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Effect of thermal annealing on the structure of LiCoO2 powders prepared by co-precipitation method
(2021-12-01)
Khejonrak, Awadol
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Chanlek, Narong
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Sukkha, Usa
;
Triamnak, Narit
;
Chirawatkul, Prae
Lithium cobalt oxide (LiCoO<inf>2</inf>) powder was prepared by co-precipitation method and annealed at different temperatures of between 300 and 700 °C. The effect of annealing temperature and effect washing process with deionized water on the crystal structures of the prepared LiCoO<inf>2</inf> powders were thoroughly studied by Synchrotron powder X-Ray Diffraction (Syn-XRD), X-ray Absorption Spectroscopy (XAS), Dispersive Raman Microscopy (Raman) techniques. The change in chemical composition as a function of annealing temperature was also investigated by X-ray Photoelectron Spectroscopy (XPS) technique. The crystal structural results identified the phase evolution of the prepared LiCoO<inf>2</inf> powders upon heat treatment. The formation of HT-LiCoO<inf>2</inf> phase was observed at annealing temperature as low as 300 °C.
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Temperature dependent local structure of LiCoO2 determined by in-situ Co K-edge X-ray absorption fine structure (EXAFS)
(2020-10-01)
Ekwongsa, Chinawat
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Rujirawat, Saroj
;
Butnoi, Pichitchai
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Vittayakorn, Naratip
;
Suttapun, Manoon
Recently, lithium cobalt oxide (LiCoO<inf>2</inf>) has a great attention as active cathode material lithium ion batteries. In this work, LiCoO<inf>2</inf> powder was prepared by solid state reaction and co-precipitation method. The synthesis parameters and phase formation behavior were investigated in details via several techniques, including thermal analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM). A change in local structure depending on temperature around Co atoms was investigated using in-situ extended X-ray absorption fine structure (EXAFS). The temperature ranged between 300 °C and 700 °C under air condition was applied for this study.
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Synchrotron-based NEXAFS analysis of thermal-treated diamond-like carbon films
(2020-10-01)
Chunjaemsri, Thanun
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Chanlek, Narong
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Sukkha, Usa
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Nakajima, Hideki
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Rujirawat, Saroj
Diamond-like carbon (DLC) film properties are known to vary with important factors such as the ratio of sp3 to sp2 hybridization, film thickness, and contaminations. In this work, the carbon bonding contents in DLC thin films, thermal-treated with various temperatures between room temperature to 250 °C, were studies by near-edge X-ray absorption fine structure (NEXAFS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. From NEXAFS measurements, the sp3/sp2 ratios of DLC films were found to be unaffected by the thermal treatments. The results indicate that thermal treatment below 250 °C does not affect the carbon bonding contents in DLC thin film.
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Synthesis and characterization of CH3NH3PbI3 and CH3NH3PbI(3-x)Clx perovskite solar cell materials
(2019-11-18)
Kamonpha, Phitsamai
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Padchasri, Jintara
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Rujirawat, Saroj
;
Sukkha, Usa
;
Kidkhunthod, Pinit
The emerging of perovskite solar cell has attracted many interests in the synthesis and characterization of hybrid perovskite materials related to methylammonium iodide (MAI) due to various promising properties. In this work, we found a faster way to synthesize hybrid perovskite CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> and CH<inf>3</inf>NH<inf>3</inf>PbI<inf>(3-x)</inf>Cl<inf>x</inf> (x = 0,1,2) powders from a different solvent in the preparation process of MAI precursor. In addition, it was found that in CH<inf>3</inf>NH<inf>3</inf>PbI<inf>(3-x)</inf>Cl<inf>x</inf> powders, as characterized by XRD and XAS, with a solid-state method employed Cl atoms cannot directly substitute for I in the perovskite (ABX<inf>3</inf>) structure.
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Determination of miscibility in MgO-ZnO nanocrystal alloys by x-ray absorption spectroscopy
(2011-12-26)
Limpijumnong, Sukit
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Jutimoosik, Jaru
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Palakawong, Nirawith
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Klysubun, Wantana
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Nukeaw, Jiti
The local structure of Mg <inf>x</inf>Zn <inf>1-x</inf>O nanocrystals is studied using synchrotron x-ray absorption near edge structures (XANES) over the full range of composition, from x = 0 to 1. Mg and Zn K-edges XANES measurements allow us to selectively study the local environments around Mg and Zn atoms in these nanocrystalline samples. Our results indicate that, for MgO-ZnO alloys, Zn is highly miscible in the rocksalt domain (i.e., up to ∼50 at.%) while the miscibility of Mg in the wurtzite domain is much less but is still substantial (i.e., up to ∼20 at.%). The simulated XANES spectra, based on first principles methods, are consistent with the observed spectra, confirming our finding. Because it is short-ranged and element-specific, the technique is useful for local structure and crystal phase determination of nanostructures, quantum dots, and mixed-phase alloys in general. © 2011 American Institute of Physics.
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X-ray absorption spectroscopy of indium nitride, indium oxide, and their alloys
(2010-04-16)
T-Thienprasert, Jiraroj
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Rujirawat, Saroj
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Nukeaw, Jiti
;
Limpijumnong, Sukit
To investigate the local structure of InN, In<inf>2</inf>O<inf>3</inf> and their alloys, synchrotron (In L<inf>3</inf>-edge) X-ray absorption near edge structures (XANES) of indium oxynitride samples with varied O contents are used in conjunction with first-principles calculations. A good agreement between the measured and simulated spectra is obtained. It is found that the spectra are sensitive to the coordination number of the In atoms, i.e., fourfold for InN-like structures and sixfold for In<inf>2</inf>O<inf>3</inf>-like structures. Moreover, the spectra are quite insensitive to the species (N or O) around In. The calculated band structures and density of states are also presented and discussed. © 2010 Elsevier B.V. All rights reserved.
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