The research on electroluminescence based on europium(Ⅲ) complexes has come to an important phase. This article reviewed the progresses in photoluminescence and electroluminescence of Eu(Ⅲ) complexes in recent years from the views of the design of Eu(Ⅲ) com-plexes and optimization of device structures,and discussed some important factors influencing electroluminescence performance. The prob-lems existing in the practical application such as the volatility and thermal stability of Eu(Ⅲ) complexes in this area were discussed,and the possible corresponding solutions were briefly prospected.
The phosphor Y2SiO5:Ce3+ was prepared by a sol-gel method and the particle growth process was investigated by XRD, SEM and TEM. After heating at 400 °C, the as-dried gel became a powder composed of mixed phases of polycrystalline Y2O3 and amorphous SiO2. With an increase in temperature, the crystallinity of Y2O3 improved. The sample quickly changed to the pure Y2SiO5 phase when it was heated at 1400 °C for 10 min. SEM indicated that the as-dried gel consisted of large porous particles. At an annealing temperature of higher than 400 °C, the pores in the large particles gradually expanded and grains started to appear. Consequently, the large particles disintegrated into small particles. When the sample was heated at 1400 °C, we obtained fine phosphor particles (around 2 μm) with smooth surfaces. The optimized condition for the preparation of the Y2SiO5:Ce3+ phosphor was to heat at 1400 °C for 2 h.
Amorphous phosphor 1.4Y2O3·2.5Al2O3·0.1Tb2O3 (the same composition as Y2.8Tb0.2Al5O12) was prepared via a sol-gel method at relatively low temperature (i.e., below 650 °C), which is much lower than that for the preparation of polycrystalline Y3Al5O12:Tb3+ (above 1400 °C). The amorphous phosphor prepared in the optimized conditions showed a bright green-yellowish luminescence, the intensity of which was comparable with that of polycrystalline sample and the emissions of which were assigned to 5D4 → 7Fj transitions of Tb3+. Besides the emissions of Tb3+, the amorphous samples prepared at temperatures below 500 °C presented a weak blue emission band around 420 nm.
