Effects of excess Te on the thermoelectric properties of p-type 25% Bi2Te3-75% Sb2Te3 single crystal and hot-pressed sinter

Effects of excess Te on the thermoelectric properties of p-type 25% Bi2Te3- 75% Sb2Te3 single crystal and hot-pressed sinter were characterized and und erstood with the micro-phase diagram near the stoichiometric composition ob tained by measuring the equilibrium Seebeck coefficient. Thermoelectric pro perties of the 25% Bi2Te3-75% Sb2Te3 single crystal were varied with the am ount of excess Te, as delta -phase of the single crystal becomes less Te-de ficient with adding more excess Te. However, thermoelectric properties of t he hot-pressed sinter were not varied with the amount of excess Te, because the composition of delta -phase is not changed with the amount of excess T e. While a maximum figure-of-merit of 2.39 x 10(-3)/K at 300 K was obtained for the 25% Bi2Te3-75% Sb2Te3 single crystal by adding 6 wt % excess Te, t he hot-pressed 25% Bi2Te3-75% Sb2Te3 sinter exhibited the figure-of-merit o f 2.97 x 10(-3)/K regardless of the excess Te amount. (C) 2001 Kluwer Acade mic Publishers.