The thermoelectric properties (resistivity and thermopower) of single crystals of the function of temperature from 10K < T < 320K. Both parent materials exhibit a resistive transition peak, T_p approx approx 80K for Hf Te_5 and T_p approx approx 145K for ZrTe_5. Each display a large poisitive (p-type) thermopower ( alhap >= + 125 mu V/K) around room temperature, which undergoes a change to a large negative (n-type) thermopower ( alpah <= -125 mu V/K)below the peak temperature. The magnitude of this resistive anomaly is typically 3-7 times the room temperature value of approx approx q m OMEGA centre dot cm. Through isoelectronic substitution of Zr for Hf (Hf_(1-X)Zr_XTe_5), a systematic shift is observed in T_p as the Zr concentration increases. Small Ti substitution of Hf and Zr affects the electronic properties strongly, producting a substantial rreduction in T_p for either parent compound. However, the large values of thermoposer and the magnitude of the resistive peak remain essentially unchanged. Substitutions of Se or Sb on the Te site greatly affects the electronic behavor of the parent materials. Se doping increases the thermoposer values by approx approx 20
展开▼
