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.

In recent years, high-entropy metal carbides (HECs) have attracted significant attention due to their exceptional physical and chemical properties. The combination of excellent performance exhibited by bulk HEC ceramics and distinctive geometric characteristics has paved the way for the emergence of one-dimensional (1D) HECs as novel materials with unique development potential. Herein, we successfully fabricated novel (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C nanowires derived via Fe-assisted single-sourced precursor pyrolysis. Prior to the synthesis of the nanowires, the composition and microstructure of (Ti,Zr,Hf,Nb,Ta)-containing precursor (PHECs) were analyzed, and divinylbenzene (DVB) was used to accelerate the conversion process of the precursor and contribute to the formation of HECs, which also provided a partial carbon source for the nanowire growth. Additionally, multi-branched, single-branched, and single-branched bending nanowires were synthesized by adjusting the ratio of PHECs to DVB. The obtained single-branched (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C nanowires possessed smooth surfaces with an average diameter of 130–150 nm and a length of several tens of micrometers, which were a single-crystal structure and typically grew along the [1 $\overline{1}$1] direction. Also, the growth of the (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C nanowires was in agreement with top-type vapor–liquid–solid mechanism. This work not only successfully achieved the fabrication of HEC nanowires by a catalyst-assisted polymer pyrolysis, but also provided a comprehensive analysis of the factors affecting their yield and morphology, highlighting the potential application of these attractive nano-materials.