We elucidate the amphoteric nature of antimony as a dopant in PbTe. Band-structure calculations show that Sb substituting for Pb is a donor and that Sb on the Te site is an acceptor giving rise to a large excess density of states (DOS). Experimentally, in Te-rich ${\text{Pb}}_{1-\text{x}}{\text{Sb}}_{\text{x}}\text{Te}$ samples, ${}^{125}\text{T}\text{e}$ NMR spectroscopy shows that Sb substitutes for Pb and transport data reveal that it then acts as a simple donor. In Pb-rich ${\text{PbSb}}_{\text{x}}{\text{Te}}_{1-\text{x}}$ samples, ${}^{125}\text{T}\text{e}$ NMR shows that little Sb substitutes for Te when samples are prepared above 770 K and then quenched; ${}^{207}\text{P}\text{b}$ NMR shows four types of charge carriers, but only a majority hole and a minority electron contribute to transport. Sb acts as an acceptor in ${\text{PbSb}}_{\text{x}}{\text{Te}}_{1-\text{x}}$, but the large DOS calculated must correspond to a large concentration of localized holes and the Seebeck coefficient is not enhanced.

• Received 26 May 2009

DOI:https://doi.org/10.1103/PhysRevB.80.125208