RESUMO
Simple hydrothermal method can be applied for synthesizing rod shape Gd2O3:Eu3+ phosphors. X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy are used for the characterizations of samples. Increase of Eu3+ concentration in Gd2O3:Eu3+ can cause red shift in the charge transfer band (CTB) of Eu - O. The nature of Eu3+ surroundings is asymmetric. It is ascertained from PL emission studies. The calculation of second order crystal field parameter from PL spectra corroborates the asymmetric environment of Eu3+. PL emission and decay lifetime studies confirm the existence of quenching due cross-relaxation. The quantum yield for Y2O3:Eu3+ (19 at.%) under 265 nm excitation is found to be 7%.
RESUMO
A multicolor tunable CaWO4:xDy3+ nanophosphors have been synthesized via hydrothermal route. X-Ray Diffraction and Fourier transform infrared confirm the formation of CaWO4:Dy3+ nanophosphors. Transmission electron microscopy image and selected area electron diffraction (SAED) reveal the formation of nanosize and crystalline CaWO4:Dy3+. Dependence of energy transfer rate from WO42- to the activator (Dy3+) is observed from the photoluminescence studies. An enhancement of energy transfer efficiency from 36% to 90% is observed after annealing the as-prepared samples at 800 °C. The exchange type energy transfer mechanism is observed to be dominant in as-prepared samples while the electric dipole-dipole interaction is dominant in annealed samples. Variation in energy transfer rate from the host to Dy3+ activator ions leads to the tuning of color emission from this nanophosphor. A near white light emission could be achieved with 6 at.% Dy3+ doped CaWO4 annealed at 800 °C with x = 0.310 and y = 0.327.