Hexagonal-structured ε-NbN: ultra-incompressibility, high shear rigidity and a possible hard superconducting material
- State Univ. of New York (SUNY), Stony Brook, NY (United States); Jilin Univ., Changchun (China). State Key Lab. of Superhard Materials
- State Univ. of New York (SUNY), Stony Brook, NY (United States)
- Brookhaven National Lab. (BNL), Upton, NY (United States); State Univ. of New York (SUNY), Stony Brook, NY (United States)
- Jilin Univ., Changchun (China). State Key Lab. of Superhard Materials
Exploring the structural stability and elasticity of hexagonal ε-NbN helps discover correlations among its physical properties for scientific and technological applications. Here, for the first time, we measured the ultra-incompressibility and high shear rigidity of polycrystalline hexagonal ε-NbN using ultrasonic interferometry and in situ X-ray diffraction, complemented with first-principles density-functional theory calculations up to 30 GPa in pressure. Using a finite strain equation of state approach, the elastic bulk and shear moduli, as well as their pressure dependences are derived from the measured velocities and densities, yielding BS0 = 373.3(15) GPa, G0 = 200.5(8) GPa, ∂BS/∂P = 3.81(3) and ∂G/∂P = 1.67(1). The hexagonal ε-NbN possesses a very high bulk modulus, rivaling that of superhard material cBN (B0 = 381.1 GPa). The high shear rigidity is comparable to that for superhard γ-B (G0 = 227.2 GPa). We found that the crystal structure of transition-metal nitrides and the outmost electrons of the corresponding metals may dominate their pressure dependences in bulk and shear moduli. In addition, the elastic moduli, Vickers hardness, Debye temperature, melting temperature and a possible superconductivity of hexagonal ε-NbN all increase with pressures, suggesting its exceptional suitability for applications under extreme conditions.
- Research Organization:
- Stony Brook Univ., NY (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- NA0001815; SC00112704
- OSTI ID:
- 1466791
- Alternate ID(s):
- OSTI ID: 1226032; OSTI ID: 1466789
- Report Number(s):
- BNL-108266-2015-JA; PII: BFsrep10811
- Journal Information:
- Scientific Reports, Vol. 5, Issue 1; ISSN 2045-2322
- Publisher:
- Nature Publishing GroupCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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