Structural Evolution from Neutron Powder Diffraction of Nanostructured SnTe Obtained by Arc Melting

Among chalcogenide thermoelectric materials, SnTe is an excellent candidate for intermediate temperature applications, in replacement of toxic PbTe. We have prepared pure polycrystalline SnTe by arc melting, and investigated the structural evolution by temperature-dependent neutron powder diffraction (NPD) from room temperature up to 973 K. In this temperature range, the sample is cubic (space group Fm-3m) and shows considerably larger displacement parameters for Te than for Sn. The structural analysis allowed the determination of the Debye model parameters and provided information on the Sn-Te chemical bonds. SEM images show a conspicuous nanostructuration in layers below 30 nm thick, which contributes to the reduction of the thermal conductivity down to 2.5 W/m center dot K at 800 K. The SPS treatment seems to reduce the number of Sn vacancies, thus diminishing the carrier density and increasing the Seebeck coefficient, which reaches 60 mu V K-1 at 700 K, as well as the weighted mobility, almost doubled compared with that of the as-grown sample.

Automated summary

Among chalcogenide thermoelectric materials, SnTe is a promising alternative to toxic PbTe for intermediate temperature applications. Pure polycrystalline SnTe was obtained by arc melting and its structural evolution was studied using temperature-dependent neutron powder diffraction (NPD) from room temperature up to 973 K. The sample exhibited a cubic crystal structure (space group Fm-3m) with pronounced displacement parameters for Te atoms. The structural analysis allowed the determination of Debye model parameters and provided insights into the Sn-Te chemical bonds. SEM images revealed nanostructuration in layers below 30 nm, contributing to a reduced thermal conductivity of 2.5 W/m center dot K at 800 K. The SPS treatment appeared to reduce Sn vacancies, resulting in decreased carrier density, increased Seebeck coefficient (up to 60 mu V K-1 at 700 K), and nearly doubled weighted mobility compared to the as-grown sample.