Abstract
Nanoparticles of Dy3+ and Eu3+ doped YVO4 (core) have been prepared by urea-hydrolysis in ethylene glycol medium and further heated at 500 and 900 °C to grow particles as well as remove unwanted hydrocarbon/H2O, which acts as quencher in luminescence. Samples show emission peaks at 488 (blue), 537 (green), 572 (yellow), 592 (orange), and 617 nm (red). The emission intensity decreases when excitation wavelength changes from 300 [V–O charge transfer band (CTB)] to 255 nm (Eu/Dy–O CTB) and then to 355/395 nm (direct excitations of Dy3+/Eu3+). This is attributed to energy transfer from V–O to Eu3+/Dy3+, Eu/Dy–O to Eu3+/Dy3+. Energy transfer from Dy3+ to Eu3+ is more than that from Eu3+ to Dy3+. With heat-treatment temperature increases from 500 to 900 °C, emission intensity is improved due to the extent of decrease in nonraditive transition probability arising from surface. To the best of authors’ knowledge, local/site symmetry of Eu3+ and Dy3+ in same host is not detail discussed in literature. In the same host, asymmetric ratio of electric dipole allowed transition to magnetic dipole transition in both ions should be same but this was not happen. This study will give the origin of this. After covering core-nanoparticles with undoped YVO4 shell, luminescence intensity is further improved due to the extent of reduction in surface Eu3+/Dy3+ of particles and cross-relaxation reduction among Eu3+/Dy3+ ions.
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