N. Can

Comparisons of Tin Depth Profile Analyses in Float Glass

Abstract Data are presented showing the profile of tin diffusion during the production of float glass, by measuring non-destructively the refractive index profiles in the diffused layer. The optical waveguide modes give unequivocal evidence for an anomaly in the tin depth distribution. The results are compared with those from sectioning techniques, used in depth profiles determined by ion beam analyses and cathodoluminescence (CL). There is agreement between these methods which confirm the presence of a maximum in the tin concentration below the surface which had been in contact with the tin bath (this had been linked by Mossbauer data to a rise in the Sn 4+ concentration). The ion beam analyses record different depth profiles for Si, Na and Ca. The Sn 4+ feature increases the refractive index, as does the diffusion of Sn 2+ . The index becomes constant at large tin concentrations. We suggest that Sn 4+ is linked to CL emission at 2.68 eV and Sn 2+ to the 1.97 eV CL emission. Iron impurities give a 1.73 eV signal. Contrary to earlier suggestions, we propose that the luminescence associated with the presence of tin arises from intrinsic defects stabilised by the tin, not from tin acting directly as a luminescence site.

Ion beam analysis of float glass surface composition

Abstract Data are reported on ion beam surface analysis methods of proton-induced X-ray emission (PIXE), and helium-induced X-ray emission (HIXE), made simultaneously with Rutherford backscattering spectrometry (RBS), which were taken with samples from across the full width of a float glass production line. Data are given for both clear and green glass. Significant variations are recorded between signals from the lower surface, (the face in contact with tin), and the upper surface, not only for the uptake of the tin, but also for the consequent changes in the near surface composition of the other main elements of the glass. In particular, the tin alters the local compositions of iron, caalcium, silicon, and sodium. The changes are interpreted in terms of the furnace temperature gradients and chemical interactions. In all cases, including the green glass, iron is depleted from the non-tin face relative to the bulk composition, and the changes of surface content of the iron differs on the two faces relative to the bulk value.

Luminescence behavior and Raman characterization of jade from Turkey.

Results are presented for the cathodoluminescence (CL), radioluminescence (RL) and thermoluminescence (TL) of jade from Turkey. Jade samples show broad band luminescence from green to red, which, using lifetime-resolved CL, reveals seven overlapping emissions, of which two are dominant. Green emission obtained using spatially resolved CL was associated with Mn(2+) and emission bands centered near at 480 and 530 nm were attributed to (3)P(0)-(3)H(4) and (1)D(2)-(3)H(4) transitions of Pr(3+), respectively. Different shifts of the peak-wavelengths for 326 and 565 nm were observed with varying jade compositions. The incorporation of the larger K ion causes non-linear variations of the cell dimensions and therefore changes in the Fe-O band distance. We suggest that stress of the jade structure can be linked to the luminescence emission at 326 nm. Raman spectra have also been recorded in order to provide an unequivocal identification of the type of jade. The mechanism for the luminescence of the jade is considered.

Thermal Effect on the Cathodo- and Thermoluminescence Emission of Natural Topaz (Al2SiO4(F,OH)2)

ABSTRACT The authors report about the influence of temperature on the thermoluminescence (TL) and cathodoluminescence (CL) behavior of a well-characterized topaz from Badajoz, Spain. Cryogenic treatments induce drastic decrease on the CL and TL intensity over 400 nm involving OAl* intrinsic defects and iron point defects. It suggests that low-energy emissions should be more associated with point defects and low wavebands to structural or intrinsic defects in the lattice. The tests of thermal stability of the UV-blue TL signal at different temperatures (in the range of 473–673 K) seem to confirm a continuous trap distribution system.

Nonextensive thermostatistical approach to the thermoluminescence decay

In this study, thermoluminescence decay is investigated within Tsallis thermostatistics (TT). We believe that this is the first attempt to handle the thermoluminescence decay process within TT. The generalized form of glow intensity vs temperature is examined and the effect of the nonextensitivity is shown for various values of the entropic index q. The results are interpreted in terms of the entropic index q and the occupied trap density n.

Characterisation and luminescence studies of Tm and Na doped magnesium borate phosphors.

In this study, structural and luminescence properties of magnesium borate of the form MgB4O7 doped with Tm and Na were investigated by X-ray diffraction (XRD), Raman spectroscopy and cathodoluminescence (CL). The morphologies of the synthetised compounds exhibit clustered granules and road-like materials. As doping trivalent ions into a host with divalent cations requires charge compensation, this effect is discussed. The CL spectra of undoped MgB4O7 shows a broad band emission centred around 350 nm which is postulated to be produced by self-trapped excitons and some other defects. From the CL emission spectrum, main emission bands centred at 360, 455, 475 nm due to the respective transitions of (1)D2→(3)H6,(1)D2→(3)F4 and (1)G4→(3)H6 suggest the presence of Tm(3+) ion in MgB4O7 lattice site. CL mechanism was proposed to explain the observed phenomena which are valuable in possibility of the developing new luminescent materials for different applications. In addition, the experimental Raman spectrum of doped and undoped MgB4O7 were reported and discussed.

Absorption and photoluminescence spectroscopy of Er3+-doped SrAl2O4 ceramic phosphors

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 µm, 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 4I15/2 level to 2H9/2, 4F7/2, 2H11/2, 4F9/2, 4I11/2, 2H11/2, and 4I13/2 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.

Ionoluminiscencia de silicatos de utilización en cerámica a temperaturas criogénicas

Memoria presentada por Daniel Jareno Gomez para optar al grado de Doctor por la Universidad de Castilla La Mancha-Departamento de Ciencia y Tecnologia Agroforestal y Genetica en el Instituto de Investigacion en Recursos Cinegeticos (IREC-CSIC-UCLM-JCCM).El presente trabajo ha sido financiado por NERC-UK (AAF y PDT) y por la CICYT (VC) (proyecto BFM2002-00048), por una beca de movilidad de investigadores del Ministerio de Educacion y Cultura Espanol (JGG) y por otra de la Royal Society of London y el Consejo Cientifico y Tecnologico de Turquia (TUBITAK) (NC).

Optical spectroscopy of the Ce-doped multicomponent garnets.

Here, we report our results referring to the preparation of Ce doped Y2.22MgGa2Al2SiO12, Y1.93MgAl4SiO12 and Y2.22Gd0.75Ga2Al3O12 using solid state reaction at high temperature. Several complementary methods (i.e. powder x-ray diffraction (XRPD), energy dispersive analysis of X-rays (EDX), scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR)) were studied to examine the effects of the synthesis procedure on the morphology and structure. XRD analyses revealed that all compounds include yttrium aluminate phase with garnet structure. Cathodoluminescence (CL), radioluminescence (RL) and photoluminescence (PL) measurements were carried out for clarification of relationship between host lattice defects and the spectral luminescence emissions. Luminescence emission of phosphors is peaked at 530nm assigned to 5d-4f transitions of the dopant Ce(3+) ions with a broad emission band in 400-700nm range. Under electron irradiation, the emission spectrum of Ce doped (YGd)3Ga2Al3O12 is well defined and has a characteristic fairly narrow and sharp emission band peaking at 312nm and 624nm corresponding to transition of (6)P7/2 →(8)S7/2 and (6)GJ→(6)PJ (Gd(3+)), respectively. We suggest some of phosphors might be excellent phototherapy phosphor materials under electron excitation.

Rare Earth Photoluminescence in Bismuth-Germanate Crystals

ABSTRACT In the present work, the photoluminescence (PL) spectra of bismuth germanate (BGO) doped with trivalent rare earth element (REE) ions with different doping concentrations (0.03 wt% Eu, 0.4 wt% Tm, and 1.1 wt% Nd) are reported in the temperature range from 10 to 300 K using different detectors, namely, photomultiplier tube (PMT), InGaAs (IGA), and Si. The luminescence in the NIR region was also measured at room temperature. Two broad emission bands attributed to undoped BGO were found at circa 1350 and 1800 nm, respectively. The broad-band emissions are replaced by narrow-band line emissions defined by the trivalent rare earth dopants. The emission spectra from rare earth ion–doped BGO extend from 500 to 2000 nm. Rare earth ions act as the dominant recombination centers and define the emission spectra. This is interpreted as resulting from direct charge transfer from intrinsic defect traps to rare earth recombination centers. The temperature-dependent luminescence of BGO doped with 0.4 wt% Tm is also presented.