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Detailed Program
Paper Number : GL-O04
Time Frame : 11:46~11:58
Presentation Date : Thurse day, 27, November
Session Name : Glass & Optp-Electonic Materials
Session Chair 1# : Yong Gyu Choi
Session Chair 2# : Atsunobu Masuno
Fabrication of Sn2+-doped Phosphate Glasses for Phosphor Applications
Hirokazu MASAI
Kyoto University
Phosphors have been used in several applications in our daily lives. In contrast to most of trivalent rare earth cations, the emission of the ns2-type emission center can be widely tailored by tuning the local coordination state because of the electron in the outermost shell. Recently, we have reported Sn2+-doped phosphate glass phosphor that shows high quantum efficiency comparable to conventional crystalline phosphor [1]. The Sn2+ emission center appears to be very advantageous from the viewpoint of unique emission mechanisms in a random matrix; the coexistence of high efficiency and broad emission [2]. However, neither the correlation between actual concentration of Sn2+ centers and emission properties nor the local coordination states has been fully clarified.
In this paper, we report correlation between preparation conditions and the photoluminescence properties of Sn2+ centers in a zinc phosphate glass. When prepared in air, the local coordination state of Sn2+ centers depends on the starting material due to oxidation of Sn2+ into Sn4+. In contrast, PL properties of Sn2+ centers of the glass prepared in inert atmosphere conditions is independent of the starting material because of elimination of the oxidation reaction. 119mSn Mössbauer and X-ray absorption fine structure analyses indicate that most of Sn2+ centers in the glass prepared in the inert atmosphere exists at a SnO-like coordination state. Because most Sn2+ centers take on a coordination state similar to that of Sn2+ in SnO crystals, it was determined that the coordination state was the origin of the PLE band at lower photon energy that accompanies high quantum efficiency. Since existence of two PLE band is characteristic of Sn2+ center in glass material, glass phosphor will be a novel light-emitting material that is quite different from the conventional crystalline phosphor. For future emitting devices, we believe that these oxide glasses will be one of the most industrially favorable inorganic materials possessing transparency and emitting properties.


Figure 1 Optical absorption and PLE spectra of SZP glasses prepared in air and in Ar.

References:
[1] H. Masai, Y. Takahashi, T. Fujiwara, S. Matsumoto, and T. Yoko, Appl. Phys. Express, 3 (2010) 082102.
[2] H. Masai, T. Fujiwara, S. Matsumoto, Y. Takahashi, K. Iwasaki, Y. Tokuda, T. Yoko, Opt. Lett. 36, (2011) 2868.

Acknowledgements :