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

Thermoluminescence and optically stimulated luminescence of gamma-irradiated mineral zircon

Thermoluminescence (TL) manifested by gamma-irradiated mineral zircon has shown a strong TL peak at about 165 °C which is due to recombination of electrons and Dy3+ related shallow hole traps. After they have been removed by a short preheat we have observed two TL peaks at 300-320 °C and ≈420 °C, which are mainly due to recombination of electrons and Tb3+ related hole traps centres yielding its characteristic luminescence. The experimental results indicate that optically stimulated luminescence (OSL) is due to luminescent emission of Tb3+ ions and [SiO4]4– groups. The deep traps related to the 420 °C TL peak contribute to the Tb3+ related OSL. The deep traps related to the 300-320 °C TL peak contribute to OSL associated with the luminescent emission of [SiO4]4– groups.

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

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

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

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

Dommages d'irradiation dans Ti3SiC2

Les carbures, de par leurs propriétés remarquables, sont pressentis comme matériau de structure autour du combustible du réacteur de génération IV. Parmi ceux étudiés, Ti3SiC2 se distingue car il associe les propriétés des céramiques à celles des métaux. Cependant, son comportement sous irradiation n'est pas connu. Des caractérisations ont été réalisées sur des échantillons irradiés aux ions Kr à 75 MeV. Elles ont permis de mettre en exergue que TiO2 (formé en surface de Ti3SiC2) est pulvérisé par l'irradiation et que la maille cristalline de Ti3SiC2 se dilate suivant c

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