Structural and spectroscopic properties of Eu3 +-activated nanocrystalline tetraphosphates loaded in silica-hafnia thin film

Nanoparticles of lithium lanthanum tetraphosphates doped with different concentration of Eu3+ ions were synthesized. The selected tetraphosphate was used to fabricate a transparent composite where nanocrystals were immobilized in a sol-gel-derived silica-hafnia amorphous film. The structural and spectroscopic properties of the systems were investigated by XRD analysis, Raman spectroscopy, and photoluminescence measurements. For all the samples with the Eu3+ ions concentration from 1 to 100 mol% the monoclinic structure with a space group C12/c1 was determined. The mean diameter of nanocrystals determined by Scherrer equation was in the range of 40-55 nm. The luminescence of 10%Eu3+:LiLa(PO3)4 in silica-hafnia matrix indicated the immobilization of Eu3+ ions into a distorted environment. The dependence of both luminescence intensity and lifetime on the Eu3+ concentration demonstrated effective reduction of concentration quenching in the tetraphosphate nanopowders.