We have examined long lasting luminescence of transparent alumna and Tb~(3+)-Zn~(2+)(Ca~(2+))-codoped alumina films prepared by the aqueous sol-gel method. A strong luminescence of 300-500 nm was observed for nondoped alumina, and was shown to depend on the treat temperature of gel. The luminescence was not observed for alumina treated at temperatures higher than 600℃. The luminescence band was composed of plural components due to oxygen defect sites in alumina. The lasting luminescence of Tb~(3+)-Zn~(2+)(Ca~(2+))-codoped alumina were observed after irradiation for several seconds using a UV lamp (15 W). The results indicated that the oxygen defect sites of alumina serve as a photoelectron trap center and that the Al~(v) site serves as a hole trap center, which can be thermally released at room temperature.
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