2002 Fiscal Year Final Research Report Summary
Preparation of long-lasting transparent glass-ceramic phosphor
| Project/Area Number |
11555167
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | OKAYAMA UNIVERSITY |
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Principal Investigator |
MIURA Yoshinari Faculty of Environ. Sci. & Tech., Department of Environ. Chem. & Mater., Professor, 環境理工学部, 教授 (80032952)
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| Co-Investigator(Kenkyū-buntansha) |
傳 傑 株式会社オハラR&Dセンター(H11年度のみ参加), 主任研究員
NANBA Tokuro Faculty Environ Sci. & Tech., Department of Environ Chem & Mater., Ass. Professor, 環境理工学部, 助教授 (80218073)
JIE Fu Ohara Inc. R & D Center Reseacher
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| Project Period (FY) |
1999 – 2002
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| Keywords | long-lasting phosphors / transparent glass-ceramics / alkaline-earth aluminum oxides / akermanite crystals / rare earth ions / crystallizing heat-treatment at reducing condition / glass-melting at reducing condition / ultrasonic surface treatment (UST) |
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| Research Abstract |
The preparation of the transparent glass-ceramics with long lasting phosphorescence (LLP) was tried by precipitation of crystals from glassy materials by means of various experimental methods. The glass-ceramics containing calcium aluminate crystals co-doped with Eu^<2+> and Nd^<3+> or akermanite (strontium magnesium silicate) type crystals co-doped with Eu^<2+> and Dy^<3+>. The glass in the system 45CaO・45Al_2O_3・10SiO_2 (mol%) containing 0.5Eu_2O_3+1Nd_2O_3 showed very weak LLP property due to glassy state even though Eu ions were effectively reduced to Eu^<2+> ion state by melting the glass with reducing agents like sugar or graphite. Therefore to keep a certain crystal state is necessity to excellent LLP property. The effects of ultrasonic surface treatment (UST) on the crystallization behavior and optical emission properties were investigated for the transparent glass-ceramics prepared from calcium aluminosilicate glasses co-doped with Eu^<2+> and Nd^<3+>. The glass-ceramics A wer
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e prepared by sintering a glass 45CaO・45Al_2O_3・10SiO_2 (mol%) containing O.5Eu_2O_3+1Nd_2O_3 under a 2%H_2+98%Ar reducing atmosphere. In the glass-ceramics A, three crystalline phases, CaAl_2O_4(CA), CaAl_4O_7(CA2) and Ca_2Al_2SiO_7(CAS) were commonly confirmed by X-ray diffraction. No drastic change in the amount of the precipitated crystalline phases was observed even in the case using UST of CA powders. It was suggested that the optical emission properties of the glass-ceramics A was responsible for the CA2 crystals. The glass-ceramics B were also prepared from a 51CaO・42Al_2O_3・7SiO_2 glass. The CA crystals were separately precipitated in the glass-ceramics B. In particular, a large amount of CA was successfully produced by stirring the UST suspension to prevent the sedimentation of the UST particles. The glass-ceramic B so-prepared showed strong photoluminescence but weak phosphorescence compared with other glass-ceramics B, indicating that the photoluminescence and phosphorescence were originated in different electron-trapping levels. The amount of the trap levels associated with the long lasting phosphorescence, such as oxygen vacancies, was probably small in the glass-ceramic B prepared with the stirring UST. When the glasses were melted with reducing agent like sugar and partially crystallized under a reducing atmosphere glass-ceramics showed excellent LLP properties. The glass-ceramics with LLP precipitated akermanite type crystals co-doped with Eu^<2+> and Dy^<3+> were also obtained by melting and crystallizing under reducing conditions. Less
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