• Title/Summary/Keyword: $SrAl_2$$O_4$

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Synthesis and Photoluminescence of the Sr1-xBaxAl2O4:Eu2+, Dy3+ Long Phosphorescence Phosphor (Sr1-xBaxAl2O4:Eu2+, Dy3+계 축광성 형광체의 합성과 그의 발광특성)

  • Park, Jin-Woo;Kim, Jung-Sik
    • Journal of the Korean Ceramic Society
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    • v.43 no.6 s.289
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    • pp.333-337
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    • 2006
  • In this study, the $Sr_{1-x}Ba_{x}Al_{2}O_{4}:Eu^{2+},Dy^{3+}$ phosphor were prepared by the solid-state reaction method and its photoluminescence properties were investigated. Starting powders of $SrCO_3,\;BaCO_3,\;and\;Al_{2}O_3$ were mixed with $Eu_{2}O_3$ as activator, $Dy_{2}O_3$ as co-activator and $B_{2}O_3$ as flux. Then, the mixed powders were heated at the temperature of $1100{\sim}1400^{\circ}C$ for 3 h under the reducing ambient atmosphere of $95%Ar+5%H_2$. The effect of Ba addition from 0.0 to 1.0 mol on photoluminescence was investigated. As the amount of Ba increased, the intensity of emission increased and the optimum long phosphorescence occurred at the amount of 0.1 mol Ba. The optimum sintering condition for long phosphorescent phosphor of $Sr_{1-x}Ba_{x}Al_{2}O_{4}:Eu^{2+},Dy^{3+}$($x=0{\sim}1.0mol$) was found at $1400^{\circ}C$. The excitation spectra showed a broad band of $250{\sim}450nm$ with maximum peak at 360 nm. The maximum peak intensity of emission spectra occurred at the range of $480{\sim}520nm$, depending on Ba content.

Synthesis and After-Glow Characteristics of Eu Activated Sr-Al-O Long Phosphorescent Phosphor (Eu 부활형 Sr-Al-O 계 장잔광 형광체의 합성과 잔광특성)

  • Lee, Young-Ki;Kim, Jung-Yeul;Kim, Byung-Kyu;Yu, Yeon-Tae
    • Korean Journal of Materials Research
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    • v.8 no.8
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    • pp.737-743
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    • 1998
  • The synthesis of $SrAI_2O_4:Eu^{2+}$ phosphor and its properties of both photoluminescence and long-phosphorescent were investigated as a function of sintering condition. Single phase of $SrAl_2O_4$ was obtained by sintering the mixtures of $SrCO_3$, $Eu_2O_3$, $AI_2O_34 and 3wt% $B_2O_3$ powders over 100$0^{\circ}C$ in Ar/H2 atmosphere. The optimum sintering condition for the long-phosphorescent phosphor of $SrAI_2O_4:Eu^{2+}$ was found at 130$0^{\circ}C$ for 3hours. The PL emission spectrum of $SrAI_2O_4:Eu^{2+}$ shows a maximum peak intensity at 520nm(2.384eV) with a broad emission extending from 450 to 650nm which resulted from the $4f^65d^1$$\rightarrow$$4f^7$ transition of $Eu^{+2}$ under 360nm exitation. Monitored at 520nm. the excita¬tion spectrum of $SrAI_2O_4:Eu^{2+}$ exhibits a maximum peak intensity at 360nm (3.44eV) with a broad absorption band extending from 250 to 480nm.

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Direct Observation of Crack Tip Stress Field Using the Mechanoluminescence of SrAl2O4:(Eu,Dy,Nd) (SrAl2O4(Eu,Dy,Nd) 압광체를 이용한 균열첨단에서의 응력장 가시화 연구)

  • 김지식;손기선
    • Transactions of Materials Processing
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    • v.12 no.5
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    • pp.493-497
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    • 2003
  • The present investigation aims at visualizing the crack tip stress field using a mechanoluminescence material. The well known compound $SrAl_2O_4$:$Eu^{2+}$ was adopted as a mechanolurninescence material. Two more trivalent rare-earth elements such as Dy and Nd were taken into consideration as codopants to provide the appropriate trap levels. Samples of a variety of compositions were prepared by varing $Eu^{2+}$, $Dy^{3+}$, and $Nd^{3+}$ doping contents, for which the combinatorial chemistry method was used. In order to search for the optimum composition for the highest mechanoluminescence, the luminescence induced by a compressive device including a CCD camera. In parallel, a compact tension specimen was prepared by mixing the luminescence powders of optimum composition and epoxy resin. Crack initiation from the mechanically machined sharp note tip and its growth during loading were found to be associated with the extent of light emission from $SrAl_2O_4$.

Crystallization of srAl2O4 Synthesized by the Polymerized Complex Method (착체중합법으로 합성한 srAl2O4의 핵생성 관찰)

  • 김형준;박정현
    • Journal of the Korean Ceramic Society
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    • v.41 no.6
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    • pp.439-443
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    • 2004
  • SrAl$_2$O$_4$ powder was prepared by polymerized complex method and its nucleation was observed at different temperatures and times. Problems of inhomogeneity and high synthesis temperature induced by solid state reaction could be solved by using polymeric precursors. The process of decomposition by heat treatment above 40$0^{\circ}C$ was observed by Scanning Electron Microscopy (SEM) and elemental analyzer. Crystallization of SrAl$_2$O$_4$ occured at about 90$0^{\circ}C$ and its crystalline size. which was determined by using Transmission Electron Microscopy (TEM) and X-Ray Diffractometer (XRD). was about 30∼50 nm.

The Luminescent Properties of SrTiO$_3$ :Al, Pr Red Phosphor (Al과 Pr이 첨가된 SrTiO$_3$ 적색 형광체의 발광 특성)

  • 박정규;류호진;박희동;최승철
    • Journal of the Korean Ceramic Society
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    • v.36 no.5
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    • pp.478-482
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    • 1999
  • SrTiO3 :Al, Pr phosphor as an oxide compound phosphor is expect to be applied for a field emission display(FED). In this phosphor the excitation spectrum shows a different tendency according to an addition Al3+ and Pr3+ In this excitation spectrum the main peak at 359 nm represent excitation level of Pr3+(1S0longrightarrow1D2 transition) and the absorption characteristic according to Ti/Sr molar ratio is influenced by the structure symmetry. The emission spectrum exhibits the red luminescence with the radiative decay of the 1D2 states(1D2 longrightarrow3H4 transition) The concentration quenching phenomena at 1D2 state shows up as Al3+ and Pr3+ ion concentration increases.

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A study of the inorganic element contents for the ginsengs of Keumsan, Chungnam

  • Song, Suck-Hwan;Sik, Chang-Gyu
    • Proceedings of the Ginseng society Conference
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    • 2008.05a
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    • pp.74-75
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    • 2008
  • This study is for geochemical relationships between ginsengs and soils from three representative soil types from Keumsan, shale, phyllite and granite. For these study, ginsengs, with the field and weathered soils were collected from the three regions, and are analysed for the major and trace elements. In the weathered soils(avg.), the granite and phyllite areas are high in the most of elements while the shale area is low. In the correlation coefficients, negative correlations are shown in the $Al_2O_3$-MgO pair while positive correlations, are shown in the Ba-Sr, Zr, Sr-Zr and Cs-Ge pairs. In the field soils(avg.), the granite and phyllite areas are, generally, high in the most of elements while the shale area is low. In the shale area, the major elements are high in the 4 year soils, but low in the 2 year soils. The LFS(Ba, Sr, Cs) and transitional elements are high in the 2 year soils, but low in the 4 year soils. The HFS(Y, Zr) is high in the 4 year soils. In the correlation coefficients, most of the elements from the 4 year show positive relationships. Positive correlations are shown in the $Al_2O_3$-CaO, MnO-MgO, V-Tl, and Ba-Sr pairs in all localities. In the ginseng contents, clear chemical differences with the ages are shown in the shale and granite ares, but not clear in the phyllite area. In the shale area Mn, Mg, Ba, Sr, and Y contents, increase with ages but decrease in Al, Cs, Be and Cd. In the correlation coefficients, degrees of the correlations for the major elements become low with the ages. Positive correlations are shown in the Al-Mn, Ti, Mn-Ti, Mg-Ca, Ca-K, Ba-Cs, Y and Cs-Y pairs. Comparisons with ginsengs of the same ages from the different areas suggest that generally, the 2 years in the shale and 3 and 4 years in the granite area are distinctive. Relative ratios(granite/ shale area) of the ginsengs are below 1 in the major elements except Mn in the 2 year ginsengs and above 1 in the other elements except Mg and Na in the 4 year. Relative ratios(granite/ phyllite area) of the ginsengs are high in the 3 year from the phyllite area. In the relative ratios(weathered/field soils) of the soils, numbers of the elements showing the ratios of above 1 increase from the shale, to phyllite and granite in the case of the major elements, but decrease in the case of the trace elements. These results suggest that major elements are high in the granite while trace elements are high in the shale area. In the relative ratios between field soils and ginsengs(field soils/ginseng), the shale area, regardless of the ages, show differences of several hundred times in the $Al_2O_3$, $TiO_2$, Y and Tl, of several ten times in the MnO, MgO and Ba and of several times in the CaO contents. These results suggest that ginseng contents are significantly different from the field soils in the $Al_2O_3$, $TiO_2$, Y and Tl, but similar in the CaO contents. The phyllite area, regardless of the ages, show differences of several hundred times in the $Al_2O_3$, $TiO_2$, Y, Tl and Be, of several ten times in the MnO, MgO, $Na_2O$ and Ba, and of several times to ten times in the CaO, $K_2O$ and Sr contents. These results suggest that ginseng contents are significantly different from those of the field soils in the $Al_2O_3$, $TiO_2$, Y, Tl and Be, but similar in the CaO, $K_2O$ and Sr contents. The granite area, regardless of the ages, show differences of several hundred times in the $Al_2O_3$, $TiO_2$, Tl and Be, of several ten times in the Ba, and of several times to ten times in the MgO and CaO contents. Of the other elements, differences of several times to ten times are shown in the MnO, $K_2O$ and Sr contents. These results suggest that ginseng contents are significantly different from those of the field soils in the $Al_2O_3$, $TiO_2$, Tl and Be, but similar in the $K_2O$ and Sr contents. Comparisons among the different ages from the same area suggest that, in the case of shale area, differences of several hundred times in the $Al_2O_3$ and $TiO_2$, of the several ten times in the MnO, MgO and Ba and several times in the CaO and $K_2O$ are shown in the 2 year ginsengs. Differences of several hundred times in the $Al_2O_3$, $TiO_2$, Cs, Y, Tl and Be, of above several ten times in the MnO, MgO, $K_2O$ and Ba, and of several times in the CaO and Sr are shown in the 3 year ginsengs. Differences of several hundred to thousand times in the $Al_2O_3$, of above several hundred times in the $TiO_2$, Cs and Y, and of several ten times in the MnO, MgO, $K_2O$ and Ba, and of several times in the $Na_2O$ are shown in the 4 year ginsengs. These relationships suggest that, regardless of the localities in the shale area, $Al_2O_3$ contents of the soils show big differences from those of the ginsengs. Regardless of the ages of ginsengs, comparisons with the overall average contents of each area show differences of several hundred times in the $Al_2O_3$, $TiO_2$, Cs and Tl and of several ten times in the MnO. These overall relationships suggest that the $Al_2O_3$, $TiO_2$, Cs and Tl contents of the soils are higher than those of the ginsengs, show big differences between two and low different contents are found in the MnO. In detail, differences of several hundred times in the Y, and ten times in the MgO and Sr, and of several times in the CaO, $Na_2O$, $K_2O$ in the case of shale area, are shown. These results suggest that the soils are higher than the ginsengs in the Y and significantly differences in Y, and moderately differences in the MgO and Sr, and low differences in the CaO, $Na_2O$ and $K_2O$ are shown between soils and ginsengs.

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Lattice strain effects on superconductivity in $La_{2-x}Sr_{x}CuO_{4}$ single-crystalline films grown by IR-LPE technique

  • Tanaka, I.;Islam, A.T.M.N.;Wataudhi, S.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.13 no.4
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    • pp.172-175
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    • 2003
  • We have investigated effects of the lattice mismatch between the LPE films and the substrates. We have grown $La_{2-x}Sr_{x}CuO_{4}$(x=0.1 to 0.15) single crystalline films on single crystalline substrates having different lattice parameter ratio c/a e.g., $La_{2-x}Sr_{x}Cu_{1-y}Zn_{y}O_{4},\;La_{2-x}Ba_{x}CuO_{4},\; LaSrAlO_{4}\;and\;La_{2-x}Sr_{x}Cu_{1-y}Al_{y}O_{4}$ etc., using the IR-LPE technique. The superconducting properties of the grown films were found to vary significantly depending on the lattice mismatch with different substrates.

Photoluminescence of SrO-$Al_2O_3$ Doped with Eu and Ce Excited at near UV

  • Han, Sang-Hyuk;Kim, Young-Jin;Chung, Sung-Mook
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.654-656
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    • 2004
  • The effect of excitation energy and various dopants(Eu and Ce) on the emission wavelength and intensity were investigated. According to PL spectra, SrO-$Al_2O_3$ phosphors had wide absorption band at nUV. By substituting Ce for Eu, the emission band and excitation wavelength were shifted to shorter wavelength. Ce doped $SrAl_2O_4$ and $Sr_4Al_{14}O_{25}$ showed greenish blue(475nm) and blue(400nm), respectively.

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