Thermoelectric characteristics of solvothermally prepared (Bi,Sb)2Te3 mats containing nanosize of sheet-tubes

We report thermoelectric characterization of Bi
2-x
Sb
x
Te
3
(x = 0.5, 1.0, and 1.5) synthesized by a solvothermal method using DMF as solvent. For Bi
2
Te
3
, the size of the edge and thickness of the hexagonal nanoplatelets are 200–250 nm and 20–25 nm, respectively. Bi
2
Te
3
nanosheets appear to grow epitaxially from the surface of the Te tubes, which forms in the first step and acts as the template for the formation of the nanostructure. Upon doping with Sb, the morphology of Bi
1.5
Sb
0.5
Te
3
changes to a cluster of nanoparticles with the size of ∼100 nm. The morphology of Bi
0.5
Sb
1.5
Te
3
consists of mainly nanoplatelets with a size of less than 100 nm and warped nanosheets growing along the Te tube. The nominal composition of Bi
2
Te
3
mats containing sheet-tubes shows a negative thermopower of ca. −94 μV/K at 280 K, whereas Bi
0.5
Sb
1.5
Te
3
shows a positive thermopower of ca. 200 μV/K at 280 K