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