Study of the structure and optical properties of rare-earth-doped aluminate particles prepared by an amorphous citrate sol-gel process

Calcium aluminate, doped with neodymium and europium ions, was prepared by a citrate polymeric precursor sol-gel method. The influence of the synthesis mixture composition and the thermal treatment parameters on the structure, morphology and optical properties of the material were investigated by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, diffuse reflectance, emission and excitation spectroscopy. The amount of organic component in the precursor had an effect on the crystal structure and the morphology of the material particles. The thermal treatment had no direct influence on the optical properties of material. Polymeric precursors treated at 1000 °C gave white aluminate powder, with absorption bands due to the rare earth ions and the host levels. Luminescence from the Eu3+ ion levels gave emission spectra with sharp peak at 611 nm and color purity. Energy transfer was observed from the excited state of the host to the Eu3+ ion levels.