RESUMO
A new potassium dysprosium polyborate, K3DyB6O12, has been prepared via the high-temperature molten salt method and structurally characterized by single-crystal X-ray diffraction analysis. The structure can be described as a three-dimensional framework composed of isolated bicyclic [B5O10]5- groups and Dy3+ and K+ ions. The Fourier transform IR (FT-IR) and ultraviolet-visible (UV-Vis) spectra were investigated. A series of K3Gd1-xDyxB6O12 phosphors was prepared and their photoluminescence properties were studied. The K3Gd1-xDyxB6O12 phosphors exhibit a strong yellow emission band at 577â nm (the 4F9/2â6H13/2 transition of Dy3+) under UV excitation of 275â nm (the 8S7/2â6IJ transition of Gd3+), suggesting the occurrence of the energy transfer Gd3+âDy3+. The optimized doping concentration of the Dy3+ ion was 8â mol%. We may expect that K3Gd1-xDyxB6O12 is a promising pale-yellow emission phosphor for visual displays or solid-state lighting.
RESUMO
An anhydrous orthophosphate, K3Eu5(PO4)6 (tripotassium pentaeuropium hexaphosphate), has been prepared by a high-temperature solid-state reaction combined with hydrothermal synthesis, and its crystal structure was determined by single-crystal X-ray diffraction analysis (SC-XRD). The results show that the compound crystallizes in the monoclinic space group C2/c and the structure features a three-dimensional framework of [Eu5(PO4)6]∞, with the tunnel filled by K+ ions. The IR spectrum, UV-Vis spectrum and luminescence properties of polycrystalline samples of K3Eu5(PO4)6, annealed at temperatures of 650, 700, 750, 800 and 850â °C, were investigated. Although with a full Eu3+ concentration (9.96 × 1021â ionsâ cm-3), the self-activated phosphor K3Eu5(PO4)6 shows s strong luminescence emission intensity with a quantum yield of 37%. Under near-UV light excitation (393â nm), the series of samples shows the characteristic emissions of Eu3+ ions in the visible region from 575 to 715â nm. The sample sintered at 800â °C gives the strongest emission and its lifetime sintered at 800â °C (1.88â ms) is also the longest of all.