The luminescence of ion-exchangeable defect pyrochlore KNbWO6·H2O:xEu3+

Abstract

KNbWO₆·H₂O:xEu³⁺ is prepared by ion exchange under hydrothermal conditions. Three K⁺ ions of KNbWO₆·H₂O are exchanged for one Eu³⁺ ion and KNbWO₆·H₂O:xEu³⁺ keeps its defect pyrochlore structure. Thermal analysis results indicate that the Eu³⁺ ion incorporates into the channels of the defect pyrochlore structure in the form of the aqueous ion [Eu(H₂O)n]³⁺. [Eu(H₂O)n]³⁺ in the channel looses water at 450 °C, which is much higher than that of KNbWO₆·H₂O. The hydration of the Eu³⁺ ion in the pyrochlore structure has significant influence on the luminescence properties of KNbWO₆·H₂O:xEu³⁺. The emission intensity increases 10 times when the as-prepared KNbWO₆·H₂O:xEu³⁺ is annealed at 450 °C for 2 h.