INVESTIGATION OF THE NEPTUNIUM-ZIRCONIUM SYSTEM BY X-RAY-DIFFRACTION

X-ray powder diffraction analysis at 25 degrees C has been used to fur ther characterize the Np-Zr phase diagram. We have studied a variety o f Np-Zr aggregate compositions obtained by different preparative metho ds, including are melting of the components. For the materials at ambi ent temperature, obtained by either slow cooling or quenching from ele vated temperatures, we observed one or more of the following product p hases: alpha-Np, alpha-Zr, NpZr2 and one new phase. The last was inter preted tentatively to be either Np4Zr or Np6Zr. Calculations based on the X-ray data suggested a limited solubility of Np in alpha-Zr and an even lower solubility of Zr in alpha-Np. The X-ray data for the NpZr2 phase showed that it possesses hexagonal symmetry and is isostructura l with UZr2 and PuZr2. Annealing of Np-Zr composites at selected tempe ratures did not enhance the formation of NpZr2.