The lattice stability and structure of δ-UZr2 at elevated temperatures

The lattice stability and structure of δ-UZr2 were studied by thermal analysis and high-resolution neutron diffraction techniques. The δ structure was confirmed to be the modified C32 (AlB2-type) structure as in the ω phase of Zr. The temperature dependence of the lattice parameters in the δ phase was determined between room temperature and 880 K. The heat effects at the phase transition from δ to BCC solid solutions were determined to be 5.6-4.4 kJ g-atom-1 for XZr=0.67-0.81. >From the composition dependence, the transition enthalpy from ω to β (BCC) phase in pure Zr was estimated to be 2.8 kJ g-atom-1. (authors)