A few compounds with polar crystal structures existing in the Ag/Cu-Ge-Q (Q = S, Se, Te) phase diagrams have been reported as promising thermoelectric materials with low thermal conductivities. Ag2GeS3 was identified as another promising thermoelectric compound based on its polar crystal structure (space group Cmc21) and relationship with previously reported thermoelectric materials. Polycrystalline Ag2GeS3 sample was synthesized through a simple one-step solid-state method at high temperature and consolidated into a dense pellet via spark plasma sintering (SPS). The high-temperature thermoelectric properties measurements reveal a very low thermal conductivity of the dense pellet. A possible structural conversion from Ag2GeS3 to Ag10Ge3S11 and GeS2 was observed during the SPS process. The thermal stability of Ag2GeS3 is currently under further investigation with in-situ synchrotron powder X-ray diffraction technique in addition to the thermogravimetric analysis and differential scanning calorimetry measurements. Density functional theory calculations will be preformed to understand the origin of the low thermal conductivity and compare it with the experimental result.

Thermal stability and low thermal conductivity of Ag2GeS3 and Ag10Ge3S11

ACS Spring Meeting 2021

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