Crystal Research and Technology
Cryst. Res. Technol. 41, 41 (2006) - Abstract -

Recharging processes of Cr ions in Mg2SiO4 and Y3Al5O12 crystals under influence of annealing and γ - irradiation

S. M. Kaczmarek, W. Chen*, and G. Boulon*

Institute of Physics, Szczecin University of Technology, Al. Piastow 48, 70-310 Szczecin, Poland
*Physical Chemistry of Luminescent Materials, Claude Bernard /Lyon 1 University, UMR CNRS 5620, Bat. A. Kastler, 10 rue Ampere, 69622 Villeurbanne, France

Keywords chromium, forsterite, yttrium aluminum garnet, annealing, gamma-irradiation, photoluminescence
PACS 61.72.Ji, 61.80.Ed, 42.70.Iij
DOI 10.1002/crat.200410527

Recharging processes of chromium ions were investigated for Mg2SiO4 :Mg, Cr single crystals using annealing in O2 and in air and γ-irradiation, as compare to YAG :Ca, Cr single crystals. The formation of tetravalent Cr ions in the Mg2SiO4 :Mg, Cr is related not only to the initial Cr content in the melt, oxygen partial pressure and O2- vacancy existing in the crystal, but also to the external field such as γ-irradiation. The additional absorption after γ-irradiation shows the decrease in intensity of the absorption of Cr3+ and Cr4+ ions in some part of the spectrum and increase in the other giving evidence on recharging effects between Cr3+ and Cr4+. There arises also color centers observed between 380 nm and 570 nm that may participate in energy transfer of any excitation to Cr4+ giving rise to Cr4+ emission. Opposite to forsterite crystal, absorption spectrum of YAG:Ca, Cr crystal after γ-irradiation reveals only increase in the absorption of the Cr bands. The observed behavior of the absorption spectrum of YAG:Ca, Cr crystal under influence of γ-irradiation suggests that γ-irradiation ionizes only Cr ions.




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