Mechanism of long-lasting phosphorescence of Eu 2+ in melilite

Abstract

UV excitation for several Eu 2þ -doped melilite crystals, Eu 2þ :Ca 2 Al 2 SiO 7 (CASM), Eu 2þ :CaSrAl 2 SiO 7 (CSASM), and Eu 2þ :Sr 2 Al 2 SiO 7 (SASM) produces long-lasting phosphorescence (1-10 2 s) from Eu 2þ ions besides the intrinsic Eu 2þ luminescence. The distribution of the radiative decay rates is due to the recombination of distant pairs of trapped electrons and holes in the crystals. The intensities of the phosphorescence for these crystals were measured as functions of temperature and time. The most intense phosphorescence was obtained from the Eu 2þ : SASM crystal. The decay curves measured for Eu 2þ :SASM below 400 K fit t Àn (n 1). This fact shows that the recombination of the distant pairs occurs through tunneling below 400 K. The temperature dependence of the intensities integrated in a time domain obeys the Arrhenius's equation with two thermal activation energies including radiative and non-radiative processes. These results suggest that holes and electrons recombine radiatively at Eu 2þ sites in the SASM crystal through thermal hopping and tunneling. On the other hand, Eu 2þ :CASM and Eu 2þ :CSASM show different behavior on the decay curves at low temperatures, satisfying t Àn (n > 1). This discrepancy may be removed by several electron and=or hole centers with different trapping energy levels.

A novel phosphor for glareless white light-emitting diodes

“…We expected the layering to stabilize the chemically unstable metal chloride layer. As phosphors with layered structures often suffer from substantial thermal quenching of luminescence owing to loose interlayer bonding 23,24 , we explored materials that exhibited a small degree of thermal quenching.…”

Luminescence properties of red-emitting Ca2Al2SiO7:Eu3+ nanoparticles prepared by sol-gel method

“…Recently, several groups in China found that Ce 3+ -Tb 3+ -or Eu 3+ /Eu 2+ -doped Ca 2 Al 2 SiO 7 materials can emit green, red, and blue light with high brightness under near UV irradiation, showing great advantages in fabricating the white light-emitting diode (w-LED) [10][11][12][13]. The Ca 2 Al 2 SiO 7 :Ce 3+ single crystal has a long afterglow emission and can be used in tunable solid-state laser materials [14][15][16]. As we all know, different material preparation methods have some important effects on material microstructure and physical properties.…”

Photoluminescence of Eu single doped and Eu/Dy codoped Sr2Al2SiO7 phosphors with long persistence

“…Therefore the silicate-based long afterglow phosphors are regarded as one of the promising materials in the field. Eu 2+ and Ce 3+ caused long-lasting behavior in melilites together with their afterglow mechanism, were reported in recent years by several groups [15][16][17][18][19], showing the potential research interest in rare-earth-doped melilite materials. However, when compared to the achievements researchers made in aluminate system, works in silicate system need further investigation.…”