Abstract
We report synthesis of single-crystal VN and CrN through high-pressure ion-exchange reaction routes. The final products are stoichiometric and have crystallite sizes in the range of 50–120 μm. We also prepared VN and TiN crystals using high-pressure sintering of nitride powders. On the basis of single-crystal indentation testing, the determined asymptotic Vickers hardness for TiN, VN, and CrN is 18 (1), 10 (1), and 16 (1) GPa, respectively. The relatively low hardness in VN indicates that the metallic bonding prevails due to the overfilled metallic σ bonds, although the cation−anion covalent hybridization in this compound is much stronger than that in TiN and CrN. All three nitrides are intrinsically excellent metals at ambient pressure. In particular, VN exhibits superconducting transition at Tc ≈ 7.8 K, which is slightly lower than the reported values for nitrogen-deficient or crystalline-disordered samples due to unsuppressed “spin fluctuation” in the well-crystallized stoichiometric VN. The magnetostructural transition in CrN correlates with a metal–metal transition at TN = 240(5) K and is accompanied by a ∼40% drop in electrical resistivity. In addition, more detailed electronic properties are presented with new insights into these nitrides.
Submitted Version
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call