Structural features of ball-milled nanostructured K2Bi8Se13 thermoelectric material

In this work, K2Bi8Se13 material was ball-milled in order to develop nanostructures through the modification of structural features. Structural changes during ball-milling were followed by powder X-ray diffraction measurements, Scanning Electron Microscope images and High Resolution and conventional Transmission Electron Microscopy studies. Powder X-ray diffraction patterns presented a significant broadening in the peak patterns with the increase of the ball-milling time that was attributed to the formation of nanocrystalline as well as amorphous material. TEM studies showed the formation of K2Bi8Se13 nanostructured material consisting of nanocrystals that were surrounded by an amorphous matrix. Preliminary measurements of thermoelectric properties have shown that Seebeck coefficient is increased in ball-milled samples where as thermal conductivity is decreased. Sintering process that was applied on the ball-milled material leads to its recrystallization and the growth of grains.