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Spectral characteristics of Pr3+-doped lead phosphate glasses for optical display device and gain media applications
(2020-10-26)
Basavapoornima, Ch
;
Maheswari, T.
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Kesavulu, C. R.
;
Pecharapa, W.
;
Kaewkhao, J.
The present work is concentrated on spectral analysis of Pr3+-doped lead phosphate (PPbKANPr) glasses for visible lasers and optical amplifier applications where the PPbKANPr glasses were prepared by a melt quenching technique. Based on the absorption spectrum and the well-known Judd-Ofelt (JO) theory, the JO intensity parameters were determined and then used to calculate the various radiative parameters for higher excited luminescent states of Pr3+ ion. The derived JO parameters (× 10-20 cm2) were found to be ω2 = 1.51, ω4 = 18.03 and ω6 = 19.81. The luminescence spectra exhibit emission bands in the visible region of 480-780nm and with the increasing of Pr3+ ion concentration, the emission intensities were decreased due to concentration quenching. The analysis of the results confirms that the PPbKANPr glasses are useful for visible lasers as well as optical amplifiers.
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TiO2 Hybridized with Natural Ilmenite Nanocomposites for Enhanced Visible Light Photocatalytic Activity
(2019-09-16)
Chongsri, K.
;
Phoohinkong, W.
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Pavasupree, S.
;
Mekprasart, W.
;
Boonyarattanakalin, K.
The activated ilmenite nanocomposite of TiO<inf>2</inf> hybridized were prepared by natural ilmenite and commercial TiO<inf>2</inf> anatase assembled using sugar as cross-link agents and carbon source. The heterostructure interface of anatase-ilmenite junction, crystallinity and chemical state were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy (XPS). Composite morphologies and structures were investigated by scanning electron microscope (SEM). Synergistic of low energy gap in range of visible light and interfacial charge separate from TiO2 to ilmenite junction was evaluated in photocatalytic degradation of organic dye. The result from visible light catalytic dye degradation suggests that narrow bandgap energy is associated to ilmenite phase and sensitization by carbon with low recombination rate of generated electron-hole pair transfer. This mechanism occurred by multiphase junction could enhance visible light photocatalytic activity.
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Effect of Milling Speed and Time on Ultrafine ZnO Powder by High Energy Ball Milling Technique
(2019-09-16)
Prommalikit, C.
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Mekprasart, W.
;
Pecharapa, W.
The particle size of commercial zinc oxide (ZnO) powder has been found in micron scale. For the improvement of ZnO properties, size reduction in nanoscale is required. In this work, the particle size of ultrafine ZnO powder was reduced by high energy ball milling technique. commercial grade ZnO powder with average size 0.8 μm was used as starting material. Milling speed and time of high energy milling process are considered as crucial parameters affecting size reduction of ZnO particles. Crystalline structure, surface morphological and particle size of the milled samples were investigated by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and particle analyzer, respectively. The results suggested that ZnO patterns after milling process with various milling speed and time were identically in hexagonal crystalline phase affirmed by XRD result. SEM images indicate that size of ZnO products distinctly decrease according to the increase of milling time and speed. ZnO particle size after milling process was found in ultrafine power in range of 200-400 nm. These results suggest that particle size of the commercial ZnO powders can be effectively minimized to few hundred nanometer range depending on force attraction and suitable rotation during milling process with specific speed and time. Moreover, the significant milling parameters will be studied to find the optimum condition for the production of ZnO particles in nanoscale.
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Low leakage current Ni/CdZnTe/In diodes for X/γ-ray detectors
(2018-01-21)
Sklyarchuk, V. M.
;
Gnatyuk, V. A.
;
Pecharapa, W.
The electrical characteristics of the Ni/Cd<inf>1−</inf><inf>x</inf>Zn<inf>x</inf>Te/In structures with a metal–semiconductor rectifying contact are investigated. The diodes, fabricated on the base of In-doped n-type Cd<inf>1−</inf><inf>x</inf>Zn<inf>x</inf>Te (CZT) crystals with resistivity of ∼10<sup>10</sup> Ω⋅ cm, have low leakage current and can be used as X/γ-ray detectors. The rectifying contact was obtained by vacuum deposition of Ni on the semiconductor surface pretreated with argon plasma. The high barrier rectifying contact allowed us to increase applied reverse bias voltage up to 2500 V at the CZT crystal thickness of 1 mm. Dark (leakage) currents of the diodes with the rectifying contact area of 4 mm<sup>2</sup> did not exceed 3–5 nA at bias voltage of 2000 V and room temperature. The charge transport mechanisms in the Ni/CZT/In structures have been interpreted as generation–recombination in the space charge region within the range of reverse bias of 5–100 V and as currents limited by space charge at both forward and reverse bias at V >100 V.
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Influence of baking temperature on relevant properties of sol-gel Ga-doped ZnO thin films annealed at low temperature
(2018-01-01)
Ruangon, K.
;
Khamon, W.
;
Pecharapa, W.
Ga-doped ZnO(GZO) transparent thin films were grown onto glass substrates by sol-gel based spin coating process. After each coating, the as-deposited film was thermally baked at different moderate temperatures ranging from 100°C to 250°C followed by calcinations at certain temperature lower than 400°C. Characterization were conducted on calcined samples using scanning electron microscope (SEM), X-ray diffraction (XRD), optical spectroscopy and Fourier transform infrared spectroscopy (FTIR). The influence of baking temperature on crucial properties including structural, morphological and optical properties of Ga-doped ZnO transparent thin films were extensively investigated. XRD patterns exhibited typical polycrystalline of hexagonal wurtzite structure of as-deposited thin films and baking temperature is considered as one of essential key parameters affecting the crucial properties of the prepared films.
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Ag nanoparticle-doped SiO2/TiO2 hybrid optical sensitive thin film for optical element applications
(2016-11-25)
Junlabhut, P.
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Boonruang, S.
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Mekprasart, W.
;
Pecharapa, W.
The optical sensitive thin film by Ag nanoparticles doped SiO<inf>2</inf>/TiO<inf>2</inf> hybrid was successfully deposited via sol-gel spin coating technique. Photo-induced polymerization of photosensitive Ag-doped SiO<inf>2</inf>/TiO<inf>2</inf> hybrid initiated by irgacure 784 photoinitiator was illustrated under visible region by He[sbnd]Cd laser 442 nm. Silane coupling was used as a starting precursor to providing cross-linking in the photochemical reaction process. The structural properties and existing elements of photosensitive films were characterized by XRD, TEM and EDX. Meanwhile, surface morphology of the photosensitive hybrid films was monitored by FE-SEM. Moreover, the optical absorption of the photosensitive hybrid films was analyzed by UV–Vis spectroscopy. These results indicated that the compatibility of photosensitive hybrid material was formed. The SiO<inf>2</inf>/TiO<inf>2</inf> photosensitive hybrid films with uniformly distributed Ag ions and intensive coloration characteristic for surface plasmon resonance phenomena relating to the enhancement of optical absorption in visible region. As-prepared photosensitive hybrid films with enhanced optical properties can be proposed for optical elements.
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Effect of PVP concentration on microstructure and physical properties of electrospun SnO2 nanofibers
(2016-10-12)
Santibenchakul, S.
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Chaiyasith, S.
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Pecharapa, W.
The various exceptional crystalline morphologies of tin oxide (SnO<inf>2</inf>) nanofibers were fabricated using conventional electrospinning and calcination process. Polyvinylpyrrolidone (PVP) was used as polymer template and tin (IV) chloride (SnCl<inf>4</inf>·5H<inf>2</inf>O) was chosen as starting material for electrospun SnO<inf>2</inf> nanofibers. The concentration of PVP was varied from 6%w/w to 12%w/w while the concentration of SnCl<inf>4</inf>·5H<inf>2</inf>O was kept constantly. The diameter of the as-spun SnO<inf>2</inf> nanofiber was ranging from 154 to 464 nm. After calcination at 600°C for 3 h, the crystal structure can be identified to the tetragonal structure of SnO<inf>2</inf> with various morphologies. The EDX analysis confirmed the existence of major elements and formation of SnO<inf>2</inf> from starting precursor. SEM results revealed that low PVP concentration led to the formation of porous SnO<inf>2</inf> nanofibers comprising long chain of SnO<inf>2</inf> nanobeads. When the PVP concentration was reached to 12%w/w, the arrangement of crystalline of SnO<inf>2</inf> became the cluster of SnO<inf>2</inf> plates.
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Influence of annealing temperature on optical properties of fluoride doped tin oxide films grown by the sol-gel spin-coating method
(2016-10-12)
Kahattha, C.
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Noonuruk, R.
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Pecharapa, W.
Fluoride-doped Tin Oxide (FTO) thin films were deposited on glass and silicon substrates by the sol-gel spin-coating method using stannic chloride pentahydrate (SnCl<inf>4</inf>·5H<inf>2</inf>O) and ammonium fluoride (NH<inf>4</inf>F) as starting precursors for Sn and F sources. As-deposited films were annealed at different temperatures ranging from 300–600°C. The effect of annealing temperature on structural and optical properties of FTO thin films including crystallinity, surface morphology, optical transparency, optical reflectivity and optical band gap are investigated by X-ray diffraction, scanning electron microscopy and UV-VIS spectrophotometry. The XRD results suggest that the prominent peak in the (110) orientation can be indexed to the polycrystalline SnO<inf>2</inf> structure without any impurity phase caused by fluoride doping. The transmittance spectra of fluoride-doped tin oxide thin films show good transparency in the visible region with noticeable variation in its structural and optical reflectance properties depending on annealing temperature.
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Physical properties of Ti-doped ITO nanoparticles synthesized by co-precipitation method
(2016-04-26)
Chongsri, K.
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Kanoksinwuttipong, J.
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Techitdheera, W.
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Pecharapa, W.
Ti-doped indium tin oxide (ITO) nanoparticles (TITO) with different molar ratios of Ti:ITO were synthesized by co-precipitation method using Ti(OCH2CH2CH2CH3)4, InCl3 and SnCl4·5H2O as starting precursors. Deionized (DI) water was selected as the solvent in this process. The as-precipitated powders were calcined at different temperature in range of 700 °C for 2 h. For all samples, their crystal structures, Optical property and morphologies were investigated by X-ray diffraction (XRD), UV-Vis absorption spectroscopy and Scanning electron microscope (SEM), respectively. XRD results reveal that the purity of as-synthesized sample is increased by the increase of calcination temperatures. Moreover, it is noticed that the incorporation of Ti into ITO matrix significantly affects to their relevant physical properties especially optical properties. In addition, SEM micrographs show that the sample agglomeration is noticeably influenced by Ti doping content.
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Physical, electrical and optical properties of F/Sb Codoped SnO2 synthesized via sonochemical process
(2016-01-02)
Noonuruk, R.
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Mekprasart, W.
;
Vittayakorn, N.
;
Sritharathikhun, J.
;
Pecharapa, W.
F/Sb-codoped SnO<inf>2</inf> nanoparticles were synthesized via sonochemical process using stannic chloride pentahydrate (SnCl<inf>4</inf>·5H<inf>2</inf>O) as host precursor while antimony(III) chloride (SbCl<inf>3</inf>) and ammonium fluoride (NH<inf>4</inf>F) were chosen as Sb and F dopant precursors, respectively. Their physical properties and morphologies were investigated using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscope while their electrical and optical properties were investigated by Hall measurement and diffuse reflectance spectroscopy. As-synthesized powder of polycrystalline phase SnO<inf>2</inf> nanoparticles can be obtained by one-step sonochemical process and its crystallinity can be improved by calcination process. The formation of crystalline phase of SnO<inf>2</inf> is assisted by cavitation effect provided by intense ultrasonic radiation via rapid collision. The characterization results disclose that Sb dopant has strong influence on both physical and electrical properties while F dopant provide considerable effect on electrical property of the samples. It is noticed that the codoping of both elements with certain contents can significantly heighten its electrical conductivity.

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