The Eu3+ charge transfer energy and the relation with the band gap of compounds

Electronic structure and optical properties of the lanthanide activated RE3(Al1−xGax)5O12 (RE=Gd, Y, Lu) garnet compounds

Phosphor yttrium aluminum garnet Y3Al5O12 (YAG), activated with trivalent cerium (Ce3+) was synthesized by different methods: solid-state reaction (SS), co-precipitation (CP) with ammonium bicarbonate, sol–gel (SG) with citric acid and combustion (CB) with urea. The crystallization, morphologies, particle size and luminescent character of the phosphors obtained under different experimental conditions were studied. The influences of various factors on the luminescence intensity of the phosphor were investigated, such as sintering time, repeated calcinations, reaction temperature, and quantities of urea used in CB.

Comparative investigation on synthesis and photoluminescence of YAG:Ce phosphor

Transparent polycrystalline Nd:YAG ceramics were fabricated by solid-state reactive sintering a mixture of commercial Al2O3, Y2O3, and Nd2O3 powders. The powders were mixed in methanol and doped with 0.5 wt% tetraethoxysilane (TEOS), dried, and pressed. Pressed samples were sintered from 1700° to 1850°C in vacuum without calcination. Transparent fully dense samples with average grain sizes of ∼50 μm were obtained at 1800°C for all Nd2O3 levels studied (0, 1, 3, and 5 at.%). The sintering temperature was little affected by Nd concentration, but SiO2 doping lowered the sintering temperature by ∼100°C. Abnormal grain growth was frequently observed in samples sintered at 1850°C. The Nd concentration was determined by energy-dispersive spectroscopy to be uniform throughout the samples. The in-line transmittance was >80% in the 350–900 nm range regardless of the Nd concentration. The best 1 at.% Nd:YAG ceramics (2 mm thick) achieved 84% transmittance, which is equivalent to 0.9 at.% Nd:YAG single crystals grown by the Czochralski method.

Xian-Bi Yang

Papers

Synthesis of Y3Al5O12:Eu3+ phosphor by sol-gel method and its luminescence behavior