Tuning of Mg content to enhance the thermoelectric properties in binary Mg2+δ Si (δ = 0, 0.1, 0.15, 0.2)
Year: 2019
Type: article
Abstract: We report the enhanced thermoelectric properties of binary Mg 2 Si by tuning the Mg content. Polycrystalline Mg 2+ δ Si (where δ is the excess Mg content in the starting composition of the samples and δ = 0, 0.1, 0.15, 0.2) samples were processed by solid-state synthesis route using ball milling followed by rapid spark plasma sintering in order to minimize the Mg loss during processing. Microstructural and x-ray diffraction analysis revealed that, Mg content ( δ ) of 0.1–0.15 is required to get the binary Mg 2 Si phase without any elemental Mg/Si phase. Hall effect measurement and Fourier Transform Infrared Spectroscopy analysis show that, the excess Mg content helps to enhance the carrier concentration and charge carrier effective mass due to the occupancy of Mg at the interstitial site in Mg 2 Si structure. The influence of Mg content on thermoelectric properties, viz ., electrical resistivity, Seebeck coefficient and thermal conductivity is investigated from 300 K to 780 K. A marked enhancement in thermoelectric power factor (∼1.6 mW m −2 K −2 ) is obtained for Mg 2.15 Si sample at 780 K. The occupancy of excess Mg at interstitial sites reduces the lattice thermal conductivity by lowering lattice symmetry. A maximum figure of merit (ZT) ∼ 0.39 ± 0.03 at 780 K has been achieved in Mg 2.15 Si sample, the highest among that reported in n-type binary Mg 2 Si system. This suggests that excess Mg content in the starting composition of Mg 2+ δ Si helps in stabilizing the phase as well as improves the thermoelectric properties of the Mg 2 Si.
Source: Materials Research Express
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
Award: G977969243
OpenAlex ID: W2990054586