Abstract
Sol-gel method has been successfully used for preparation of Ce-doped yttrium (YPS) and lutetium (LPS) pyrosilicates in powder form and of composite materials (REPS:Ce)0.1-(SiO2)0.9, RE=Y,Lu. XRD measurements showed that the crystallization of YPS take the place at 1100oC in the case of pure powder sample while, in the case of nanocomposites, it is shifted to the range of 1200-1300oC.
Moreover, in the latter case, it is accompanied by simultaneous crystallization of SiO2 matrix leading to non-transparent samples. TEM images of (REPS:Ce)0.1-(SiO2)0.9, RE=Y,Lu revealed the regular round shapes nanoparticles in the silica matrix.
Its average size increases with the temperature of heat treatment from 30 nm (heat treated at 1100oC) to 100 nm (heat-treated at 1300oC). Luminescence spectra of powder YPS:Ce were found low energy shifted in comparison to the single crystal analogue which might be due to extensive perturbation of Ce3+ centers by the grain surface and structural flaws.
LPS:Ce emission characteristics showed to be closer to the bulk single crystal. Photo- and radioluminescence spectra of YPS:Ce and LPS:Ce crystallized nanophase in SiO2 host appeared very similar to their bulk single crystal analogs.
Slightly shortened Ce3+ decay times in REPS:Ce/SiO2 can indicate the effect of small size of REPS:Ce nanospheres and different refractive index of surrounding medium.