Investigations on Valence-Change Behaviors of Europium Ions in Eu-Doped Aluminate and Silicate Phosphors

摘要

Compounds of Sr3Al2O6∶Eu, Sr4Al 14 O 25 ∶Eu, and BaZnSiO4∶Eu were synthesized by high-temperature solid state reactions. The doping Eu 3+ ions were partially reduced to Eu 2+ in Sr4Al 14 O 25 ∶Eu and BaZnSiO4∶Eu prepared in an oxidizing atmosphere, N2+O2. However, such an abnormal reduction process could not be performed in Sr3Al2O6∶Eu, which was also prepared in an atmosphere of N2+O2. Moreover, even though Sr3Al2O6∶Eu was synthesized in a reducing condition CO, only part of the Eu 3+ ions was reduced to Eu 2+ . The existence of trivalent and divalent europium ions was confirmed by photoluminescent spectra. The different valence-change behaviors of europium ions in the hosts were attributed to the difference in host crystal structures. The higher the crystal structure stiffness, the easier the reduction process from Eu 3+ to Eu 2+ .