Ultra-fast synthesis and composition-dependent formation behavior of (Hf_xZr_1−x)B₂ solid solution nanopowders

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 (Hf_xZr_1−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 (E_sol) 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 (Hf_0.8Zr_0.2)B₂ (1700 °C). In addition, (Hf_0.8Zr_0.2)B₂ also exhibits superior phase and thermodynamic stability, as demonstrated by its more negative ΔG_mix, lower DOS value at E_f, 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.