[en] When ZrO₂ films and nanocrystals are irradiated with a 325 nm laser light in an evacuated chamber, each luminescence-intensity increases, creating a broad visible luminescence. Then, introducing O₂ gas into the specimen chamber, the photoluminescence spectrum returns reversibly to the original luminescence under the same laser light irradiation. After removing the laser light, each luminescence state is stored for a long time at room temperature under room light, regardless of any changes of atmosphere. The observed phenomena are explained by means of the photo-induced oxygen defect creation and annihilation at/near the ZrO₂ surface. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)