Surfactant-Assisted Hydrothermal Synthesis of Eu³⁺-Doped White Light Hydroxyl Sodium Yttrium Tungstate Microspheres and Their Conversion to NaY(WO₄)₂

Abstract

In this work, large-scale three-dimensional "flake-ball" microarchitectures of Eu(3+) doped white light hydroxyl sodium yttrium tungstate were prepared by the well-known hydrothermal approach at 180 degrees C for 48 h in the presence of triblock-copolymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123). NaY(WO(4))(2):Eu(3+) phosphor was formed by annealing the hydrothermal product at approximately 630 degrees C for 2 h. A time-dependent microstructure evolution study was performed under hydrothermal reaction. The evolution process is the self-assembly process of P123, and the effects of other reaction parameters, such as influence of the concentration of P123 on morphology, and the influence of temperature on PL. The mechanism by which the "flake-ball" particles are formed is discussed in detail. The PL spectra of Eu(3+)-doped hydroxyl sodium yttrium tungstate phosphor contain two parts: the broad blue-green band and the (5)D(0)-->(7)F(J) (J = 1, and 2) characteristic transition of Eu(3+). This approach provides a facile route for the production of high-quality hydroxyl sodium yttrium tungstate microstructures with an interesting optical property.

Self-assembled three-dimensional NaY(WO4)2:Ln3+ architectures: Hydrothermal synthesis, growth mechanism and luminescence properties

“…On the basis of the above results, it is clear that the blue emission of WO 4 2− groups and red emission of the doped Eu 3+ occur simultaneously and yield a white light emission. Such mechanism of the formation of the white light of the as-prepared precursor is consistent with the NaY(WO 4 ) 2 :Eu 3+ precursor reported by Zheng and Lei [22,25]. The corresponding CIE coordinates (x = 0.317, y = 0.267) for the emission spectrum of as-prepared Eu 3+ doped precursor locate in the white light region (point a, Fig.…”

“…As shown, the excitation spectrum of the precursor (Fig. 6A, left) monitored with 615 nm consists of a strong and broad band from 200 to 300 nm with a maximum at about 237 nm, which corresponds to the charge transfer absorption from the 2p orbitals of the oxygen ligands to the 5d orbitals of the central tungsten atoms in the WO 4 2− groups [22,25]. In the longer wavelength region, some weak peaks ascribed to the f-f transitions of the Eu 3+ ions can also be observed.…”

“…As one kind of important solid-state materials, rare-earth tungstates have gained much attention because of their remarkable properties in the areas of catalysts, quantum electronics and lasers [23]. Among them, scheelite-like alkali rare earth double tungstates with the general formula of ARE(WO 4 ) 2 (A represents alkali metal ions; RE represents rare earth ions) are interesting phosphors for visual display as good laser crystal materials [24,25]. Singly doped and Tm 3+ /Ho 3+ co-doped NaY(WO 4 ) 2 as laser materials were synthesized successfully by Sun et al [26].…”

Hydrothermal synthesis, multicolor tunable luminescence and energy transfer of Eu3+ or/and Tb3+ activated NaY(WO4)2 nanophosphors

“…Tungstates are well-known classical self-activated luminescence materials, which can effectively absorb ultraviolet (UV) and X-ray, then simultaneously migrate the absorbed energy to the doped rare-earth ions through energy transfer, and give their characteristic emissions. Therefore, they are recently considered as promising host materials for rare-earth luminescent centers because of the special properties of WO 4 2-& Guixia Liu liuguixia22@163.com group [11][12][13][14]. From the report of Huang et al [15], it was seen that tungstate host essentially showed a little weaker blue emission at room temperature compared to the absorption in excitation spectrum, owing to efficient energy transfer from WO 4 2-group to activators.…”

“…In consideration of this problem, the hydrothermal method is preferred because the synthesis conditions such as temperature and reaction time can be easily adjusted. Furthermore, the hydrothermal process has proved to be a facile and fast route with low cost and energy consumption, which has been widely employed for the synthesis of inorganic materials including alkali rare earth tungstates [11,12,[28][29][30]. Among the alkali rare earth tungstates, the NaY(WO 4 ) 2 lattice belongs to the scheelite CaWO 4 structures, which consists of two formula units in the unit cell, with space group C 4h 6 (I41/a).…”