Max PL Grain Size Max PL Grain Size Max PL Grain Size 1100 2 hrs 1100 4.5 hrs 1100 14 hrs 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 Emission Intensity Grain Size (nm) 800 900 1000 1100 Intensity (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 Panu 1 , Courtney A. Mitchell 1 , Sarah L. Gollub 2 , Bridget R. Rogers 1 , Greg Walker 3 1 Vanderbilt University Department of Chemical and Biomolecular Engineering 2 Vanderbilt University Interdisciplinary Material Science Program 3 Vanderbilt 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 [Y 3x Gd 3(1-x) Ga 5x Al 5(1-x) O 12 ] GGAG [Gd 3 Ga 5x Al 5(1-x) O 12 ] YGAG [Y 3x Gd 3(1-x) Al 5 O 12 ] Particle Morphology GAG GGAG YGAG YGGAG Scherrer’s Equation = Grain sizes can be estimated using the following: Garnet 1 (GAG) Gd 3 Al 5 O 12 Perovskite 2 (GAP) GdAlO 3 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 Intensity (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 Emission Intensity (a.u.) Yttrium Atomic % YGGAG YGAG x 10 -3 PL Emission Intensity Maximized at 10% Y 3+ Concentration 550 555 560 565 570 575 580 0 10 20 30 Emission Wavelength (nm) Gallium Atomic % YGGAG GGAG Emission Wavelength Blue Shifts With Increasing Ga 3+ Concentration Scanning electron microscope (SEM) images of material