reu poster- final - vanderbilt university · reu poster- final.pptx author: megan burcham created...
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Max PL Grain Size Max PL Grain Size Max PL Grain Size
1100 2 hrs 1100 4.5 hrs 1100 14 hrs
Average of all 4cmobustion temperatures
0.003182 41.211384 0.003549 46.274556 0.003938 48.877492
0.001
0.01
0.1
1
10
100
Max PL Emission Intensity Increased With Increasing Grain Size
Max
PL
Emis
sio
n In
ten
sity
G
rain
Siz
e (n
m)
800 900 1000 1100
Inte
nsi
ty (
a.u
.)
Heat Treatment Temperature (°C)
300 °C 500 °C
400 °C 600 °C
Combustion Temperature
Combustion Synthesis of Gadolinium Aluminum Garnet (GAG) Phosphor Marc Panu1, Courtney A. Mitchell1, Sarah L. Gollub2, Bridget R. Rogers1 , Greg Walker3
1Vanderbilt University Department of Chemical and Biomolecular Engineering 2Vanderbilt University Interdisciplinary Material Science Program
3Vanderbilt University Department of Mechanical Engineering
Conclusions • The most garnet phase material was created when the
precursor was combusted at 500°C, then annealed at 1100°C for 4.5 hours
• The most intense PL emission occurred when 10% of the gadolinium was replaced with yttrium; indicating that composition has the greatest effect on PL
• The emission wavelength can be tuned within a 25 nm range by varying the concentration of gallium between 0 and 30 atomic percent
• Gallium and yttrium doping effects are mutually exclusive
Future Work • Design a system to better utilize the internal energy
released by the combustion in order to eliminate the need for annealing
• Develop a method to control particle size • Mechanism to crush particles to a desired radius • Size-controlled synthesis process
• Investigate the effects that other dopants have on PL • Complete study on the effects of stoichiometry
(varying Y from 0-100% and Ga from 0-100%)
What am I doing?
Objectives • Maximize photoluminescent (PL) emission intensity • Synthesize pure garnet phase material • Define relationships between stoichiometric
composition and PL emission (wavelength and intensity)
Combustion Synthesis
Crystal Structure
GAG (420)
GAP (112)
Relative intensity of the GAG (420) XRD peak increases with increasing heat treatment temperature and GAP (112) decreases with increasing heat treatment temperature. Thus, the most GAG phase material is synthesized at 1100 °C
This work was supported by the National Science Foundation grant DMR‐ 0907619, Defense and Threat Reduction Agency grant HDTRA 1-10-1-0112, and Department of Education for a Graduate Assistance in Areas of National Need (GAANN) Fellowship under grant number P200A090323
Why GAG?
There is still a need for improvement in the quality of white light emissions in solid-state lighting devices. Yttrium Aluminum Garnet (YAG) is a commonly used and well researched phosphor, but there is
a need for a longer wavelength emitting phosphor. GAG is a similar phosphor, but due to differences in atomic size, GAG can emit longer wavelengths of light and theoretically improve white light emissions.
PL emission intensity increases monotonically with increasing heat treatment. However, the maximum intensity does not occur when the most garnet phase material is present. This indicates crystal structure is not the sole determinant in PL emission intensity for samples with consistent composition.
Composition
YGGAG [Y3xGd3(1-x)Ga5xAl5(1-x)O12]
GGAG [Gd3Ga5xAl5(1-x)O12]
YGAG [Y3xGd3(1-x)Al5O12]
Particle Morphology
GAG GGAG YGAG YGGAG
Scherrer’s Equation
𝜏 =𝛫𝜆
𝛽 𝑐𝑜𝑠 𝜃
Grain sizes can be estimated using the following:
Garnet1 (GAG) Gd3Al5O12
Perovskite2 (GAP) GdAlO3
Gd-Al-O
Synthesis
Process GAG
Combustion Factors
Raw Materials
Post- Processing
Factors
Crystal Structure
Composition
Particle Size
PL Emission
intensity + wavelength
www.newswise.com
Crystal structure pictures adapted from [1] staff.aist.go.jp [2] www.camsoft.co.kr
X-ray photoelectron spectroscopy (XPS) spectra
80 °C 3 hours
300-600 °C 10 minutes
800-1100 °C 2-14 hours
Photoluminescence under black light excitation
Crushed powder (no heat treatment)
Airy combustion products
XPS was used to analyze the elemental composition of the products
Notations for various materials
0
1
2
3
4
800 900 1000 1100
Max
PL
Inte
nsi
ty (
a.u
.)
300°C
400°C
500°C
600°C
Combustion Temperatures
x 10-3
Heat Treatment Temperature (°C)
0
2
4
6
0 10 20 30
Emis
sio
n In
ten
sity
(a.
u.)
Yttrium Atomic %
YGGAG
YGAG
x 10-3
PL Emission Intensity Maximized
at 10% Y3+ Concentration
550
555
560
565
570
575
580
0 10 20 30
Emis
sio
n W
avel
en
gth
(n
m)
Gallium Atomic %
YGGAG
GGAG
Emission Wavelength Blue Shifts
With Increasing Ga3+ Concentration
Scanning electron microscope (SEM) images of material