Probe–impurity interaction in dilute alloy ZrxHf1−x (x~0.98): Results from perturbed angular correlation measurements

• Zr metal with ~2 at% Hf is studied by TDPAC.
• Two quadrupole interactions are observed.
• Pure component with 12 NN Zr increases with temperature.
• Ratio of impurity to pure fraction follows the Arrhenius law.
• Formation entropy and binding energy of probe–impurity are measured.

Time-differential perturbed angular correlation measurements have been performed in Zr metal with ~2 at% Hf to understand the results of previous measurements. From present measurements at different temperatures two interaction frequencies have been found. One of these produces an asymmetry parameter η=0 as expected for a hcp crystal while the other one gives a non-zero value of η. The component with η=0 gives a value of quadrupole frequency ωQ=47.4(3) Mrad/s at 298 K while the second component produces values of ωQ=49.5(2) Mrad/s, η=0.22(1) at room temperature. The component with η=0 has been attributed to a configuration where all the 12 nearest neighbor (NN) to the probe has Zr atoms while the non-zero η component arises due to the presence of 1 NN Hf. The site fractions for these two components depend on temperature and it is found that with increase in temperature, the ratio f/(1−f) decreases following the Arrhenius behavior, f is the component fraction for the probe–impurity interaction. The entropy of formation and binding energy for the probe–impurity pair have been determined in the present report.