Browsing by Author "Sung, N.E."

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Correlation between glaze-colors and structural properties of the HIZEN celadons produced in the Edo period of Japan, by means of X-ray diffraction (?)
(Cer?mica, 2011) Hidaka, M.; Ohashi, K.; Wijesundera, R.P.; Kumara, L.S.R.; Watanabe, M.; Koga, K.; Choi Jae-Young; Sung, N.E.; Park, Y.J.
HIZEN celadons produced at Arita and Imari areas in Japan from 1630's to 1790's (Edo period) have been investigated by means of X-ray fluorescence analysis, and X-ray diffraction and X-ray absorption spectra using synchrotron radiation. It is found that, in the HIZEN celadons, the color brightness of the celadon glazes depends on the structural property of the raw basic ceramics taken at Imaizumi (Arita) and Ohkwachi (Imari), where the former is mainly Quartz-SiO2, and the later is Sanidine ((K,Na)Si3O8). It is confirmed that CaCO3 of natural wood ash added artificially into the raw celadon ceramics makes a glassy glaze on the surface of the basic body of the HIZEN celadons. Transition-metal ions (Cr, Cu, Zn) of very small amount are detected in the celadon glazes, in addition to Fe and Mn of small amount. It is considered that Cu and Cr are related to the color brightness of green-brown and blue-green in the HIZEN celadon glazes, respectively.
Correlation Between Local Structures and Partial Electronic Band States in Ferroelectric Bi4?Xlaxti3o12; 0.0?X?1.46
(Ceramics-Silik�ty, 2009) Hidaka, M.; Wijesundera, R.P.; Kumara, L.S.R.; Noguchi, Y.; Miyayama, M.; Choi Sun-Hee; Sung, N.E.; Kim, M.G.
The local structures and the partial band states near a Fermi level (EF) have been studied at room temperature in the ferroelectric phase of Bi4?XLaXTi3O12 (BLT) with 0.00?x?1.46 by means of X?ray absorption spectra (XAS) including EXAFS and XANES. The EXAFS spectra suggest that, as increasing the substituted La ions, the local structures around Ti and Bi ions in perovskite-blocks of (Bi2?XLaXTi3O10)-2 are gradually deformed till x=0.85, and are largely changed by a structural phase transition occurring between x=0.85 and 1.20. The XANES spectra suggest that there is a strong hybridization between Ti-3d(t2g) and O-2p bands and between Bi-6s and O-2p bands in the valence band states, while between Ti-3d(eg) and O-2p bands and Bi-6p and O-3s bands in the conduction band states. All of the XAS show interesting dependency on the concentration of the substituted La ions in BLT. The results suggest that, in BLT, a reducing spontaneous polarization induced by the La-substitution results from the deformation of the local structures around Ti and Bi ions and from modulation of the hybridized band states near EF.
Correlation between the green-like coloration and the structural and electronic properties of celadon glazes
(Cer�mica, 2012) Hidaka, M.; Takeuchi, K.; Wijesundera, R.P.; Kumara, L.S.R.; Watanabe, M.; Choi Jae-Young; Sung, N.E.
Correlation between the Izumiyama porcelain ceramics and the red-overglaze enamels of the Kakiemon-style porcelains
(Ceramics International, 2008) Kajihara, S.; Hidaka, M.; Wijesundera, R.P.; Kumara, L.S.R.; Kobayashi, H.; Koga, M.; Tsuru, T.; Koga, K.; Shimomura, K.; Choi Jae-Young; Sung, N.E.; Park, Y.J.
The Kakiemon-style porcelains made from 17th century at Arita are famous Japanese porcelains, characterized mainly by their colored underglaze and overglaze and by their original design of coloring spatial patterns in the porcelain surface. Raw materials of the red-overglaze enamels have been investigated by means of X-ray diffraction and X-ray absorption spectra using synchrotron radiations. It is found that Izumiyama porcelain ceramics of yellow color can produce the Kakiemon red-overglaze enamels by thermal treatment and water-washing, where Izumiyama is a collecting place of the raw porcelain ceramic at Arita. The brightness of the red-overglaze enamels is related on the local structure around Fe ions and the electronic band states of Fe ions near a Fermi level in ?-Fe2O3, in addition to the spatial density of the ?-Fe2O3 fine particles. The structural and electronic properties are slightly affected by an electron-hybridization between Fe ions of ?-Fe2O3 and oxygen ions of the (SiO2?Al2O3) complexes in the red overglaze.
Effects of annealing on the properties and structure of electrodeposited semiconducting Cu?O thin films
(Physica Status Solidi (basic solid state physics), 2007) Wijesundera, R.P.; Hidaka, M.; Koga, K.; Sakai, M.; Siripala, W.; Choi Jae-Young; Sung, N.E.
The structures and the electronic states in electrodeposited semiconductor Cu?O thin films have been investigated for each annealing temperature (TA) by X-ray diffraction (XD) and X-ray absorption spectroscopy (XAS) near the Cu K edge using synchrotron radiation. The thin films prepared as grown and annealed at TA ? 175 �C, 200 �C ? TA ? 300 �C, TA = 400 �C are characterized mainly by the pure Cu2O-type structure, the pseudo-Cu2O-type having a superlattice structure, and two phases of Cu2O-type and CuO-type structures, respectively, while the film annealed at TA = 500 �C is single-phase CuO-type. The XAS spectra suggest that there is a structural phase transition occurring at about 400 �C, which induces a modulation of the local structure around Cu ions observed in the extended X-ray absorption fine structure (EXAFS) and the occupational electronic band states of Cu-4p localized just above the Fermi level, taken from X-ray absorption near edge structure (XANES). The open-circuit voltage suggests that the photosensitivity of the Cu?O thin films strongly depends on the annealing treatment and shows a crossover from an n-type to a p-type semiconductor. (? 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic states and local structures of Cu ions in electrodeposited thin films of Cu and Cu2O from X-ray absorption spectra
(Physica Status Solidi b (basic solid sates physics), 2006) Wijesundera, R.P.; Hidaka, M.; Siripala, W.; Choi Sun-Hee; Sung, N.E.; Kim, M.G.; Lee, J.M.
X-ray absorption spectra near Cu K edges have been obtained for Cu and Cu2O thin films potentiostatically electrodeposited in an acetate bath. The electronic states of Cu ions and the local structures around these ions are studied using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy, respectively. The inner strains in micro-size crystals of the electrodeposited Cu thin film are less than those of a commercial Cu foil. The partial electronic states of Cu ions near the Fermi level (EF) and the local structure around these ions show a systematic transformation from a Cu2O single phase (Phase I), to a Cu2O?Cu intermediate phase (Phase II) and a Cu single phase (Phase III) in thin films electrodeposited on titanium substrates for the deposition potential range of ?100 to ?900 mV. Phase II consists of independent Cu2O-like and Cu-like local structures, but not a Cu2O?Cu complex. Phase II is also characterized by a transition region from the semiconductor Cu2O to the metal Cu for the Cu electronic state having a p-like character near the Fermi level in the oxygen O-2p conduction band. (? 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Local structures and electronic band states of ?-Fe2O3 polycrystalline particles included in the red-color overglazes and the transparent glazes of the Kakiemon-style porcelains by means of X-ray absorption spectra (II)
(Cer�mica, 2009) Hidaka, M.; Horiuchi, H.; Ohashi, K.; Wijesundera, R.P.; Kumara, L.S.R.; Sung, N.E.
Kakiemon-style porcelain is mainly characterized by the porcelain body of white color or milky-white color and the elegant and bright patterns of the colored overglazes on its white body. The porcelains were first developed and completed by Kakiemon-kiln family in 1650-80's. The red-color overglazes and the transparent glazes of the present porcelain pieces, which were produced in the early 17th century to the middle 18th century, have been investigated by means of X-ray absorption spectrum using synchrotron radiation. The structure of ?-Fe2O3 as red-color emission element is slightly deformed in the red-color overglazes by the other surrounding oxides (SiO2, Al2O3, K2O, Na2O, MgO, PbO), and/or the new complexes of (SiO2-Al2O3,) systems constructed by the raw materials. The Fe ions in the transparent glazes are in the glass-state with the other oxides. However, the electronic valence, Fe3+, of Fe ions is the same with that of the ?-Fe2O3 in the red-color overglazes. The lead oxides (PbO, Pb3O4) used in the Edo period to increase the brightness in the fritted red-color overglazes were perfectly decomposed, and Pb ions were in the glass-state of the porcelains.
Local structures and electronic band states of ??Fe2O3 polycrystalline particles in the glazes of the HIZEN celadons produced in the Edo period of Japan, by means of X-ray absorption spectra (II)
(Cer�mica, 2011) Hidaka, M.; Ohashi, K.; Wijesundera, R.P.; Kumara, L.S.R.; Sugihara, S.; Momoshima, N.; Kubuki, S.; Sung, N.E.
HIZEN celadon glazes produced in 1630's to 1790's (Edo period, Japan) have been investigated by means of X-ray absorption spectra (XAS) near a Fe-K edge by using synchrotron radiation and a M�ssbauer spectrum. The XAS suggest that the local structure around Fe2O3 fine powders is slightly different between the Izumiyama ceramics of mainly the Quartz-SiO2 and Ohkawachi ceramics of mainly the feldspar of (K,Na)Si3O8 (Sanidine), and that the glazes of the HIZEN celadons include the Fe2O3 fine powders in the glassy state, though the X-ray diffraction patterns of the glassy celadon glazes do not show any peaks of the Fe2O3 structure. The M�ssbauer spectrum suggests that the celadon glaze of Seiji (m) includes only Fe3+ ions, but not Fe2+ ions. This indicates the existence of Fe2O3 in the celadon glaze. It is interpreted that the colored brightness of the HIZEN celadons is induced by the structural properties of the used raw celadon ceramics and the other transition-metal ions of Cr, Cu, Zn in the celadon glazes, but not by the chemical reaction from Fe2O3 to FeO under the deoxidizing thermal treatment at higher temperature in a kiln.
Metal-insulator transition induced by electronic and structural modulations in oxygen-deficient perovskite-type TbBaCo2O5.5
(Physica Status Solidi b (basic solid state physics), 2006) Hidaka, M.; Soejima, M.; Wijesundera, R.P.; Soda, M.; Sato, M.; Choi Sun-Hee; Sung, N.E.; Kim, M.G.; Lee, J.M.
The metal?insulator (M?I) transition at about 340 K (TMI) in TbBaCo2O5.5 has been investigated by X-ray absorption spectra near Tb-LIII, Ba-LII, and Co-K edges. In the metallic and insulating phases, the high-density unoccupied bands of Tb-6d? and Ba-6d? occupy just above a Fermi level (EF), while the positive charge-transfer Tb-5dnLm and Ba-5dnLm bands are just below EF. The narrow positive charge-transfer Co-3d7(eg)L band is just below EF, where L represents a hole induced in the valence band of O-2p. It is considered that the metallic conductivity above TMI results from the (p?d) hybridized holes in the top region of the O-2p valence band and the hopping electrons in the bottom of the O-2p conduction band. The spin-state transition for Co ions in the CoO6 octahedra and the CoO5 pyramids does not occur at TMI. The local structural distortion induced around the Ba ions, but not around the Tb and Co ions, mainly affects the electronic configuration interaction between the Ba-5d and the O-2p orbitals in BaO. (? 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and Electronic Properties of Electrodeposited Heterojunction of CuO/Cu2O
(Ceramics-Silik�ty, 2010) Wijesundera, R.P.; Hidaka, M.; Koga, K.; Choi Jae-Young; Sung, N.E.
The structures and the electronic band states of the electrodeposited thin film CuO/Cu2O heterojunction have been studied by means of the X-ray diffractions (XRD) and the X-ray absorption spectra (XAS) with different grazing angles of the incident X-ray beam using the synchrotron radiation. The heterojunction of about 2 ?m consists of n-type Cu2O (~1 ?m) and p-type CuO (~1 ?m) thin films bi-layer. Scanning electron micrographs (SEMs) show the existence of two different polycrystalline grain layers and the XRD reveals that the different grain layers are high quality CuO-type and Cu2O-type structures respectively. Photoactive performances of the Ti/CuO/Cu2O/Au heterojunction are Voc of ~210 mV and Jsc of ~310 mA/cm2. It reveals that the Cu2O grains are grown from the surfaces of the CuO polycrystalline grains and make very good contact with the CuO grains. It is found that the XAS of CuO/Cu2O heterojunction are convoluted independently by X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structures (XANES) spectra of the Cu2O and CuO grains, depending on the grazing angles. Present study reveals that bottom of the conduction band (Cu-4pp) of the Cu2O in the CuO/Cu2O heterojunction reduces by 0.57 eV relative to the Ti/Cu2O ohmic contact.
Structural properties of the red-color overglaze for the HIZEN porcelains produced in the early Edo period of Japan
(Ceramics International, 2009) Hidaka, M.; Ohashi, K.; Kajihara, S.; Wijesundera, R.P.; Kumara, L.S.R.; Choi Jae-Young; Sung, N.E.
HIZEN porcelains made in 1650s to 1750s (early Edo period) in Arita areas sited in south Japan (SAGA) are famous Japanese porcelains, which are characterized by elegant and bright colors in the overglaze and the underglaze. Red-overglazes and transparent glazes of the HIZEN porcelains have been investigated by means of X-ray diffraction (XRD) and X-ray absorption spectra (XAS) using synchrotron radiation. The results suggest that the red-color brightness of the Hizen porcelains is mainly induced by micro-structural correlation between ?-Fe2O3 fine particles of red-color emission element and the oxide complexes of SiO2?Al2O3?CaO?KNaO or SiO2 in the fritted overglazes. The stability of the red-color overglaze on the porcelain body of white-color results from interfacial fusion between both glass-states in the fritted overglaze and the transparent glaze coating the porcelain body. The refined local structures around Fe ions of the ?-Fe2O3 structure taken EXAFS spectra give the technical and historical relation among four kinds of the HIZEN porcelains for fritted materials of the overglazes and thermal treatment at high-temperature in the porcelain kilns.