Ultrasonic Spray Pyrolysis Technique Research Articles

Supercapacitor performance of pure and Ni-doped CuO electrodes prepared by USP

Abstract In this study, the ultrasonic spray pyrolysis (USP) technique was employed to fabricate pure and 3% Ni-doped copper oxide (CuO) thin films (TFs) on In2O3/SnO2 (ITO) coated glass substrates. X-ray diffraction (XRD) analysis revealed that both pure and 3% Ni-doped CuO TFs exhibit a polycrystalline structure with the tenorite phase oriented preferentially along the (111) plane. The morphological properties of these TFs were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM) imaging. Energy dispersive x-ray spectroscopy (EDX) confirmed that the deposited TFs achieved the desired stoichiometry. The electrochemical properties of both pure and 3% Ni-doped CuO TFs were evaluated using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS). At a current density of 1 A g−1, the specific capacitance of pure CuO TFs was found to be 78 F g−1, decreasing to 2 F g−1 at 10 A g−1. In contrast, Ni-doped CuO TFs exhibited a specific capacitance of 722 F g−1 at 1 A g−1 and 20 F g−1 at 10 A g−1. These results indicate that Ni-doping significantly enhances the specific capacitance values. The superior performance of Ni-doped CuO electrodes is attributed to their uniformly high porosity and improved electrical conductivity, demonstrating Ni-doped CuO as an optimal electrode material for pseudocapacitors.

Investigation of the Annealing and Cu Doping Effect on Structural and Optical Properties of CdZnS Nanomaterial Deposited by Ultrasonic Spray Pyrolysis

This study investigates doped CdZnS thin films synthesized through the ultrasonic spray pyrolysis technique, followed by annealing at temperatures of 400 and 500 °C. X-ray diffraction analysis demonstrated that both undoped CdZnS and Cu-doped CdZnS thin films exhibit cubic crystal structures, with a preferred orientation along the (111) plane. Scanning electron microscopy (SEM) measurements indicated that the CdZnS thin film has a smooth surface, whereas the Cu-doped CdZnS film shows clustered particles, attributed to the effect of copper doping acting as an activator metal ion. Electron dispersive scanning (EDS) analysis confirmed that the Cd, Zn, and S elements are present in acceptable chemical stoichiometry (Cd + Zn/S = 1:1), with a ratio of 3:1, consistent with the molar amounts used in the precursor solutions. The band gap of the CdZnS thin film decreased from 3.12 to 2.56 eV after annealing at 500 °C, attributed to an increase in crystal size. In contrast, the band gap of the Cu-doped CdZnS thin film decreased from 2.51 to 2.22 eV, lower than that of pure CdZnS, due to the formation of additional phases such as zinc oxide and copper oxide within the CdZnS host structure during annealing.

Zn2-xGeO4-GeO2:(x)Mn2+ films with long persistence, intense brightness and high quantum efficiency, deposited by ultrasonic spray pyrolysis

This work shows the synthesis and characterization of the Zn2-xGeO4-GeO2:(x)Mn2+ (x = 0.10, 0.25, and 0.50 at.%) films using the Ultrasonic Spray Pyrolysis (USP) technique. These films were deposited at 500 °C and heat treated at 800 °C for 13 h. X-ray diffraction (XRD) measurements showed the rhombohedral and hexagonal phases of Zn2-xGeO4 (78.8 %) and GeO2 (21.2 %), respectively. SEM micrographs exhibited the surface morphology of these films. The STEM and HAADF show Ge, Zn, and O atomic layers. In addition, XPS was carried out to observe the oxidation states of Mn2+ (75.4 %) and Mn3+ (24.6 %) for the films doped with Mn ions (0.10 at.%). Incorporating manganese ions into the Zn2-xGeO4-GeO2 host lattice generated an extremely green emission, exciting at 250 nm. The photoluminescence and persistence luminescence properties were studied in accordance with the manganese doping concentration. For photoluminescence, it was found that the optimal doping percentage was 0.25 at.%, and for persistence luminescence, it was 0.10 at.% Mn with λex = 250 nm. Quantum efficiency measurements gave a result of 100 %. In addition, preliminary CL measurements were exhibited.

Nanorod inside hollow-nanosphere structured magnetoelectric nanocatalyst for remotely controlled electrocatalysis assisted environmental remediation

We introduce a highly efficient method for the catalytic breakdown of organic compounds using nanorods embedded within hollow nanospheres structured magnetoelectric nanocatalyst (MENC). MENCs were fabricated through a single-step process utilizing the ultrasonic spray pyrolysis technique. The dynamic electric dipole generation capability due to synergistic interaction between nanorods at the core and the hollow nanosphere shell creates a nanoscale magnetoelectric device capable of electrocatalysis-assisted water purification through advanced oxidation processes under remotely applied magnetic field excitation. Our study examines the electrocatalytic degradation of organic pollutants by MENCs under magnetic field excitation, achieving an unprecedented 90% removal efficiency for synthetic dyes. This remarkable efficiency is a result of surface redox reactions facilitated by electron and hole transfer, resulting in the production of Reactive oxygen species (ROS) such as O2•− and •OH. Additionally, antioxidant experiments were performed to confirm the ROS generation capability of MENCs under magnetic field excitation. Furthermore, trapping experiments performed employing specific scavengers for individual reactive species reveal the mechanism responsible for the magnetic field-driven catalytic breakdown of organic contaminants by MENCs. Interestingly, the MENCs exhibit >95% reduction in Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria, respectively, within 90 min of exposure to a (20 mT& 1.9 kHz) AC magnetic field.

Enhancing π-SnS thin films and fabrication of p-SnS/n-Si heterostructures through flow rate control in ultrasonic spray pyrolysis for improved photovoltaic performance

This study presents findings related to the characterization of cubic SnS (π-SnS) thin films and p-SnS/n-Si heterojunction structures produced simultaneously using the ultrasonic spray pyrolysis technique. In this context, the impact of different spray solution flow rates on the morphological, structural, optical, and electrical characteristics of the films was examined. Morphological analyses revealed that higher flow rates resulted in films with denser and smoother surfaces, approximately 6 nm in roughness. Additionally, it was observed that both the thickness and the growth rate of the films could be adjusted through the modulation of the flow rate. Structural analyses determined that the crystallite size increased and micro-strain values decreased with increasing flow rates. Optical evaluations indicated a decline in the optical band gap of the thin films from about 1.8 eV to 1.7 eV as the flow rates increased. This trend was consistently observed in the data obtained using the Tauc method and the derivative of transmission with respect to wavelength versus photon energy graphs. Electrical analyses revealed that the resistivity values of the thin films increased from 5.24 × 105 Ωcm to 1.64 × 106 Ωcm with increasing flow rates. Furthermore, I-V analyses of the Au/p-SnS/n-Si/Ag heterojunction structures indicated significant variability in key electrical properties. The saturation currents displayed a broad range, suggesting varying efficiencies in charge carrier collection across different samples. Similarly, the change of ideality factors pointed to differences in charge transport mechanisms, while the shifts in barrier heights indicated changes in junction properties with different fabrication conditions. The results of this study offer valuable perspectives for future research.

Photocatalytic activity of rare earth elements (Gd and ce) co-doped ZnO nanostructured films

Organic dyes, which are one of the main sources of surface and groundwater pollution, cause health problems as well as environmental hazards. For this reason, ZnO, which stands out among the promising semiconductor photocatalysts in wastewater treatment due to its advantages, was preferred. In particular, Gd–Ce co-doped ZnO nanostructured films, which have been studied for the first time in the literature, were produced by ultrasonic spray pyrolysis (USP) technique and photocatalytic degradation of Methylene blue (MB) dye was carried out. Ultraviolet–Visible Spectrophotometry (UV–Vis) and Field Emission Scanning Electron Microscopy (FESEM) were used to obtain the transmittance and morphology of thin films. According to the FESEM analysis results, morphological changes in the type of nanostructure were observed after the doping. While the photocatalytic degradation percentage of the ZnO film with Gd doping was 65.84 %, when both Gd and Ce were doped, the degradation percentage increased significantly, reaching 91.58 %. Photocatalytic studies revealed that Gd–Ce co-doped ZnO films exhibited better photocatalytic efficiency compared to only Gd doped ZnO films. Therefore, when all the results are evaluated, it is concluded that ZnO:Gd:Ce photocatalysts may have a significant potential application in environmental remediation.

Imparting Chemiresistor with Humidity-Independent Sensitivity toward Trace-Level Formaldehyde via Substitutional Doping Platinum Single Atom.

The modification of metal oxides with noble metals is one of the most effective means of improving gas-sensing performance of chemiresistors, but it is often accompanied by unintended side effects such as sensor resistance increases up to unmeasurable levels. Herein, a carbonization-oxidation method is demonstrated using ultrasonic spray pyrolysis technique to realize platinum (Pt) single atom (SA) substitutional doping into SnO2 (named PtSA-SnO2). The substitutional doping strategy can obviously enhance gas-sensing properties, and meanwhile decrease sensor resistance by two orders of magnitude (decreased from ≈850 to ≈2 MΩ), which are attributed to the tuning of band gap and fermi-level position, efficient single atom catalysis, and the raising of adsorption capability of formaldehyde, as validated by the state-of-the-art characterizations, such as spherical aberration-corrected scanning transmission electron microscopy (Cs-corrected STEM), in situ diffuse reflectance infrared Fourier transformed spectra (in situ DRIFT), CO temperature-programmed reduction (CO-TPR), and theoretical calculations. As a proof of concept, the developed PtSA-SnO2 sensor shows humidity-independent (30-70% relative humidity) gas-sensing performance in the selective detection of formaldehyde with high response, distinguishable selectivity (8< Sformaldehyde/Sinterferant <14), and ultra-low detection limit (10 ppb). This work presents a generalized and facile method to design high-performance metal oxides for chemical sensing of volatile organic compounds (VOCs).

Effect of fluorine doping on the improvement of electrical and photocatalytic properties of ZnO films

ZnO:F thin films were produced by ultrasonic spray pyrolysis (USP) technique. For photovoltaic and photocatalytic applications, the properties of ZnO films have been tried to be improved by adding the flourine (F) element. The average optical transmittance was higher than 85%. Photoluminescence (PL) spectra depict blue, green and yellow emission in deposited films. Photocatalytic activity of ZnO and ZnO:F thin films was evaluated with methylene blue (MB) organic pollutant under UV irradiation. 5% doped ZnO:F film successfully decomposed ~ 80% using MB as photocatalyst. The lowest resistivity (3.54 × 10–3 Ωcm), high carrier concentration (2.52 × 1020 cm−3) and high hall mobility (8.28 cm2V−1 s−1) were observed in ZnO:F (5%) film. With this study, it was concluded that F-doped ZnO films were effective in the degradation of MB, which is widely used in the food and pollutant industries. Therefore, it makes ZnO:F films a promising material in both optoelectronic and photocatalytic applications due to their optimum properties.

Fine-tuning SnO2 films: Unleashing their potential through deposition temperature optimization by ultrasonic spray pyrolysis

In this study, the optimization of the deposition temperature, which directly affects the crystallinity, morphology, and electrical conductivity of SnO2 films deposited onto Corning Eagle XG glass substrates using the ultrasonic spray pyrolysis technique, was investigated to tailor their physical properties for various applications. Structural analyses revealed that the films had a tetragonal rutile structure, and while films deposited at lower temperatures exhibited a higher prevalence of (200) oriented planes, yet this decreased with an increase in deposition temperature. Morphological analyses showed that the films consisted of grains with octahedral shapes, and films deposited at lower temperatures were found to be more compact. The films had bandgap energy ranges between 3.96 eV and 4.02 eV. Hall effect measurements revealed that not only the carrier concentration decreased from 4.52 × 1019 cm−3 to 0.80 × 1019 cm−3, but the mobility also decreased from 23.32 cm2/Vs to 12.85 cm2/Vs. Among all the films, it was noted that the films deposited at 350 °C had the highest figure of merit which is 12.3 × 10−4 Ω−1. It can be concluded that the changes underlying these variations are associated with structural and morphological changes depending on the substrate temperature. Also, significant results have been attained in applications where precise control over crystal structure and surface morphology is crucial.

Jettability and printability of customized gold nanoparticles-based ink on flexible substrate through inkjet printing process

Among the different metal nanoparticles for formulating inkjet-based conductive inks, gold remains the best choice for fabricating different patterns on economical and bio-degradable substrates such as commercial photo papers for developing low-cost sensing devices. Formulating customized gold nanoparticle (AuNPs) inks remains challenging as the ink must meet specific physical, chemical and rheological properties to achieve appropriate jettable behaviour and printable characteristics. It should exhibit well-controlled viscoelastic response for the smooth and optimized flow through the nozzles and then cure immediately to facilitate the shape retention of deposited feature. In this work, the jettability window definition framework using dimensionless numbers such as Re, We, Ca, and Z are defined for the aqueous-based AuNPs inks synthesized via ultrasonic spray pyrolysis technique and formulated into three concentration levels of 300, 600, and 1200 ppm. A theoretical CFD based simulation study is conducted to observe the ink droplet formation behaviour at different droplet velocities through inkjet nozzle. Among these formulated inks, 1200 ppm shows the most favourable behaviour as obtained through the simulation and jettability window results. It is tested further to see how different printing settings, like pulse voltage and number of repetitions, affected the continuity and density of the ink, affecting the quality of the printed AuNPs. This work demonstrates the process capabilities of inkjet printing technology by testing the formulated AuNPs ink.

Spray pyrolysis-based synthesis of pure molybdenum powder with nanoscale primary particles and its sintering characteristics

Molybdenum (Mo) is a refractory metal with exceptional high-temperature stability, resistance to creep, and low coefficient of thermal expansion, it thus has great potential for various high-temperature applications. Nevertheless, conventional methods of synthesizing Mo powder, such as mechanical milling and wet chemical processing, have encountered limitations in producing sintered bodies with high relative density and a fine grain structure while maintaining a low sintering temperature. Therefore, it is crucial to develop an efficient powder synthesis method that enables precise and uniform control over the powder's size and shape while minimizing contamination. Such an approach would contribute to achieving excellent formability and sinterability for the resulting Mo sintered body. In this study, we successfully demonstrated the ultrasonic spray pyrolysis (USP) technique in combination with hydrogen reduction for synthesizing pure Mo powder. The resulting Mo powder exhibited micro-sized secondary particles composed of nanoscale primary particles, leading to improved formability and sinterability, essential for fabricating high-quality sintered bodies. In order to comprehensively understand the properties of the as-prepared molybdenum oxide and hydrogen-reduced Mo powder, we employed various methods to analyze its physicochemical characteristics systematically. Subsequently, the fine Mo particles were subjected to a pressureless sintering process after a conventional uniaxial powder molding. Due to its excellent formability and sinterability, we achieved a Mo sintered body with a grain size of approximately 3 μm while maintaining a relatively high sintering density of 98.3% at a comparatively low sintering temperature of 1400 °C. The resulting microstructure contributed to a relatively high hardness of around 234 Hv. These results indicate the successful synthesis of pure Mo powder with desirable properties and highlight its potential in various applications, particularly those requiring high-quality sintered bodies with enhanced hardness.

Fabrication and characterization of green ZnS:Tb AC- electroluminescent devices by ultrasonic spray pyrolysis

MISIM (metal-insulator-semiconductor-insulator-metal) structures of alternating current thin film electroluminescent (ACTFEL) devices were deposited on ATO/glass substrates by the ultrasonic spray pyrolysis technique. Zirconium oxide and terbium doped zinc sulfide were used as dielectric and semiconductor phosphor layers, respectively. A focused ion beam equipment was used to prepare a lamella of the MISIM structure, for cross-sectional scanning electron microscopy analysis in the STEM mode. Chemical analysis by energy-dispersive X-ray spectroscopy (EDS) elemental maps was also made for the identification of the distribution of the elements through the layers composing the MISIM structure. Characteristic Tb3+ emission bands due the 5D4 ->7FJ transitions were obtained by AC voltage application at 10 kHz with the main peak centered at 542 nm. An increase in the electroluminescent intensity and a shift of the CIE coordinates toward a purer green color with increasing the applied voltage was observed. The threshold voltage of these green electroluminescent devices was 46 Vrms, and a luminance up to 41 cd/m2 was obtained for the maximum applied voltage of 76.9 Vrms.

Insight into the photoluminescence and morphological characteristics of transition metals (TM = Mn, Ni, Co, Cu)-doped ZnO semiconductor: a comparative study

In this work, undoped and transition metal (TM = Mn, Ni, Co, Cu)-doped ZnO thin films were grown on Si substrate using the ultrasonic spray pyrolysis technique, adhering to the same deposition conditions to compare their morphological and photoluminescent characteristics. X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), and Photoluminescence (PL) spectroscopy were used to investigate the chemical composition, morphology, and luminescence properties, respectively. XPS results indicate that Mn and Ni ions have bivalent and trivalent electronic states coexisting in the ZnO lattice, Cu ions have both monovalent and bivalent states, and Co ions have only bivalent states. Besides, there is a considerable increase in the level of oxygen vacancies observed upon TM doping. The topographic and phase-contrast AFM images, supported by their associated statistical parameters and mean height distribution histograms, reveal that TM doping increases the tendency for crystalline grains to coalesce in 3D, resulting in a more roughened surface, larger grains with prominent boundaries, increased porosity, and an inhomogeneous height distribution. PL spectra of TM-ZnO show a broadening of the ZnO band gap accompanied by different luminescence behavior compared to pure ZnO regarding both UV and visible emissions. CuZnO is characterized by a green luminescence, CoZnO and MnZnO by a red luminescence, and ZnO and NiZnO by a broad visible luminescence. The possible mechanism for defect luminescence in each TM-ZnO sample was systematically investigated. The chromaticity color coordinates of the PL emissions show that the films provide different color regions well distributed on the CIE chromaticity diagram. The findings regarding the coexistence of two valence states of TM doping, the level of oxygen vacancies, the grain coalescence process, and the luminescence characteristics are carefully correlated and discussed herein.

Morphological Evolution of TiO2 Nanoparticle Deposited on QCM Sensor at Various Calcination Temperature

The morphology of TiO2 nanoparticles deposited on a QCM sensor is crucial in its mechanical loading. Different heating treatments transform the morphology of TiO2 nanoparticles, affecting the loading and hence shifting the resonant frequency and changing the impedance QCM value. In this research, the deposition of TiO2 nanoparticles was carried out above QCM using the ultrasonic spray pyrolysis (USP) technique with variations in calcination temperature of 200, 230, and 250 °C. The analysis results show that the increase in the agglomeration and particle size causes an increase in the inertial mass of TiO2 nanoparticles. HIGHLIGHTS The size of TiO2 agglomerates and their particles increases as the calcination temperature is raised Higher calcination temperature resulted in a larger frequency shift of the QCM oscillation due to the layer inertial mass increase Larger TiO2 nanoparticle size significantly increases the layer’s resistance, contributing to higher impedance GRAPHICAL ABSTRACT

Improving optical and morphological properties of Mn-doped ZnO via Ar ion sputtering followed by high-temperature UHV annealing

Abstract Using the ultrasonic spray pyrolysis technique, pure (ZnO) and manganese (4at%)-doped zinc oxide (ZnMnO) thin films were synthesized and treated with Ar+ sputtering in the UHV (ultra-high vacuum) system. In this regard, XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy), PL (photoluminescence), and AFM (atomic force microscopy) techniques were applied to investigate the electronic and photonic properties of ZnO. XRD and XPS allowed us to identify the successful incorporation of Mn as a substitute for Zn, while PL and AFM images reveal a high tendency for crystalline grains on theZnMnO surface to aggregate to form small grains. However, bandgap narrowing, a redshift with considerable fluctuations in excitonic emission, and a perfect quenching of visible emission (400–640 nm) were observed. Investigations into defect-related emission in ZnMnO and ZnO compounds were conducted. The PL spectra of the prepared samples were measured and analyzed using Gaussian fitting. The PL of undoped ZnOexhibited an intense broad band with a peak at 550 nm. Two effects were shown to occur as a result of Mn doping: (i) a sharp quenching of self-activated PL with a progressive red-shift of the quenching’s spectral boundary; (ii) the appearance of a new emission band with a peak at 1.64 eV (756 nm), which dominates the PL spectrum and is noted in a band diagram; as well as a slight shift in the main line of ZnO, which is located at energy 3.275 eV (378.57nm).

Zinc doping effects on the microstructural, electrical and optical properties of nanostructured ZnxBi2-xS3 ([formula omitted]) thin films grown by ultrasonic spray pyrolysis

Zinc-doped bismuth sulfide (Bi2-xZnxS3) nanocrystalline thin films were deposited on glass substrates by using an ultrasonic spray pyrolysis (USP) technique and their structural, morphological, electrical and optical properties experimentally addressed. X-ray diffraction (XRD) and micro-Raman spectroscopy have confirmed the generation of a single-phase polycrystalline orthorhombic material. The crystallite size and micro-deformation of the films was found to depend on the dopant concentration. The surface appears condensed and dense with a uniform spatial grain distribution, as revealed by scanning electron microscopy (SEM) images. Energy dispersive X-ray spectroscopy (EDS) studies revealed a certain Bi deficiency in both undoped and Zn-doped films. When the nominal Zn doping concentration increases from x = 0 to x = 0.09, the crystallite size decreases from 30 to 21 nm. The optical band gap of the films increased from 1.62 to 1.65 eV with Zn content increasing up to x = 0.06, then reducing to 1.58 eV for the maximum Zn content. Optical measurements showed a high absorption coefficient (α > 104 cm−1) in the visible and near-infrared ranges. The Urbach energy followed a similar behavior as a function of doping concentration. The electrical conductivity as well as the sheet carrier mobility of the Bi2-xZnxS3 films increase sharply by increasing the Zn content up to x = 0.06. For this doping concentration, mobility reaches 1.37 × 105 cm2/Vs while keeping carrier concentration above 1017 cm−3. Our experimental results provide strong evidence that Zn-doping is a suitable method to increase Bi2S3 light-harvesting efficiency in solar cell devices.

Study of Ni/Y2O3/Polylactic Acid Composite.

This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the application of ultrasound-assisted precipitation using the ultrasonic spray pyrolysis technique. They were collected in a water suspension with polyvinylpyrrolidone (PVP) as the stabiliser. The presence of the Y2O3 core and Ni shell was confirmed with transmission electron microscopy (TEM) and with electron diffraction. The TEM observations revealed the formation of round particles with an average diameter of 466 nm, while the lattice parameter on the Ni particle's surface was measured to be 0.343 nm. The Ni/Y2O3 nanocomposite particle suspensions were lyophilized, to obtain a dried material that was suitable for embedding into a polylactic acid (PLA) matrix. The resulting PLA/Ni/Y2O3 composite material was extruded, and the injection was moulded successfully. Flexural testing of PLA/Ni/Y2O3 showed a slight average decrease (8.55%) in flexural strength and a small decrease from 3.7 to 3.3% strain at the break, when compared to the base PLA. These findings demonstrate the potential for utilising Ni/Y2O3 nanocomposite particles in injection moulding applications and warrant further exploration of their properties and new applications in various fields.

Physical properties of ZnO:B:Ce nanofiber like thin films prepared by ultrasonic spray pyrolysis technique

Physical properties of ZnO:B:Ce nanofiber like thin films prepared by ultrasonic spray pyrolysis technique

MnPc Films Deposited by Ultrasonic Spray Pyrolysis at Low Temperatures: Optical, Morphological and Structural Properties.

In this work, we report how manganese phthalocyanine (MnPc) films obtained using the ultrasonic spray-pyrolysis technique at 40 °C deposited on glass substrate subjected to thermal annealing at 100 °C and 120 °C. The MnPc films were characterized using UV/Vis spectroscopy, Raman spectroscopy, X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). The absorption spectra of the MnPc films were studied in a wavelength range from 200 to 850 nm, where the characteristic bands of a metallic phthalocyanine known as B and Q bands were observed in this range of the spectrum. The optical energy band (Eg) was calculated using the Tauc equation. It was found that, for these MnPc films, the Eg has the values of 4.41, 4.46, and 3.58 eV corresponded to when they were deposited, annealing at 100 °C and 120 °C, respectively. The Raman spectra of the films showed the characteristic vibrational modes of the MnPc films. In the X-Ray diffractograms of these films, the characteristic diffraction peaks of a metallic phthalocyanine are observed, presenting a monoclinic phase. The SEM images of these films were studied in a cross-section obtaining thicknesses of 2 μm for the deposited film and 1.2 μm and 0.3 μm for the annealed films at 100 °C and 120 °C. Additionally, in the SEM images of these films, average particle sizes ranging from 4 to 0.041 µm were obtained. The results agree with those reported in the literature for MnPc films deposited by performing other techniques.

White luminescent emissions from HfO2 and HfO2:Al3+ layers deposited by ultrasonic spray pyrolysis technique

Polycrystalline HfO2 and HfO2:Al3+ coatings were synthesized by the spray pyrolysis technique. The photoluminescence and cathodoluminescence characteristics of the coatings were studied as a function of the synthesis parameters; the temperature of deposition and the dopant content (Al3+ions). A blue, bluish-white and warm white emission was found in the coatings, depending on the substrate temperature, doping concentration and excitation wavelength. The photoluminescence emission was enhanced with the increment of the deposition temperature and a quenching effect was also observed with the dopant concentration. The CIE chromatic coordinates: (0.3067, 0.3462), (0.3091, 0.3502) and (0.3073, 0.3498), were close to the ideal white emission. CCT values for some of the coatings make them potentially useful in white lighting systems. The structural characterization was also carried out by X-ray diffraction, SEM, HRTEM and EDS elemental composition.