TDPAC and XRPD measurements of the polycrystalline Hf2Ni phase

Abstract

The high-resolution time-differential perturbed angular correlation technique (TDPAC) has been used to study the electric field gradient at Ta-181 impurities in the polycrystalline intermetallic compound Hf2Ni in the wide temeperature range 78-1314 K. The single-phase BCT CuAl2 (C16)-type structure of the compound was confirmed by X-ray diffractogram, with lattice constants found to be a = 6.479(3) angstrom and c = 5.271(3) angstrom at room temperature. The coincidence measurements between gamma rays in the cascade were recorded with a time resolution better than 0.75 ns for the 133-482 keV y-y cascade of Ta-181 nuclei. The results of measurements reveal the presence of a single nuclear quadrupole interaction (NQI) WO and its linear dependence with temperature in the range 78-1134 K. In the high temperature region (1134-1314 K) the significant appearance of disordering in the lattice structure of Hf2Ni was revealed, in the vicinity of the melting point of 1473 K. The XRPD measurements in the high temperature range can help in better interpretation and understanding of this complex structural and microdinamic behavior of the Hf2Ni phase.