Luminescence of Eu3+/Gd3+ co-doped silicate sol-gel powders

Eu3+/Gd3+ co-doped silicate sol-gel powders have been successfully obtained. The effect of high concentration of gadolinium ions on visible emission of europium ions in prepared materials has been studied under different excitation wavelengths. Spectroscopic properties of Eu3+ and Gd3+ ions in prepared powders were determined based on excitation and emission measurements as well as luminescence decay analysis. In the visible spectral range the observed emission bands correspond to transitions of trivalent Eu3+ and Gd3+ ions. The changes of excitation mechanism of optically active dopants significantly affect the increase of luminescence intensities. The luminescence lifetime for the 5D0 level of Eu3+ ions in examined samples upon excitation at λexc=273 nm (8S7/2→6IJ transition of Gd3+) is about 12 times longer in comparison to excitation at λexc=393 nm (7F0→5L6 transition of Eu3+). The luminescence intensity coefficient R (Eu3+) was also calculated, and it was found that ratio of the intensity of red to orange emission depends on the excitation wavelength. Based on determined spectroscopic parameters the energy transfer process from Gd3+ to Eu3+ ions was confirmed.