S. Buddhudu

Fluorescence spectra of Eu3+:Ln2O2S (Ln = Y, La, Gd) powder phosphors

This paper reports the preparation and analysis of the photoluminescence spectra of Eu3+-doped lanthanide oxysulfide [Y2O2S, La2O2S, and Gd2O2 S]powder phosphors. These phosphors have displayed bright red color under a UV source. The richness of the red color has been verified by determining their color coordinates (X, Ȳ) from the CIE standard charts, and this red emission has been assigned to the transition [5D0 → 7F2]at 625 nm. Besides this stronger emission transition, four weaker fluorescent transitions have been observed, and for these the relative fluorescence intensity ratios (R) have been determined.

Optical properties of LnPO4:Eu3+ (Ln=Y, La and Gd) powder phosphors

Abstract The synthesis, single and dual host compositional effects on the fluorescence spectra of Eu3+-doped YPO 4 , LaPO 4 , GdPO 4 , ( La , Gd ) PO 4 , (La,Y)PO4 and (Gd,Y)PO4 powder phosphors are studied. From the fluorescence spectra the emission transition 5 D 0 → 7 F 1 has been found to be more prominent over the normal red emission transition ( 5 D 0 → 7 F 2 ) . Under a UV-source these phosphors have been fluorescent in orange–red color. The observed absorption frequencies (ν,cm−1) are reported from the measured FT-IR spectra. Scanning electron microscopic investigations are carried out to understand the surface morphological features and the grain size. The room temperature lifetime measurements are made for the two emission transitions ( 5 D 0 → 7 F 1,2 ) of all these phosphors. Qualitative analysis of the elements (Y, La, Gd, Eu, O and P) has been carried out by the SEM/EDAX technique.

Emission spectra of LnPO4:RE3+ (Ln=La, Gd; RE=Eu, Tb and Ce) powder phosphors

Abstract This paper reports the emission spectra at room temperature and presents an optimum concentration for each of the dopants in GdPO4:Eu3+, LaPO4:Tb3+ and LaPO4:Ce3+ powder phosphors for the observation of bright reddish-orange, green and UV emission, respectively. FT-IR and a thermal analysis of these phosphor materials have been carried out. Scanning electron microscopic investigations were also conducted to understand surface morphological features (shape) and the grain size in the powder phosphor systems.

Absorption and emission spectral studies of Sm3+ and Dy3+ doped alkali fluoroborate glasses

Absorption and photoluminescence spectra of Sm 3 + and Dy 3 + doped alkali fluoroborate glasses of the composition 90.5 B 2 O 3 + 4 AlF + 5 RF + 0.5 LnF 3 (R= Li, Na, K and Ln = Sm, Dy) are reported. On excitation, with 402 nm, the Sm 3 + glasses were found to be orange fluorescent in colour and richness of that colour was high in the Na + glass, compared to Li + and K + glasses. Similarly, on excitation with 398 nm, the Dy 3 + glasses were fluorescent yellow and that colour was richer in the K + glass.

Spectroscopic properties of Tb3+-doped fluoride glasses

Abstract In this paper, the preparation is reported of a new family of Tb-doped fluoride glasses with the following composition: 30BaF2 + 30InF3 + 10ThF4 + 9ZnF2 + 20RF (where RF = LiF, NaF and KF). These glasses have been used for a systematic study on the optical absorption, excitation and photoluminescence spectral properties from the near UV to the NIR. On the basis of the measured values of densities and refractive indices, the dielectric constant, reflection losses, molar-refraction, Tb3+ ion concentration in glasses, and several other physical properties were determined. From the measured absorption spectral intensities of five different states, the validity of the Judd-Ofelt model was examined in the evaluation of the intensities, transition probabilities, relaxation rates and radiative lifetime of the 5D4 luminescent level. The lifetime of the 5 D 4 → 7 F j fluorescence was examined at both 300 K and 77 K and it was found it compared well with the theoretical value. The effects of the alkali cation change on the induced emission cross-section, quantum efficiency and branching ratios of this luminescent level based on the measured and computed fluorescence lifetimes were also studied.

Optical properties of LnPO4 :Tb3+ (Ln = Y, La and Gd) powder phosphors

Abstract The synthesis and fluorescence properties of Tb3+-doped YPO4, LaPO4, GdPO4, (La,Gd)PO4, (La,Y)PO4 and (Gd,Y)PO4 powder phosphors are reported. Under UV-source these phosphors have been fluorescing in green color due to the emission transition ( 5 D 4 → 7 F 5 ). FT-IR absorption spectra of such samples were recorded. Scanning electron microscopy investigations were carried out to understand the surface morphological features and the grain size. The room-temperature lifetime measurements were made for the different emission transitions of these powder phosphors. X-ray energy dispersive analysis (EDAX) was also performed.

Spectra of Sm3 and Dy3: B2O3–P2O5–R2SO4 Glasses

Abstract This paper reports the production of both samarium and dysprosium glasses in the composition of 44.5B 2 O 3 + 44.5P 2 O 5 + 10R 2 SO 4 (where R = Li, Na, and K). For these optical glasses, physical, absorption, and photoluminescence spectral properties have been studied. On excitation with 402 nm, the Sm 3+ glasses were found to be orange fluorescent in color and the richness of that color was high in the K + glass, compared to the Li + and the Na + glasses. Similarly, on excitation with 398 nm, the Dy 3+ glasses were fluorescent yellow in color and that color was more rich in the K + glass.This paper reports the production of both samarium and dysprosium glasses in the composition of 44.5B{sub 2}O{sub 3} + 44.5P{sub 2}O{sub 5} + 10R{sub 2}SO{sub 4} (where R = Li, Na, and K). For these optical glasses, physical, absorption, and photoluminescence spectral properties have been studied. On excitation with 402 nm, the Sm{sup 3+} glasses were found to be orange fluorescent in color and the richness of that color was high in the K{sup +} glass, compared to the Li{sup +} and the Na{sup +} glasses. Similarly, on excitation with 398 nm, the Dy{sup 3+} glasses were fluorescent yellow in color and that color was more rich in the K{sup +} glass.

Fluorescence spectra of Sm3+-doped lanthanide oxychloride powder phosphors

Abstract The fluorescence properties of Sm 3+ -doped LaOCl, GdOCl, YOCl, (La, Gd)OCl, (La, Y)OCl and (Gd, Y)OCl powder phosphors are reported. The measured photoluminescence spectra have been analysed by determining their colour coordinates ( X , Y ), the relative fluorescence intensity ratios ( red orange ) and their stimulated emission cross sections ( σ P E ). These Sm 3+ -phosphors have displayed bright reddish-orange colour due to the transitions 4 G 5 2 → 6 H 9 2 (red) and 4 G 5 2 → 6 H 7 2 (orange) under a UV source (150 W xenon arc lamp). The LaOCl phosphor could be suggested as a promising material for the reddish-orange colour emission for its use on the screens of optical electronic systems.

Fluorescence spectra of (GD,Y)OCl: Eu(3+) powder phosphors

This paper describes the fluorescence properties of Eu(3+):(Gd,Y)OCl Powder Phosphors emitting RED colour. The suitability of the host matrix and the influence of Eu(3+) concentrations on observing brighter fluorescence were studied. The measured emission bands of these luminescent phosphors have been characterized by determining their stimulated emission cross-sections and also by a computation of their colour co-ordinates.

Luminescence spectra of Eu3+-doped GeO2-PbO-Bi2O3 glasses

Abstract Europium-doped germanium-lead bismuth based glasses in the chemical composition of 62GeO 2 -(13-X) PbO-25Bi 2 O 3 -XEu 2 O 3 (where X = 0.1, 0.2, 0.5, 1.0, and 1.5 mol%) have been prepared and carried out in a systematic study on their emission spectra. Upon exposure to the UV source (200–270 nm) these glasses have shown bright reddish orange phosphorescent color that lasted for about half an hour. From the measured glass refractive index (n d = 1.871) and density (5.965 g·cm −3 ), glass reflectivity, number of luminescent ions (N eu 3+ ), and inter ionic distance (r eu-eu ) values of these europium glasses have been computed. The PL spectra of these glasses have shown emission transitions ( 5 D 0 → 7 F 1,2,3&4 ) at 593, 612, 652, and 697 nm. We have examined the dependence of the emission spectra and decay curves on the excitation wavelengths at 228, 246, 259, 361, and 393 nm from a Xe source. Decay curves of the emission transitions have been characterized by a double exponential fitting procedure. From the photoluminescence spectra, concentration quenching at the values of the dopant ion content above 1.0 mol% has been noticed.