A. Garcia

Luminescent properties of Eu3+-activated lithium rare earth borates and oxyborates

Abstract The luminescence characteristics of Eu 3+ in the borates Li 6 Y(BO 3 ) 3 and Li 3 La 2 (BO 3 ) 3 and the recently discovered oxyborates LiLa 2 O 2 BO 3 , LiLn 6 O 5 (BO 3 ) 3 (Ln=Y,Gd) and Li 2 Lu 5 O 4 (BO 3 ) 3 have been investigated and compared to those in the borates LnBO 3 (Ln=La,Y) and the oxyborates “Ln 3 BO 6 ” (Ln=La,Gd). The probability of electric dipole f–f transitions is generally markedly higher in oxyborates than in borates. This is ascribed to the highly anisotropic environment of rare earth ions and the low position of the charge transfer states. Consequently, the Eu 3+ -activated oxyborates are characterized by a deeper red emission and faster decay.

Reversible photoionization process in luminescent Ce3+ doped elpasolite-type fluoroindates

Abstract Ce3+ luminescence was investigated in elpasolite fluoroindates A2BInF6 (A = K, Rb; B = Na, K). All A2BInF6:Ce3+ have been synthesized by solid state reactions from stoichiometric mixtures in sealed gold tubes at 700°C. Transparent colourless Rb2KInF6:Ce3+ crystals were grown by Bridgman method in 10% Rh-Pt crucibles sealed under dry argon atmosphere. At room temperature Rb2KInF6:Ce3+ presents a blue-green broad-band emission when excited with a 315 nm UV radiation. This emission can be ascribed to the Ce3+ ions in In3+ site. Two other emissions in the blue and UV can be assumed to originate from Ce3+ ions located in the 6 coordinated potassium and 12 coordinated rubidium sites. Under a steady 315 nm UV excitation the main blue-green Ce3+ emission decreases progressively, giving rise to a new emitting centre which exhibits a red emission under 255 nm excitation. This phenomenon is optically reversible and moreover the original state can be thermally regenerated. An hypothesis based on the ln(III)-...

Indium disilicate, a new fast scintillator

Abstract We describe the luminescence and scintillation of indium disilicate (In 2 Si 2 O 7 ), an inorganic scintillator containing a large amount of 115 In. The maximum fluorescence occurs in the near UV range at 335 nm with a complicated decay including a fast component of less than 100 ns and a long one of more than a microsecond. Room temperature emission intensity was quite weak while the quantum efficiency became reasonably good at cryogenic temperature. Scintillation was measured using α-particles of 6.09 MeV and 8.785 MeV from 300 to 4 K. A maximum of intensity is observed at 50 K. A fast component (τ ⋍ 20 ns) with a constant intensity superimposes to a slow one of which the intensity has a maximum at 50 K and for which the decay constant rises as the temperature decreases.

LUMINESCENCE OF IN+ IN CE3+ AND TB3+-DOPED ELPASOLITE-TYPE FLUOROINDATES

This work deals with the identification of In+ ions in octahedral symmetry and the study of their optical properties in crystalline Rb2KInF6:Ce3+ and Rb2KInF6:Tb3+. The presence of In+ ions in the sites of In3+ has been confirmed exciting the Ce3+-doped sample at 41u200a600 and 32u200a360 cm−1 and exciting the Tb3+-doped sample at 41u200a600 cm−1. An hypothesis based on the In3+–Ce3+ and In3+–Tb3+ redox couples for the Ce3+- and Tb3+-doped elpasolite-type fluoroindates has been proposed in order to explain the presence of In+ at the mentioned excitation energies. This redox process is more efficient for the In3+–Ce3+ couple than for the In3+–Tb3+ one. Emission spectra and luminescence decays of In+ have been investigated at 5–300 K in both samples under the above mentioned excitations. Our experimental results have been compared to those obtained for In+-type ions as In+, Ga+, and Tl+ in alkali halides in literature. The transitions between the 5s5p excited configuration and the 5s2 configuration of In+ ions modified...

Luminescence and scintillation properties of In2Si2O7

We report the physical properties of a new fast indium-based scintillator. The technique of elaboration and the crystal structure of indium disilicate (In 2 Si 2 O 7 ) are presented as well as the analysis of an intense ultraviolet photoluminescence at low temperature. A complex fast fluorescence decay is recorded with two time domains separated by more than one order of magnitude. Scintillation was measured showing a rather good quantum efficiency comparable to Bi 4 Ge 3 O 12 .