Elsevier

Materials Research Bulletin

Volume 73, January 2016, Pages 96-101
Materials Research Bulletin

Controllable synthesis and tunable luminescence of glass ceramic containing Mn2+:ZnAl2O4 and Pr3+:YF3 nano-crystals

https://doi.org/10.1016/j.materresbull.2015.08.029Get rights and content

Highlights

  • Glass ceramic containing ZnAl2O4 and YF3 nano-crystals is fabricated.

  • Mn2+ and Pr3+ are selectively incorporated into ZnAl2O4 and YF3, respectively.

  • The luminescence color can be tuned by adjusting the excitation wavelength.

Abstract

Glass ceramic containing spinel ZnAl2O4:Mn2+ and orthorhombic YF3:Pr3+ nano-crystals has been successfully prepared by a melt-quenching technique. X-ray diffraction and transmission electron microscopy demonstrated that two nano-phases, i.e. ZnAl2O4 and YF3, were homogeneously distributed among the glass matrix. Importantly, the selective incorporation of Pr3+ ions into the Y3+ nine-fold coordinated sites of YF3 and the segregation of Mn2+ dopants in the Zn2+ tetrahedral sites of ZnAl2O4 were confirmed based on the excitation/emission spectra and the crystal field calculation. Under blue light excitation, both Pr3+ and Mn2+ in the glass ceramic can be simultaneously excited, and emit red and green luminescence, respectively, owing to the suppression of energy transfer between them. The luminescence color of the obtained glass ceramic can be easily tuned by adjusting the excitation wavelength. These results indicate the potential application of the glass ceramic as converting phosphor to generate white-light after coupling with the blue LED chip.

Introduction

White light-emitting diodes (WLEDs) are regarded as the new generation state-of-the-art lighting technology due to their properties of high brightness, environmental friendliness, energy saving, and long lifetime [1]. Generally, the commercial WLED combines a blue InGaN chip with a yellow-emitting Ce3+:Y3Al5O12 (Ce3+:YAG) phosphor packed on the chip surface using epoxy resin or silicone. Unfortunately, with increasing brightness and total flux of WLEDs, the organic resin or silicone with low thermal conductivity and poor thermal stability may age easily and turn yellow since the temperature of LED chip is locally increasing up to 150–200 °C [2]. Moreover, WLEDs developed by this method are poor in color-rendering index due to the deficiency of red luminescence [3]. Thus, a novel phosphor for next-generation WLEDs will be required.

To solve these problems, active ions doped glass ceramic (GC) has been developed as alternative material for Ce3+:YAG due to its excellent thermal and chemical stability, high-temperature resistance, simple manufacturing procedure, and organic resin-free in assembly process [4], [5], [6], [7]. However, the practical exploitation of glass ceramic as luminescent converter material is largely limited because the incorporation process of the active ions in the nano-composite is still poorly understood [8], [9]. Importantly, the optical properties of glass ceramic are depending on the active ions and the precipitated nano-crystals, such as the distribution of dopants in the hosts, the local environment around the dopants and the complex energy transfer between the co-doped ions [9], [10], [11], [12], [13], [14].

In the paper, Mn2+/Pr3+ co-doped glass ceramic containing ZnAl2O4 and YF3 nano-crystals was fabricated to achieve desirable optical performance for WLEDs. The partition behaviors of Mn2+ and Pr3+ in the glass ceramic were systematically investigated, and the distribution-related luminescence was detected. It was found that Mn2+ dopants incorporated into spinel ZnAl2O4 lattice, while Pr3+ ones entered into orthorhombic YF3 nano-crystals, resulting in the producing of color-tunable luminescence. Finally, the assessment of potential application of the fabricated glass ceramic in the blue chip excited WLEDs has been carried out.

Section snippets

Experimental

Composition (in mol%) of the precursor glass is 37.0SiO2–23.5Al2O3–8.5ZnO–8.5YF3–6.0NaF–8.0LiF–8.5Ga2O3. Mn2+ and Pr3+ additives were introduced in the form of MnO and PrF3 with concentrations of 1.0% and 0.5%, respectively. The precursor glass was fabricated by melting a mixture of the reagent grade chemicals in a covered corundum crucible at 1450 °C for 1 h in air, then poured it into a 300 °C preheated copper mold to form the precursor glass. After cooling to room temperature, the obtained

Results and discussion

To identify the crystallization phases of the obtained glass ceramic, XRD measurements were carried out and displayed in Fig. 1. As expected, the pattern of the precursor glass exhibits a typical amorphous structure originating from the oxide glass. For the precursor glass heat-treated at 660 °C, the characteristic peaks assigned to spinel ZnAl2O4 (JCPDS No. 71-0968) appear on the diffuse humps, and no second phase is detected. Further increasing annealing temperature to 760 °C, the additional

Conclusion

Mn2+/Pr3+ co-doped glass ceramic containing spinel ZnAl2O4 and orthorhombic YF3 nano-crystals has been successfully prepared by the melt quenching method. It is experimentally demonstrated that Mn2+ and Pr3+ are selectively incorporated into the ZnAl2O4 and YF3 nano-crystals respectively, leading to a unique multicolor luminescence. Depending on the employed excitation wavelength, the color of luminescence could be tuned from yellow green to yellow and finally to orange red. The results of this

Acknowledgments

This work was supported by the National Natural Science Foundation of China (51202244) and the Nature Science Foundation of Fujian Province (2015J01632). The authors thank Prof. Yuansheng Wang of Fujian Institute of Research on the Structure of Matter for the measurements of photoluminescence spectra and decay curves.

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