Sintering behavior and mechanical properties of Ta₄HfC₅-based composites with ZrB₂ additive

Ta₄HfC₅ powder was synthesized using TaCl₅, HfCl₄ and phenolic resin as raw materials. Then, Ta₄HfC₅–10 vol% MoSi₂ ceramics and Ta₄HfC₅–10 vol% MoSi₂ with different proportions of ZrB₂ (10 – 30 vol%) ceramics were sintered by spark plasma sintering. Zr atoms substituted Ta and Hf atoms in Ta₄HfC₅ during the sintering process at 2000 °C. The sintering behavior and microstructure evolution upon the ceramics are discussed. The mechanical properties of the composites were improved compared to the pure Ta₄HfC₅ ceramics. The hardness of Ta₄HfC₅–MoSi₂ with 30 vol% ZrB₂ increased from around 10 GPa to almost 13 GPa, the flexural strength increased from around 245–435 MPa, and the fracture toughness increased from 2.56 ± 0.12 MPa⋅m^1/2 to 4.46 ± 0.20 MPa⋅m^1/2.