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This work investigates the thermoelectric and electrical performance of nanostructured thin films of antimony (Sb)-doped Bi2Te3 (thickness ∼ 60 nm) and Bi0.5Sb1.5Te3 (thickness ∼ 60 nm). The films were deposited on a glass substrate by thermal evaporation under high vacuum conditions. The structure and morphology of the films was investigated by standard characterization techniques. X-ray diffraction was used to identify the formation of different phases during the synthesis of the films. The Van der Pauw and Harman methods were employed to measure the conductivity (σ) and figure of merit (ZT). Further, samples were subjected to annealing under a high vacuum at 200°C for 1 h to improve the quality and ZT of the deposited films. The Sb-doped Bi2Te3 film was found to be ∼ 6.5 times more conductive than the Bi0.5Sb1.5Te3 film. However, the two films exhibited comparable ZT values owing to the small value of the Seebeck coefficient (S) of Sb. This study represents a significant contribution in the field of thermoelectric materials and device applications.

Thermoelectric properties of high energy ball milled nano structured bismuth telluride (Bi2Te3) have been reported. By high energy ball milling, alloyed bulk crystalline ingots crush into nanopowder and followed by spark plasma sintering (SPS), we have demonstrate high figure of merit (ZT) in bismuth telluride pellet samples. In this work systematic study carried out on three pellet samples of Bi2Te3, synthesized by high ball milling for the time period of 4 hours, 8 hours and 12 hours and followed by SPS at the same processing parameters. A peak value of dimensionless figure of merit of about 1.22 at the temperature of 473 K has been achieved for 8 hours ball milled pellet sample. This enhancement in ZT value is mostly due to decrease in thermal conductivity. Results of this study demonstrate that ball milling and SPS has a major effect in controlling the density of grain boundaries of Bi2Te3 nano particles, while the pressure exerted on the powder samples during SPS introduce stress at the boundaries of the crystallites. These disordered crystallite boundary regions exert scattering of thermal energy carriers which reduced the thermal conductivity of the materials.

The synthesis of thin films of ITO (Indium Tin Oxide) is synthesized by thermal evaporation technique under high vacuum conditions and further annealing at different conditions of temperature. These films were further characterized by using SEM, XRD, AFM, photoluminescence spectroscopy and UV-Visible in order to understand the structural and optical properties associated with them. Parameters to synthesize uniform, homogeneous, single phase and highly transparent ITO thin films have been optimized.

Thermoelectric properties of n-type bismuth telluride and its nanocomposite reinforced with different concentration of multi wall carbon nanotubes (MWCNTs) are reported. Nanocomposites of bismuth telluride with MWCNTs were synthesized by using high energy ball milling followed by spark plasma sintering (SPS). MWCNTs reinforced nanocomposites of bismuth telluride resulted improvement in its figure of merit ZT from 0.76 (for Bi2Te3) to 0.85 (for Bi2Te3 + 2%MWCNTs) at 473K temperature. Thermoelectric parameters of nanocomposites of Bi2Te3 were characterized by Laser Flash Technique. The improvements found in ZT value may be due to decrease in thermal conductivity of the nanocomposites. Concentration of MWCNTs in bismuth telluride leads to dampening the phonon propagation with addition to the interface scattering of phonons from phase boundaries as well as grain boundaries which leads to decrease in thermal conductivity. Copyright © 2016 VBRI Press.

Nanocrystalline indium oxide thin films of thickness about 100 nm have been deposited using thermal vacuum evaporation technique at room temperature on glass and quartz substrates and subsequently annealed at different temperatures (150℃, 200℃, 250℃, 300℃, 350℃, 500℃ and 700℃) for 2 hr and 4 hr in the oxygen atmosphere. Structural and optical properties of these films have been investigated by using XRD, SEM, HRTEM, AFM, UV-Visible, and photoluminescence spectroscopy. Response of gas towards the thin films is obtained. X-ray diffraction studies of deposited and annealed films show the transformation of indium into indium oxide thin films at 300℃. UV-visible and PL studies reveal the band gap of 3.7 eV. The transparency of thin films is about 83%. Gas response is obtained 3.55 for ethanol vapours. Structural features associated with the indium oxide thin films have been correlated with optical parameters.