Suppression of the resistivity anomaly and corresponding thermopower behavior in the pentatelluride system by the addition of Sb:Hf1−XZrXTe5−YSbY

Abstract

The electrical resistivity \ensuremath{\rho} and the thermopower \ensuremath{\alpha} of the transition-metal pentatelluride system ${\mathrm{Hf}}_{1\ensuremath{-}X}{\mathrm{Zr}}_{X}{\mathrm{Te}}_{5\ensuremath{-}Y}{\mathrm{Sb}}_{Y}$ have been measured over a broad range of temperature, $10\mathrm{K}<T<300\mathrm{K}.$ The systematic Sb doping of these materials has been performed over a range from $0<Y<0.75,$ where Y is the nominal Sb concentration. Both parent materials $({\mathrm{HfTe}}_{5}$ and ${\mathrm{ZrTe}}_{5})$ exhibit an anomalous resistive peak, ${T}_{P}\ensuremath{\approx}80\mathrm{K}$ for ${\mathrm{HfTe}}_{5}$ and ${T}_{P}\ensuremath{\approx}145\mathrm{K}$ for ${\mathrm{ZrTe}}_{5}.$ Each parent material displays a large positive (p-type) thermopower $(\ensuremath{\alpha}>~+125\ensuremath{\mu}\mathrm{V}/\mathrm{K})$ around room temperature, which undergoes a change to a large negative (n-type) thermopower $(\ensuremath{\alpha}<~\ensuremath{-}125\ensuremath{\mu}\mathrm{V}/\mathrm{K})$ below the peak temperature. At a specific level of Sb doping the resistive anomaly is no longer evident and results in a semimetallic temperature dependence. In addition the thermopower monotonically decreases with temperature with no change in sign as in the parent materials. X-ray-diffraction data reveals that the pentatelluride structure is still preserved at all doping concentrations.