Nanocrystalline Y₂O₃:Eu powder was synthesized via chemical vapor reaction. X-ray diffraction revealed the structure of cubic yttria with crystallite sizes of about 5 nm. The Eu-dopand concentrations for the samples were determined by EDX-spectra and resulted in values in the range from 0.3% up to 16.5%.

Luminescence of the nanopowders was investigated by continuous and timeresolved UV fluorescence spectroscopy and compared to a microcrystalline Y₂O₃:Eu phosphor as a reference. Emission spectra show increasing intensity for higher doping concentrations. Compared to the microcrystalline material, however, the yield was significantly lower. The lifetime τ of the ⁵D₀→⁷F_J transition in the nanocrystalline Y₂O₃:Eu was strongly enhanced in the lowest doped sample (3.71 ms for the 611 nm line) compared to the microcrystalline reference (1.07 ms). By increasing the Eu-content the lifetime τ decreased until reaching a value of 1.20 ms for the highest doping concentration.

The concentration dependent lifetime behaviour was interpreted by energy transfer between Eu ions among each other and between Eu ions and impurities as a competing process to the radiating ⁵D₀→⁷F_J transition.

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