Nuclear quadrupole interaction at 181Ta in hafnium dioxide fiber: Time differential perturbed angular correlation measurements and ab initio calculations

The thermal behavior of hafnium dioxide fiber has been investigated with the aid of time differential perturbed angular correlation (TDPAC) technique along with XRD and SEM measurements. This study has proved a good thermal stability of the fibrous material up to 1173 K and the fiber loses its crystallinity to a meager extent at 1673 K. No phase transition has been observed up to 1673 K in this fiber. TDPAC parameters for the HfO₂ fiber annealed at 1173 K are ω_Q=124.6 (3) Mrad/s and η=0.36 (1). These values remain unaltered for the HfO₂ fiber annealed even at 1673 K. Electronic structure calculations based on the density functional theory (DFT) for HfO₂ doped with tantalum impurity have been performed and the calculated EFG parameters are in reasonable agreement with the experimental values.