Thermoelectric Power of Tl-Doped PbTe Monocrystal

TL;DR

This study measures the thermoelectric properties of Tl-doped PbTe monocrystals across a wide temperature range, revealing sign changes and anomalies linked to impurity states, advancing understanding of doped thermoelectric materials.

Contribution

It provides new experimental data on thermoelectric behavior of Tl-doped PbTe and discusses mechanisms behind observed anomalies, including impurity valence models.

Findings

Double sign change of thermoelectric power at specific Tl concentrations.

Positive thermoelectric power in pure and heavily doped samples.

Anomalies potentially explained by impurity with mixed valences.

Abstract

Results of the measurements of thermoelectric properties of thin semiconductor microwires of Pb1-xTlxTe (x=0,001-0,02, d=5-100mkm) in the temperature region 4,2-300 K, which were obtained from solution melt by the filling of the quartz capillary with the following crystallization of material are presented. For the samples corresponding to chemical composition with concentration of thallium 0,0025 < x <0,005 double change of the sign of thermoelectric power is observed. In pure samples and samples with thallium concentration more than 1 at% thermoelectric power it is positive in the whole temperature range. Various mechanisms which can lead to observable anomalies, including Kondo-like behavior of a non-magnetic degenerate two-level system are discussed. Obtained experimental results let suppose that the observed anomalies can be interpreted on the basis of model of an impurity with mixed valences.