Temperature Dependent Fluorescence of Nanocrystalline Ce-doped Garnets for Use as Thermographic Phosphors

Four samples of (Y1-xCex)(3)(Al1-y Ga-y)(5)O-12 (where x=0.01, 0.02 and y=0, 0.5) were synthesized via the simple, efficient combustion synthesis method in order to determine the effect of substituting Ga3+ for Al3+ on the temperature-dependent fluorescent lifetime. X-ray diffraction shows that the Ga-doped samples have longer lattice constants and transmission electron microscopy data show that each sample consists of nanocrystallites which have agglomerated in micron-sized particles. Photoluminescence data reveal that the addition of gallium into the YAG:Ce matrix induces a red shift in the absorption spectra and a blue-shift in the emission spectra. The laser-induced fluorescent lifetime was determined as a function of temperature over the range of 0-125 degrees C using two different emission filters. Increasing the amount of dopant ultimately results in a decrease of the fluorescent lifetime. The quenching temperatures for the Ga-doped samples were lower than the samples without gallium. The results of this work show that combustion synthesis is viable method for making highly luminescent, nanocrystalline TGPs. In addition, these results show that the quenching temperature of YAG:Ce can be altered by substituting ions which alter the location of the charge transfer state and by changing the morphology of the sample.