Self‐Activated Vanadate Compounds Toward Realization of Rare‐Earth‐Free Full‐Color Phosphors

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 2− ion and four F ‐ ions as the ligands, as they exhibited the reddish PL .