Micro and Nanocrystalline LuPO4(Ln3+: Nd, Pr) - Morphology, Luminescence and Inter-ionic Interplays

The effect of dopants (Nd3+, Pr3+) introduced into micro and nanocrystals of LuPO4 on their structural, morphological, and luminescent properties has been examined. The tetragonal structure of the synthesized phosphates was confirmed by means of an X-ray diffraction study. Transmission electron microscopy of LuPO4 samples doped with 0–2% Pr3+ and 0–3% Nd3+ obtained by the microwave hydrothermal method showed the formation of the nanocrystalline samples with a size of 40–90 nm. Spectroscopic study of Lu1-x-yPrxNdyPO4 micro and nanocrystals showed that effective energy transfer occurs between the selected optically active ions. Due to significant ion–ion interactions in the co-doped orthophosphates, the contribution of nonradiative processes to the relaxation of the luminescent levels of praseodymium and neodymium effectively increases. The energy transfer in the micro and nanocrystals Lu1-x-yPrxNdyPO4 from Pr3+ ions to Nd3+ ions results in the efficient near-infrared emission in the region of the spectrum between 1064 and 1350 nm, whereas for Lu1-x-yPrxNdyPO4 nanocrystals doped with Pr3+ and Nd3+ ions, a particularly intense Nd3+ luminescence appears at 1064 nm. There is a significant impact of concentration of the Pr3+ and Nd3+ ions on near-infrared luminescence intensity of the studied Lu1-x-yPrxNdyPO4 phosphates. The relaxation dynamic of the neodymium metastable excited state is substantially sensitive to a variety of praseodymium admixtures, and inversely, the experimental lifetime of 1D2 Pr3+ emission level gradually decreases with increasing Nd3+ concentration.