A combinatorial approach has been used to generate solid state thin-film of different garnet structures (A1-xBx)3-z(C1-y,Dy)5O12:Ce3+z (called libraries), where A, B = Y, Gd, Lu, La; C, D = Al, Ga, Sc; x and y = 0 to 1.0; and z = 0.03. X-ray diffraction was used to select library samples of the crystalline garnet phase. Combinatorial chemistry methods were used as a tool to rapidly synthesize and screen potential inorganic phosphors for use as blue to yellow conversion phosphors in white LEDs. Libraries of these various garnets were then characterized spectroscopically. Emission and excitation trends are reported for various libraries and were found to reproduce previous trends in literature. Lattice constants, chromaticity, and PL intensity are also examined as a function of the different compositions. Emission and excitation trends reveal that as larger cations are substituted for the Y (dodecahedral) site in YAG, emission and excitation are red-shifted and as larger cations are substituted for the Al (octahedral and tetrahedral) site, emission and excitation are blue-shifted. If smaller ions are substituted for those respective sites an opposite trend is observed.
|