Synthesis, optical properties, and packaging of Dy3+ doped Y2WO6, Y2W3O12, and Y6WO12 phosphors

doi:10.1016/j.materresbull.2020.110846

Materials Research Bulletin

Volume 126, June 2020, 110846

https://doi.org/10.1016/j.materresbull.2020.110846 Get rights and content

Highlights

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Y₂WO₆, Y₂W₃O₁₂, and Y₆WO₁₂ were synthesized.
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The Dy³⁺ doped Y₂WO₆ has the strongest PL intensities.
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The Dy³⁺ optimal doping concentration was 2 mol% in Y₂WO₆ phosphor.
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2 mol% Dy³⁺ doped Y₂WO₆ phosphor kept 74 % intensity of 50 °C at 150 °C.
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WLEDs were obtained by combining the phosphor with 308 nm chips.

Abstract

Through a solid-state reaction method, Dy³⁺ doped monoclinic phase of Y₂WO₆, Y₂W₃O₁₂, and hexagonal phase of Y₆WO₁₂ phosphors were synthesized. The Y₂WO₆ and Y₂W₃O₁₂ were composed of micrometre-scale particles, and the Y₆WO₁₂ was composed of nanometre particles. The energy-dispersive spectra (EDS) suggested that the atom ratio of Y to W decreased with the sequence of Y₆WO₁₂, Y₂WO₆, and Y₂W₃O₁₂ phosphors. The E_g values were calculated based on the diffuse reflection (DR) spectra. The Dy³⁺ doped Y₂WO₆ phosphor had the most intense photoluminescence (PL) intensities and the optimal doping concentration was 2 mol%. The energy transfer efficiency from WO₆⁶⁻ to Dy³⁺ was calculated. The lifetime of ⁴F_9/2→⁶H_13/2 transition of Dy³⁺ was a few hundred nanoseconds. At 150 °C, the 2 mol% Dy³⁺ doped Y₂WO₆ phosphor kept 74 % intensity of 50 °C. The white light emitting diode (WLED) devices were fabricated by combining phosphors with 308 nm LED chips.

Graphical abstract

PL excitation and emission spectra of Dy³⁺ doped Y₂WO₆, mixture of Y₂WO₆ and Y₂W₃O₁₂, Y₂W₃O₁₂, and Y₆WO₁₂ phosphors.

Introduction

Owing to its applications in white light, laser emissions, temperature sensing, etc., rare earth ion Dy³⁺ has received attractive attentions [[1], [2], [3], [4], [5], [6]]. The Dy³⁺ has characteristic emissions originated from the ⁴F_9/2→⁶H_15/2 transition located at blue area and the ⁴F_9/2→⁶H_13/2 transition located at yellow region. In general, there are two methods being used and explored to obtain phosphor converted white-light-emitting diodes (WLEDs). One is combining a blue-emitting chip with yellow phosphor (usually Ce³⁺ doped yttrium aluminum garnet YAG). The other is packaging red, green and blue phosphors together to an ultraviolet (UV) chip. For the Dy³⁺ has blue and yellow emissions simultaneously, it is expected that white emission can be obtained in Dy³⁺ single doped phosphors [7,8].

It is well known that the tungstate is a kind of self-activated phosphor and can produce a broad band emission under UV excitation [9]. In general, metal tungstates can be divided into two groups based on the coordination environment around the tungsten. One group is regular WO₄²⁻ tetrahedra with scheelite-type structure [10,11]. The other group is six-fold coordinated distorted WO₆^6- octahedra with wolframite-type structure [12]. RE₂WO₆ (rare earth = RE) tungstates have the wolframite-type structure. The charge transfer band (CTB) of WO₆^6- usually locates at around 300 nm. The energy transfer process from the WO₆^6- group to RE³⁺ can happen and intense luminescence of RE-doped tungstates can be obtained [13]. Color-tunable emissions in Sm³⁺, Eu³⁺, Tb³⁺, Dy³⁺ doped Y₂WO₆ or Y₆WO₁₂ have been reported and researched [[14], [15], [16], [17], [18], [19]]. Rarely reports on other yttrium tungsten oxides were reported [20]. Some yttrium tungsten oxide phosphors of Dy³⁺ doped Y₂WO₆, Y₂W₃O₁₂, and Y₆WO₁₂ were synthesized by a solid-state reaction method. The obtained materials were characterized by crystalline structures, particle sizes and compositions, energy transfer processes, energy transfer efficiencies, optical properties, and thermal stabilities, et al. The obtained 2 mol% Dy³⁺ doped Y₂WO₆ phosphor was packaged into WLED devices and gave bright white light under forward bias.

Section snippets

Experimental section

Dy³⁺ doped yttrium tungsten oxide phosphors were synthesized using the same solid-state reaction method as reported in ref. [21]. Tungsten oxide (WO₃, A.R.) were used to replace molybdenum trioxide (MoO₃, 99.99 %), yttrium oxide (Y₂O₃, 99.99 %) were used to replace lutetium oxide (Lu₂O₃, 99.99 %), and dysprosium oxide (Dy₂O₃, 99.99 %) were used to replace europium oxide (Eu₂O₃, 99.99 %) as raw materials. For the synthesis of 1, 2, 4, 6, and 10 mol% Dy³⁺ doped Y₂WO₆ phosphors, stochiometric of Dy

Structural analysis

Fig. 1 presents XRD patterns of materials synthesized with different ratios of Y(Dy)₂O₃ to WO₃. The reference data are also illustrated in Fig. 1. With molar ratio of Y(Dy)₂O₃:WO₃  = 1:1 and fixed Y₂O₃:Dy₂O₃ = 99:1 in molar ratio, the obtained XRD pattern can be well indexed to the reference data of monoclinic phase of Y₂WO₆ with JCPDS card 23-1489, which suggests that the Dy³⁺ doped monoclinic phase of Y₂WO₆ was obtained. With the molar ratio of Y(Dy)₂O₃:WO₃ = 1:2, some peaks marked * can be

Conclusion

In conclusion, the Dy³⁺ doped monoclinic phase of Y₂WO₆, Y₂W₃O₁₂, hexagonal phase of Y₆WO₁₂, and undoped Y₂WO₆ phosphors were synthesized through a solid-state reaction method. The FE-SEM images suggests that the materials were composed of micrometre particles except Y₆WO₁₂ phosphor. The EDS patterns confirmed the compositions of the materials. The DR spectra consisted well with the PL excitation spectra and the E_g values were deduced from the DR spectra. The results suggested that the Dy³⁺

CRediT authorship contribution statement

Chunyan Cao: Conceptualization, Methodology, Writing - original draft, Writing - review & editing, Project administration, Funding acquisition. Shoujin Wei: Formal analysis, Investigation. Yongxing Zhu: Formal analysis, Investigation. Tao Liu: Formal analysis, Investigation. An Xie: Methodology, Supervision. Hyeon Mi Noh: Project administration. Jung Hyun Jeong: Project administration, Funding acquisition.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The research work was supported by the Natural Science Foundation of Fujian Province (Grant nos. 2017J01719, 2018J01429), Fujian Key Laboratory of Functional Materials and Application open projects (Grant nos. fma2017106, fma2018001), Pandengketi of Xiamen University of Technology (XPDKT19038), and Program for Innovative Research Team in Science and Technology in Fujian Province University (IRTSTFJ). This research was also supported by Basic Science Research Program through the National

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Synthesis, optical properties, and packaging of Dy3+ doped Y2WO6, Y2W3O12, and Y6WO12 phosphors

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Experimental section

Structural analysis

Conclusion

CRediT authorship contribution statement

Declaration of Competing Interest

Acknowledgments

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Synthesis, optical properties, and packaging of Dy³⁺ doped Y₂WO₆, Y₂W₃O₁₂, and Y₆WO₁₂ phosphors