Macro to Nano: Scaling Effects of Bi2Te3 Thermoelectric Generators for Applications in Space

Abstract

Abstract:For decades research and development has been committed to improving the Figure of Merit (ZT) of Bismuth Telluride (Bi2Te3) Thermoelectric Generators (TEG) and has reached its limit at ≈1. This Meta-study aims to determine if further improvements can be made when the size of TEGs decrease. To quantify the change from macro to nano scale the change in ZT, thermal and electrical conductance, Seebeck coefficient and power factor as the size of the thermoelements decrease has been investigated as well as how Wiedemann-Franz (WF) law holds on the nanoscale. This meta-study was conducted by evaluating and comparing developments in TEGs for the past three decades. Based on theory it was expected that increases in ZT would occur as the thermoelement dimensions are reduced due to increased scattering of electrons and phonons as well as the increased density of electronic states. Increases to ZT due to these effects was not observed in experimental data due to difficulties in nanoscale production. This meta-study observed some indicators that the theory is correct in reduced thermal conduction from increased phonon and electron scattering and that phonon scattering was greater than electron scattering. Furthermore, a weak indication that WF law is not applicable on the nanoscale due to the scattering suggesting a decoupling of electrical and thermal conduction which is not achievable in macro scale TEGs

Structure evaluation of bismuth telluride (Bi2Te3) nanoparticles with enhanced Seebeck coefficient and low thermal conductivity

“…These are found to be related to the size and the shape of the nanoparticles (sphere, tube, rod and plate) that can achieve high ZT value for more efficient TE material. The ZT value kept around 1 over the last 50 years whereas the value of ZT must be increased for about 4 to be economically competitive with normal power generators [5].…”

Development of Bismuth Telluride Nanostructure Pellet for Thermoelectric Applications

“…An acceptable TE material is indicated by large density and mobility of charge carriers, at the coinciding by the low thermal conductivity and high electrical conductivity. Another attractive aspect is that the efficient energy conversion adaptability of a TE material is performed by the extensive dimensionless figure of merit: ZT = (S 2 σT)/K, where S is the Seebeck coefficient, σ is the electrical conductivity, K is the thermal conductivity and T is the temperature.Nowadays, Bi 2 Te 3 nanostructure has a great deal of interest in thermoelectric applications such as thermoelectric heating and cooling, thermoelectric generators and portable power supply [1][2][3][4][5][6][7][8][9][10]. Recent studies suggest that Bi 2 Te 3 material usage in nanostructure form generates the higher ZT (from 0.62 to 1.13) values [11][12][13][14][15][16][17].…”