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

Abstract

Rare‐earth‐free phosphors based on vanadate compounds were investigated, where the vanadates included chloride vanadates (MII2VO4Cl), pyrovanadates (MII2V2O7), orthovanadates (MII3(VO4)2) with divalent cations MII of Mg, Sr, Ba, and Zn, and oxofluorovanadates (AIVOF4) with an alkali metal AI. 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 VO4 clusters against the ultraviolet (UV) light irradiation. The colors of PL covered almost the whole visible‐light region from blue to yellow as Sr2VO4Cl (deep blue), Ca2VO4Cl (sky blue), Ba2V2O7 (green), Sr2V2O7 (yellowish green), Zn3(VO4)2 (yellow), and Mg3(VO4)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 VO4 tetrahedra in the crystal structures led to the longer wavelength in PL. This seemed to be also applicable for the oxofluorovanadates AIVOF4 (AI = K and Cs) which contain the VOF4 polyhedra with one O2− ion and four F‐ ions as the ligands, as they exhibited the reddish PL.