Energy Conversion of X-Ray, Ultraviolet and Infrared Radiation in Gd2O3 Crystals Doped with Er3+ Ions.

Spectra of photoluminescence (PL) and X-ray excited luminescence (XRL) in region of 1.5-5.0 eV, PL excitationspectra (2.8-5.8 eV), PL decay kinetics were measured in Gd2O3 crystals doped both with Er3+ and Zn²⁺ ions. Synchrotron radiation (VEPP-3 storage ring, Novosibirsk, Russia) were used for XRL measurements. PL spectra were studied at room temperature and T= 88 K under excitation with energy Eexc: a) in fundamental absorption region (Eexc⩾Eg); b) in intracenter excitation region (Eexc<Eg); c) in infrared region (Eexc<<Eg) with using laser 980 nm diode as exciting photons (up-conversion processes). The probability of radiative transitions from excited states of the impurity center depends on Eexc. The photoluminescence efficiency in Gd2O3 doped with both Er3+ and Zn2+ ions in the green region decreases, 4F9/2 → 4I15/2 transitions dominate in the red region both in XRL and PL spectra. This effect is also clearly manifested in the spectra of anti-Stokes luminescence. Energy transfer between the excited Er3 + states of the impurity center and the crystal lattice defect is observed. Decrease of the lifetime of 4S3/2 excited state in Gd2O3:Er3++Zn2+ from 120 to 10 μs is observed. This fact indicated s a nonradiative energy transfer between impurity center and defect. Otherwise, the defect concentration variation (by means of doping with heterovalent ions) provides the ability to control the energy conversion efficiency as well as the phosphorus color. [ABSTRACT FROM AUTHOR]