The temperature dependence of luminescence from a long-lasting phosphor exposed to ionizing radiation

The temperature dependence of luminescence from a long-lasting phosphor (LLP), SrAl2O4: Eu2+, Dy3+, exposed to ionizing radiation has been measured to understand the LLP luminescence mechanism. Evaluation of the decay constants of the LLP exposed to alpha-, beta- or gamma-rays at temperatures from 200 to 390 K showed that the decay constant is divided into four components ranging from 10(-4) to 10(-1) s(-1) with activation energies of 0.02-0.35 eV. Total luminous intensity from the LLP with changing irradiation temperature has its maximum value around the room temperature. Irradiation at elevated temperature (390K) has the total luminescence pattern with monotonous decrease as temperature rises. As a result of evaluating the temperature dependence of luminescence, the luminescence mechanism is considered as follows: I. holes generated by irradiation are stored at Dy3+ sites (hole traps) and then released to recombine with electrons trapped at Eu2+ sites (luminescence centers) with photon emission (J. Electrochem. Soc 143 (1996) 2670 and J. Lumin. 72-74 (1997) 287); 2. hole release rate increases with temperature; 3. some holes and electrons recombine without photon emission (non-radiation transition); and 4. the proportion of non-radiation transition to radiation transition increases with temperature. (C) 2002 Elsevier Science B.V. All rights reserved.