The electric quadrupole interaction of181Ta in the Hf−As system

The temperature dependence of the electric quadrupole interaction of¹⁸¹Ta in the Hf?As system has been investigated using the time-differential perturbed angular correlation technique. The sample was prepared by thermal diffusion of¹⁸¹Hf into arsenic metal and the measurements were made at 77, 300, 423, 573 and 673 K. Two quadrupole interaction frequencies were observed which had considerably high values and showed little variation over the entire temperature range. A TEM analysis of the sample showed the presence of two intermetallic compounds HfAs and HfAs₂ to which the two frequencies were assigned.