Identification and characterization of single crystal Bi2Te3-xSex alloy

The results of experimental investigation of n-type semiconductor based on Bi2Te3 alloy were presented. This material is used in manufacture of thermoelectric coolers and electrical power generation devices. Bi2Te2.88Se0.12 solid solution single crystal has been grown using the Czochralski method. Monitoring of structure changes of the sample was carried out by electron microscope. The elemental composition of the studied alloy was obtained by energy dispersive spectrometry (EDS) analysis and empirical formula of the compound was established. X-ray diffraction analysis confirmed that the Bi2Te2.88Se0.12 sample was a single phase with rhombohedral structure. The behavior upon heating was studied using differential thermal analysis (DTA) technique. Changes in physical and chemical properties of materials were measured as a function of increasing temperature by thermogravimetric analysis (TGA). The lattice parameters values obtained by X-ray powder diffraction analyses of Bi2Te2.88Se0.12 are very similar to Bi2Te3 lattice constants, indicating that a small portion of tellurium is replaced with selenium. The obtained values for specific electrical and thermal conductivities are in correlation with available literature data. The Vickers microhardness values are in range between HV 187 and HV 39.02 and decrease with load increasing. It is shown that very complex process of infrared thermography can be applied for characterization of thermoelectric elements and modules.