Ultra-fast synthesis and composition-dependent formation behavior of (Hf _x Zr _{1− x} )B ₂ solid solution nanopowders

Abstract Ultrafine boride solid solutions offer immense potential for extreme environmental applications, yet their rapid synthesis with nanoscale compositional control remains a challenge. Herein, we exploit ultrafast high-temperature sintering to achieve the rapid synthesis of a (HfxZr1−x)B2 solid solution with exceptional nanoscale homogeneity. The phase composition and evolution during solid solution formation, as well as the formation tendency with varying Hf/Zr molar ratios, were systematically investigated. First-principles calculations reveal a progressively enhanced tendency to form a single-phase solid solution with increasing Hf content, which is attributed to the lower solution energy (Esol) for Zr atoms incorporating into the HfB2 lattice compared with the reverse process. This finding is consistent with the result of a lower synthesis temperature for (Hf0.8Zr0.2)B2 (1700 °C). In addition, (Hf0.8Zr0.2)B2 also exhibits superior phase and thermodynamic stability, as demonstrated by its more negative ΔGmix, lower DOS value at Ef, and reduced average bond length. This work not only establishes an efficient pathway for powder synthesis but also delivers foundational insights for the rational design of multidiboride ceramics.