Abstract
Nanosized Eu/γ- and/or η-Al2O3 ([Eu2О3] = 0.00, 0.02, 0.45 and 0.92 wt%) powders with the particle size from <10 nm to 21 nm synthesized by cw CO2 laser vaporization were studied. It was shown that photoluminescence (PL) properties of the obtained samples are caused by luminescence of the Eu3+ and Eu2+ ions incorporated to the Al2O3 matrix in crystallographic positions with the C3v local symmetry. A scheme based on the formation of Eu2+ ions in the Al2O3 lattice via the charge compensation by oxygen vacancies (F centers) located in the first coordination sphere of europium was proposed. The influence of size effects on PL of Eu/Al2O3 nanoparticles consists first of all in shortening the lifetime of 4f – 4f transitions in Eu3+ ions as a result of increased probability of nonradiative relaxation owing to OH groups and various structural defects. It was found that the conditions of laser vaporization (gas composition and pressure) can change the structure of the resulting Eu/Al2O3 nanoparticles.
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