Sound Velocities, Elasticity, and Mechanical Properties of Stoichiometric Submicron Polycrystalline δ-MoN at High Pressure

Yongtao Zou; Ke Liu; Pei Wang; Daowei Wang; Mu Li; Ying Li; Leiming Fang; Hongbin Zhuo; Shuangchen Ruan; Cangtao Zhou; Yusheng Zhao

doi:10.1021/acs.inorgchem.1c00406

Sound Velocities, Elasticity, and Mechanical Properties of Stoichiometric Submicron Polycrystalline δ-MoN at High Pressure

Inorg Chem. 2021 Aug 16;60(16):11897-11906. doi: 10.1021/acs.inorgchem.1c00406. Epub 2021 Jul 28.

Authors

Yongtao Zou^{1

2}, Ke Liu³, Pei Wang⁴, Daowei Wang¹, Mu Li¹, Ying Li², Leiming Fang⁵, Hongbin Zhuo¹, Shuangchen Ruan¹, Cangtao Zhou¹, Yusheng Zhao⁴

Affiliations

¹ Shenzhen Key Laboratory of Ultraintense Laser and Advanced Material Technology, and College of Engineering Physics, Shenzhen Technology University, Shenzhen 518118, China.
² United Laboratory of High-Pressure Physics and Earthquake Science, Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China.
³ College of Physics and Electronic Engineering, Sichuan Normal University, Chengdu 610101, China.
⁴ Academy for Advanced Interdisciplinary Studies and Department of Physics, Southern University of Science and Technology (SUSTech), Shenzhen 518055, China.
⁵ Key Laboratory for Neutron Physics, Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China.

PMID: 34319708
DOI: 10.1021/acs.inorgchem.1c00406

Abstract

Acoustic velocities and elasticity of stoichiometric submicron polycrystalline δ-MoN have been reported at high pressure using ultrasonic measurements and first-principles calculations. Using the finite-strain equation-of-state approach, the bulk modulus and shear rigidity, as well as their pressure derivatives, are derived from the current experimental data, yielding B_S0 = 360.0(8) GPa, G₀ = 190.0(5) GPa, ∂B_S/∂P = 3.4(2), and ∂G/∂P = 1.4(1). Based on our experimental data and the velocity-elasticity correlated models, the mechanical/thermal properties (i.e., hardness, fracture toughness, Grüneisen parameter, Debye temperature, Poisson's ratio) are also derived. Interestingly, we find that hexagonal δ-MoN is almost as incompressible as superhard cubic boron nitride (cBN) (∼384 GPa) and its hexagonal ε-NbN (∼373 GPa) counterpart, and its shear rigidity (G = 190 GPa) is comparable to that of the superhard diamond composite (G = 204 GPa). Moreover, the fracture toughness of submicron δ-MoN polycrystals is achieved up to ∼4.3 MPa·m^1/2, which is comparable to superhard diamond (4-7 MPa·m^1/2) and cBN (2-5 MPa·m^1/2). The Vickers hardness of submicron δ-MoN is estimated to be H_v ≈ 17.4 GPa using Chen's model, which is found to be almost as hard as hexagonal ε-NbN and δ-WN, and may be very important for its applications in extreme environments.