Investigation of the neptunium-zirconium system by X-ray diffraction

Abstract

X-ray powder diffraction analysis at 25 °C has been used to further characterize the NpZr phase diagram. We have studied a variety of NpZr aggregate compositions obtained by different preparative methods, including arc melting of the components. For the materials at ambient temperature, obtained by either slow cooling or quenching from elevated temperatures, we observed one or more of the following product phases: α-Np, α-Zr, NpZr 2 and one new phase. The last was interpreted tentatively to be either Np 4Zr or Np 6Zr. Calculations based on the X-ray data suggested a limited solubility of Np in α-Zr and an even lower solubility of Zr in α-Np. The X-ray data for the NpZr 2 phase showed that it possesses hexagonal symmetry and is isostructural with UZr 2 and PuZr 2. Annealing of NpZr composites at selected temperatures did not enhance the formation of NpZr 2.