Crystal Structure and Luminescent Properties of R2鈥?i>xEux(MoO4)3 (R = Gd, Sm) Red Phosphors

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• 作者：Vladimir A. Morozov ; Maria V. Raskina ; Bogdan I. Lazoryak ; Katrien W. Meert ; Katleen Korthout ; Philippe F. Smet ; Dirk Poelman ; Nicolas Gauquelin ; Johan Verbeeck ; Artem M. Abakumov ; Joke Hadermann
• 刊名：Chemistry of Materials
• 出版年：2014
• 出版时间：December 23, 2014
• 年：2014
• 卷：26
• 期：24
• 页码：7124-7136
• 全文大小：938K
• ISSN：1520-5002

文摘

The R₂(MoO₄)₃ (R = rare earth elements) molybdates doped with Eu³⁺ cations are interesting red-emitting materials for display and solid-state lighting applications. The structure and luminescent properties of the R_2鈥?i>xEu_x(MoO₄)₃ (R = Gd, Sm) solid solutions have been investigated as a function of chemical composition and preparation conditions. Monoclinic (伪) and orthorhombic (尾鈥? R_2鈥?i>xEu_x(MoO₄)₃ (R = Gd, Sm; 0 鈮?x 鈮?2) modifications were prepared by solid-state reaction, and their structures were investigated using synchrotron powder X-ray diffraction and transmission electron microscopy. The pure orthorhombic 尾鈥?phases could be synthesized only by quenching from high temperature to room temperature for Gd_2鈥?i>xEu_x(MoO₄)₃ in the Eu³⁺-rich part (x > 1) and for all Sm_2鈥?i>xEu_x(MoO₄)₃ solid solutions. The transformation from the 伪-phase to the 尾鈥?phase results in a notable increase (鈭?4%) of the unit cell volume for all R_2鈥?i>xEu_x(MoO₄)₃ (R = Sm, Gd) solid solutions. The luminescent properties of all R_2鈥?i>xEu_x(MoO₄)₃ (R = Gd, Sm; 0 鈮?x 鈮?2) solid solutions were measured, and their optical properties were related to their structural properties. All R_2鈥?i>xEu_x(MoO₄)₃ (R = Gd, Sm; 0 鈮?x 鈮?2) phosphors emit intense red light dominated by the ⁵D₀鈫?sup>7F₂ transition at 鈭?16 nm. However, a change in the multiplet splitting is observed when switching from the monoclinic to the orthorhombic structure, as a consequence of the change in coordination polyhedron of the luminescent ion from RO₈ to RO₇ for the 伪- and 尾鈥?modification, respectively. The Gd_2鈥?i>xEu_x(MoO₄)₃ solid solutions are the most efficient emitters in the range of 0 < x < 1.5, but their emission intensity is comparable to or even significantly lower than that of Sm_2鈥?i>xEu_x(MoO₄)₃ for higher Eu³⁺ concentrations (1.5 鈮?x 鈮?1.75). Electron energy loss spectroscopy (EELS) measurements revealed the influence of the structure and element content on the number and positions of bands in the ultraviolet鈥搗isible鈥搃nfrared regions of the EELS spectrum.