Effects of Annealing and Doping on Nanostructured Bismuth Telluride Thick Films

Abstract

Bismuth telluride is the state-of-the-art thermoelectric (TE) material for cooling applications with a figure of merit of ∼1 at 300 K. There is a need for the development of TE materials based on the concept of thick films for miniaturized devices due to mechanical and manufacturing constraints for the thermoelement dimensions. We reported earlier a method for the fabrication of high-quality nanostructured bismuth telluride thick films with thickness from 100 to 350 µm based on electrochemical deposition techniques. In this paper, annealing is performed to further improve the TE performance of the nanostructured bismuth telluride thick films and n/p-type solid solutions are successfully fabricated by doping Se and Sb, respectively. The conditions for both annealing and doping for the thick films are investigated, and the effects of annealing and doping on morphology, crystalline phase, grain size, Seebeck coefficient, homogeneity, electrical conductivity, and power factor of the bismuth telluride thick films have been studied.

Optimizations of Pulsed Plated p and n‐type Bi2Te3‐Based Ternary Compounds by Annealing in Different Ambient Atmospheres

“…[ 19 ] The results indicated good control over the fi lms' compositions, but satisfactory control of the morphology and thermoelectric performance was not reported until later works exhibited Seebeck coeffi cients up to 180 μ V K − 1 after annealing up to 300 ° C for about 1h in argon atmosphere. [ 20 ] Potentiostatic electrodeposition from electrolytes based on nitric acid with tartaric acid added in order to increase the solubility of Sb in the aqueous solutions was reported by Xiao et al [ 21 ] Works by Tittes et al [ 22 ] and in 2008 by Li et al [ 23 ] report the successful deposition of (Bi x Sb 1−x ) 2 Te 3 fi lms , but they lack the thermoelectric characterization of the deposited materials. Nedelcu et al and Li et al [ 24 , 25 ] reported (Bi x Sb 1−x ) 2 Te 3 fi lms with Seebeck coefficients of + 150 μ V K − 1 and + 119 μ V K − 1 and power factors of 322 μ W K − 2 m − 1 and 112 μ W K − 2 m − 1 , respectively.…”

“…However, the thermal treatment of as deposited samples can achieve signifi cant improvements due to a decrease in structural defects. [ 23 ] In this work, samples deposited over a wide potential range are annealed in He atmosphere during in situ XRD measurements for structural analysis. In order to further improve the thermoelectric performance of the fi lms, they were annealed for ≥ 60 h at 250 ° C in an equilibrium Te atmosphere, since this treatment proved its ability to refi ne the ratio of V-VI elements in semiconductors.…”

A Simple and Quick Chemical Synthesis of Nanostructured Bi2Te3, Sb2Te3, and BixSb2-xTe3

“…During the last few years, there have been many reports on the preparation of these materials in nanocrystalline form, using techniques, such as electrochemical deposition, [9][10][11] hydro/ solvothermal synthesis, 12,13 colloidal processing [14][15][16] and microwave irradiation. 17,18 These methods for synthesizing nanostructured materials generally require prolonged heating or complex apparatus.…”

Effect of substrate on the spatial resolution of Seebeck coefficient measured on thermoelectric films

“…But, when measuring the Seebeck coefficient of thermoelectric thin films, we found that the inverse method using deconvolution reveals the difficulties in recovering to the original signal. Li et al [23] showed that the temperature affecting zone can also heat the material of the substrate, yielding an integrated Seebeck coefficient of both the sample and substrate. However, no report has provided a suitable solution to compensate for the additional Seebeck signal distortion caused by substrate.…”