Submillimeter‐Scale ZrB ₂ Single‐Crystals: Efficient Molten‐Salt Synthesis and Outstanding Physical Properties

ABSTRACT Owing to the absence of grain boundaries and their hindrance effects on stress transfer and electron/phonon transmissions, single‐crystalline materials possess the theoretically‐utmost physiochemical properties that are greatly superior to those of their poly‐crystalline counterparts. However, due to their strong covalent‐bonding strengths, which resulted in ultra‐high melting points and extremely‐low diffusion coefficients, single‐crystalline IVB‐VB transition‐metal diborides with macroscopic‐scale sizes cannot be obtained by the conventional methods for preparing single‐crystalline materials. Herein, benefiting from the advanced molten salt method co‐modified by the techniques of chemical doping, pre‐compaction treatment, and microwave‐radiation, submillimeter‐scale V‐doped ZrB 2 single‐crystals with rod‐like morphologies and aspect ratios up to 1000 were successfully prepared. And the necessitated processing conditions of 1473 K/40 min were remarkably milder than those of its counterpart methods. More importantly, the elastic modulus, electrical resistivities, and thermal conductivities of as‐obtained (Zr 0.95 V 0.05 )B 2 single‐crystals were determined to be up to 278.6 GPa, 21.6 µΩ·cm, and 56.3 W·m −1 ·K −1 , respectively, which obviously outperformed those of their poly‐crystalline counterparts. This research was predicted to offer a promising route for energy‐saving and highly‐efficient preparation of single‐crystalline IVB‐VB transition‐metal diborides with macroscopic‐scale sizes and intrinsically exceptional physiochemical properties, thus satisfying the demands of directly utilized high‐performance devices.