京都大学教育研究振興財団助成事業
成 果 報 告 書
2019 年

3月9日

公益財団法人京都大学教育研究振興財団会 長 藤
洋 作 様助 成 の 種 類

所属部局・研究科

工学部・材料化学専攻

職 名・学 年

博士後期課程・二回生

氏

GAO YUAN名

平成３０年度 ・国際研究集会発表助成

研 究 集 会 名

第35回日韓国際セラミックスセミナー

発 表

形 式

□ 招 待

発 表

題 目

Achieving Spatially- Selective Dopant Distribution in Glass
Ceramics for Warm Light Emitting Diodes

開 催場 所Lakai resort in Gangneung, Korea

渡 航期 間2018 年

成 果 の 概 要

・

■ 口 頭

11 月

20 日・～□ ポスター ・ □ その他（2018）年 11 月 25 日

タイトルは「成果の概要／報告者名」として、A４版２０００字程度・和文で作成し、添付して下さい。 「成果の概要」以外に添付する資料 ■ 無□ 有()
交付を受けた助成金額

100，000円

使 用 し た 助 成 金 額

100. 000円

返納すべき助成金額0円
往復航空運賃： 50，000 円

会 計報 告学会登録費： 13，000 円
助 成 金 の 使 途 内 訳

当財団の助成について宿泊代： 30, 000 円
交通費： 7, 000 円

自身の研究発表以外にも、世界的に著名な研究者の講演や、世界最大規模の会議だからこその幅広いテーマの研究発表を聴講することができ、知見や興味を広げることができた。
この貴重な経験は、今後の研究生活に十分に活かしていきたい。今回の国際会議への参加は私にとって非常に有意義なものとなりました。このような機会と多大なるご支援をいただ
きました貴財団に深くお礼申し上げます。

成果の概要GAO YUAN
1.国際会議の概要
The 35th International Japan-Korea Seminar on Ceramics was held in Gangneung,
Korea during November 21st to 24th, 2018. In its 35-year history, this is the first visitof the Japan-Korea Seminar on Ceramics to the city of Gangneung in Korea.
Gangneung City is a beautiful city located in the northern part of the east coast ofKorea, about 300km from the Seoul, and asset of winter olympic game held in 2018.
This seminar is the one of most famous in sector of ceramics between Japan andKorea. Japan and Korea hosted the annual meeting alternatively to promote the active
communication of researchers and students in terms of ceramic science & technology
also human resources. This conference covers broadband subject, such us fuel cell,batteries, secondary cells, solar cell, thermoelectrics, electronic ceramics, magneticceramics, piezoelectrics, sensor materials, structure and 3D printing, including powerprocess, soft material, bio-applications, basic science of ceramics, glasses,nanoceramics, thin films, coatings, industry ceramics and so on. During this event,there are 146 papers were scheduled, including 33 invited, 54 oral presentations and59 poster presentations made by many of the world's most prominent researchers fromacademia and industry.

Figure 1 opening ceremony

Figure 2 Doacuments

2.研究テーマと討論内容
In this meeting, my talk presentation was performed in the symposium G-01, which isabout nanocermaics general sessions, on November 23 at 13:00-13:15. I presented myresearch with the title as "Achieving Spatially- Selective Dopant Distribution in Glass
Ceramics for Warm Light Emitting Diodes". As well known, white light-emitting
diodes (WLEDs) are used extensively in backlights, flashlights and handlights as
replacements for conventional incandescent and ﬂuorescent lamps because of theirhigh energy eﬃciency, durability, reliability, and capacity for use in products withvarious sizes and more eco-friendly components. Phosphors have been widely
investigated for use in phosphor-converted WLEDs. The most widely used WLED
combines the yellow phosphor Y3Al5O12:Ce3+ (YAG) with a blue InGaN LED chip.
However, this LED presents a low color rendering index (CRI) (Ra < 70) and highcorrelated color temperature (CCT > 6000 K) because of the absence of red emissionin its spectrum. In this study, we have fabricated Eu-doped oxy-fluoride
glass-ceramics containing two kinds of crystalsNa5Gd9F32 and NaAlSiO4 nano- andmicrocrystals by melt-quenching and post-annealing for warm WLEDs. Annealing
above 640ºC lead to the two crystalline phases precipitated in the glass matrix (Fig.
3(a)), and the glass-ceramics exhibited green broad emission at 540 nm and sharp redemission at 610 nm. The analysis including STEM-EDX, SEM-CL, and confocal PLmicroscopy revealed that the emission came from the selective distribution of Eu3+and Eu2+ in Na5Gd9F32 and NaAlSiO4 phases, respectively. The glass-ceramics excitedwith InGaN UV chip (λex=395nm) showed warm white emission (Fig. 3(b)) with CCTof less than 3000 K and CRI of over 70, while photoluminescence quantum yield wasover 35%. Furthermore, we examined thermal quenching of photoluminescence at573K; the photoluminescence integral intensity is still about 58% of that measured atroom temperature. We believe that the glass-ceramics we found are applicable to highpower W-LEDs and displays.

Figure 3 (a) X-ray diffraction pattern of glass-ceramics. (b) Photoluminescence
spectrum excited with an InGaN UV chip.
I made my 10 minute-oral presentation, with 5 minutes questions-and-answers time.
Approximately 20 people attended my talk. I received a couple of questions. Q#1:
You were able to control the color of your glass-ceramics sample under 393 nm UV
source excitation from pink region to yellowish region, does it mean that thephotoluminescence color can be adjusted between two kinds of emission spectra?","A#1: The photoluminescence color changed dramatically with the formation ofNaAlSiO4 containing Eu2+, especially, with the heat-treatment temperature increased
from 620 to 640 degree C, which led to the precipitation of second phase ofNaAlSiO4 microcrystals, where Eu2+ primarily selectively distributed, there is a close
relationship with the formation of NaAlSiO4 second phase and the shift ofphotoluminescence color. So, in this case, it would be possible in principle forsomeone to control the photoluminescence color by changing the concentration ofNaAlSiO4. However, under high temperature, we have difficulty in precisely
controlling the phase formation process volume by changing the concentration ofNaAlSiO4 due to the fact that the rate of crystallization is very fast." "Q#2: Since theglass-ceramics is opaque, how can it be used in illumination for WLEDs?", "A#2:
Actually, the opaque glass-ceramics was good for this purpose because it absorbs
more UV excitation, and converts it to white light more so than that of transparent one.
Moreover, UV light is harmful for human eyes". A couple of people got interested inmy talk and we were able to make meaningful discussions with each other in ourresearch fields, after the talk.

3.国際会議に出席した成果（コミュニケーション・国際交流・感想）
The international Japan-Korea annual seminar on cermaics is a well-organized anddeeply impressive conference, where I truly learned something new and broadened
my horizons. In this meeting, there are presentations in various fields as well as mysession, participating in announcements and demonstrations in different research
fields has become a big stimulus for themselves. Also, after both oral and poster
presentations, there was opportunity for discussion with researchers who caome fromin the same and different research fields, and it was very meaningful to obtainknowledge about future research activities. This is my second times to attend
Japan-Korea seminar in ceramics, I attend this seminar at Hamamatsu,. Japan inNovember. 2017. In my first time to attend this conference in the 34th Japan-Korea
seminar in ceramics, the communication with researchers from all over the world isgreatly inspired and unforgettable. Attending the international conference was a greatexperience for me and I was able to gain an incredible experience to meet theatmosphere of the international conference and people from oversea researchers. I
answered the question I received as much as I could.

Figure 34 Banquet of Conference.
In this conference, During and after my presentation, I received some comments andquestions, which are our important for our future work. Besides learning some newknowledge about optical measurement and manufacture, closely related my research
field, I learned many technologies in fabrication method, temperature measurement
and analysis ways et al. It was very impressive. At first day (22th November) of mytravel, I listened invited speakers talk at plenary session. The speakers from Korea
University, Shizuoka University, Zhejiang University et al, look very powerful andthose people gave me vitality to do my research more structural, more beneficial andalso more goal-seeking. Especially, Professor Jong-Heun Lee who come from Korea
University, tasking title is "Highly Sensitive, Selective, and Robust Oxide
Semiconductor Gas Sensors: New Opportunities and challenges", which include theuse of hollow and hierarchical nanostructures with high gas accessibility,
microspheres with tri-modal porosity, p-type oxide semiconductors with high catalytic
activity, yolk-shell micro-reactors to promote the reforming of inactive gases to morereactive forms, bilayer sensing film consisting of nano-scale catalytic overlayer, andhetero-nanostructures as sensing materials or platforms. I think all the attendees
enjoyed this keynote speech and were touched by his rigorous attitude. At the sameday, I also enjoyed poster session, including these title of "Synthesis of Mn4+ doped
red phosphor by using atmosphere furnace", "Novel Inorganic Pigment with Ce3+ as a
Coloring Source", "thick-film phosphor-in-glass with Nd3+-ion doped phosphate glass
for white LED with wide color gamut" and "Up-conversion studies on Er3+/Yb3+
co-doped fluorophosphate glasses" and so on. There are some poster presentation wasinterested and deep impressive in my research, such as Masashi MAEDA gave aposter title with "Synthesis of Mn4+ doped red phosphor by using atmosphere", insuch work, he clarified the mechanism of high emission intensity, using various
microscale to nanoscale characterization techniques: X-ray diffraction, a scanningelectron microscope, and X-ray absorption fine structure spectroscopy. The emission
intensity was closely related to the ratio of Mn4+ and structure of the phosphor. I learn
various kind of measurement method and its mechanism, and I received informationthat next international Japan-Korea seminar in ceramics will be held in Tottor-shi ofJapan in 2019 with further deeply communication, and sometimes we can useing both
English and Japanese. Moreover, the title is "thick-film phosphor-in-glass with
Nd3+-ion doped phosphate glass for white LED with wide color gamut" made by Yoon
Hee NAM, a female student who come from Kongju University of Republic of Korea.
In her study, a glass containing Nd3+-ion and fabricated a phosphor-in-glass thick film
on a glass substrate which dose not require further processes were developed Strongabsorption at 580 nm due to Nd3+-ion was introduced to adjust spectral shape of thegreen and red phosphor. Thick-film phosphor-in-glass with 50 μm in thickness wereobtained via simple screen printing process. The Nd3+-ion doped glass frit andLu3Al5O12:Ce3+ as green phosphor, and CaAlSiN3: Eu3+ as a red phosphor were mixedto obtain white light varying their contents. Doping concentration of Nd3+-ion within
the glass matrix was also optimized for color gamut improvement. Various opticalproperties were measured after mounting on top of the blue LED by an integratingtion
sphere such as color coordinates, correlated color temperature, color rendering index
and color gamut. I also enjoyed talk with other student for their own country culture
and exchange e-mail of each other. In the second day, I present my research. Before
my talk, I felt kind of fear that someone could not understand my research, if I
received unfamiliar question that I couldnʹt give answer and so on. But after that, I
understood that there was no need to feel heartbeat, because everyone was trying toexchange knowledge and learn new things. In addition, I enjoy talking with many top
students of the field of inorganic ceramics. Many provided and inspired me to theirresearch with novel methods and materials. This was my first international conferenceon oversea in my doctor course. I was amazed by the profound discussions andsharing of knowledge of researchers during presentations to improve each research.

Figure 45 Picture with Korea student.
Finally, let me take this opportunity to express my deep gratitude for the support andgrant of the international conference attendance from The Kyoto Uuniversity
education research Ffoundation. I am honored and thankful to have been chosen forthis financial support. Thus, I would like to express my sciesincerence gratitude to mysupervisor Prof. Shunsuke MURAI and Prof. Katsuhisa TANAKA for their help andguidance.

Figure 56 The Mascots of winter Olympic in 2018.