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Chemical conditions for thorium phosphate gel preparation have been determined. The transparency is of good optical
quality and the gel is very stable for a long time. Under drying condition, this gel can give rise to the xerogel which is still
transparent. We can also prepare this xerogel by simple evaporation at room temperature of a very concentrated solution of
thorium phosphate. From this viscous medium, the xerogel can be obtained in various kinds of shapes : threads, slabs and
blocks. Solidification time depends on the final volume desired and spreads from few minutes to several weeks. Absorption
spectrum of pure gel and xerogel have been recorded. Gel and xerogel doped with very well known probes like Nd3 and Er3+
were examined to compare their optical properties with aqueous medium of the same chemical composition. Eu3+ doped gel
and xerogel were also studied using their fluorescence properties.
The optical properties of Cr3 in doped gel and xerogel allowed us to determine the kinetics of hydration sphere
modification during the drying period. Finally, as xerogel synthesis takes place at room temperature, fragile organic dye can
be used as dopant, so Rhodamine 60 absorption and emission spectra have been studied in these conditions.When, at that
time, the xerogel is doped with Coumarin 460 and Th3+,an energy transfer is observed between dye and Th3+ ions, which
contributes to enhance the fluorescence of Th3+ ions. Eu3+ behaves similarly. In conclusion, gel and xerogel of thorium phosphate tested with usual probes such as 3d, 4f ions and dyes seem to be
very promissing matrices.
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