Conventional Spray Pyrolysis Research Articles

Study of structural, optical and electrical properties of Nickel doped ZnO (Ni–ZnO) nanorods grown by chemical bath deposition

To investigate the effect of Nickel on ZnO thin films, doped ZnO (Ni–ZnO) thin films were synthesized using chemical bath deposition on seed layers which were first grown using the conventional spray pyrolysis method. Structural, optical and electrical properties were studied at different doping levels of Ni (0, 2, 4, 6, 8 %). All samples exhibited a highly defined (002) peak indicating a strong hexagonal crystal structure orientation. The samples showed a red shift at E2L and E2H Raman modes indicative of structural alterations. The undoped, 2 % and 4 % Ni doping levels showed lower mean roughness values compared to the 6 % and 8 % Ni doping. The Introduction of Ni into the ZnO structure appears to reduce the grain size from 167 nm to the lowest 79 nm at 2 % Ni concentration. Optical and electrical properties showed that the introduction of Ni as a dopant led to improved transmittance of up 70 % within the visible range and reduced resistivity from 3.590*10−3 (Ωcm) at undoped ZnO to 0.616*10−3 (Ωcm) 2 % Ni doped ZnO concentration.

Elimination of Secondary Oxide Phases in CdTe Nanostructured Thin Films Prepared by Conventional Spray Pyrolysis, and the Influence of Thermal Annealing

Elimination of Secondary Oxide Phases in CdTe Nanostructured Thin Films Prepared by Conventional Spray Pyrolysis, and the Influence of Thermal Annealing

Construction of Economical Dip-Coater for the Fabrication of Hydrophobic Coatings

D.C. motors are considered the basic components for the construction and development of various nanotechnology research equipment due to their constant speed and high efficiency. Spin coater, dip-coater, and spray pyrolysis were a few among them which utilize the above-mentioned component for the production of thin-film coatings on the desired substrates. Conventional spin coater, dip-coater, and spray pyrolysis are expensive to install in research laboratories. In this letter, we report the economical construction of an Arduino-based dip-coater that uses a linear actuator consisting of a D.C. motor for the production of hydrophobic coatings. The dip and drawl rate of the as-constructed machine was estimated to be 3mm/sec and can be varied according to the requirement without any interferences of vibration. Further, the dip-coater was tested with TiO2 gel for the production of hydrophobic coatings on cotton fabrics. The coated fabrics were characterized using an X-ray diffractometer (XRD), which confirmed the presence of TiO2, and reflectance analysis using ultraviolet-visible and near-infrared spectroscopy (UV-VIS-NIR) on the coated fabric revealed an increase in the visible and IR range and a decrease on the ultraviolet spectral region. The goniometer investigation with a water droplet on the treated fabric revealed 137O contact angle and the coating is proved as a super hydrophobic coating.

Low-Temperature Large-Area Zinc Oxide Coating Prepared by Atmospheric Microplasma-Assisted Ultrasonic Spray Pyrolysis

Zinc oxide (ZnO) coatings have various unique properties and are often used in applications such as transparent conductive films in photovoltaic systems. This study developed an atmospheric-pressure microplasma-enhanced ultrasonic spray pyrolysis system, which can prepare large-area ZnO coatings at low temperatures under atmospheric-pressure conditions. The addition of an atmospheric-pressure microplasma-assisted process helped improve the preparation of ZnO coatings under atmospheric conditions, compared to using a conventional ultrasonic spray pyrolysis process, effectively reducing the preparation temperature to 350 °C. A program-controlled three-axis platform demonstrated its potential for the large-scale synthesis of ZnO coatings. The X-ray diffraction results showed that the ZnO coatings prepared by ultrasonic spray pyrolysis exhibited (002) preferred growth orientation and had a visible-light penetration rate of more than 80%. After vacuum treatment, the ZnO reached a 1.0 × 10−3 Ωcm resistivity and a transmittance of 82%. The tribology behavior of ZnO showed that the vacuum-annealed coating had a low degree of wear and a low coefficient of friction as the uniformly distributed and dense coating increased its load capacity.

Band structure controlled solid solution of spray deposited Cd1-x ZnxS films: Investigation on photoluminescence and photo response properties

Nano crystalline Cd1-xZnxS (x = 0.00–1.00 at. %) films were deposited on glass substrates through conventional chemical spray pyrolysis method at different temperatures. The films with x < 0.70 have exhibited hexagonal phase beyond which cubic phase was noticed. The shifting of XRD peaks with higher Zn content, confirmed the formation of Cd1-xZnxS solid solutions. The film crystallinity improved at higher deposition temperatures, while it decreased with increasing x. SEM images showed nearly spherical granular shapes for x = 0, which gradually deteriorate in size at higher x and changed to fibrous structure for x > 0.60. Further the films with x = 0.40–0.60 seem to be porous and well-suited for gas sensing applications. The EDS confirmed the presence of Cd, Zn and S with expected stoichiometry. The optical transmittance and the energy band gap increased with increasing temperature and x. The shift of absorption edge to the shorter wavelength with Zn content has made film high transparent in blue region. The extinction coefficient reduced with x and Urbach energy has shown the formation of defects. Photoluminescence spectra exhibited broad emission bands which could be deconvoluted to multiple peaks attributable to defect states. The film resistivity increased with x that resulted in decrease of carrier concentration which was determined through Hall Effect measurements. The crystallinity was found to influence the photo-response of the films. The films with high Cd contents showed excellent photo response which can be used as photo-detector due to its rapid decline of resistance in the band edge region. The smaller grain and fibrous structured films with large open surface area obtained here, can be used in gas sensing while, the films with x > 0.60 are well-suited for the fabrication of window layers of solar cells.

Development of automated spray pyrolysis setup for chemical vapour deposition like growth of thin solid films

This paper presents a simple electronic interface for spray pyrolysis to deposit high quality thin solid films. The exhibited electronic circuit with the Arduino based microcontroller is acting as the interface between the primary process parameters and the computer running National Instruments{®} LabVIEW{®}. The proposed setup and deposition flow achieve a reproducible, repeatable, and uniform deposition of thin films through the spray pyrolysis technique, which improves the conventional spray pyrolysis technique. The conventional spray nozzle was replaced by the therapeutic aerosol nebulizer, a cost viable replacement, for uniform, smooth, chemical vapor deposition (CVD)-like deposition. The efficacy of the automated nebulizer spray pyrolysis (n-SP) setup was demonstrated by depositing fluorine doped tin oxide (SnO2:F), zinc oxide (ZnO) and zinc sulfide (ZnS) thin films and also by comparing the characterization results of the films with the literature. Results suggest that the proposed automated nebulizer spray pyrolysis setup has the ability to change the commercial production of device quality thin films from complex chemical vapor deposition to cost-effective, simple and automated nebulizer spray pyrolysis method.

Comparative study on deposition of fluorine-doped tin dioxide thin films by conventional and ultrasonic spray pyrolysis methods for dye-sensitized solar modules

Fluorine-doped tin dioxide (FTO) thin films were produced via conventional spray pyrolysis and ultrasonic spray pyrolysis (USP) methods using alcohol-based solutions. The prepared films were compared in terms of crystal structure, morphology, surface roughness, visible light transmittance, and electronic properties. Upon investigation of the grain structures and morphologies, the films prepared using ultrasonic spray method provided relatively larger grains and due to this condition, carrier mobilities of these films exhibited slightly higher values. Dye-sensitized solar cells and 10×10 cm modules were prepared using commercially available and USP-deposited FTO/glass substrates, and solar performances were compared. It is observed that there exists no remarkable efficiency difference for both cells and modules, where module efficiency of the USP-deposited FTO glass substrates is 3.06% compared to commercial substrate giving 2.85% under identical conditions. We demonstrated that USP deposition is a low cost and versatile method of depositing commercial quality FTO thin films on large substrates employed in large area dye-sensitized solar modules or other thin film technologies.

Fabrication of robust TiO2 thin films by atomized spray pyrolysis deposition for photoelectrochemical water oxidation

Photoelectrodes are highly essential for the photoelectrochemical water splitting process and development of novel fabrication techniques is vital for further enhancement of activity. In this study, we successfully fabricated highly active TiO2 thin films by using novel atomized spray pyrolysis deposition (ASPD) technique. The ASPD technique utilizes a unique atomization process to produce highly fine aerosols which resulted in a highly crystalline TiO2 nanostructure. The deposition process was optimized by controlling deposition temperatures and precursor amounts. XRD and SEM studies confirmed the formation of anatase TiO2 phase and a highly interconnected nano-flakes on FTO substrate at 550°C. The photoelectrochemical activity of the optimized thin films showed a photocurrent density of ∼5mAcm−2 at 1.0V (vs. Ag/AgCl) in 0.1M Na2SO4 (aq) under 375nm (150mWcm−2) illumination. This photocurrent was much higher than the two other anatases TiO2 thin films fabricated by conventional spray pyrolysis deposition (SPD) using the same precursor and anatase TiO2 powder (particle size ∼21nm). Transient IR absorption study revealed that the SPD powder based thin films have deeply trapped electrons, whereas ASPD thin films consisted with only free and/or shallowly trapped electrons. Higher crystallinity and enhanced electron conductivity of the TiO2 thin films fabricated by ASPD are responsible for this stable and high photoelectrochemical activity.

Annealing effects on Ga‐doped ZnO thin films grown by atmospheric spray pyrolysis using diethylzinc solution

Polycrystalline a‐axis oriented Ga‐doped ZnO thin film could be grown on glass substrate by a conventional atmospheric spray pyrolysis at 150 °C using diethylzinc‐based solution. The n‐type Ga‐doped ZnO thin film had a resistivity of 1.5 × 10−3 Ω cm, a carrier concentration of 2.0 × 1020 cm−3 and a mobility of 20.0 cm2 (Vs)−1 at an optimal Ga content of 2 wt.% upon hydrogen annealing at 450 °C. It was assumed that an increase of the n‐type carrier concentration is due to increase oxygen vacancies by reacting hydrogen and oxygen in ZnO from X‐ray photoelectron spectroscopy.

Nanostructured CdS thin films deposited by spray pyrolysis method

Influence of solution pH on the structural and optical properties of CdS films deposited by conventional spray pyrolysis technique was studied. X‐Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Photoluminescence spectroscopy (PLS), and Spectroscopic Ellipsometry (SE) methods were used for the characterization of the deposited films. PL spectrum of the film deposited from the solution with pH = 10.2 shows broad‐band PL emission located at 460 nm (2.7 eV), which can be attributed to the quantum size effect at grain sizes of &lt;10 nm. No shifts of ϵ1 and ϵ2 due to the quantum size effect are observed in dielectric function spectra, what can be caused by low concentration of nano‐sized (&lt;10 nm) CdS grains. The change in the film properties with the pH of the solution was analyzed in terms of variation of grain sizes of the polycrystalline films.

Growth and characterization of Cd0.8Zn0.2S thin films by spray pyrolysis method

Sulphides of zinc and cadmium have been utilized effectively in various opto-electronic devices. Cd0.8Zn0.2S thin films have been deposited on glass substrate by the conventional spray pyrolysis method. The structural, optical and electrical properties have been investigated through the X-ray diffractometer; UV–vis spectrophotometer and Keithley two probe set up. The X-ray diffraction pattern of films show that the films are polycrystalline in nature exhibiting hexagonal structure with preferential orientation along the (002) plane. The optical band gap of the films has been studied by using transmission spectra in wavelength range 325–600nm. The DC electrical conductivity of the films has been measured in vacuum by a two probe technique.

Influence of pH of spray solution on optoelectronic properties of cadmium oxide thin films

Highly conducting transparent cadmium oxide thin films were prepared by the conventional spray pyrolysis technique. The pH of the spray solution is varied by adding ammonia/hydrochloric acid. The effect of pH on the morphology, crystallinity and optoelectronic properties of these films is studied. The structural analysis showed all the films in the cubic phase. For the films with pH < 7 (acidic condition), the preferred orientation is along the (111) direction and for those with pH >7 (alkaline condition), the preferred orientation is along the (200) direction. A lowest resistivity of 9.9 × 10−4 Ω·cm (with carrier concentration = 5.1 × 1020 cm−3, mobility = 12.4 cm2/(V·s)) is observed for pH ≈ 12. The resistivity is tuned almost by three orders of magnitude by controlling the bath pH with optical transmittance more than 70%. Thus, the electrical conductivity of CdO films could be easily tuned by simply varying the pH of the spray solution without compromising the optical transparency.

CH₃NH₃PbI₃-based planar solar cells with magnetron-sputtered nickel oxide.

Herein we report an investigation of a CH3NH3PbI3 planar solar cell, showing significant power conversion efficiency (PCE) improvement from 4.88% to 6.13% by introducing a homogeneous and uniform NiO blocking interlayer fabricated with the reactive magnetron sputtering method. The sputtered NiO layer exhibits enhanced crystallization, high transmittance, and uniform surface morphology as well as a preferred in-plane orientation of the (200) plane. The PCE of the sputtered-NiO-based perovskite p-i-n planar solar cell can be further promoted to 9.83% when a homogeneous and dense perovskite layer is formed with solvent-engineering technology, showing an impressive open circuit voltage of 1.10 V. This is about 33% higher than that of devices using the conventional spray pyrolysis of NiO onto a transparent conducting glass. These results highlight the importance of a morphology- and crystallization-compatible interlayer toward a high-performance inverted perovskite planar solar cell.

Synthesis and characterization of hollow mesoporous BaFe12O19 spheres

A facile method is reported to synthesize hollow mesoporous BaFe12O19 spheres using a template-free chemical etching process. Hollow BaFe12O19 spheres were synthesized by conventional spray pyrolysis. The mesoporous structure is achieved by alkaline ethylene glycol etching at 185°C, with the porosity controlled by the heating time. The hollow porous structure is confirmed by SEM, TEM, and FIB-FESEM characterization. The crystal structure and magnetic properties are not significantly affected after the chemical etching process. The formation mechanism of the porous structure is explained by grain boundary etching.

Electrochemical properties of tungsten sulfide-carbon composite microspheres prepared by spray pyrolysis.

Tungsten sulfide (WS2)–carbon composite powders with superior electrochemical properties are prepared by a two-step process. WO3-carbon composite powders were first prepared by conventional spray pyrolysis, and they were then sulfidated to form WS2-carbon powders. Bare WS2 powders are also prepared by sulfidation of bare WO3 powders obtained by spray pyrolysis. Stacked graphitic layers could not be found in the bare WS2 and WS2–carbon composite powders. The amorphous bare WS2 and WS2–carbon composite powders have Brunauer–Emmett–Teller (BET) surface areas of 2.8 and 4 m2 g−1, respectively. The initial discharge and charge capacities of the WS2–carbon composite powders at a current density of 100 mA g−1 are 1055 and 714 mA h g−1, respectively, and the corresponding initial Coulombic efficiency is 68%. On the other hand, the initial discharge and charge capacities of the bare WS2 powders are 514 and 346 mA h g−1, respectively. The discharge capacities of the WS2–carbon composite powders for the 2nd and 50th cycles are 716 and 555 mA h g−1, respectively, and the corresponding capacity retention measured after first cycle is 78%.

Effect of the deposition temperature on the electrochemical properties of La0.6Sr0.4Co0.8Fe0.2O3−δ cathode prepared by conventional spray-pyrolysis

La0.6Sr0.4Co0.8Fe0.2O3−δ (LSCF) cathodes have been deposited by conventional spray pyrolysis on Ce0.8Gd0.2O1.9 (CGO) electrolytes at different temperatures between 250 and 450 °C, obtaining electrodes with different microstructure and porosity. Highly porous and macroporous electrodes are obtained at deposition temperatures of 250 °C and 450 °C, respectively, with an average grain size of 30–50 nm. The influence of the post-annealing treatment on the microstructure and on the electrochemical properties is investigated by scanning electron microscopy and impedance spectroscopy in air and as a function of the oxygen partial pressure to identify the different contributions to the polarization. Samples annealed at 650 °C show similar values of area specific resistance 0.04–0.06 Ω cm2 at a measured temperature of 650 °C. However, after annealing the samples at 850 °C, the ASR values increase up to 0.1–0.6 Ω cm2 with the lowest value corresponding to the film deposited at 250 °C due to the large porosity and surface area of this film. The performance degradation upon annealing is attributed to decreasing reaction sites induced by grain growth and densification.

Barium hexaferrite nanoparticles with high magnetic properties by salt-assisted ultrasonic spray pyrolysis

Herein, we synthesized non-agglomerated barium hexaferrite nanoparticles by salt-assisted ultrasonic spray pyrolysis at different reaction temperatures. NaCl was used as an added salt, melted at 850, 900, and 950 °C to act as a solvent in the reaction processes. It was found that at 950 °C, the salt melted sufficiently and therefore accelerated the subsequent nucleation and growth of barium hexaferrite nanoparticles. The barium hexaferrite nanoparticles synthesized by the salt-assisted ultrasonic spray pyrolysis method were exquisitely compared with the barium hexaferrite synthesized by conventional ultrasonic spray pyrolysis method. The particles were characterized by XRD, SEM, and TEM analyses. The salt-free barium hexaferrite obtained at 950 °C revealed the presence of hematite, whereas the salt-added barium hexaferrite nanoparticles synthesized at 950 °C showed the existence of only barium hexaferrite phase. The salt-added barium hexaferrite nanoparticles synthesized at 950 °C showed a hexagonal plate shape, 72 nm in size and with good crystallinity. The magnetic properties were investigated by vibrating sample magnetometer (VSM) at room temperature. The magnetic properties of the salt added barium hexaferrite at 950 °C showed the coercivity of 5735 Oe and saturation magnetization of 63.2 emu/g.

Optical and electrical characteristics of pure CdS thin Films for different thickness

Conventional spray pyrolysis technique was employed for the preparation of cadmium sulphide (CdS) thin films that deposited onto glass substrates at 573 K from cadmium acetate and thiourea precursor solution for different deposition time. The surface morphology, compositional study and optical properties of the films have been characterized by Scanning Electron Microscopy (SEM) attached with an EDX and UV spectroscopy, respectively. The SEM micrographs of deposited film showed uniform deposition over the substrate. The EDX spectra of CdS thin films revealed that films are stoichiometric. All the films demonstrated more than 70% transmittance at wavelengths longer than 600 nm. The optical absorption coefficient (?) of the CdS films was determined from transmittance spectra. For different thickness (110 - 250nm) of the films, the direct band gap was found in the range of 2.15~2.48 eV. Resistivity (?) of CdS thin films was measured in the temperature range of 300 to 550 K. Activation energy (?E) was found in the range from 0.047 to 0.078 eV. DOI: http://dx.doi.org/10.3329/jbas.v37i1.15678 Journal of Bangladesh Academy of Sciences, Vol. 37, No. 1, 33-41, 2013

Double flame spray pyrolysis as a novel technique to synthesize alumina-supported cobalt Fischer–Tropsch catalysts

The controlled deposition of a catalytically active material on a support, resulting in defined particle sizes and shapes, as well as control over the specific surface area of the active material and the support are usually limited when applying conventional catalyst preparation techniques. Flame spray pyrolysis offers the potential to overcome this limitation and is tested for the preparation of Fischer–Tropsch catalysts. Conventional single flame spray pyrolysis and, for the first time, double flame spray pyrolysis are compared for the synthesis of alumina supported cobalt catalysts. In the latter process the metal oxide precursors are combusted individually in two opposing nozzles. The key parameter for defining the final material composition is the intersection distance of the flames, which was systematically varied. The Fischer–Tropsch performance of the Co-based catalysts was studied in a fixed bed reactor at 230°C and 20bar. The catalytic results are discussed on the basis of structural characterization of the different catalysts by XRD, BET, TPR, UV–vis and TEM/EF-TEM. While catalysts made by single flame spray pyrolysis were inactive in the Fischer–Tropsch reaction regardless of whether cobalt was subsequently mixed with alumina or the supported catalyst was directly prepared in the flame reactor, the double flame sprayed catalysts showed good catalytic activity. Depending on the intersection distance of the two flames, the formation of cobalt oxide and alumina occurred separately in each flame reactor. In spite of the independent particle growth in the two flames, the double flame reactor geometry lead to good adhesion of the two oxides resulting in good stabilization of cobalt nanoparticles on the alumina support during the Fischer–Tropsch reaction.

Optical and electrical characterization of transparent Ga‐doped ZnO thin films grown by atmospheric spray pyrolysis using diethylzinc solution

AbstractNon‐doped and Ga‐doped ZnO film on glass substrate were successfully grown at 150 °C by conventional atmospheric spray pyrolysis using diethylzinc‐based solution. The samples had an average optical transmittance of more than 80% and were strongly a‐axis orientated according to the results of optical transmittance and X‐ray diffraction analysis, respectively. The n‐type Ga‐doped ZnO films had a low resistivity of 2.3 × 10–3 Ωcm, a carrier concentration of 1.1 × 1020 cm–3 and a mobility of 10 cm2 (Vs)–1 at an optimal Ga content of 2 at% upon UV irradiation. (© 2013 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)