Preparation and thermoelectric properties of mixed valence compound Sn2S3

The preparation and thermoelectric properties of Sn2S3 polycrystalline samples were reported. An almost single-phase Sn2S3 polycrystalline sample was obtained by heating Sn and S mixed powders: the sample was successfully densified using a spark-plasma-sintering method. Sn2S3 building blocks with electron lone pairs were weakly bonded via van der Waals force. Similar to other compounds with electron lone pairs, a thermal conductivity lower than 1.4W&m%1&K%1 was obtained for the Sn2S3 sample from 298 to 701 K. Although the Sn2S3 sample exhibited a high absolute value of Seebeck coefficient, its electrical conductivity was considerably low, leading to a low dimensionless figure of merit, zT, of 9.6 ' 10%4 at 700 K. The poor electrical transport properties indicated that the Sn2S3 sample was a semiconductor with an extremely low carrier density, which was confirmed by measurements of its band gap and by calculations of the temperature dependence of Seebeck coefficient.