Effect of Annealing on Thermoelectric Properties of Crystals Yb<sub>x</sub>Bi<sub>2-x</sub>Te<sub>3</sub>

Abstract

The work is devoted to the study of the thermoelectric properties of solid crystal Yb_xBi_2-xTe₃. In the work presents the results of studies of the thermoelectric properties of Yb_xBi_2-xTe₃ (х≤0.10) solid solutions before and after annealing in the temperature range (300-580)K. Regularities of changes in the electrical conductivity, Seebeck coefficient and total thermal conductivity of the samples depending on the content of ytterbium (Yb) are established. Dependences of electrical conductivity, Seebeck coefficient, thermal conductivity on temperature for the crystal under study are plotted. Temperature curves were recorded using a Termoscan-2 low-frequency temperature recorder at a heating rate of 283 K/ min. Temperature measurements of phase transformations were carried out with combined chromel-alumel thermocouples. Studies of conductivity σ, thermoelectric power (S). were carried out by the four-probe method at direct current in the temperature range of 300-600 K. Ohmic contacts were applied using alloys. It has been established that the optimal combination of these thermoelectric characteristics is achieved for the compositions x = 0.1, which are characterized by the maximum thermoelectric index (ZT=0.87) of the figure of merit in the temperature range of 420-500 K after annealing at 500 K for τ=240 hours. It was revealed that the Yb_xBi_2-xTe₃ systems under study are n-type semiconductor thermoelectric materials in the temperature range of 300-600K.