Time differential perturbed angular correlation (TDPAC) measurement performed on the 482 keV level of¹⁸¹Ta probe nuclei inp-implantedNbHf sample shows that hydrogen decorated vacancy complexes are trapped by 6% of probe nuclei experiencing a Lorentzian distribution of quadrupole frequencies with a width of 32 MHz having a mean value of 545 ± 10 MHz with an asymmetry parameter 0·32. Measurements at RT following isochronal annealing treatment of the sample shows that the onset of detrapping of H-V complexes from probe nuclei occurs at 373 K and gets completed at 573 K. Hydrogen atoms stabilized vacancy clusters are found to be trapped by probe nuclei. The role played by other gaseous impurities in the sample in stabilizing the lattice defects bound to probe nuclei is discussed, to have a complete understanding of the recovery of defects in the sample.

Time differential perturbed angular correlation (TDPAC) and positron life-time measurements on cold-worked and hydrogen chargedNbHf indicate a strong binding of hydrogen decorated vacancy clusters with Hf impurities. Both TDPAC and positron lifetime results are mutually consistent on this aspect. Transformation of H-vacancy clusters into H-bubbles is indicated by the positron lifetime behaviour at annealing temperatures beyond 900 K. Impurity effects like oxygen pickup and coating of voids cannot be ruled out at elevated temperatures.