Dislocation Evolution and Migration at Grain Boundaries in Thermoelectric SnTe

The close relationship between sample preparation processes and microstructure can lead to significant variations in the electrical and thermal transport properties of materials. Here, we use (scanning) transmission electron microscopy to study differences in microstructure between Sn 0.995 In 0.005 Te samples that were synthesized by three different methods: water quenched ingot as cast (IAC); hand milled + spark plasma sintered pellet (HMS); and ball milled + spark plasma sintered pellet (BMS). We find that dislocations are relocated from within the grains in the IAC sample to form arrays of dislocations at grain boundaries in the HMS and BMS samples. We suggest that the locations and types of the dislocations affect the scattering of charge carriers and heat-carrying phonons and are responsible for the different thermoelectric behaviors of the samples. Our results may shed light on the relationship between sample synthesis, microstructure, and thermoelectric properties in such materials.