Local structure study of Hf dopants in Zr2Pd and ZrPd2 intermetallics

Abstract

The intermetallic compounds Zr2Pd and ZrPd2 have been investigated by perturbed angular correlation (PAC) spectroscopy considering anomalies in their hydrogen absorption properties. It is known that both these compounds have same crystal structure, but Zr2Pd forms an excellent hydride while ZrPd2 does not, even at high pressure. From PAC measurement at room temperature in annealed ZrPd2 sample, this phase is found as a minor component (∼27%) while the dominating phase is identified to be the ZrPd3 (∼73%). In Zr2Pd, this phase has been found to be predominant (∼86%) along with a minor phase (∼14%) due to ZrPd. In ZrPd2, unlike Zr2Pd, a weak temperature dependence of electric field gradient (EFG) has been found from present PAC measurements. Also, site occupancies for both Zr and Pd atoms by the Ta-probe atoms have been found in ZrPd2 and ZrPd3 (formed in ZrPd2). In ZrPd3, Pd site occupancy by the probe is found to be maximum while a small fraction for Zr site occupancy has been found. But, in case of Zr2Pd and ZrPd, no Pd site occupancy of the probe is observed. Calculation of electric field gradients at 181Ta impurity atom for different phases have been performed by density functional theory based on the all electron full potential linearized augmented plane wave plus local orbitals (FP-(L)APW + lo) method to assign the different components observed from PAC measurements. Measurements by XRD have also been carried out to confirm the presence of component phases in the samples. © 2019