Papers by Keyword: Thermoelectric Properties

Abstract: Thermoelectric materials are useful for various application in daily life. Their application such as sensors, generators and electronic components, making thermoelectric materials widely studied. Antiperovskite compounds that can have semiconducting behaviour is probable candidate for thermoelectric materials. In this article, thermoelectric properties of anti-perovskite X₃SiO (X = Sr and Ba) were investigated using density functional theory (DFT) method and Boltzmann Transport Equations (BTE). Electronic properties such as band structure, partial density of states were computed using the generalized gradient approximation with Perdew-Burke-Ernzerhof (GGA-PBE) functional in CASTEP code. The thermoelectric properties such as Seebeck coefficient, electrical conductivity, and power factor are calculated using BoltzTraP code that utilised BTE. The calculated band structures of Ba₃SiO and Sr₃SiO show that these compounds having semiconductor behaviour with direct band gap of 0.44 and 0.43 eV respectively at Γ-Γ k-point. It was found that Ba₃SiO is a better candidate for thermoelectric materials due to its higher Seebeck coefficient (-4.90 10^-4 V/K) at room temperature compared to calculated Seebeck coefficient (-5.84 10^-4 V/K) of Sr₃SiO. The power factor value of Ba₃SiO which is 2.96 x 10^-4 W/mK² is also higher compared to power factor of Sr₃SiO at 7.12 x 10^-7 W/mK² at room temperature.

Abstract: Inorganic thermoelectric (TE) materials have gained significant attention because of their salient properties. However, they possess some significant drawbacks, including high production costs, high heat loss, and fragility. Recently, Organic conducting polymers presented a promising platform as an alternative TE material because of their great mechanical flexibility, high stretchability, and environmental friendliness. In this work, we report for the first time on the TE properties of n-PEDOT:PSS film prepared using spray coating technique. The structural, optical and TE properties of the obtained n-PEDOT:PSS thin film was investigated using X-ray diffraction spectroscopy, UV-vis spectroscopy and Seebeck coefficient measurement systems, respectively. The n-PEDOT:PSS layer showed excellent optical properties with a band gap ranges from 3.91 to 3.78. In addition, the Seebeck coefficient and power factor (PF) were obtained to be 1096.77 µVK^-1 and 298.59 µWm^-1K^-2 respectively, making n-PEDOT:P PSS to be regarded as efficient TE material.

Abstract: In this paper, we have investigated the electronic, optical and thermoelectric properties of the puckered Si₂SeTe monolayer when subjected to various levels of biaxial strain ranging from −10% to +10%. The structural stability, as determined by the cohesive energy, shows that the puckered Si₂SeTe structure is energetically stable. The results reveal that the unstrained Si₂SeTe monolayer is an indirect band gap semiconductor with an energy gap of 0.5 eV, which can be effectively adjusted with biaxial strain. The semiconductor–metal phase transition occurs when the monolayer is compressed by −4% biaxial strain. Moreover, the optical properties, including the real ε₁(ω) and imaginary ε₂(ω) components of the dielectric function, extinction coefficient K(ω), reflectivity R(ω), refractive index n (ω), and absorption coefficient α (ω), were evaluated as a function of the energy of light and under biaxial strain. We discovered that the puckered Si₂SeTe monolayer is capable of absorbing light in the visible region of 64.7×10⁴ cm⁻¹, 73.8×10⁴ cm⁻¹ for equilibrium state and under the compression strain (−8%), respectively. Lastly, the influence of biaxial strain on thermoelectric properties such as electrical conductivity (σ/τ), electronic thermal conductivity (k_e/τ), Seebeck coefficients, and electronic figure of merit (ZT_e) was studied. The calculated electronic figure of merit ZT_e presents an improvement in the p-type doping (μ<0) under the tensile biaxial strain. Taking into account the optical and thermoelectric properties, the puckered Si₂SeTe monolayer is a promising material for use in optoelectronic devices and energy conversion technologies.

Abstract: In the last few years, materials that may have favorable thermoelectric properties have aroused great interest, because they have the ability to generate electricity through the thermoelectric effect. In this work, the temperature effect on the transport properties of a ZnSb compound having an orthorhombic structure is studied, using the local density approximation with the modified approach of Becke and Johnson (LDA + mBJ), within the framework of density functional theory (DFT). To do this, we use the BoltzTrap package implemented in the Wien2k code, with a constant relaxation time of the charge carriers. All transport properties were studied in the temperature range of 300 to 600 K. Moreover, for high temperatures, the prediction of the figure of merit of ZnSb indicates that the compound is much more suitable for thermoelectric devices. Also, the Pauli magnetic susceptibility of zinc antimonide showed that this material is non-magnetic.

Abstract: PEDOT:PSS (poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate)) has the advantages of excellent thermoelectric properties, good environmental stability, outstanding processability, etc. It is a new type of polymer thermoelectric material with great development potential to improve its conductivity and Seebeck coefficient by compounding or doping with nanomaterials. In this study, PEDOT:PSS was composited with carbon nanotubes (CNTs) to prepare PEDOT:PSS/CNT composite films with excellent thermoelectric properties. The ionic liquid (IL) and polymer surfactants (PEG, PEG-PPG-PEG) doping on the thermoelectric properties of the composite system. The maximum electrical conductivity and Seebeck coefficient of the prepared PEDOT:PSS/CNT composite film are 1581.06 S/cm (CNT content of 10 wt%) and 20.28 μV/K (CNT content of 40 wt%), respectively, and the maximum power factor can reach 52.51 μW ·m^-1·K^-2 (CNT content is 30wt%). After the introduction of PEG doping, the Seebeck coefficient can reach up to 23.62 μV/K.

Abstract: The thermoelectric properties of compounds with variable valence Mn_1-ХRe_ХS (0 ≤ X ≤ 0.2) in the temperature range of (80 – 1100) K are studied. The maxima on the temperature dependences of the Seebeck coefficient (thermal EMF) for all substitution concentrations and the change of the sign of the Seebeck coefficient from positive to negative with an increase in the substitution concentration in Mn_1-XYb_XS are determined. A model of impurity donor 4f-states is proposed and a satisfactory agreement with the data on the thermal EMF is obtained.

Abstract: This paper displays the fabrication of a thermoelectric (TE) generation module using n-ZnSb and p-Zn_0.25Cd_0.75Sb bulk TE materials. TE properties of the Zn_1-xCd_xSb bulks with x= 0, 0.5 and 0.75, in terms of the electrical conductivity () and Seebeck coefficient (S) were measured in the range of 300-500K. The higher power factor (S²σ) values for n-ZnSb and p-Zn_0.25Cd_0.75Sb bulks were obtained about 2.410^-4mW/mK² at 303K and 1.1810^-5 mW/mK² at 468K, respectively. By variation of the thermal conditions, the maximum output power (P_max) with two p-n couples generator module was 1.3810^-5 mW at hot side temperature of 355K and temperature difference () of 40K. The internal (R_in = 0.17 m) and contact resistances (R_c = 0.67 m) between legs and electrodes were discussed below.

Abstract: The thermoelectric properties of hexagonal SiGe doped with Sn with doping percentage of 12.5% and 25% were investigated using linearised augmented plane wave method using the WIEN2k package and semiclassical Boltztmann Transport equation using the BoltzTraP software for the purpose of understanding the role of Sn as a dopant in the SiGe. For temperature range of 300 to 1000 K, it can be seen that by doping with Sn, there is an improvement in overall thermal conductivity of the samples with the highest improvement is in the 25% doped sample. The conductivity vs temperature for 25% Sn doped SiGe also shows higher value through temperature range from 300 K to 1000 K, however the Seebeck coefficient decreases with Sn doping percentage for the same temperature range. Due to lower Seebeck coefficient and higher thermal conductivity values, the overall thermoelectric coefficient, ZT, of the doped compound is lower than the SiGe values with highest ZT equal to 0.29 and 0.17 at 650 K for 12.5% and 25% respectively while the ZT of simulated SiGe at 650 K is 0.35. Thus 25% Sn doping actually reduce the ZT but enhanced the thermal and electrical conductivity of SiGe for temperature range of 300 to 1000 K.

Abstract: Cu₃SbSe₄-based thermoelectric materials are a class of thermoelectric materials with diamond-like structure which exhibit high thermoelectric properties at moderate temperature region and have broad research prospects. In this study, the p-type Co-doped Cu_3-xCo_xSbSe₄ (x=0-0.015) thermoelectric materials were fabricated by melting-annealing-ball milling-hot pressing process to investigate the effects of Co doping on the thermoelectric properties of Cu₃SbSe₄. It is found that the average power factor of Cu_2.995Co_0.005SbSe₄ was increased by 30% compared with the pure sample, indicating that Co doping had a great effect on the electrical properties of Cu₃SbSe₄. The energy gap of ternary p-type semiconductor Cu₃SbSe₄ was around 0.27eV. As the Co content increasing, the lattice distortion enhanced the phonon scattering, which led to the decrease in lattice thermal conductivity. The maximum thermoelectric figure of merit, ZT_max, reached 0.46 at 600K for the Cu_2.995Co_0.005SbSe₄.

Abstract: The growth, structure, optical, electrical and thermoelectric properties of calcium silicides of various compositions on silicon substrates with (100) and (111) orientations were experimentally studied. It was found that when the atoms of Ca and Si are co-deposited on atomically clean silicon, the basis phases in the composition of the formed films depends on the substrate temperature and the annealing temperature: Ca₂Si (T_Si = 20°C, T_ann = 330°C), CaSi (T_Si = 190-320°C, T_ann = 330°C) and CaSi₂ (T_Si = 500°C). It was established that the Ca₂Si phase is a direct-gap semiconductor with a band gap of 0.82±0.02 eV, large contribution of defect levels to the absorption coefficient at energies 0.25 - 0.50 eV and huge transmission up 90% in the far IR region. In CaSi-based films the high transmission (30-40%) up to 25 μm was observed, which corresponds to a semimetal with a constant density of states near the Fermi level. It was found that CaSi-based films have the maximum Seebeck coefficient and the power factor (up to 430 μV/K and up to 1.14 × 10^-6 W/(K²m), respectively) at 330K. CaSi₂ films with CaSi₂ lattice stretching and epitaxial ordering relative to the Si (100) substrate exhibit semimetal properties, with very high conductivity and light transparency (up 12%) in the photon energy range 0.06 - 0.65 eV.