Metal Nanoinclusions (Bi and Ag) in Bi 2 Te 3 for Enhanced Thermoelectric Applications
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1267-DD07-11
Metal Nanoinclusions (Bi and Ag) in Bi2Te3 for Enhanced Thermoelectric Applications. Sumithra Santhanam1, Nathan J.Takas1, Nathaniel L. Henderson1, Westly M. Nolting 1,3, Dinesh K. Misra1, Pierre F.P.Poudeu 1,2 and Kevin L. Stokes 1,3 1
Advanced Materials Research Institute(AMRI), University of New Orleans, New Orleans 70148.
2 3
Department of Chemistry, University of New Orleans, New Orleans 70148. Department of Physics, University of New Orleans, New Orleans 70148.
ABSTRACT Metal nanoinclusions inside the bulk thermoelectric matrix have the potential to increase the power factor and reduce the lattice thermal conductivity. We have synthesized Bi2-xTe3+x (x=0, 0.5)compositions, to achieve better tenability in Seebeck and electrical conductivity. In this matrix phase, different volume fractions of Bi metal nanoinclusions were incorporated and its effect on thermoelectric properties is discussed. Ag metal nanoinclusions were incorporated into Bi2Te3(2:3) composition, and its effect on power factor is discussed here. INTRODUCTION The size of the dimensionless thermoelectric figure of merit (ZT=S2σ/K, where K=Ke+Klattice, is the sum of the electronic and lattice components of the thermal conductivity), is limited by interdependent transport parameters, the electrical conductivity (σ), Seebeck Coefficient (S), electronic thermal conductivity (Ke). Early research in thermoelectrics resulted in degenerate semiconductors with novel complex structures, with emphasis on tuning the power factor (S2σ), by appropriate chemical substitutions and the reduction in Klattice by phonon scattering point defects, or mass fluctuations in alloys. The approaches for both power factor enhancement and Klattice reduction lead to thermoelectric materials with ZT~1.Bi2Te3 is one of the best tuned last generation material which is still the present state of the art material with a maximum ZT~1 near room temperature. The present generation thermoelectric research has further evolved with a new approach of nanostructuring for further reduction in lattice component of thermal conductivity (Klattice), due to phonon scattering at grain boundaries. Lattice thermal conductivity reduction can further improve thermoelectric figure of merit in materials with a good power factor. Nanostructuring can be achieved in superlattice structures where the phonon confinement can alter the phonon dispersion relation to reduce specific heat and phonon group velocity. Venkatasubramanian et. al and Harmans et.al. have also shown significant reduction in Bi2Te3/Sb2Te3 thin film superstructures and quantum dot superlattice of PbTe/PbSeTe, which could improve the ZT[2]. Nanostructuring in bulk can be achieved by precipitating secondary phase from melt into bulk thermoelectrics. Kanatzidis et al. have demonstrated the growth of nanoscale inclusions in AgPbm-SbTe2+m(LAST), by embedding the secondary nanoscale phase into the matrix phase, resulting in a ZT value of ~1.4 to 1.6 at 700K[3]. This approach of increasing ZT came only from the decrease in lattic
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