Synthesis and photoluminescence of nanocrystalline lutetium pyrosilicate doped with Ce3+

The nanocrystalline Lu2Si2O7:Ce3+ (LPS:Ce) phosphor was obtained as a result of a solid state reaction at 1250 degrees C of LU2O3 and SiO2. Compared to the monocrystals grown by the Czochralski method (below 0.5%) the procedure of the synthesis allows much higher level of the activator doping (5%). Two samples, one in air (LPS:Ce-O) and the second one in N-2/H-2 atmosphere (LPS:Ce-R) were synthesized for comparison. X-ray diffraction analysis confirmed crystallization of a single phase of LPS in the indicated temperature. The UV excited optical luminescence spectrum of LPS:Ce-O at 10 K consists of two wide bands centered at 380 and 407 nm. The positions of the bands and the decay time of 35 ns characteristic for the parity allowed 5d-4f fast emission of the Ce3+ ion. The overlap between a self-trapped (STE) emission of the host (between 320 and 470 nm) and 4f-5d absorption of Ce3+ (centered at 350 nm) allows the energy transfer, which explains the scintillation efficiency of LPS:Ce. Two luminescence mechanisms were detected for the LPS:Ce-R sample. The decay times of 30 ns and 200 mu s cannot have the same origin. as they defer too much. According to the tentative explanation the fast emission is a result of the 5d-4f transition of Ce3+ and the slow component of the Ce4+ charge transfer luminescence associated with defects caused by reducing atmosphere. (C) 2008 Elsevier B.V. All rights reserved.