Solution Processing of Bismuth Telluride and its Alloys
Solution Processing of Bismuth Telluride and its Alloys for Improving Thermoelectric Properties Zhongfen Ding Department of Chemistry and Biochemistry And Exotic Materials Institute University of California, Los Angeles Introduction Bismuth telluride and its alloys are currently the best thermoelectric materials known at room temperature and are therefore used for solid-state refrigeration. If the thermal electric figure of merit ZT could be improved by a factor of
about 3, quiet and rugged solid-state devices could replace conventional compressor based cooling systems. In order to test a theory that improved two dimensional materials could enhance ZT due to lower thermal conductivity, we are developing solution processing methods. These solutions could also be used to create microthermoelectric devices. Bismuth telluride and its p-type and n-type alloys have layered structures consisting of 5 atom thick Te-Bi-Te-Bi-Te sheets. Lithium ions are intercalated into the layered materials using liquid ammonia. The lithium-intercalated materials are then exfoliated in water to form colloidal suspensions. The layers are then deposited on substrates forming highly c-axis oriented thin films, which can be annealed at low temperatures. The exfoliated layers can potentially be restacked with other ions or layered materials in between the sheets to form
novel structures. The materials are characterized by powder X-ray diffraction, atomic force microscopy (AFM) and dynamic light scattering. Structure of Bi2Te 3 A b C A a b
C Te B C a A c B
A Te Te B c Te
Te Te Bi Bi Bi Bi Te Bi 2Te3 =
Te Te Bi Bi Li Intercalation Exfoliation
Li ion Solvated Li ion Exfoliation Molecular ions Flocculation Polymers Restacking Synthesis of LixBi2Te 3
Stopcock Liquid NH3 Li Bi2Te 3 Bi2Te 3 Li xBi2Te 3
Line Profile Measurements of Bismuth Selenide Deposited on Mica 160.0 120.0 80.0 40.0 0.0 0 0.4
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