Hydrated rare-earth-metal ion-exchanged zeolite a : characterization by luminescence spectroscopy. Part 1.—The Gd3+ ion

Abstract

The luminescence properties under high-resolution excitation and emission conditions at 4.2 K of hydrated Gd³⁺ion-exchanged zeolite A are reported. From these luminescence measurements it is found that in a sample containing 0.8 wt.% Gd³⁺, only one site appears to be occupied by Gd³⁺. In a freshly prepared sample containing 5 wt.% Gd³⁺ one site inside the zeolite is occupied by Gd³⁺. Other Gd³⁺ ions appear on silica surfaces present in the sample. When measurements on this sample were repeated a few months after preparation, Gd³⁺ ions were found in three sites within the zeolite cages. Information on the surroundings of the Gd³⁺ ions in the different sites was obtained from the emission spectra. In this way the possibility of characterizing the coordination of rare-earth-metal ions in zeolites by luminescence spectroscopy was evaluated.