Melt growth of crystalline α-SrSi₂ by the vertical Bridgman method and its thermoelectric characteristics

As a candidate thermoelectric material operating in the low-temperature regime (room temperature to 473 K), we have examined α-SrSi₂: a narrow bandgap semiconductor material, which is composed of environmentally benign elements. We are able to report the successful production of single-crystalline-like α-SrSi₂ with clear semiconducting properties by melting synthesis, a thermodynamically stable and thermally equilibrium process that reduces unexpected process contamination and improves crystallinity. The crystals up to 20 × 20 × 5 mm³ have been obtained for a solid–liquid phase reaction temperature of 1308 K for 10 h with a growth rate averaging at 0.617 K/h in the temperature range from 1403 K to 1373 K. The band gap of this material was measured at 48 meV, which is higher than the values previously reported. The power factor was measured at 2.9 mW/mK² at 300 K, which is the highest value ever reported for undoped α-SrSi₂. Based on the experimental bandgap values, the hybrid functional was used to correct the first-principles calculation method, and the Seebeck coefficient obtained from the first-principles calculation was compared with experimental values. Which values showed good agreement with experimental values.