OPTICAL MATERIALS

This paper reports the luminescence emission spectra of Y(Ta,Nb)04 activated by rare earth ions such as Eu3+ and Tb3+. The influence of these rare earth ions on the radioluminescence (RL) of yttrium niobate and tantalate phosphors was investigated. The luminescent properties were studied under X-ray and preliminary RL measurements to further evaluate prepared materials. The emission centers of the rare earth activators (Eu3+, Tb3+) were found to contribute efficiently to the total luminescence. With their various luminescence chromaticities, these rare earth activated phosphors are promising materials for solid-state lighting applications as well as for X-ray intensifying screens in medical diagnosis, providing the broad band variation of visible RL from blue to red. (c) 2012 Elsevier B.V. All rights reserved

JOURNAL OF LUMINESCENCE

Chemical analyses performed on chrysoprase from Turkey have shown many trace elements as well as rare earth impurities. Quantitative chemical analyses of inclusions in minerals can improve our understanding of the chemistry of surface. The environmental scanning electron microscope (ESEM) with an attached X-ray energy dispersive system (EDS) is capable of producing rapid and accurate major element chemical analyses of individual inclusions in crystals larger than about 30 mu m in diameter. The samples were examined with lifetime-resolved and spatially-resolved cathodoluminescence (CL), and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Spatially resolved CL results at room temperature were recorded for two different areas. Bulk area displays with low CL emission and pores contain iron phases such as chromite, hematite and anatase which cause the green color. For the raw data in the lifetime resolved CL spectrum, at least three broad emission bands were detected in a yellow band of the highest intensity at about 550 nm, a weaker orange band at about 650 nm, and a red band at 720 nm. It is assumed that there are links between the CL emissions and the presence of some transition metal and REE elements, but it is obvious that all trace elements do not play a direct role. Micro-Raman measurements were performed on chrysoprase and these showed a characteristic intensive Raman band peaked at 464 cm(-1) which can be inferred to nu(2) doubly symmetric bending mode of [SiO4/M] centers. Raman spectrum of all inclusions found in the material are also given and discussed in detail. (C) 2012 Elsevier B.V. All rights reserved

OPTICAL MATERIALS

Phosphors for radiation detection require efficient energy transfer from the ionization track to the luminescent centers. In this work, the radioluminescence (RL) spectra of SrAl2O4 phosphor ceramics doped with individual trivalent rare earth element (REE) ions (Sm, Eu and Dy) are reported at the room temperature. Although there is some intrinsic UV/blue emission from the host lattice, the dominant signals are from the rare-earth sites, with signals characteristic of the REE2+ and REE3+ states. The shapes of the emission bands are different for each dopant. The sharp emission properties show that the SrAl2O4 is a suitable host for rare-earth ion doped phosphor material. (C) 2011 Elsevier B.V. All rights reserved

JOURNAL OF ALLOYS AND COMPOUNDS

In this paper, we report on structural and optical properties of terbium and europium doped barium stannate phosphors (BaSnO3) synthesised by conventional solid state reaction method. We have studied those materials by using X-ray diffraction (XRD), radioluminescence (RL) and photoluminescence (PL) techniques. XRD patterns confirm that the BaSnO3 sintered at 1400 degrees C exhibit orthorhombic structure and that the Tb3+ and Eu3+ substitution of Ba2+ does not change the structure of the BaSnO3 host. The optical emission spectrum is characterized a broad band centered at 897 nm (1.38 eV), with a high-energy tail approximately 750 nm from the host lattice. Other emission signals that are characteristic of the 3 + oxidation state of rare earth elements were generated by Eu and Tb doping. Luminescence measurements show that the series of emission states D-5(4) -> F-7(6), D-5(4) -> F-7(5), D-5(4) -> F-7(4) and D-5(4) -> F-7(3) corresponding to the typical (4)f -> (4)f infra-configuration forbidden transitions of Tb3+ are appeared and the major emission peak at 540 nm is due to D-5(4) -> F-7(5) transitions of Tb3+. On the other hand, the emission spectrum of Eu doped BaSnO3 phosphor exhibits a series of emission bands, which are attributed to the D-5(0) -> F-7(j) (j = 0-4) transitions of Eu3+ ions. The dominant emission of Eu3+ corresponding to the electric dipole transition D-5(0) -> F-7(2) is located at 613 nm. The sharp emission properties exhibited demonstrate that the BaSnO3 is a suitable host for rare-earth ion doped phosphor material. This work clearly confirms the unusual near infrared (NIR) PL discovered by H. Mizoguchi et al. in BaSnO3 at room temperature. (C) 2013 Elsevier B.V. All rights reserved

SPECTROSCOPY LETTERS

A novel green-emitting phosphor copper-doped barium aluminate was synthesized by the conventional ceramic method. The crystallographic phase and microstructure identification were performed by powder X-ray diffraction and scanning electron microscopy. The X-ray diffraction pattern of the sample confirms the formation of the phosphor, and the scanning electron microscope image was recorded to observe the surface morphology. Differential thermal analysis results show that the initiatory decomposition temperature of barium carbonate starts at about 728 degrees C. Cathodoluminescence studies have been undertaken to ensure the successful incorporation of copper ions in the barium aluminate host lattice. Under the excitation of the electron beam, the phosphor can efficiently display a broad green emission centered at 490nm, corresponding to the transition from the conduction band edge to the excited state of copper in the barium aluminate host. However, there are no data available on copper luminescence in barium aluminate. New results on 3d activators of copper emission in the barium aluminate host are reported in this article, thus extending the list of copper-activated phosphors. These results strongly indicate that the copper-activated barium aluminate is a potential material used as a new high-brightness green phosphor for ultraviolet light-emitting diode and display devices

JOURNAL OF LUMINESCENCE

We report, for the first time on luminescence from a Er3+ doped SrAl2O4 phosphor. Effects of Eu3+ doping were also studied. The influence of rare-earth doping in crystal structure and its optical properties were analysed by means of X-ray diffraction (XRD), Raman scattering, optical absorption, excitation and emission (PL) spectroscopy, thermally stimulated luminescence (TSL) and scanning electron microscope (SEM). Luminescence spectra and luminescence decay curves for Er3+ transitions in the near infrared region were recorded. The PL maximum for Eu doped SrAl2O4 is obtained at 620 nm and corresponds to the orange region of the spectrum. Diffraction patterns reveal a dominant phase, characteristic of the monoclinic SrAl2O4 compound and the presence of dopants has no effect on the basic crystal structure of SrAl2O4. The shapes of the glow curves are different for each dopant irradiated with either a Sr-90-Y-90 beta source, or UV light at 311 nm, and in detail the TL signals differ somewhat between Er and Eu dopants. (C) 2011 Elsevier B.V. All rights reserved

JOURNAL OF LUMINESCENCE

The optical properties of alkaline earth aluminates doped with rare earth ions have received much attention in the last years and this is due to. their chemical stability, long-afterglow (LAG) phosphorescence and high quantum efficiency. However, there is a lack of understanding about the nature of the rare earth ion trapping sites and the mechanisms which could activate and improve the emission centers in these materials. Therefore a new phosphor material composition, SrAl2O4:Mn2+, co-doped with Nd3+ was synthesized by a traditional solid-state reaction method. The influence of transition metal and rare earth doping on crystal structure and its luminescence properties have been investigated by using X-ray diffraction (XRD), Raman scattering, Photoluminescence (PL) and Radioluminescence (RL). Analysis of the related diffraction patterns has revealed a major phase characteristic of the monoclinic SrAl2O4 compound. Small amounts of the dopants MnCO3 and Nd2O3 have almost no effect on the crsytalline phase composition. Characteristic absorption bands from Nd3+ 4f-4f transitions in the spectra can be assigned to the transitions from the ground state I-4(9/2) to the excited states. The luminescence of Mn2+ activated SrAl2O4 exhibits a broad green emission band from the synthesized phosphor particles under different excitation sources. This corresponds to the spin-forbidden transition of the d-orbital electron associated with the Mn2+ ion. In photo- and radio-luminescence spectra, Nd3+ 4f-4f transition peaks were observed. The emitted radiations for different luminescence techniques were dominated by 560, 870, 1057 and 1335 nm peaks in the visible and NIR regions as a result of I-4(9/2) -> (4)G(7/2) and F-4(3/2) -> I-4(J) (J=9/2, 11/2 and 13/2) transitions of Nd3+ ions, respectively. Multiple emission lines observed at each of these techniques are due to the crystal field splitting of the ground state of the emitting ions. The nature of the emission lines is discussed. (C) 2013 Elsevier B.V. All rights reserved

PHILOSOPHICAL MAGAZINE LETTERS

A spectroscopic characterization of Er3+-doped SrAl2O4 phosphor materials synthesized by a solid-state reaction method with Er concentrations varying from 0.1 to 1 mol% has been performed by studying photoluminescence (PL) in the temperature range 10 to 360 K and absorption spectra. PL signals containing five emission bands at 1492, 1529, 1541, 1558, and 1600 nm, respectively, have been observed at room temperature for Er3+ transitions in the near infrared region. The samples exhibit a main luminescence peak at 1.54 mu m, which is assigned to recombination via an intra-4f Er3+ transition. Sharp bands centered at around 378, 488, 521, 651, 980, 1492, and 1538 nm in the absorption spectra can be associated with transitions from I-4(15/2) level to H-2(9/2), F-4(7/2), H-2(11/2), F-4(9/2), I-4(11/2), H-2(11/2), and I-4(13/2) levels, respectively. The sharp emission peaks and excellent luminescence properties show that SrAl2O4 is a suitable host for rare-earth-doped phosphors, which may be suitable for optical applications

Synthesis and optical properties of Er3+ and Eu3+ doped SrAl2O4 phosphor ceramic

We report, for the first time on luminescence from a Er3+ doped SrAl2O4 phosphor. Effects of Eu3+ doping were also studied. The influence of rare-earth doping in crystal structure and its optical properties were analysed by means of X-ray diffraction (XRD), Raman scattering, optical absorption, excitation and emission (PL) spectroscopy, thermally stimulated luminescence (TSL) and scanning electron microscope (SEM). Luminescence spectra and luminescence decay curves for Er3+ transitions in the near infrared region were recorded. The PL maximum for Eu doped SrAl2O4 is obtained at 620 nm and corresponds to the orange region of the spectrum. Diffraction patterns reveal a dominant phase, characteristic of the monoclinic SrAl2O4 compound and the presence of dopants has no effect on the basic crystal structure of SrAl2O4. The shapes of the glow curves are different for each dopant irradiated with either a Sr-90-Y-90 beta source, or UV light at 311 nm, and in detail the TL signals differ somewhat between Er and Eu dopants