We studied the processes occurring in the 5d(1) excited state of Ce3+ in Gd3Ga3Al2O12 (GGAG) host. Energy transfer from Gd3+ to Ce3+ was evidenced by photoluminescence excitation spectra of Ce3+ emission. We measured temperature dependences of prompt nanosecond decays and millisecond delayed recombination decays of Ce3+ in GGAG host. The decrease of nanosecond decay times above approximately 200 K is due to thermally induced ionization of the 5d(1) excited state of Ce3+. Thermal stimulated luminescence glow curve measurements after X-ray or UV (within 4f-5d(1) absorption of Ce3+) irradiation at RT provide another support for the ionization effect around this temperature. (C) 2013 Elsevier B.V. All rights reserved.