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Aoyama M.,Nagoya Institute of Technology | Amano Y.,Nagoya Institute of Technology | Inoue K.,Mie Industrial Research Institute | Honda S.,Nagoya Institute of Technology | And 2 more authors.
Journal of Luminescence | Year: 2013

Mn-doped LiAlO2 powders were synthesized by the sol-gel method. The crystalline phase of the sol-gel-derived host lithium aluminate could be successfully controlled as α-LiAlO2 single phase by heat treatment at 700 °C. The results of electron spin resonance spectroscopic analyses revealed that Mn ions existed as isolated Mn4+ and clustered cations in the host α-LiAlO2 matrix, and a part of the isolated Mn4+ were thought to substitute the Al3+ octahedral sites. The red emission peaks derived from d-d transitions of the Mn4+ (3d3) configuration from 2E to 4A2 were observed around 670 nm. The emission intensity increased consistently with the Mn-doping concentration, and the highest intensity was achieved at the Mn-doping of 0.10 mol. At and above 0.10 mol Mn-doping, the concentration quenching was observed. Based on these results, the relationships between the crystalline phases of the LiAlO2 phosphor matrix, amount of the doped-manganese, and the photoluminescence properties were discussed from a viewpoint to develop a novel α-LiAlO2:Mn 4+ red phosphor. © 2012 Elsevier B.V. All rights reserved.

Aoyama M.,Nagoya Institute of Technology | Amano Y.,Nagoya Institute of Technology | Inoue K.,Mie Industrial Research Institute | Honda S.,Nagoya Institute of Technology | And 2 more authors.
Journal of Luminescence | Year: 2013

By using the conventional sol-gel technique, γ-LiAlO2 and LiAl5O8 powders were synthesized from appropriate gel precursor composition of Li/Al=1/1 and Li/Al=1/5, respectively. The precursor gel having Li/Al=1/1 was converted into α-LiAlO2 at 600°C. Subsequently, α-/γ-LiAlO2 phase transformation completed at 800°C. Further heat treatment at and above 1200°C leads to the in-situ formation of LiAl5O8, which could be accompanied by the excessive evaporation of Li species from γ-LiAlO2. Another precursor gel with the stoichiometric composition (Li/Al=1/5) could be successfully converted into LiAl5O8 at 800°C. However, above 1200°C, LiAl5O8 was decomposed to yield α-Al2O3. The samples exhibited the maximum PL emission peak around 670 nm (λex.=270 nm) assigned to the d-d transitions of the Fe3+ (3d5) configuration from 4T1 (4G) to 6A1 ( 6S). The highest PL red emission intensity was found to be achieved for the in-situ formed LiAl5O8 from γ-LiAlO 2 by heat treatment up to 1600°C, and the amount of the Fe 3+ activator in this material was determined to be 0.8 ppm by the chemical composition analysis. As a host material for the Fe3+- activated PL red emission, LiAl5O8 was found to be much better than γ-LiAlO2, and the PL emission properties of LiAl5O8 in terms of the red emission intensity, the quantum efficiency, and the red color index were found to be improved consistently with the crystallite size and the crystallinity. © 2012 Elsevier B.V.

Nasu H.,Mie University | Ninagawa S.,Mie Industrial Research Institute | Inoue K.,Mie University | Hashimoto T.,Mie University | Ishihara A.,Mie University
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan | Year: 2012

Trivalent cation oxides were added to zinc phosphate glasses by conventional melt-quenching technique to dope excess electrons in order to create donor electrons easily excited by the incident light, in specific Ga 2O 3 and Sb 2O 3. By exciting 200 and 250nm light, the glasses containing Sb 2O 3 emitted visible light, while no emission from those containing Ga2O3 could be observable. The intensity of emission light depend mol% Sb 2O 3 addition was most effective for the emission, and concentration quenching was seen in over 5 mol%Sb 2O 3 addition.With respect to necessity of the presence of ZnO was explored by replacing ZnO by CaO and BaO. Even by changing of ZnO by CaO and BaO, the emission intensity was not influenced. Further, we used borate glasses instead of phosphate glasses. Since only weak emission was obtained from borate glasses, P 2O 5 can be considered to be indispensable for photoluminescence (PL) phenomena. © 2012 The Ceramic Society of Japan. All rights reserved.

Sago T.,Mie Industrial Research Institute | Inoue K.,Mie Industrial Research Institute | Amano Y.,Nagoya Institute of Technology | Iwamoto Y.,Nagoya Institute of Technology
IDW'10 - Proceedings of the 17th International Display Workshops | Year: 2010

Sol-gel-derived lithium aluminate powders were synthesized by heat treatment at 600-1600 °C for 1 h. The gel composition with Li:Al=1:1 yielded α-LiAlO2 at 600 °C. Then α/γ phase transformation at 800 to 1200 °C, and subsequent decomposition lead to the formation of LiAl5O8 above 1200 °C. At 1600°C, the red emission band is observed with the maximum around 685 nm (λex.=254 nm). © 2010 ITE and SID.

Ishikawa Y.,Nagoya Institute of Technology | Hayakawa T.,Nagoya Institute of Technology | Inoue K.,Mie Industrial Research Institute | Nogami M.,Nagoya Institute of Technology
Journal of Sol-Gel Science and Technology | Year: 2013

Transparent, luminescent films of Pr3+-doped (Ca 0.6Sr0.4)TiO3 (CSTO) have been prepared for cathodo-excitation of pure red luminescence by a sol-gel method from a stabilized sol with Ca2+, Sr2+, Pr3+ ions and titanium-isopropoxide in acetic acid. The structure and surface morphology of the obtained films are characterized by X-ray diffraction and Atomic Force Microscopy, respectively. The photoluminescence and cathodoluminescence (CL) properties of the films are evaluated. The films exhibit a strong single line of 1D2 → 3H4 red photoluminescence of Pr3+ ions doped, which increases almost linearly with the number of the dip-coated layers. It is also found that strong single red photoemission is observed and the CL intensity increases with increasing acceleration voltage. The results demonstrate that it is potential for application in field-emission display devices. © 2012 Springer Science+Business Media New York.

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