Electrical Properties of Hydrides and Deuterides of Zirconium

Electrical properties of hydrides and deuterides of zirconium have been investigated between 1.1 and 410°K. The metallic nature of these materials is evident in the fact that for compositions approaching Zr${\mathrm{H}}_2$, the hydride is a better conductor than is high-purity zirconium. Above ∼150°K the electrical resistivity exhibits an interesting upturn, which arises from scattering from the optical-model lattice vibrations. Excellent fits to the ideal-resistivity data are obtained with a simple additive combination of Grüneisen and Howarth-Sondheimer functions for the respective acoustical- and optical-mode scattering contributions. The corresponding acoustical- and optical-mode characteristic temperatures are in good accord with expectations based on earlier inelastic neutron scattering data. Moreover, the optical-mode characteristic temperature exhibits the expected hydride-deuteride isotope shift of $\sqrt{2}$. The observed Hall coefficients are large in magnitude (much greater than for pure Zr), and indicate majority hole conduction for the fcc $\delta$ phase and majority electron conduction for the face-centered tetragonal $\epsilon$ phase. The thermoelectric power also changes from positive to negative with increasing hydrogen concentration in the range Zr${\mathrm{H}}_{1.5}$-Zr${\mathrm{H}}_2$.