We find that Ag-interstitial (Ag 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 (Ag I + ) defect becomes the major defect under Pb-rich condition. Due to the small formation energy and small diffusion barrier of Ag I + , Ag can be easily dissolved into the PbTe matrix.The temperature behavior of the Ag defect formation energy well explains the Ag 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.
Identifying an ideal microstructure for efficient thermoelectric materials has been complicated by the interplay between the electrical and thermal properties. The electrical properties of thermoelectric materials are often compromised to...
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