Defects responsible for abnormal n-type conductivity in Ag-excess doped PbTe thermoelectrics

Abstract

We find that Ag-interstitial ($A{g}_I$) acts as an electron donor and plays an important role in Ag-excess doped polycrystalline PbTe thermoelectric materials. When Ag is heavily doped in PbTe, the neutral (Ag-Ag) dimer defect is formed at the Pb-site and the environment becomes Pb-rich/Te-poor condition. Then the positively ionized Ag interstitial ($A{g}_I^{+}$) defect becomes the major defect under Pb-rich condition. Due to the small formation energy and small diffusion barrier of $A{g}_I^{+}$, Ag can be easily dissolved into the PbTe matrix. The temperature behavior of the Ag defect formation energy well explains the $A{g}_I^{+}$ solubility, the electron carrier generation, and the increasing electrical conductivity in Ag-excess doped polycrystalline PbTe at high temperature. This abnormal doping behavior by forming interstitial defects is also found for Au-doped PbTe.

18 pages, 4 figures

References in corpus (2)

• Theory of enhancement of thermoelectric properties of materials with nanoinclusions
• Ab initio studies of electronic structure of defects in PbTe