Photoluminescence Properties of Eu[sup 3+]-Activated Y[sub 2]GeO[sub 5] Phosphors

Abstract

The luminescence and energy transfer properties of Eu 3ϩ in Y 2 GeO 5 have been investigated. The critical concentration at which the concentration quenching occurred under UV excitation were x ϭ 0.4 in (Y 1Ϫx Eu x ) 2 GeO 5 . To investigate the distinction of photoluminescence behavior of two transitions ͑i.e., 5 D 0 → 7 F 1 and 5 D 0 → 7 F 2 transition͒ for the Eu 3ϩ ion, the decay curves for both 5 D 0 → 7 F 1 and 5 D 0 → 7 F 2 transition have been analyzed. Furthermore the energy migration process of this sample was investigated using Yokota and Tanimoto's formula based on diffusion limited quenching.The (Y 2 O 3 -GeO 2 ) phosphor has recently found an oxide phosphor as a phosphor material for the emitting layer of thin-film electroluminescent ͑TFEL͒ devices. 1,2 Because of high luminous efficiency, (Y 2 O 3 -GeO 2 ):Mn phosphor has been studied as a promising material for TFEL displays as well as plasma display panels and field emission displays. 3 In this view, it seems interesting to study the luminescence of some rare earths in the (Y 2 O 3 -GeO 2 ). Among them, the Eu 3ϩ ion has attracted great attraction due to the application as red phosphors. [4][5][6][7] In this work, we prepared Eu 3ϩ -activated Y 2 GeO 5 phosphor by conventional solid-state reaction and found that this phosphor has a very high critical concentration. Dexter and Schulman, 8 have described that the concentration quenching of the activator is related to cross relaxation and/or energy migration to quenching sites. These phenomena can be due to electromagnetic multipolar interaction or exchange interaction. To obtain insight into the mechanism responsible for the concentration quenching of the Eu 3ϩ emission in this case, we have investigated Y 2 GeO 5 :Eu phosphor over a wide concentration range. ExperimentalThe powder samples with the general formula (Y 1Ϫx Eu x ) 2 GeO 5 were prepared by the solid-state reaction method. The starting materials used in the preparation of this phosphor were powders of greater purity than 99.99% of Y 2 O 3 , GeO 2 , and Eu 2 O 3 . Preweighed powders were mixed thoroughly in acetone in an agate mortar and dried at 130°C for about 24 h to drive off the solvent and successively heat-treated at several conditions of temperature and duration time, followed by an additional grinding and firing in nitrogen atmosphere. The resulting powders were identified using an X-ray diffraction ͑XRD͒ system with Cu K␣ radiation ͑Ni filter͒. Here, only samples heat-treated at 1500°C for 3 h have been considered.The excitation and emission spectra of the fired samples were measured using a Perkin-Elmer LS-50 luminescence spectrometer with a xenon flash lamp (⌬v 1/2 ϭ 10 s). The decay measurement was performed at 594 nm emission for 5 D 0 → 7 F 1 transition and 611 nm emission for 5 D 0 → 7 F 2 transition, respectively. The pumping source was 254 nm and the pulse duration was 6 ns. Results and DiscussionIn the XRD patterns of the Y 2 GeO 5 powders heat-treated with different amounts of Eu 3ϩ , most peaks correspond to the Y 2 ...

Structural differences in the luminescence properties of lanthanide doped orthorhombic and monoclinic phases of Y2GeO5

“…The value is $3.0 for both of the samples (there may be some uncertainty in this value for the orthorhombic phase because of severe overlapping of the peaks attributable to the 5 D 0 / 7 F 2 and 5 D 0 / 7 F 1 transitions). The emission spectrum obtained for the monoclinic sample in the present study is comparable to that observed by Park et al, 11 for 0.007 mol% Eu 3+ doped monoclinic Y 2 GeO 5 . It is worth noting that the intensity of the electric dipole transition, 5 D 0 / 7 F 4 , is signicantly higher for the orthorhombic phase compared to the monoclinic phase, suggesting a higher electric dipole transition probability in the orthorhombic phase.…”

“…The former is attributed to Eu 3+ ions in the bulk, while the latter is assigned to Eu 3+ ions present in the grain boundaries of the particles. The decay proles and lifetime values for the monoclinic sample are similar to those reported by Park et al 11 The sample heated at 1400 C (monoclinic form) has a higher extent of grain boundaries in comparison to the sample heated at 900 C. At the grain boundaries, the environment around the Eu 3+ ions is highly distorted leading to poor luminescence and an associated decrease in the lifetime values. Interestingly, the 5 D 0 lifetime value is higher (almost double) for the orthorhombic phase compared to the monoclinic form.…”

“…Zhao et al 8 and Ma et al 10 prepared bulk monoclinic Y 2 GeO 5 doped with different concentrations of various lanthanide ions and generated primary as well as white colors. Park et al 11 have investigated the luminescence and energy transfer properties of Eu 3+ doped monoclinic Y 2 GeO 5 and observed the differences in the decay proles of 5 D 0 / 7 F 1 and 5 D 0 / 7 F 2 transitions from Y 2 GeO 5 :Eu.…”

Synthesis and Characterization of Eu-Metallofullerenes from Eu@C74 to Eu@C90 and Their Nanopeapods

“…The Eu ion is well-known for its “europium red” luminescence at approximately 613 nm based on the 4f energy levels. A series of compounds activated by Eu ion have been studied for practical application as phosphors and materials. , The interaction between the Eu ion and carbon cages might influence the spectrum and lead to a new matrix of luminescence. If europium metallofullerenes were inserted into the nanotubes, which can be seen as a new one-dimensional host material, some promising applications might be opened compared to the conventional Eu ion in its glassy or crystalline hosts.…”