HYDRATED RARE-EARTH-METAL ION-EXCHANGED ZEOLITE-A - CHARACTERIZATION BY LUMINESCENCE SPECTROSCOPY .2. THE EU-3+ ION

The luminescence properties of hydrated Eu3+-exchanged zeolite A at 4.2 K are reported. The luminescence spectra indicate that the Eu3+ ions in the zeolite cages are, unlike Eu3+ ions in hydrated zeolite Y, bound to framework oxygens. High-resolution measurements suggest that Eu3+ ions are located in two sites in the zeolite samples. The results confirm the conclusions from a previous study on the equivalent Gd3+-exchanged system. Information on the water coordination numbers of the Eu3+ ions in the zeolite samples is obtained from luminescence lifetime measurements on H2O- and D2O-containing samples. The possibility of using luminescence spectroscopy of Eu3+ to characterize the coordination of rare-earth-metal ions in zeolites is evaluated.