Mössbauer-Effect Studies in Hafnium-Metal Single Crystals

The Mössbauer effect in ${\mathrm{Hf}}^{178}$ has been studied with oriented single-crystal absorbers of hafnium metal at the temperature of liquid helium. Along the [0001] axis, only the $\left|\Delta m\right|=1\mathrm{}$ component of the quadrupole spectrum is observed, and along the [1010] axis only the $\left|\Delta m\right|=1\mathrm{}$ and $\left|\Delta m\right|=2\mathrm{}$ components are observed. Combining these observations with those made using a polycrystalline hafnium-metal absorber, the magnitude of the electric field gradient was found to be $V_{\mathrm{zz}}=(0.95\mathrm{}\pm 0.04)\times {10}^{18}$ V/${\mathrm{cm}}^2$, and the asymmetry parameter $\eta <0.1\mathrm{}$. The Debye temperature of hafnium carbide has been estimated to be (350±10)°K, and the Debye temperature of hafnium metal has been found to be (227±10) and (192±13)°K, for $\gamma$ rays propagating parallel and perpendicular to the $c$ axis, respectively.