SPECTRA AND DYNAMICS OF MONOCLINIC EU2O3 AND EU3+Y2O3 NANOCRYSTALS

This paper reports site-selective excitation and fluorescence spectros copy of monoclinic Eu2O3 and Eu3+:Y2O3 nanocrystals, 14 and 23 nm aver age diameter, respectively. The nanocrystals were prepared by gas-phas e condensation using CO2 laser heating of ceramic pellets. The nanocry stals form in the monoclinic phase, and the spectra show three sets of spectral lines due to the three cation sites in this crystal structur e. Samples prepared from 0.1% Eu3+:Y2O3 starting material contained on ly Eu3+:Y2O3, and samples prepared from starting material of 0.7% or h igher contained Eu3+:Y2O3 and Eu2O3 phases. In 0.1% Eu3+:Y2O3 energy t ransfer occurs from site A to sites B and C, but no interaction is obs erved between sites B and C. Energy transfer occurs between ail sites for Eu3+ concentration of 0.7% and higher. The D-5(0) fluorescence lif etimes for sites A, B, and C in 0.1% Eu3+:Y2O3 are 1.75, 1.23, and 1.3 2 ms, respectively, as compared to a radiative lifetimes of the C-2 si te in cubic Eu3+:Y2O3 of 1.1 ms.