Effect of boundary scattering on the thermal conductivity of a nanostructured semiconductor material based on the Bi x Sb2 − x Te3 solid solution

Bulk Nanocrystalline Thermoelectrics Based on Bi-Sb-Te Solid Solution

“…Peak efficiency is reached at 90 0 С and makes ZT=1.22. Some dependences of measured thermoelectric coefficients in bulk nanostructured materials on the grain size for solid solution Bi x Sb 2-x Te 3 (Bulat et al, 2010c(Bulat et al, , 2011a will be presented in Sec. 3.2 and 3.3.…”

“…In this section the influence of boundary scattering on the thermal conductivity of bulk nanostructured materials obtained by ball-milling with subsequent hot pressing is considered following (Bulat et al, 2010c). These materials are polycrystalline with small grain sizes in the range from 10 nm to several hundreds on nanometers depending on the temperature of hot pressing.…”

“…It appears that this energy dependence is the same also for boundary scattering of holes. So the change of mobility in nanostructured material can be describe as (Bulat et al, 2010c) 1…”

“…In order to compare the values of ph  with experiment for nanostructured material based on p-Bi x Sb 1-x Te 3 (Bulat et al, 2010c) the hole contribution should be subtracted from experimental values of thermal conductivity. So the proper estimations of electrical conductivity and hole thermal conductivity are necessary.…”

“…To take the anisotropy into account it was assumed that it is connected mainly with the anisotropy of effective masses and the relaxation time is a scalar. Then using the effective medium theory for average electrical conductivity the effective mass of conductivity in polycrystalline material can be expressed as (Bulat et al, 2010c) …”