Thermoluminescence of Zircon

The thermoluminescence (TL) of synthetic zircons into which some impurities have been individually insert-ed is investigated. The results obtained show that, after X-irradiation at 77K, the synthetic zircons present three kinds of thermoluminescent emissions. The first is related to the OH- ions, the second is typical of the SiO44-groups, and the third is characteristic of RE3+ ions with RE = Dy, Tb, Gd, Eu, or Sm (RE = rare earth). The OH- emission is a large band at 285 nm which appears at 115 and 160K. The SiO44- TL emission consists of a 365 nm band observed at 100, 165, 205, 260, and 325K. The mechanisms associated with these TL peaks are fairly well described in terms of an electron trapped in the field of two positive charges, one substituted to silicon ion, the other to a neighbouring oxygen ion. For temperatures up to 350K, the characteristic emissions of RE3+ are the consequence of an energy transfer mechanism from the TL emission as a result of recombination in SiO44- host groups or OH- centres to the RE3+ emitting activators. At temperatures higher than 350K, there are also some other RE3+ characteristic peaks which are interpreted in terms of charge transfer mechanisms. The systematic compilation of results obtained with a series of natural zircons from various origins shows that the main TL properties are explained by the mechanisms described above

Dimensionless study of the total response of thermally stimulated luminescence

The response of thermally stimulated luminescence (TSL) is investigated theoretically. An original dimensionless treatment is proposed, first to highlight the key dimensionless factors rationalizing the competition between the mechanisms at play during the TSL readout, and second to clean up the approach from any particular values of the relevant physical parameters. The approach holds for an unlimited number of interactive traps. The total response from a current trap is derived and cast into simple formal expressions as a function of the recombination cross-section, the set of trapping cross-sections and of initial trap occupancies (i.e. those existing before the readout of the current peak). This allows one to calculate each peak response by taking proper account of carrier transfers accompanying the successive peak readouts

Thermoluminescence of a mixed rare earth phosphate powder La1−x−yCexTbyPO4

International audienceThe properties of thermoluminescence (TL) observed from various mixed rare earth (RE) phosphate powders La1−x−yCexTbyPO4 are reported. TL peaks appear around −175°C, −135°C, −80°C, −35°C and +25°C and the TL emission spectra of La1−x−yCexTbyPO4 are mainly composed of characteristic line transitions of Tb3+ ions. The results show that the co-doping with Ce3+ is not required to observe the TL emission of Tb3+. A model for the recombination mechanisms of the various TL peaks is discussed

Identification of point defects in tin dioxide: Experimental and theoretical approach

International audienceThermoluminescence (TL) glow curves of polycrystalline tin dioxide samples exhibit three main peaks below room temperature. Their relative intensities depend on experimental conditions. Especially, they are modified by aluminum doping or by wet air exposition. In SnO2, we suggest that ionised oxygen vacancies and hydroxyl groups are responsible for thermoluminescence. This assumption is discussed. In order to explain the behaviour of these defects, two kinds of modelling are proposed

Spectroscopic analysis of "MgAlON" spinel powders: influence of nitrogen content

International audienceThe thermoluminescence (TL) and fluorescence spectra of magnesium aluminium oxynitride "MgAlON" and magnesium aluminate MgAl2O4 spinel powders have been analysed. Two broad peaks at about 100 and 300 °C appear in the TL spectra of MgAl2O4 and seem to be related to electron and hole release from [AlMg√] and [MgAl′] traps, respectively. The intensity of each peak strongly depends on the nature of the annealing atmosphere (neutral, oxidizing or reducing). TL spectral analyses have shown the presence of two intense emissions at 520 and 690 nm attributed to the Mn2+ and Cr3+ emitting centers, respectively. A study on MgAl2O4 is used as a reference for MgAlON powders, which can be considered as a solid solution derived from magnesium aluminate. Disturbance in the emission spectrum of Cr3+ is clearly observed with the nitrogen/oxygen substitution

Effect of different fluxes on the morphology of the LaPO4 : Ce, Tb phosphor

LaPO4:Ce, Tb (LaCeT) is a green phosphor used in fluorescent lamps and plasma display panels. In order to improve the fabrication process of this phosphor, different fluxes have been used. Their influence on the particles size and shape is described thanks to SEM analyses. Fluxes were found to control the morphology of particles : LaCeT particles, from spherical to parallelepiped-like shape, with suitable sizes, from 0.1 to 10 µm, have been synthesized. Furthermore the photoluminescence emission of the obtained powders has been checked, and it has been proved that the effect of the fluxes studied is not harmful to the LaCeT final optical properties

Detection of tetragonal zirconia in alumina–zirconia powders by thermoluminescence

International audienceThe thermoluminescence (TL) after excitation by UV or X-rays radiation of alumina-zirconia powders is investigated. The composites present five of the characteristic peaks of zirconia at −170, −145, −90, 0 and 95 °C. After a thermal treatment of mixed oxides, a new peak is observed at −35 °C in TL. This peak reveals the presence of stabilized tetragonal zirconia in the material. Moreover by comparing this analysis with those realised by X-ray diffraction (XRD), it can by shown that the TL has one better limit of detection than the XRD

Characterization of B-doped polycrystalline diamond films using thermally stimulated luminescence

International audienceThe effect of different rates of boron incorporation during the growth in diamond on the thermoluminescence (TL) features of this material is investigated. TL studies performed between liquid nitrogen temperature (LNT) and 320 K show some phosphorescence and two other peaks at 226 and 266 K. For the first time, boron level in polycrystalline diamond films was identified by TL by an intense glow peak at 226 K and activation energy of about 0.35 eV. For this main peak, spectral analysis shows a prominent broad band luminescence peaking at 2.56 eV. At 77 K, another emission band was observed at 2.22 eV. This is in agreement with the fact that the recombination mechanisms involve two different recombination centers and, therefore, phosphorescence at 77 K and the main peak at 226 K are of different nature, i.e. the TL peak at 226 K is due to boron while phosphorescence is hence, probably due to a shallow donor level. The behavior of TL intensity relative to the main component at 226 K observed on all the films and linked to boron level decreases with increasing boron concentration

Detection of foreign phases in doped a-alumina powders by thermoluminescence

International audienceThe thermoluminescence (TL) after excitation by UV or X-rays radiation of doped a-alumina powders is investigated. In the case of zirconia, the alumina-zirconia composites present five of the characteristic peaks of zirconia at -170, -145, -90, 0 and 95°C. After a thermal treatment of mixed oxides, a new peak is observed at -35°C in TL. This peak reveals the presence of stabilized tetragonal zirconia in the material. In the case of calcium, the TL curves of a-alumina doped by calcium present a double peak around 110 and 130°C which can be attributed to the presence of the hibonite phase: CaAl12O19. Moreover, in the case of zirconia, by comparing this analysis with those realised by X-rays diffraction (XRD), it can be shown that the TL has one better limit of detection than the XRD

Irradiation damages in Ti3SiC2: formation and characterisation of the oxide layer

International audienceThe concept of the fuel for the IVth generation reactors should consist of fuel pellets surrounded with a matrix that must contain fission products. Thanks to their interesting thermo-mechanical properties, carbides are sensed to become this matrix. Among the studied carbides, Ti3SiC2 can be distinguished; actually, its nano-laminated structure confers to it some softness as well as a better toughness than classical carbides like SiC or TiC. However, before to use this remarkable carbide, a study of its behaviour under irradiation must be led. Thus, some characterisations were performed on 75 MeV Kr irradiated specimens. They allowed to underline that TiO2 (formed on the surface of Ti3SiC2 during the surface preparation) seems to be sputtered by irradiation, and that the unit cell of Ti3SiC2 is dilated along c axis