Synthesis and characterization of nitrides of iridium and palladium
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Synthesis and characterization of nitrides of iridium and palladium Jonathan C. Crowhursta) Lawrence Livermore National Laboratory, University of California, Livermore, California 94551
Alexander F. Goncharov Lawrence Livermore National Laboratory, University of California, Livermore, California 94551; and Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015
B. Sadigh, J.M. Zaug, and D. Aberg Lawrence Livermore National Laboratory, University of California, Livermore, California 94551
Yue Meng High Pressure Collaborative Access Team (HPCAT), Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439
Vitali B. Prakapenka GeoSoilEnviro Consortium for Advanced Radiation Sources (GSECARS), University of Chicago, Chicago, Illinois 60637 (Received 11 April 2007; accepted 11 September 2007)
We describe the synthesis of nitrides of iridium and palladium using the laser-heated diamond anvil cell. We have used the in situ techniques of x-ray powder diffraction and Raman scattering to characterize these compounds and have compared our experimental findings where possible to the results of first-principles theoretical calculations. We suggest that palladium nitride is isostructural with pyrite, while iridium nitride has a monoclinic symmetry and is isostructural with baddeleyite. I. INTRODUCTION
II. EXPERIMENT AND THEORY
Metallic and ceramic nitrides are of great technological and fundamental importance.1–6 Traditional applications have taken advantage of the hard and refractory nature of many of these compounds, but numerous more recent applications are based on their optical, electronic, and magnetic properties. Of the transition metals, most are known to form compounds with nitrogen but it is only recently that solid “bulk” nitrides (as opposed to small individual molecules) of Au,7 Pt,1,8,9 Ir,9–11 Os,11 and Pd (present work) have been reported. Synthesis techniques have included nitrogen ion irradiation (Au7), reactive laser ablation (Pt8), and the use of the laser-heated diamond anvil cell (Pt,1,9 Ir,1,9,11 Os,11 Pd). The anvil cell has also been used to synthesize novel phases of known nitrides, e.g., silicon, zirconium, and hafnium.12,13 a)
Address all correspondence to this author. e-mail: [email protected] This paper was selected as the Outstanding Symposium Paper for the 2006 MRS Fall Meeting Symposium PP Proceedings, Vol. 987. DOI: 10.1557/JMR.2008.0027 J. Mater. Res., Vol. 23, No. 1, Jan 2008
The relevant metal was placed into the diamond anvil cell (DAC) cavity either in the form of thin squares (approximately 30 m × 10 m) or fine powder. Raman scattering was used to determine when a reaction had occurred. Our combined laser-heating and Raman system, which we used to synthesize all of our samples, has been described elsewhere.14 In the case of iridium, nitrogen was loaded into the DAC cryogenically for all synthesis experiments. For palladium, several cryogenic loadings were also performed, but for one synthesis nitrogen was loaded under high pressure at
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