Exciton and antisite defect‐related luminescence in Lu₃Al₅O₁₂ and Y₃Al₅O₁₂ garnets

Abstract

Intrinsic emission of complex oxides with garnet structure was studied by means of the analyses of the time-resolved luminescence spectra and decay kinetic for single crystals (SC) and single-crystalline films (SCF) of Y 3 Al 5 O 12 (YAG) and Lu 3 Al 5 O 12 (LuAG) garnets under excitation by the pulse X-ray and synchrotron radiation at 8 -300 K. YAG and LuAG SC and SCF are characterized by significantly different concentration of the Y Al and Lu Al antisite defects (AD) due to the substantial difference in the conditions of their crystallization. For this reason, LuAG and YAG SC and SCF are very useful model objects for the study of nature of the intrinsic emission of these oxides, consisting of the excitons and AD luminescence.

Time-resolved luminescent spectroscopy of YAG:Ce single crystal and single crystalline films

“…Under excitation by SR with energy of 3.71 eV in the 5d 1 Ce 3þ absorption bands the decay times of the Ce 3þ luminescence in YAG:Ce SCF (70.7 ns) and both SCs (79-80 ns) is somewhat different (Fig. 3, curves 1-3 excitation of the Ce 3þ luminescence in YAG:Ce SC by emission of LE(AD), Y Al and F þ -AD centers (Zorenko et al, 2007a) as well as the temporal localization of charge carriers on these centers in the RT range (Nikl et al, 2005), the decay kinetics of the Ce 3þ luminescence in both SCs is notable slower (Fig. 3, curve 2 0 and 3 0 ) than that in SCF analogue (Fig.…”

“…1), caused by the 5d 1 / 4f 2 ( 2 F 5/2,7/2 ) transitions of Ce 3þ ions, the emission spectra of both YAG:Ce SCs at 300 K consist also of the intrinsic emission bands in the UV range peaked at 305, 372 and 400 nm. By the analogy with the structure of the intrinsic luminescence of undoped YAG SC (Zorenko et al, 2007a), the nature of the mentioned UV bands in YAG:Ce SC can be caused by radiation decay of an exciton localized around Y Al AD (LE(AD) centers), recombination luminescence of Y Al AD with formation of excitons bound with these centers, and the luminescence of F þ centers, perturbed by the nearest Y Al AD (F þ -AD centers) (Pujats and Springis, 2001). Meanwhile, we can not exclude the influence of Ce 3þ ions on formation of the intrinsic emission centers in YAG:Ce SC.…”

“…2) consist: (i) the band peaked at 7.95 eV related to the onset of YAG interband transition (Zorenko et al, 2007a); (ii) the dominant bands peaked in 6.67-6.885 eV range, corresponding to the formation of exciton bound with the Ce 3þ ions; (iii) the band peaked at 5.67 eV, related to 4f-5d( 3 T 2g ) transition of Ce 3þ ions; (iv) the band peaked 4.74 eV, caused by the 1 S 0 / 3 P 1 transition of Pb 2þ flux dopant in the SCF (Scott and Page, 1977). Due to Y Al AD presence and formation of Ce-AD coupled centers, the excitation spectra of Ce 3þ luminescence in YAG:Ce SC (Fig.…”

“…The presence of AD is an inevitable consequence of high-temperature (w2000 C) growth of SC of garnets from melt by the Czochralski or Bridgman methods (Kuklja, 2000;Stanek et al, 2006). Due to the AD presence, the YAG SC can be considered as a specific type of self-activated phosphors where the Y Al AD as analogues of cation isoelectronic impurities create the emission centers in the UV range and trapping centers as well (Zorenko et al, 2007a;Nikl et al, 2005). Due to comparable concentration of both Ce 3þ ions and AD (up to 0.2 at.…”

Luminescence and scintillation characteristics of YAG:Ce single crystalline films and single crystals

“…The AD presence is the consequence of high-temperature (w2000 C) growth of bulk SC of these garnets from melt by the Czochralski or Bridgman methods and energetically favourable creation of such defects (Kuklja, 2000;Stanek et al, 2006). The Y Al and Lu Al ADs in YAG:Ce and LuAG:Ce SC play the role of emission centers in UV range (Zorenko et al, 2007a) and trapping centers . These centers participate in the excitation of the Ce 3þ luminescence and are responsible for large amount of slow components in scintillation decay of YAG:Ce and LuAG:Ce SCs (Nikl, 2005;Zorenko et al, 2007b).…”