Strength and equation of state of molybdenum triboride under 80 GPa pressure, using radial X-ray diffraction

ABSTRACT

The strength and equation of state of molybdenum triboride have been determined under nonhydrostatic compression up to 80 GPa, using an angle-dispersive radial X-ray diffraction technique in a diamond anvil cell (DAC). The RXD data yield a bulk modulus and its pressure derivative as K₀= 342(6) GPa with K₀′ = 2.11(17) at ψ = 54.7°. Analysis of diffraction data using the strain theory indicates that the ratio of differential stress to shear modulus (t/G) ranges from 0.002 to 0.050 at pressures of 4–80 GPa. Together with theoretical results on the high pressure shear modulus, our results here show that molybdenum triboride sample under uniaxial compression can support a differential stress of ∼10 GPa when it started to yield with plastic deformation at ∼30 GPa. In addition, we draw a conclusion that MoB₃ is not a superhard material but a hard material.

KEYWORDS:

• Strength
• equation of state
• molybdenum triboride
• high pressure
• radial X-ray diffraction
• diamond anvil cell

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Financial supports from the National Natural Science Foundation of China [Nos.10875142 and 41572357] and Key Project of Education Department of Sichuan Province (16za0355) are gratefully acknowledged. This work was performed at 4W2 beamline of Beijing Synchrotron Radiation Facility (BSRF), which is supported by Chinese Academy of Sciences [grant numbers KJCX2-SWN03 and No. KJCX2-SW-N20].