Effect of nonstoichiometry on the thermoelectric properties of GeBi4Te7

Polycrystalline samples of GeBi4Te7 with different compositional deviations from stoichiometry have been prepared and characterized by Seebeck coeffic ient and electrical resistivity measurements over the temperature range 100 -750 K. At room temperature all samples exhibit n-type conductivity and a h igh concentration of electrons in the range 1.7x10(19)-2.4x10(20) cm(-3). T he width of the energy band gap of GeBi4Te7 was 0.21+/-0.02 eV as determine d from the temperature dependence of electrical resistivity in the intrinsi c region. A dominant point defects model is proposed to explain the influen ce of compositional nonstoichiometry on the transport properties. (C) 1999 American Institute of Physics.