Crystals (Feb 2023)

Reactive Spark Plasma Sintering and Thermoelectric Properties of Zintl Semiconducting Ca<sub>14</sub>Si<sub>19</sub> Compound

  • Doaa Omar A. Ali,
  • Marco Fabbiani,
  • Loïc Coulomb,
  • Simon Bosc,
  • Benjamin Villeroy,
  • Camille Estournès,
  • Claude Estournès,
  • Michael Marek Koza,
  • Mickaël Beaudhuin,
  • Romain Viennois

DOI
https://doi.org/10.3390/cryst13020262
Journal volume & issue
Vol. 13, no. 2
p. 262

Abstract

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We present a new reactive spark plasma sintering (RSPS) technique for synthesizing the rhombohedral Ca14Si19 phase. The RSPS approach reduces the synthesis time from several weeks to a few minutes. The RSPS was found to be sufficient for obtaining a high level of purity of the Ca14Si19 under a pressure of 100 MPa for a dwell period of 5 min at a temperature of 900 ∘C. From electrical resistivity measurements, we were able to determine the energy band gap of Ca14Si19 to Eg=0.145(15) eV. The Seebeck coefficient shows Ca14Si19 as a p-type semiconductor at room temperature. It becomes n-type with increasing temperature pointing to significant bipolar and conduction band contributions due to the narrow bandgap of the compound.

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