Impact of Annealing Time on Structural Evolution of Pure and Dy3+-Doped CeO2 Nanopowder, Rietveld Refinement and Optical Behavior

2021 ◽  
pp. 2150033
Author(s):  
Rajni Vats ◽  
Rachna Ahlawat
Keyword(s):  
Band Gap ◽  
Rietveld Refinement ◽  
Annealing Time ◽  
Structural Parameters ◽  
Texture Coefficient ◽  
Sol Gel ◽  
Bond Distance ◽  
Oxygen Storage ◽  
Average Grain Size ◽  
Vis Spectroscopy

This work reports about annealing time effect on structural and optical properties of pure and Dy[Formula: see text]-doped CeO2 nanocrystallites. The nanopowders with an average grain size 13–15[Formula: see text]nm are successfully synthesized via a conducive and neoteric Pechini-type sol–gel technique. Surface morphology, composition, band gap and photoluminescence properties of the prepared samples are examined by multifarious characterization techniques like Rietveld refinement, FESEM, HRTEM, FTIR, UV–Vis spectroscopy and PL. The effects of annealing time on structural parameters including lattice parameter, bond distance, bond angle, strain, crystallite size and texture coefficient are computed for all prepared samples which are further ensured by Rietveld refinement. In absorption spectra, blue shift in the band gap of as-prepared samples has been observed due to well-known quantum size effect, however, red shift is noticed in further annealed samples. PL emission peaks are observed in violet, blue and green regions that are devoted to various defect levels and color centers such as F, F[Formula: see text], F[Formula: see text], etc. It is suggested that defects like oxygen vacancies play vital role in tailoring the band gap of prepared samples and therefore enhance its utility in photonics and oxygen storage appliances.

scholarly journals Effect of Re and Tm-site on morphology structure and optical band gap of ReTmO3 (Re: La, Ce, Nd, Gd, Dy, Y and Tm: Fe, Cr) prepared by sol-gel method

2018 ◽  
Vol 64 (4) ◽  
pp. 381
Author(s):  
Muhammad Tufiq Jamil ◽  
Javed Ahmad ◽  
Syed Hamad Bukhari ◽  
Murtaza Saleem
Keyword(s):  
Band Gap ◽  
Sol Gel ◽  
Xrd Analysis ◽  
Sem Analysis ◽  
X Ray Diffraction ◽  
Orthorhombic Crystal ◽  
X Ray ◽  
Average Grain Size ◽  
Auto Combustion ◽  
Uv Visible

Rare earth nano sized pollycrystalline orthoferrites and orthocromites ReT mO3 (Re = La, Nd, Gd, Dy, Y and T m = Fe, Cr) have been synthesized by sol-gel auto combustion citrate method. The samples have been characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and UV-visible spectroscopy. The samples are single phase as confirmed by XRD analysis and correspond to the orthorhombic crystal symmetry with space group pbnm. Debye Scherer formula and Williamson Hall analysis have been used to calculate the average grain size which is consistent with that of determined from SEM analysis and varied between 25-75 nm. The elemental compositions of all samples have been checked by EDX analysis. Different crystallographic parameters are calculated with strong structural correlation among Re and Tm sites. The optical energy band gap has been calculated by using Tauc relation estimated to be in the range of 1.77 - 1.87 eV and 2.77 - 3.14 eV, for ReFeO3 and ReCrO3, respectively.

scholarly journals Zn Doped α-Fe2O3: An Efficient Material for UV Driven Photocatalysis and Electrical Conductivity

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 273 ◽  
Author(s):  
Suman ◽  
Surjeet Chahal ◽  
Ashok Kumar ◽  
Parmod Kumar
Keyword(s):  
Band Gap ◽  
Room Temperature ◽  
Uv Light ◽  
Sol Gel ◽  
High Energy ◽  
Lattice Parameter ◽  
Dielectric Behavior ◽  
Energy Storage Devices ◽  
Vis Spectroscopy ◽  
Potential Applications

Zinc (Zn) doped hematite (α-Fe2O3) nanoparticles with varying concentrations (pure, 2%, 4% and 6%) were synthesized via sol-gel method. The influence of divalent Zn ions on structural, optical and dielectric behavior of hematite were studied. X-ray diffraction (XRD) pattern of synthesized samples were indexed to rhombohedral R3c space group of hematite with 14–21 nm crystallite size. The lattice parameter (a and c) values increase upto Zn 4% and decrease afterwards. The surface morphology of prepared nanoparticles were explored using transmission electron microscopy (TEM). The band gap measured from Tauc’s plot, using UV-Vis spectroscopy, showed reduction in its values upto Zn 4% and the reverse trend was obtained in higher concentrations. The dielectric properties of pure and Zn doped hematite were investigated at room temperature and followed the same trends as that of XRD parameters and band gap. Photocatalytic properties of nanoparticles were performed for hazardous Rose bengal dye and showed effective degradation in the presence of UV light. Hence, Zn2+ doped hematite can be considered as an efficient material for the potential applications in the domain of photocatalysis and also higher value of dielectric constant at room temperature makes them applicable in high energy storage devices.

INFLUENCE OF ANNEALING TEMPERATURE ON THE CHARACTERISTICS OF NANOCRYSTALLINE SnO2 THIN FILMS PRODUCED BY Sol–Gel AND CHEMICAL BATH DEPOSITION FOR GAS SENSOR APPLICATIONS

2017 ◽  
Vol 24 (07) ◽  
pp. 1750104 ◽  
Author(s):  
SELMA M. H. AL-JAWAD ◽  
ABDULHUSSAIN K. ELTTAYF ◽  
AMEL S. SABER
Keyword(s):  
Band Gap ◽  
Gas Sensor ◽  
Chemical Bath Deposition ◽  
Annealing Temperature ◽  
Optical Band Gap ◽  
Sol Gel ◽  
Dip Coating ◽  
Rutile Structure ◽  
Sensor Applications ◽  
Average Grain Size

Pure nanocrystalline SnO2 films were grown on a clean glass substrate by using sol–gel dip coating and chemical bath deposition (CBD) techniques for gas sensor applications. The films were annealed in air at 300[Formula: see text]C, 400[Formula: see text]C, and 500[Formula: see text]C for 60[Formula: see text]min. The deposited films with a thickness of approximately 300 [Formula: see text] 20 nm were analyzed through X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical absorption spectroscopy. Results revealed that the films produced by dip coating exhibited a tetragonal rutile structure and those produced by CBD showed a tetragonal rutile and orthorhombic structure. The crystalline sizes of the films produced by dip coating annealed at 300[Formula: see text]C, 400[Formula: see text]C, and 500[Formula: see text]C were 8, 14, and 22.34 nm and those for CBD films at these temperatures were 10, 15, and 22 nm, respectively. AFM and SEM results indicated that the average grain size increased as annealing temperature increased. The transmittance and absorbance spectra were then recorded at wavelengths ranging from 300[Formula: see text]nm to 1000[Formula: see text]nm. The films produced by both the methods yielded high transmission at visible regions. The optical band gap energy of dip-coated films also increased as annealing temperature increased. In particular, their optical band gap energies were 3.5, 3.75, and 3.87[Formula: see text]eV at 300[Formula: see text]C, 400[Formula: see text]C, and 500[Formula: see text]C, respectively. By comparison, the energy band gap of CBD-prepared films decreased as annealing temperature increased, and their corresponding band gaps were 3.95, 3.85, and 3.8[Formula: see text]eV at the specified annealing temperatures. The films were further investigated in terms of their sensing abilities for carbon monoxide (CO) gas at 50 ppm by measuring their sensitivity to this gas at different times and temperatures. Our results demonstrated that dip-coated and CBD-prepared films were highly sensitive to CO at 200[Formula: see text]C and 250[Formula: see text]C, respectively.

scholarly journals Annealing Control on the Anatase/Rutile Ratio of Nanostructured Titanium Dioxide Obtained by Sol-Gel

Crystals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 22 ◽  
Author(s):  
V. Castrejón-Sánchez ◽  
Roberto López ◽  
M. Ramón-González ◽  
Ángeles Enríquez-Pérez ◽  
M. Camacho-López ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Titanium Dioxide ◽  
Band Gap ◽  
Annealing Time ◽  
Direct Relationship ◽  
Sol Gel ◽  
Synergetic Effect ◽  
Anatase Tio2 ◽  
Ambient Atmosphere ◽  
Complete Transformation

According to the different phases at which titanium dioxide (TiO2) crystallizes, previous studies have shown that anatase is more efficient for photocatalysis than rutile. Nowadays, the synergetic effect is well-accepted between anatase and rutile as having an effect in increasing performance in photocatalysis. In the present work, control over the anatase/rutile ratio was performed in three experimental steps. Initially, amorphous-anatase TiO2 powders were synthesized by the sol-gel method. For the crystallization of anatase, the powders were annealed at 250 °C for 2 h in ambient atmosphere. The final step was performed by using different annealing times, ranging from 35 up to 200 min at a temperature of 475 °C. The powders were characterized by Raman spectroscopy, UV–VIS, SEM and TEM techniques to determine the crystalline phase, band gap, morphology, and elemental composition, respectively. It was possible to control the anatase/rutile ratio on the nanostructured TiO2 powders from 100% of anatase until a complete transformation to rutile through the variation of the annealing time. The band gap calculated using the Tauc’s model was found in the range of 2.56 to 2.93 eV. However, no direct relationship between the anatase/rutile ratio, and the band gap was found.

Synthesis of Three-Dimensionally Ordered Macroporous (3DOM) TiO2: Photodegradation Catalyst

2017 ◽  
Vol 735 ◽  
pp. 132-135 ◽  
Author(s):  
Thipchanok Bowornhathai ◽  
Potjanart Suwanruji ◽  
Jantip Setthayanond ◽  
Sutasinee Kityakarn ◽  
Supakit Achiwawanich
Keyword(s):  
Band Gap ◽  
Colloidal Crystal ◽  
Sol Gel ◽  
Titanium Isopropoxide ◽  
Band Gap Energy ◽  
X Ray Diffraction ◽  
Sem Images ◽  
Vis Spectroscopy ◽  
Ordered Macroporous ◽  
Ordered Porous

Three-dimensionally ordered macroporous (3DOM) TiO2 were successfully synthesized by incorporating colloidal crystal template and sol-gel method using titanium isopropoxide and ethanol as precursors. After calcination at 450°C, the synthesized photocatalyst was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and diffuse reflectance UV-VIS spectroscopy (DR/UV-VIS). XRD results indicated that only anatase was presented. SEM images illustrated highly ordered macroporous structure which was a characteristic for 3DOM materials. The band gap energy of 3DOM TiO2 and nanoparticles TiO2 (NP TiO2) were 3.26 eV and 3.23 eV, respectively. Although the band gap value of 3DOM TiO2 similar to NP TiO2 but the photocatalytic performance of the 3DOM TiO2 were higher than that of commercial nanoparticle TiO2. The result suggested that its ordered porous structure is great advantage for photocatalysis.

scholarly journals Influence of zinc concentration on band gap and sub-band gap absorption on ZnO nanocrystalline thin films sol-gel grown

2017 ◽  
Vol 35 (1) ◽  
pp. 246-253 ◽  
Author(s):  
◽  
Ziaul Raza Khan ◽  
Anver Aziz ◽  
Mohd. Shahid Khan ◽  
M.U. Khandaker
Keyword(s):  
Thin Films ◽  
Band Gap ◽  
Zinc Concentration ◽  
Sol Gel ◽  
Green Emission ◽  
Band Edge ◽  
Zno Thin Films ◽  
Diffraction Field ◽  
Band Edge Emission ◽  
Vis Spectroscopy

AbstractZnO thin films were fabricated on quartz substrates at different zinc acetate molar concentrations using sol-gel spin coating method. The samples were characterized using X-ray diffraction, field emission scanning electron microscope, UV-Vis spectroscopy, FT-IR spectroscopy and photoluminescence spectroscopy. Sub-band gap absorption of ZnO thin films in the forbidden energy region was carried out using highly sensitive photothermal deflection spectroscopy (PDS). The absorption coefficients of ZnO thin films increased in the range of 1.5 eV to 3.0 eV, upon increasing zinc concentration. The optical band gaps were evaluated using Tauc’s plots and found to be in the range of 3.31 eV to 3.18 eV. They showed the red shift in the band edge on increase in zinc concentration. The PL spectra of ZnO thin films revealed the characteristic band edge emission centered at the 396 nm along with green emission centered at the 521 nm.

Morphological and Optical Properties of Different Mg Percentage of ZnO/Mg Thin Films Prepared by Sol-Gel Spin-Coating and Immersion Method

2015 ◽  
Vol 1107 ◽  
pp. 637-642 ◽  
Author(s):  
Aadila Aziz ◽  
R. Mohamed ◽  
A.N. Afaah ◽  
N.A.M. Asib ◽  
M. Rusop ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Band Gap ◽  
Spin Coating ◽  
Optical Band Gap ◽  
Sol Gel ◽  
Immersion Method ◽  
Weight Percentage ◽  
Tauc Plot ◽  
Vis Spectroscopy

We have successfully demonstrated ZnO/Mg thin films on Mg seeded-template by using sol-gel spin-coating and immersion technique. By increasing weight percentage of Mg, zinc particles become agglomerate and displayed flower formed as displayed in FESEM characterization. It was observed that the morphology of the zinc particles on Mg seeded-template change from inconsistently distribution for 1 and 3 % into cluster flower-like of zinc particles for 5 and 7 % weight percentage of Mg. The optical properties of the ZnO/Mg thin films were examined by UV-Vis spectroscopy and the Tauc plot methods was used to estimate the optical band gap. The study reveals that, 7 % weight percentage of Mg was recorded as the highest transmittance which is more than 60 % in visible wavelength compared to others. With the rise weight percentage of Mg, the transmittance of the thin films was increased except for 5 %. This gradually downgraded to below 60 % of transmission most probably due to the grain size that becomes bigger. The optical band gap can be tuned by using different Mg percentage to the ZnO/Mg thin films.

Effect of Pd Addition on the Nanostructure and Properties of Pd/TiO2 Catalysts for the Photocatalytic Degradation of 4-Chlorophenol

2014 ◽  
Vol 28 ◽  
pp. 9-20 ◽  
Author(s):  
D.S. García-Zaleta ◽  
J.A. Montes De Oca-Valero ◽  
A.M. Torres-Huerta ◽  
M.A. Domínguez-Crespo ◽  
H.J. Dorantes-Rosales ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Raman Spectroscopy ◽  
Water Treatment ◽  
Photocatalytic Degradation ◽  
Band Gap ◽  
Rietveld Refinement ◽  
Sol Gel ◽  
Rietveld Analysis ◽  
Treatment Technology ◽  
Effect Of Pd

In this work, the effect of Pd addition on nanostructured TiO2 powders is studied. The materials were obtained by the sol-gel method and characterized by XRD, Rietveld refinement, TEM, Raman and UV-vis spectroscopies. The crystal structure and the nature of the different TiO2 phases were modified by varying the palladium/TiO2 ratio: 0.01, 0.03, and 0.05. The XRD results revealed the presence of different combinations of TiO2 (B), anatase, rutile and PdO phases as well as their coexistence in the different samples. The Rietveld analysis showed that the composition of the phases is rather affected by the amount of Pd added to the TiO2 structure. The Raman spectroscopy confirmed the characteristic bands of the TiO2 phases in the samples and their variation depending on the Pd/TiO2 ratio. The TEM results indicated that the as-prepared samples displayed crystal sizes of nanometric order (˂ 80nm). The observed reduction of the band gap was also correlated with the combination of phases due to the palladium addition. All the Pd/TiO2 samples showed a significant improvement in the elimination of 4-chlorophenol during the application of water treatment technology.

Influence of Calcination Temperature towards Fe-TiO2 for Visible-Driven Photocatalyst

2017 ◽  
Vol 888 ◽  
pp. 435-440 ◽  
Author(s):  
Siti Aida Ibrahim ◽  
Muhamad Nazim Ahmid
Keyword(s):  
Visible Light ◽  
Calcination Temperature ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Combined Method ◽  
Calcination Process ◽  
Calcination Temperatures ◽  
Light Region ◽  
Average Grain Size ◽  
Vis Spectroscopy

TiO2 is one of the most promising photocatalysts that is widely used for environmental clean-up due to its ability to degrade organic pollutants in air or water. The purpose of this study is to enhance the photocatalytic activity of TiO2 by absorbing energy in visible light region in order to degrade pollutants. In this study, the nanostructured Fe-TiO2 was successfully synthesised via a combined method of sol-gel and calcination process. The calcination temperatures used varied from 400 to 800 °C. The as-prepared samples were characterized by X-ray diffraction (XRD), FESEM and UV-Vis spectroscopy (UV-Vis). XRD results show that the phases of TiO2 are dependent on calcination temperature. It is found that both TiO2 and Fe-TiO2 phases were transformed from anatase to rutile as the temperatures were increased. FESEM images revealed that the particle size was agglomerated and the average grain size was about 54 to 66 nm. UV-Vis analysis indicated that the incorporation of Fe and varied calcination temperature may affect the optical properties as the absorption profile was shifted from 445 nm to 585 nm. Thus, this results show that Fe-TiO2 is a highly potential photocatalyst to degrade pollutants under visible light irradiation.

scholarly journals Synthesis, Characterization, and Electronic Structure Studies of Cubic Bi1.5ZnTa1.5O7for Photocatalytic Applications

2015 ◽  
Vol 2015 ◽  
pp. 1-8
Author(s):  
Ganchimeg Perenlei ◽  
Jose A. Alarco ◽  
Peter C. Talbot ◽  
Wayde N. Martens
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Electronic Band Structure ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Infrared Emission ◽  
Emission Spectrometry ◽  
Electronic Band ◽  
Vis Spectroscopy

Bi1.5ZnTa1.5O7(BZT) has been synthesized using an alkoxide based sol-gel reaction route. The evolution of the phases produced from the alkoxide precursors and their properties have been characterized as function of temperature using a combination of thermogravimetric analysis (TGA) coupled with mass spectrometry (MS), infrared emission spectrometry (IES), X-ray diffraction (XRD), ultraviolet and visible (UV-Vis) spectroscopy, Raman spectroscopy, and N2adsorption/desorption isotherms. The lowest sintering temperature (600°C) to obtain phase pure BZT powders with high surface area (14.5 m2/g) has been determined from the thermal decomposition and phase analyses. The photocatalytic activity of the BZT powders has been tested for the decolorization of organic azo-dye and found to be photoactive under UV irradiation. The electronic band structure of the BZT has been investigated using density functional theory (DFT) calculations to determine the band gap energy (3.12 eV) and to compare it with experimental band gap (3.02 eV at 800°C) from optical absorption measurements. An excellent match is obtained for an assumption of Zn cation substitutions at specifically ordered sites in the BZT structure.

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