28-P-S28-08
The 13th Pacific Rim Conference of Ceramic Societies (PACRIM13)
October 27 - November 1, 2019, Okinawa Convention Center, Japan

Photoluminescence of sol−gel-derived transparent silica−(Gd,Pr)PO4 glass-ceramics
under excitation with a KrCl excimer lamp
Ryosui Nakagawa and Koichi Kajihara*
Department of Applied Chemistry for Environment, Graduate School of Urban Environmental Sciences,
Tokyo Metropolitan University, Tokyo 192-0397, Japan*E-mail: kkaji@tmu.ac.jp
Gd3+ ions exhibit a sharp ultraviolet (UV) photoluminescence (PL) band at ~313 nm originating from the 6P7/2 →7/2 4f−4f transition, which has therapeutic effect for several skin diseases. This PL band can be effectively
sensitized by codoping Pr3+ ions and exciting their 4f−5d transition at ≲ 240 nm in several inorganic rare-earth (RE)compounds including (La,Gd,Pr)PO4 [1]. We have found that RE−P codoped silica glasses prepared by a cosolventfree sol−gel method [2] were transparent glass-ceramics containing REPO4 nanocrystals [3], and transparent
silica−(Gd,Pr)PO4 glass-ceramics exhibit an intense UV emission at ~313 nm via the excitation of Pr3+ ions [3,4].
However, the emission properties were examined using a monochromated Xe lamp and conventional light sourceswere not employed. A KrCl excimer lamp emits light with a narrow spectral width at 222 nm and is expected to besuitable for the excitation of silica−(Gd,Pr)PO4 glass-ceramics. The
purpose of this study is to examine the UV PL properties of transparent
silica−(Gd,Pr)PO4 glass-ceramics under excitation with a KrClexcimer lamp.
Dilute of nitric acid was added to 25 mmol of tetraethoxysilane(TEOS) and stirred for 55 min at 20 °C, followed by the addition oftriphenylphosphine oxide (TPPO) and stirring for another 5 min.
Then an aqueous solution of ammonium acetate (AcONH4) and RE
acetates were added to form a solution with an overall TEOS : H2O :HNO3 : AcONH4: (AcO)3RE : TPPO molar ratio of 1 : 10 : 0.002 :0.01 : 0.01 : 0.01 (= zRE = zGd + zPr). The value of zPr/zRE was fixed
Fig. 1 Optical absorption spectrum andat 0.05 because photoluminescence efficiency decreases at zPr/zRE >0.1 [3]. The wet gel was aged for 24 h at 60 °C and gently dried at photograph of silica−(Gd,Pr)PO4 glassceramic prepared in this study.
60 °C. The dried gel was sintered in He at 1200 °C.
Fig. 1 shows photograph and optical absorption spectrum of a glassceramic obtained in this study. It was highly transparent and UV
absorption edge attributed to the 4f−5d transition of Pr3+ ions wasobserved at ~240 nm. Fig. 2 shows PL spectra of the glass-ceramicmeasured under excitation at 220 nm with a monochromated Xe lamp
and 222 nm with a KrCl excimer lamp. In both spectra UV PL band
originating from the 6P7/2 → 8S7/2 transition of Gd3+ ions was observed.
The internal and external quantum efficiencies (IQE and EQE,respectively) of UV PL were ~0.98 and ~0.92, respectively, under theexcitation with a monochromated Xe lamp, and ~0.99 and 0.85,respectively, under the excitation with a KrCl excimer lamp. The value
Fig. 2 PL spectra of silica−(Gd,Pr)PO4of IQE was ~1. These observations demonstrate that KrCl excimer
glass-ceramicmeasuredunderlamps can be promising candidates of the excitation sources ofexcitation at 220 nm with asilica−(Gd,Pr)PO4 glass-ceramics.
monochromated Xe lamp and 222 nmwith a KrCl excimer lamp.
Acknowledgement
We wish to thank ORC Manufacturing Co. Ltd for the provision of a KrCl excimer lamp.
8S

References[1] S. Okamoto, R. Uchino, K. Kobayashi, H. Yamamoto, J. Appl. Phys. 106 (2009) 013522.
[2] K. Kajihara, S. Kuwatani, K. Kanamura, Appl. Phys. Express 5 (2012) 012601[3] S. Yamaguchi, K. Moriyama, K. Kajihara, K. Kanamura, J. Mater. Chem. C 3 (2015) 9894.
[4] M. Suda, R. Nakagawa, K Kanamura, K. Kajihara, Dalton Trans. 47 (2018) 12085.

PACRIM 13 Program Book(C) The Ceramic Society of Japan, 2019