On the optical properties of gallium based garnet phosphors according to Ca2Ln1-xCexZr2Ga3O12 (with Ln = Y, La, Gd, Lu)

Abstract

Several samples of a gallium based garnet phosphor activated by cerium were investigated and reported upon in this work. Firstly, a solid solution corresponding to Ca2Lu1-xCexZr2Ga3O12 (x = 0.001–0.1), in which a doping level of 1 atom-% was revealed as the optimal activator concentration for high efficiency. Secondly, a range of samples according to the general composition Ca2(Y,La,Gd,Lu)0.99Ce0.01Zr2Ga3O12 was investigated to study the effect of different non emitting lanthanide ions on the optical properties. For this work various polycrystalline samples were synthesized and investigated by X-ray powder diffraction to determine the phase purity of the prepared samples. Fluorescence properties were examined employing excitation, emission, and diffuse reflectance spectroscopy. Temperature dependent emission spectra and fluorescent lifetimes were investigated to gain insight into the thermal quenching behaviour. From the spectroscopic investigation it was confirmed that the crystal field splitting of the cerium 5di components is strongly influenced by the size of the non-emitting lanthanide ion and the molar concentration of cerium. The change in crystal field splitting consequently shaped the excitation and emission wavelengths. Additionally, T1/2 values were determined from temperature dependent emission spectra and found to be between 230 and 250 K. Furthermore, luminescent lifetimes were calculated from pulsed laser excited decay curves. On the basis of the spectroscopy results potential applications of these phosphors are discussed.