The electric quadrupole interaction in ZrO₂ and HfO₂

The electric field gradients in ZrO₂ and HfO₂ have been measured by applying the differential perturbed angular correlation method to the 133-482 keV cascade in ¹⁸¹Ta. The results for HfO₂ have been compared with previous results. In general, a fairly good agreement has been found except for the electric field asymmetry parameter eta , in which the older result of Gerdau (1969) et al, rather than the more recent one of Gardner and Prestwich (1970) has been confirmed. The results for ZrO₂ show the electric field gradient to be (13.3+or-0.7)*10¹⁷ V cm^-2 which is slightly higher than the value of (12.8+or-0.6) *10¹⁷ V cm^-2 obtained for HfO₂. The corresponding values for the field asymmetry are 0.335+or-0.015 for ZrO ₂ and 0.348+or-0.016 for HfO₂. Despite the small difference of only 4% between the corresponding means, the 't' distribution shows, with confidence of better than 99%, that the results for ZrO₂ and HfO₂ are different.