Evidence of improvement in thermoelectric parameters of n-type Bi2Te3/graphite nanocomposite

Abstract

Improvement of thermoelectric parameters is reported with graphite incorporation in n-type Bi2Te3/graphite nanocomposite system. In-depth thermoelectric properties of nanostructured Bi2Te3/graphite composites are probed both microscopically and macroscopically using X-ray diffraction, Raman spectroscopy, inelastic neutron scattering and measurement of the temperature dependence of thermal conductivity , Seebeck coefficient S, resistivity ρ, and carrier concentration nH. Raman spectroscopic analysis confirms that graphite introduces defects and disorder in the system. Graphite addition induces a large (17%) decrease of , originating from a strong phonon scattering effect. A low lattice thermal conductivities L, value of 0.77 Wm -1 K -1 , approaching the min value, estimated using the Cahill-Pohl model, is reported for Bi2Te3+1 wt% graphite sample.Graphite dispersion alters the low energy inelastic neutron scattering spectrum providing evidence for modification of the Bi2Te3 Phonon Density of States (PDOS). Improvement of the other thermoelectric parameters, viz., Seebeck Coefficient and resistivity, is also reported. Theoretical modeling of electrical and thermal transport parameters is carried out and a plausible explanation of the underlying transport mechanism is provided assuming a simple model of ballistic electron transport in 1D contact channels with two different energies.

Interfacial effects in an inorganic/organic composite based on Bi2Te3inducing decoupled transport properties and enhanced thermoelectric performance

“…These signals are known as overtone modes of the A 2 1g vibration, possibly arising due to crystalline symmetry breaking induced by defects. 48,50 The PEDOT:PSS characteristic signals are found to appear in the high-frequency region above 1000 cm À1 (Fig. 3d).…”

“…Each quintuple layer is composed of ve atomic layers with covalent bonds (i.e., Te (1) -Bi-Te (2) -Bi-Te (1) ), thus affording in-plane and throughplane lattice vibrations between Te (1) and Bi. [47][48][49] The pristine Bi 2 Te 3 exhibits the Raman active vibrational modes such as E 2 g (112.5 cm À1 ) and A 2 1g (130.7 cm À1 ) as well as the infrared active vibrational mode, A 2 1u (118.6 cm À1 ) (Fig. 3b), which are categorized as in-plane (E 2 g ) and through-plane (A 2 1g , A 2 1u ) vibrations between Te (1) and Bi (Fig.…”

“…3b inlet). [47][48][49] The Bi 2 Te 3 /PEDOT:PSS composite exhibits the equivalent vibration modes at relatively high frequencies compared to the pristine Bi 2 Te 3 . This indicates that the lattice vibration between Te (1) and Bi is deformed because the PEDOT:PSS molecule in the composite may interact with the Bi 2 Te 3 QLs.…”

“…These signals are known as overtone modes of the A 2 1g vibration, possibly arising due to crystalline symmetry breaking induced by defects. 48,50…”

Enhancement of electron mobility and thermoelectric power factor of cobalt‐doped n ‐type Bi 2 Te 3

“…5 There is a revival of interest in improving the efficiency of TE materials around the world, with focus on maximizing power factor, PF (= S 2 /ρ) and lowering κ. 6 Doping, 7 alloying, 8 and nanostructuring 9 are generally considered as a route to greatly improve thermo-electric parameters by optimizing carrier concentration (n H ) and/or introducing additional scattering for phonons.…”