2, Institute of Low Temperatures and Structural Research, Wroclaw, , Poland
3, Belarusian State University, Minsk, , Belarus
The thermal conductivity χ, electrical conductivity σ and thermopower α in foils of Bi1-xSbx alloys in semimetallic and semiconducting states in the temperature range 4.2-300 K were experimentally studied. The foils of Bi1-xSbx alloys were obtained by the method of high-speed crystallization of a thin layer of melt on the inner polished surface of a rotating copper cylinder.
High crystallization rates v = 5*105 m/s ensured a uniform distribution of the components in the volume. The thickness of the foils was 10-30μm with the texture 1012 parallel to the plane of the foil and the C3 axis coinciding with the nominal foil. The semimetal-semiconductor transition is observed in Bi1-xSbx foils at x> 0.03%Sb, as in bulk single crystals of the corresponding composition
It is shown that the thermal conductivity of semimetallic Bi-3%Sb foils in the low-temperature range (T <10 K) is two orders of magnitude smaller, and in semiconductor (Bi-16%Sb) it is an order of magnitude smaller than in bulk samples of the corresponding composition. The effect is interpreted from the viewpoint of decreasing the phonon drag effect in the low-temperature region due to both surface scattering and scattering at grain boundaries of the foil texture. From the dependences ρ(T), α(T), χ(T), the thermoelectric efficiency of foils was calculated in the temperature range 5-300 K. It is established that at 100 K the thermoelectric efficiency ZT in semiconductor Bi1-xSbx foils is 2 times higher than for bulk samples with crystallographic orientation similar in foils, which can be used in low-temperature thermoelectric energy converters.
This work was supported by Institutional project 15.817.02.09A