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Title: Compressibility measurements and phonon spectra of hexagonal transition-metal nitrides at high pressure: {epsilon}-TaN, {delta}-MoN, and Cr{sub 2}N

Abstract

We report compressibility measurements for three transition metal nitrides ({epsilon}-TaN, {delta}-MoN, Cr{sub 2}N) that have structures based on hexagonal arrangements of the metal atoms. The studies were performed using monochromatic synchrotron x-ray diffraction at high pressure in a diamond anvil cell. The three nitride compounds are well-known high hardness materials, and they are found to be highly incompressible. The bulk modulus values measured for {epsilon}-TaN, Cr{sub 2}N, and {delta}-MoN are K{sub 0}=288(6) GPa, 275(23) GPa, and 345(9) GPa, respectively. The data were analyzed using a linearized plot of reduced pressure (F) vs the Eulerian finite strain variable f within a third-order Birch-Murnaghan equation of state formulation. The K{sub 0}{sup '} values for {epsilon}-TaN and {delta}-MoN were 4.7(0.5) and 3.5(0.3), respectively, close to the value of K{sub 0}{sup '}=4 that is typically assumed in fitting compressibility data in equation of state studies using a Birch-Murnaghan equation. However, Cr{sub 2}N was determined to have a much smaller value, K{sub 0}{sup '}=2.0(2.0), indicating a significantly smaller degree of structural stiffening with increased pressure. We also present Raman data for {epsilon}-TaN and {delta}-MoN at high pressure in order to characterize the phonon behavior in these materials. All of the Raman active modes for {epsilon}-TaNmore » were identified using polarized spectroscopy. Peaks at low frequency are due to Ta motions, whereas modes at higher wave number contain a large component of N motion. The high frequency modes associated with Ta-N stretching vibrations are more sensitive to compression than the metal displacements occurring at lower wave number. The mode assignments can be generally extended to {delta}-MoN, that has a much more complex Raman spectrum. The x-ray and Raman data for {epsilon}-TaN show evidence for structural disordering occurring above 20 GPa, whereas no such change is observed for {delta}-MoN.« less

Authors:
 [1]; ;  [2]
  1. Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)
  2. Christopher Ingold Laboratory and Materials Chemistry Centre, Department of Chemistry, University College London, London WC1H 0AJ, United Kingdom and Davy-Faraday Research Laboratory, Royal Institution of Great Britain, London W1S 4BS (United Kingdom)
Publication Date:
OSTI Identifier:
20976631
Resource Type:
Journal Article
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 75; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevB.75.014104; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1098-0121
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CHROMIUM NITRIDES; COMPRESSIBILITY; DIAMONDS; EQUATIONS OF STATE; HARDNESS; MOLYBDENUM NITRIDES; MONOCHROMATIC RADIATION; PHONONS; PRESSURE RANGE GIGA PA; PRESSURE RANGE MEGA PA 10-100; RAMAN SPECTRA; TANTALUM NITRIDES; TRANSITION ELEMENTS; X RADIATION; X-RAY DIFFRACTION

Citation Formats

Soignard, Emmanuel, Shebanova, Olga, and McMillan, Paul F. Compressibility measurements and phonon spectra of hexagonal transition-metal nitrides at high pressure: {epsilon}-TaN, {delta}-MoN, and Cr{sub 2}N. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.014104.
Soignard, Emmanuel, Shebanova, Olga, & McMillan, Paul F. Compressibility measurements and phonon spectra of hexagonal transition-metal nitrides at high pressure: {epsilon}-TaN, {delta}-MoN, and Cr{sub 2}N. United States. https://doi.org/10.1103/PHYSREVB.75.014104
Soignard, Emmanuel, Shebanova, Olga, and McMillan, Paul F. 2007. "Compressibility measurements and phonon spectra of hexagonal transition-metal nitrides at high pressure: {epsilon}-TaN, {delta}-MoN, and Cr{sub 2}N". United States. https://doi.org/10.1103/PHYSREVB.75.014104.
@article{osti_20976631,
title = {Compressibility measurements and phonon spectra of hexagonal transition-metal nitrides at high pressure: {epsilon}-TaN, {delta}-MoN, and Cr{sub 2}N},
author = {Soignard, Emmanuel and Shebanova, Olga and McMillan, Paul F},
abstractNote = {We report compressibility measurements for three transition metal nitrides ({epsilon}-TaN, {delta}-MoN, Cr{sub 2}N) that have structures based on hexagonal arrangements of the metal atoms. The studies were performed using monochromatic synchrotron x-ray diffraction at high pressure in a diamond anvil cell. The three nitride compounds are well-known high hardness materials, and they are found to be highly incompressible. The bulk modulus values measured for {epsilon}-TaN, Cr{sub 2}N, and {delta}-MoN are K{sub 0}=288(6) GPa, 275(23) GPa, and 345(9) GPa, respectively. The data were analyzed using a linearized plot of reduced pressure (F) vs the Eulerian finite strain variable f within a third-order Birch-Murnaghan equation of state formulation. The K{sub 0}{sup '} values for {epsilon}-TaN and {delta}-MoN were 4.7(0.5) and 3.5(0.3), respectively, close to the value of K{sub 0}{sup '}=4 that is typically assumed in fitting compressibility data in equation of state studies using a Birch-Murnaghan equation. However, Cr{sub 2}N was determined to have a much smaller value, K{sub 0}{sup '}=2.0(2.0), indicating a significantly smaller degree of structural stiffening with increased pressure. We also present Raman data for {epsilon}-TaN and {delta}-MoN at high pressure in order to characterize the phonon behavior in these materials. All of the Raman active modes for {epsilon}-TaN were identified using polarized spectroscopy. Peaks at low frequency are due to Ta motions, whereas modes at higher wave number contain a large component of N motion. The high frequency modes associated with Ta-N stretching vibrations are more sensitive to compression than the metal displacements occurring at lower wave number. The mode assignments can be generally extended to {delta}-MoN, that has a much more complex Raman spectrum. The x-ray and Raman data for {epsilon}-TaN show evidence for structural disordering occurring above 20 GPa, whereas no such change is observed for {delta}-MoN.},
doi = {10.1103/PHYSREVB.75.014104},
url = {https://www.osti.gov/biblio/20976631}, journal = {Physical Review. B, Condensed Matter and Materials Physics},
issn = {1098-0121},
number = 1,
volume = 75,
place = {United States},
year = {2007},
month = {1}
}