MODIFICATION OF THE SURFACE OF THERMOELECTRIC BRANCHES BASED ON A Bi2Te3-Bi2Se3 SOLID SOLUTION BY PULSE PHOTON TREATMENT METHOD

Abstract

Degradation of the contact of the semiconductor legs of a thermoelement based on bismuth telluride with a commutation contact is a problem that hinders the commercial production of thermoelectric generators. The solution to this problem is to modify the near-surface layers of semiconductor legs. The aim of the research is to establish the regularities of phase and morphological transformations occurring in the near-surface layer and to evaluate the mechanical properties of the modifi ed surface of semiconductor thermoelectric legs based on a Bi2Te3–Bi2Se3 (n-type) solid solution under pulsed photon treatment. Semiconductor legs based on the Bi2Te3–Bi2Se3 solid solution were obtained by isostatic pressing of powders of the appropriate composition in an argon atmosphere at a temperature of about 360–380 °C. Pulsed photon treatment (PPT) of semiconductor legs was carried out by the emission of three gas-discharge xenon lamps in vacuum (10–3 Pa) and in an Ar atmosphere. The processing time was 06–2.2 s, while the energy density of the light fl ux arriving at the surface of the samples varied from 70 to 275 J/cm2. The phase composition was studied by X-ray diffractometry, the elemental composition was investigated by the method of local X-ray spectral microanalysis, and scanning electron microscopy and atomic force microscopy were used to study the surface morphology. The hardness of the samples was investigated by the method of measuring nanoindentation. It has been established that PPT in vacuum leads to the development of the surface relief (an increase in the surface roughness and height difference) and a change in the phase composition due to the sublimation of selenium and tellurium.On the contrary, the PPT in the Ar atmosphere reduces the roughness and scarcely changes the phase composition of the legs. The research has determined the optimal modes of surface modifi cation that allow to achieve the least roughness and high surface hardness without changing the phase composition of semiconductor thermoelectric legs by the PPT method.

Keywords

• thermoelectric generator
• Bi2Te3–Bi2Se3
• pulsed photon treatment
• surface modifi cation
• mechanical properties