Antimony: a Dual Donor in Lead Telluride

Band structure calculations indicate the formation of an antimony impurity level just above the Fermi level for Pb$_{1-x}$Sb$_{x}$Te and just below the Fermi level for PbSb$_{x}$Te$_{1-x}$.~ For experimental verification, we prepare bulk samples of Pb$_{1-x}$Sb$_{x}$Te and PbSb$_{x}$Te$_{1-x}$ (x = 0.25, 0.5, 1{\%}).~~ Electrical resistivity, Seebeck, Hall and transverse Nernst-Ettingshausen coefficients of the crystals have been measured in the temperature range 2-580 Kelvin. Thermal conductivity data was measured in the range 80-800 Kelvin.~We confirm the ability of antimony to take the place of a lead atom and dope PbTe n-type or take the place of a tellurium atom and dope PbTe p-type. Antimony, however, is not as efficient an acceptor in p-type material as it is a donor in n-type material. The Fermi levels are calculated using experimental data and will be reported here. Also, a phase transition is experimentally observed at 500 K in p-type PbSb$_{x}$Te$_{1-x}$.~