The effect of photonic processing on increasing the thermoelectric Q-factor of a solid solution Bi2Te3 – Bi2Se3

Abstract

In the present work, the phase compositions, morphology, structure, and thermal conductivity of Bi2Te3 – хSeх-based semiconductor wafers before and after the photon treatment (PT) were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and laser flash methods. The semiconductor plates 10 × 10 × 2 mm in size were prepared by electric discharge cutting from the briquettes, synthesized by hot pressing of Bi2Te3 – хSeх powder. Then, the plates were annealed at 570 K in an argon atmosphere for 24 h. The PT was carried out in an Ar atmosphere by irradiation of gas-discharge xenon lamps with pulses of 1.0 and 1.4 s and energy density ranging from 125 to 175 J/cm2. As revealed, the PT initiates the formation of a thin surface layer with an inhomogeneous nanocrystalline structure and an arbitrary nanocrystals orientation. The volume of material manifests a large-block textured crystalline structure with the original elemental and phase compositions formed during the extrusion. Thereby, a gradient nanostructured region composed of nano-sized and large Bi2Te3 – хSeх crystals with tunneling contacts is formed in the process of PT. We revealed that the PT changes the material bandgap slightly, decreases the concentration of charge carriers, increasing their mobility. The scattering of carriers and photons on linear defects dominates in a wide temperature range in the studied samples. Thereby, the figure of merit rise s by 8 % after PT, due to a decrease in the phonon component of thermal conductivity.