behavior, microstructure, and mechanical properties of B₄C ceramics were systematically investigated. The results indicate that Y₃Si₂C₂ facilitates the densification of B₄C ceramics via an in situ reactive liquid-phase sintering mechanism. The formation of the Y-rich liquid phase significantly enhances particle rearrangement and mass transport, while the in situ-generated YB₄ phase pins grain boundaries and suppresses abnormal grain growth. As a result, the mechanical properties of the B₄C ceramics were significantly improved. Optimal comprehensive mechanical properties were achieved at 1800 °C with 8 wt% Y₃Si₂C₂, yielding a Vickers hardness of 31.4 GPa and a flexural strength of 694.0 MPa. This work paves the way for rare-earth silicon carbide as a novel sintering additive of B₄C ceramics to enhance the densification and mechanical performance for extreme environment applications.