RARE-EARTH OXIDE OR SULFIDE OF NANO SIZE AND PROCESS FOR PRODUCING THE SAME THROUGH PHOTOCHEMICAL REACTION

摘要

A crystalline rare-earth oxide or sulfide which has an average particle diameter of 10 nm or smaller and in which the rare earth element has a low valance, in particular, crystalline EuO or EuS of a nano size. The rare-earth oxide or sulfide is produced by irradiating an inorganic acid salt or organic acid salt of a rare earth element having a high valence with a light in the range of from ultraviolet to visible light in the presence of: a compound which, upon irradiation with the light in the range of from ultraviolet to visible light induces a photooxidation-reduction reaction and simultaneously converts the rare-earth ions having a high valence into ions having a low valence; and a chalcogen source compound which immediately reacts with the low-valence ions to form a chalcogen compound.