Abstract
Amorphous nanophosphors have been obtained for the first time by pulsed electron beam evaporation of targets from bulk polycrystalline phosphors of the composition Sr2Gd8(SiO4)6O2: Eu with oxyapatite structure. The processes of crystallization of amorphous nanopowder were studied using differential scanning calorimetry and termogravimetry (40−1400°C). It was found that the Raman spectra of the samples are modified when the particles decrease from bulk to nanodimensional state. The spectral and luminescent characteristics of the phosphors in polycrystalline and nanoamorphous states have been examined. It was established that Eu3+ forms two types of optical centers. Unlike bulk phosphors, in the nanophosphors no Eu2+ ions are formed. The ratio of red to orange luminescence intensity for nanophosphors was found to increase as compared with bulk phosphors. This effect is due to disordering of nanoparticles. A resonant transfer of excitation energy from Gd3+ to Eu3+ ions was found in bulk and nanophosphors. Upon transition from polycrystalline to nanoamorphous state and laser excitation of phosphors, the luminescence intensity of Eu3+ ions increases approximately 10 times. This effect is explained in the framework of the configuration coordinates model.
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