In this work, the thermoelectric properties of p-type layered chalcostibite CuSb 1−x Pb x Se 2 (x = 0−0.10) compounds prepared by vacuum melting reaction and uniaxial hot press, have been studied in the temperature range of 323−623 K. Further, aliovalent Pb 2+ doping at Sb 3+ site in CuSbSe 2 notably increases the hole concentration due to its acceptor nature and thereby enhances the electrical conductivity, σ. Importantly, a huge reduction in total thermal conductivity, κ total has been noticed, from ∼1.7 W/mK (pristine CuSbSe 2 ) to ∼0.72 W/mK at 323 K for CuSb 0.90 Pb 0.10 Se 2 owing to increased phonon scattering from the introduced point defects and mass-difference between Pb and Sb. As a result, the thermoelectric figure of merit, zT, has been enhanced to ∼0.27 at 623 K for the composition of CuSb 0.90 Pb 0.10 Se 2 , which is 3-fold higher than that of the undoped CuSbSe 2 . Further, the hardness value achieved was ∼125.54 Hv, which is significantly higher than the most of the state-of-the-art materials, indicating it to be an efficient thermoelectric material for intermediate temperature.
A large surface to volume ratio and easily accessible active reaction sites are key attributes for a good gas sensing material. Herein, we report synthesis, characterisation and humidity sensing properties of phase pure 420 nm thick low temperature (350°C) polycrystalline V 2 O 5 thin films deposited on quartz substrate by ultrasonic nebulized spray pyrolysis of aqueous combustion mixture (UNSPACM). The thin films were characterized by x-ray diffraction, Raman spectroscopy, atomic force microscope, field emission scanning microscope, transmission electron microscope, UV-visible spectroscopy and XPS. The highly porous and nanocrystalline characteristic of V 2 O 5 thin films synthesized by this technique provide large surface to volume ratio and easily accessible active reaction sites making it a prominent material for gas sensing applications. The fabricated humidity sensor based on V 2 O 5 thin films exhibited high sensitivity with good stability and reproducibility at room temperature. The sensor exhibited high sensitivity of 90.8% at 76% RH with response time of 35-60 s and recovery time of 7-54 s. We believe this method provides means for large-scale synthesis of V 2 O 5 thin films for several gas sensing applications.
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Thermal conductivity reduction in environmentally friendly thermoelectric composites with varying Si particle size has been experimentally measured and modelled using the crowding-factor model.
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