Comparative analysis of morphology 1D and 2D particles effect in starting powders on microstructure and thermoelectric properties of grained Bi2Te2.7Se0.3 compound

Abstract

Features in microstructure and thermoelectric properties of grained Bi2Te2.7Se0.3 compound, prepared by spark plasma sintering of starting powders with various morphologies, are comparatively examined. The 1D samples, prepared from the starting powder consisting of 1D bar-shaped particles, were weakly-textured (orientation factor is equal to ∼0.07) and preferentially consisted of bar-shaped grains. The 2D samples, prepared from the starting powder consisting of 2D plate-shaped particles, were highly-textured (orientation factor is equal to ∼0.28) and consisted of plate-shaped grains. Both weakly-textured 1D sample and highly-textured 2D sample demonstrated remarkable anisotropy in the behavior of their transport properties (specific electrical resistivity and total thermal conductivity). For highly-textured sample, this anisotropy is a typical phenomenon, resulting from recovering in crystal anisotropy, which is inherent for single-crystalline Bi2Te3-based material. For the weakly-textured 1D sample, the anisotropy in the transport properties is unexpected enough. In this case, anisotropy can be attributed to the anisotropic grain size effect on the transport properties. This effect is due to a different number of grain boundaries, overcome by the electrons or phonons under different measuring orientations. The highest value of the thermoelectric figure-of-merit (∼0.68) was found for the 1D and 2D samples and at perpendicular measuring orientation.