Submillimeter-Scale ZrB2 Single-Crystals: Efficient Molten-Salt Synthesis and Outstanding Physical Properties

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.