Effect of Phosphorus Content on Local Structures of NiP Amorphous Alloys

Abstract

Abstract. XAFS technique is used to determine the atomic and electronic structures of NiP amorphous alloys with different P concentrations prepared by chemical reduction method. From the radial structural function (RSF) obtained from EXAFS, it is found that the amorphous alloys with P content less than 10 at.% still present strong peaks corresponding to high coordination shells just like crystalline Ni. This indicates the prominent existence of Ni-rich phase with the fcc-structure, which is not remarkably modified by the P atoms. As the P content is as large as 14 at.%, only the first shell peak in the RSF can be observed and the higher shell peaks disappear. Therefore the sample is totally amorphous. The XANES results show that as the P concentration is above 26 at.%, charge transfers from Ni atoms to P atoms. For P concentration lower than 20at.%, on the contrary, charge transfers from P atoms to Ni atoms, and 3d electron density of Ni atoms reaches the maximum when P concentration is about 14~20 at.%.

Unintended Phosphorus Doping of Nickel Nanoparticles during Synthesis with TOP: A Discovery through Structural Analysis

“…Furthermore, the result is important considering that many groups have used this synthetic method for their Ni nanoparticles, which they assume to be pure fcc Ni. In a similar finding in bulk materials, retention of the Ni fcc lattice has been observed in bulk Ni–P alloys with atomic percentage of P up to 14% . In these bulk Ni–P samples the Ni fcc lattice was maintained with good crystallinity despite the high phosphorus content .…”

“…In a similar finding in bulk materials, retention of the Ni fcc lattice has been observed in bulk Ni–P alloys with atomic percentage of P up to 14% . In these bulk Ni–P samples the Ni fcc lattice was maintained with good crystallinity despite the high phosphorus content . This suggests that such phosphorus incorporation on substitutional sites may also be possible at the nanoscale.…”

“…In bulk Ni a reduction in k - and R -space intensity was previously observed when P was introduced into the lattice . With 8 atomic % P, the reduction was about 20%, and at 10 atomic % P the reduction increased to 47% . In both cases, the lattice retained the fcc structure despite this high level of P content.…”

“…The amplitude reduction can be explained by P content. In bulk Ni a reduction in k - and R -space intensity was previously observed when P was introduced into the lattice . With 8 atomic % P, the reduction was about 20%, and at 10 atomic % P the reduction increased to 47% .…”

“…The Ni nanoparticle sample and Ni foil XAS spectra (Figure a) share similar features especially within the lower energy XANES region, and therefore exhibit similar electronic structure. The K-edge in both samples is 8334 eV, a value associated with the 1s–3d atomic line. , Although the spectra for the Ni nanoparticles and the Ni foil show similar features throughout the near-edge and EXAFS regime, there is a noticeable reduction in the Ni nanoparticle sample’s EXAFS oscillation amplitude. Also, the Ni nanoparticle spectrum features a white line peak and EXAFS oscillations that are broadened compared to the sharp features in the Ni foil spectrum.…”