Effect of Photon Treatment on Structure and Substructure of Bi2Te3 –xSex Thermoelectric Material

X-ray diffractometry, scanning electron microscopy and transmission electron microscopy techniques were used to study the phase composition and morphology as well as structure and substructure of semiconductor plates based on Bi 2 Te 3 – x Se x before and after photon treatment (PT) by radiation of high-power xenon lamps (spectral range λ = 0.2–1.2 μm) in an Ar atmosphere. It was found that the PT results in recrystallization of the near-surface layers (~2 μm) of the Bi 2 Te 3 – x Se x solid solution with the formation of inhomogeneous structure in the form of microcrystals surrounded by nanocrystalline grains. It also changes the chemical composition of the near-surface layer (~5 μm) associated with an increase in the concentration of selenium. More than a 40-fold increase in the area of intergrain boundaries and the formation of nanocontacts along the boundaries of the microcrystalline phase make a significant contribution to the scattering of phonons, and a change in the concentration of tellurium and selenium leads to a decrease in the electronic component of thermal conductivity. Substructural changes correlate with a significant (up to 5%) reduction in the thermal conductivity of samples of Bi 2 Te 3 – x Se x solid solution with a surface layer modified as a result of PT.