Structural characterization of Bi2Te3 and Sb2Te3 as a function of temperature using neutron powder diffraction and extended X-ray absorption fine structure techniques

Abstract

The structure of Bi2Te3 (Seebeck coefficient Standard Reference Material (SRM™ 3451)) and the related phase Sb2Te3 have been characterized as a function of temperature using the neutron powder diffraction (NPD) and the extended X-ray absorption fine structure (EXAFS) techniques. The neutron structural studies were carried out from 20 K to 300 K for Bi2Te3 and from 10 K to 298 K for Sb2Te3. The EXAFS technique for studying the local structure of the two compounds was conducted from 19 K to 298 K. Bi2Te3 and Sb2Te3 are isostructural, with a space group of R3¯m. The structure consists of repeated quintuple layers of atoms, Te2-M-Te1-M-Te2 (where M = Bi or Sb) stacking along the c-axis of the unit cell. EXAFS was used to examine the bond distances and static and thermal disorders for the first three shells of Bi2Te3 and Sb2Te3 as a function of temperature. The temperature dependencies of thermal disorders were analyzed using the Debye and Einstein models for lattice vibrations. The Debye and Einstein temperatures for the first two shells of Bi2Te3 are similar to those of Sb2Te3 within the uncertainty in the data. However, the Debye and Einstein temperatures for the third shell of Bi-Bi are significantly lower than those of the third shell of Sb-Sb. The Einstein temperature for the third shell is consistent with a soft phonon mode in both Bi2Te3 and Sb2Te3. The lower Einstein temperature of Bi-Bi relative to Sb-Sb is consistent with the lower value of thermal conductivity of Bi2Te3 relative to Sb2Te3.

Revisiting the Local Structure in Ge-Sb-Te based Chalcogenide Superlattices

“…The R factor represents a measure of a fit effectiveness, being the sum of the square of the residuals between measured and model data, normalized to the magnitude of the experimental data. Furthermore, distances with a separation higher than δ R =  π /2 k max can be resolved by EXAFS spectroscopy40. In the CSL case of our investigation, R factor  = 0.0087 and the experiment resolution is given by δ R = 0.14 Å.…”

Direct measurement of the thermoelectric properties of electrochemically deposited Bi2Te3 thin films

“…Figure 1 d shows a typical diffraction pattern with the corresponding Rietveld refinement. The majority of peaks are fitted to the “Thellurobismutithe” file (JCPDS file n° 01-083-5976) 34 . Other peaks are assigned to the substrate, indium tin oxide (ITO, JCPDS file n° 01-089-4596) 35 and tellurium oxide (TeO 2 , JCPDS file n° 01-070-4297) 36 .…”

Preferred selenium incorporation and unexpected interlayer bonding in the layered structure of Sb2Te3− x Se x

“…A pseudo-Voigt profile function with an angle-independent Lorentzian part and two Gaussian parameters (one angle-dependent and one angleindependent) were used, and the zero shift was refined. Lattice parameters given by Mansour et al [14] for Sb 2 Te 3 were used as starting values.…”

“…Single crystals of Sb 2 Te 3−x Se x were grown by chemical vapor transport from the corresponding polycrystalline samples using iodine (99.5%, Merck) as transport agent at temperatures from 773 to 753 K over 18 h. 473.66 (10) 462.72 (19) 458.7 (5) 455.61 (10) 450.91 (8) 447.50 (8) 445.3 (2) Density 0.00637 (14) 0.0073 30.0067 30.00643 150.0063 20.0075 20.0074 2Single-crystal diffraction data were measured on a Bruker SMART APEX diffractometer with MoKα radiation. The integration was performed with Saint +, and a multiscan absorption correction using the program Sadabs [15,16] was applied.…”