SÍNTESIS DE PELÍCULAS Y POLVOS LUMINISCENTES DE ÓXIDO DE ITRIO IMPURIFICADO CON TIERRAS RARAS

Abstract

In this work the photoluminescent, cathodoluminescent and structural properties of Y2O3 thin films and powders deposited by spray pyrolysis and coprecipitation method respectively are reported. The luminescent films were obtained from Y (acac)3 dissolved in N,N-DMF at a concentration of [0.06M] for Y2O3: Eu3+ films and of [0.03M] for Y2O3:Tb3+ films. The films were deposited on crystalline Si (100) substrates at temperatures in the range from 400 to 550 ºC. For luminescent powders, the Y (NO)3 was used as precursor of Y2O3. It was dissolved in CH3OH at a concentration of [0.5M]. These powders were synthesized at temperature range of 500 to 1100ºC. The most important synthesis parameters are the reaction temperature and activator ion concentration. The luminescent properties are obtained by means of photoluminescence and cathodoluminescence. The excitation spectra of the phosphors presented: in the case of Y2O3: Eu3+ a band at 256nm attributed to a transition of charge transfer and other peaks narrow and small located at 365, 384 and 395nm corresponding 7F0 → 5D4, 7F0 → 5G3, y 7F0 → 5L6 of Eu3+. The phosphor Y2O3:Tb3+ + present a band at 308nm which corresponds to transitions of charge transfer, while the phosphor Y2O3: Pr3+ is excited with radiation of wavelength (λ) of 284nm due to the transition interconfiguracional 4 f 2 → 4 f 1d1. The emission spectra of Y2O3: Eu3+ show 4 peaks located at 537, 593, 611 and 651nm corresponding to the transitions 5D1 → 7F1, 5D0 → 7F1, 5D0 → 7F2 y 5D0 → 7F3 of Eu 3+. The most intense band was at 611nm (5D0 → 7F2) corresponding to redorange. The phosphor Y2O3:Tb3++ also showed four bands centered at 489, 547, 586 and 623nm, these were due to electronic transitions 5D4 → 7F6, 5D4 → 7F5, 5D4 → 7F4 y 5D4 → 7F3 respectively, within of Tb3 + ion. The most intense band was at 547nm (5D4 → 7F5) corresponding to the green color. The phosphor Y2O3: Pr3+ has 2 bands in the visible region: one centered at 620 and 630nm the second centered at 722 and 742nm and a band in the near infrared region centered at 823nm. These bands correspond to transitions 1D2 → 3H4, 1D2 → 3H5 y1D2 → 3H6 respectively, which are attributed to 4f 2 electron transitions intraconfigurational of Pr3+ions excited via 4f 15d1 configuration. Being the most intense wavelength at 620nm (1D2 → 3H4) corresponding to red-orange. The atomic percentages of Eu 3 + ions, Tb 3 + and Pr 3 + ions present in the host lattice that giving rise to the luminescence are 1.13a/o, 2.13a/o y 0.20a/o respectively according to the results of EDS and the O/Y atomic stoichiometric ratio of the three phosphors approaches the ideal value of 1.5 in both parameters, the variation of the impurity concentration as in the variation of temperature. The measures X-ray diffraction revealed that films and powders phosphors have a host lattice with cubic polycrystalline structure. In the case of phosphor Y2O3: Eu3+ this structure has preferred orientation (622). From infrared spectroscopy measures shows that the films and powders have bonds O-Y, confirming the presence of Y2O3. The films are flat with an average roughness of 20 nm as result of the atomic force microscopy. This high planarity with a high transmittance (> 80%) in the UV-Visible region will do these films have the possibility to be applied in electroluminescent devices. The synthesis of yttrium acetylacetonate used as a precursor to obtain Y2O3 host lattice as well as the synthesis of europium acetylacetonate and terbium acetylacetonate used as activators in Y2O3 host lattice are also presented. These synthesis are supported with their IR, NMR and MS spectra