Google Search
A2: Medium temperature materials
We report exceptional thermoelectric performance for Sb-doped PbSe with a ZT value of ~1.5 at 800 K for the optimal composition of Pb1-xSbxSe (x=0.0025). This is in sharp contrast to the Bi doped PbSe, which achieves ZT of <1. Substituting Sb or Bi for Pb in PbSe results in n-type behavior with excellent charge transport properties, thereby achieving maximum power factors of ~27 μW cm-1 K-2 for Pb0.99925Sb0.00075Se, ~24 μW cm-1 K-2 for Pb0.9975Sb0.0025Se, and ~23 μW cm-1 K-2 for Pb0.995Sb0.005Se at 400 K, 500 K, and 700 K respectively. We find that the addition of very small amounts (a low as 0.25 mol%) of Sb in PbSe generates extensive nanoscale precipitates, whereas comparable amounts of Bi in PbSe results in very few or no notable precipitates, suggesting extended solid solution contrary to Sb-doped PbSe. The Sb-rich precipitates are observed to be endotaxially embedded in the PbSe matrix, and appear remarkably effective in reducing the lattice thermal conductivity of PbSe via multiple pathways for scattering of heat carrying phonons. In turn, the corresponding Bi samples do not exhibit appreciable reduction in lattice thermal conductivity. This contrasting behavior of two apparently similar dopants in PbSe is rationalized by-the very different behavior they exhibit in the matrix.