Rare-earth-free phosphors based on vanadate compounds were investigated, where the vanadates included chloride vanadates (M II 2 VO 4 Cl), pyrovanadates (M II 2 V 2 O 7 ), orthovanadates (M II 3 (VO 4 ) 2 ) with divalent cations M II of Mg, Sr, Ba, and Zn, and oxofluorovanadates (A I VOF 4 ) with an alkali metal A I . A chloride pyrolysis method and a liquid phase precipitation method were proposed for preparing the chloride vanadates and pyro-and orthovanadates, respectively. These vanadate compounds showed self-activated photoluminescence (PL) based on the VO 4 clusters against the ultraviolet (UV) light irradiation. The colors of PL covered almost the whole visible-light region from blue to yellow as Sr 2 VO 4 Cl (deep blue), Ca 2 VO 4 Cl (sky blue), Ba 2 V 2 O 7 (green), Sr 2 V 2 O 7 (yellowish green), Zn 3 (VO 4 ) 2 (yellow), and Mg 3 (VO 4 ) 2 (yellow). A correlation was suggested from these compounds between the luminescent colors and the structural feature as the longer V-O distances in the VO 4 tetrahedra in the crystal structures led to the longer wavelength in PL. This seemed to be also applicable for the oxofluorovanadates A I VOF 4 (A I = K and Cs) which contain the VOF 4 polyhedra with one O 2ion and four Fions as the ligands, as they exhibited the reddish PL.

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