Metal Sulfide Ag₂S: Fabrication via Zone Melting Method and Its Thermoelectric Property

Metal sulfide Ag 2 S is an attractive semiconductor due to its excellent physical and chemical property that enable it with wide applications in fields of catalysis, sensing, optoelectronics in past years. In present work, 18 mm 50 mm Ag 2 S ingot was successfully prepared using zone melting method and its thermoelectric (TE) behavior was investigated. Ag 2 S has standard monoclinic P2 1 /c space group (-Ag 2 S phase) below 450 K and transfer to cubic structure (-Ag 2 S phase) over this temperature. Ag 2 S is a n-type semiconductor as the Seebeck coefficient S is always negative due to the Ag interstitial ions in the material that can provide additional electrons. S is about -1200 VK -1 near room temperature, declines to -680 VK -1 at 440 K and finally decreases to ~-100 VK -1 at -Ag 2 S state. The electrical conductivity () of -Ag 2 S is almost zero. However, the value sharply jumps to ~40000.5 Sm -1 as the material just changes to -Ag 2 S at 450 K and then gradually deceases to 33256.2 Sm -1 at 650 K. Hall measurement demonstrates that carrier concentration n H of Ag 2 S is suddenly increased from the level of ~10 17 cm -3 to ~10 18 cm -3 during phase transition. Total thermal conductivity