Enhanced photoemission in dispersed Eu2O3nanoparticles in amorphous Al2O3

Abstract

Dispersed Eu₂O₃ nanoparticles in amorphous Al₂O₃ have a strong photoemission in the visible 560 to 720 nm region of the electromagnetic spectrum. Four distinct bandgroups occur with the most intense band in the spectrum at ∼666 nm (contributing as much as 50% integrated intensity I_t in the four bands). The I_t value varies in a nonlinear function with Eu³⁺ concentration, with a maximum value at 1.0 wt% Eu³⁺, which is as much as 25 times that of other samples in this series. The four bandgroups lie at 587.0, 619.0, 665.5 and 702.0 nm in the spectrum of the 1.0 wt% Eu³⁺–Al₂O₃ sample and arise from ⁵D₀ → ⁷F_J (J = 1 to 4) electronic transitions, respectively, in Eu³⁺(4f⁶) cations. The average position of the 666 nm band does not change significantly with Eu³⁺ content, in the 0.5 to 1.5 wt% range, while the maxima of the other bands vary in a complex manner. It seems that different electron–phonon coupling processes or Eu³⁺–Eu³⁺ interactions operate in the different ⁵D₀ → ⁷F_J transitions which accounts for their different nonlinear spectral responses with Eu³⁺ concentration. The results are analyzed and discussed in correlation with the microstructure.