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Herein, the cobalt oxide thin films are elaborated by spray pyrolysis technique. The effect of temperature of substrates on several properties of cobalt oxide is studied. The thin layers are characterized by using X‐ray diffraction (XRD), Raman spectrometry (RS), and UV–vis spectrophotometer. The XRD analysis shows that Co3O4 thin layers have been formed along <111> preferential orientation. The RS displays the characteristic vibration modes of cobalt oxide phase, which confirms the formation of a single phase of spinel Co3O4 thin layers. The UV–vis spectrophotometer allows us to investigate the optical properties such as the absorbance, the transmittance, and the optical bandgap. The variation of electrical properties with the variation of temperature deposition confirms the high impact of the effect that study to make the cobalt oxide an important candidate for gas sensor devices. [ABSTRACT FROM AUTHOR]

The semiconductor realization is a very significant stage in gas sensor application. Herein, the Mn3O4 semiconductor was deposited using chemical spray pyrolysis. The effect of deposition temperature on structural, vibrational optical and electrical Mn3O4 thin layers properties were investigated through: X‐ray diffraction, Raman spectroscopy, UV‐visible spectrophotometer, and two points electrometers respectively. The X‐ray diffraction showed the appearance of spinel phase of tetragonal Mn3O4 with strong formation direction along (101) plan and without any secondary phase indicating the formation of pure Mn3O4. The Raman spectroscopy confirmed the results obtained in XRD and certified the high‐quality formation of Mn3O4. In addition, the crystallinity improvement (the increase of crystallite size and the decrease of dislocation density) was caused by the increasing of deposition temperature from 350 °C to 450 °C. Optical properties such as transmittance, absorbance and band gap energy were extracted by UV‐Visible spectrophotometer. Thus, low transmittance, high absorbance and small band gap energy were observed at the highest substrate temperature (450 °C). The electrical conductivity showed good values between 4.83 and 13.89 mS.cm−1. These properties make Mn3O4 an appropriate material to be used as a sensitive layer in gas sensors applications. [ABSTRACT FROM AUTHOR]

This study aims at synthesizing zinc sulfide (ZnS) thin films using spray pyrolysis method. The effect of the Zn concentration on the physical properties of ZnS is investigated using X‐ray diffraction (XRD), scanning electron microscope (SEM), UV–Vis spectrophotometer, photoluminescence (PL), and Raman spectroscopy. XRD shows a preferential orientation along the (111) direction corresponding to the ZnS cubic structure. Based on the XRD results, it is seen that low zinc concentrations compared to sulfur content can increase the crystalline quality of films. Raman spectra confirm the presence of the ZnS cubic structure observed by XRD and show the presence of sprayed ZnS vibrational modes for all films. PL emission spectrum of ZnS confirms the presence of Zn and S atoms at all molar concentrations. SEM reveals densely packed and uniformly distributed grains with precise shapes. The elemental analysis confirms the growth of stochiometric Zn/S ratio. The optical analysis shows a high transmittance around 88% in the visible range of the solar spectrum with optical band gaps varying from 3.4 to 3.6 eV. These properties are interesting and show that ZnS thin films can be used as buffer layers in thin film solar cells applications. [ABSTRACT FROM AUTHOR]

Our TiO2 thin films were elaborated using spray pyrolysis technique. The spray solutions were prepared by two titanium precursors: titanium (IV) propoxide and titanium chloride. The elaborated thin films were analyzed with different characterization techniques such as X‐ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and UV–visible spectroscopy. These characterizations showed that the change of precursors from titanium chloride to titanium propoxide has a significant impact on all TiO2 properties. The structural characterizations showed the formation of anatase TiO2 and the crystallization improvement when the precursor changed from titanium chloride to titanium (IV) propoxide, which proves the superiority of our TiO2 thin layers made without any type of annealing in comparison with other previous studies. The SEM images showed an improvement of the surface quality of the TiO2 thin layers with the change of TiO2 precursors' solution. The obtained optical properties confirmed the semiconducting properties of TiO2 prepared by titanium propoxide with a large band gap equal to 3.28 eV and shifted to 3.18 eV. The refractive index increases from ~1.75 to ~2.14, while the porosity decreases. To confirm the experimental results, the Wien2K code, founded on the full‐potential linearized augmented plane wave (FP‐LAPW), has been used. The theoretical study has been done by applying the generalized gradient approximation (GGA), the modified Beck‐Johnson (MBJ) exchange potential, and the local spin density approximation + Hubbard's parameter U (LSDA + U). The theoretical results varied with the variation of approximations. The obtained properties were improved with LSDA + U and acquired the real values of Eg, n, and k for anatase TiO2 (like Eg = 3.214 eV). The obtained experimental and theoretical results could be considered superposable or better than other ones recently published. [ABSTRACT FROM AUTHOR]

The semiconductor's realization is a very significant stage of optoelectronics devices. In this work, an elaboration of the TiO2 semiconductor is made with various solution flow rates via spray pyrolysis. The structural and optical properties of pure TiO2 are investigated with several characterization techniques which include: X‐ray diffraction (XRD), Raman spectroscopy, and UV–vis spectrophotometry. The XRD of elaborated TiO2 layers exhibits nanocrystalline nature with a preferential orientation at the (101), a unique phase of anatase TiO2. The apparition of vibration modes in Raman spectra confirms the TiO2 formation with a single phase. The produced TiO2 has an optical transmission varying from 90% to 70% in the visible wavelength. The energy band gaps are 3.42, 3.32, and 3.28 eV for the TiO2 elaborated at 1, 1.5, and 2 mL min−1, respectively which prove the semiconducting properties of TiO2. All other optical parameters such as refractive index (n), extinction coefficient (k), and dielectric constant (εr, εi) vary with the variation of solution flow rate. These investigations discover that the properties of TiO2 layers can be adjusted by solution flow rate. It seems that the process of spray pyrolysis provides a facile way to control the quality of TiO2 thin layers. [ABSTRACT FROM AUTHOR]

The production of thermal energy by solar water heater (SWH) systems is an idea, which has been analyzed and applied for many years. This paper presents a numerical simulation of a new hybrid SWH, in which two tubular thermoelectric generators (TTEGs) and a small water turbine are used to generate more additional electrical energy. The small water turbine is installed between the outlet of the four absorber tubes and the inlet of the water tank in order to generate more electrical energy from the cold‐water motion. Furthermore, the use of a temperature adjustment concept and an optical concentrator shows many significant improvements on the thermal and electrical performance of the new system. Our main results shows that the overall maximum electrical power of two TTEGs was approximately 348.073 W, corresponding to 2.72% of their overall maximum electrical efficiency. Also, the maximum thermal efficiency of the new system reached to 86.09% with an overall hot water quantity of 1548.57 L/d. The electrical energy produced by the small water turbine is about 89.467 W for a cold‐water flow rate of 3 kg/s. [ABSTRACT FROM AUTHOR]