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.
