Nanocomposite
Phosphor Consisting of CaI2:Eu2+ Single Nanocrystals
Embedded in Crystalline SiO2
Version 3 2018-11-15, 09:14Version 3 2018-11-15, 09:14
Version 2 2017-12-13, 09:43Version 2 2017-12-13, 09:43
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Posted on 2018-11-15 - 09:14
High
luminescence efficiency is obtained in halide- and chalcogenide-based
phosphors, but they are impractical because of their poor chemical
durability. Here we report a halide-based nanocomposite phosphor with
excellent luminescence efficiency and sufficient durability for practical
use. Our approach was to disperse luminescent single nanocrystals
of CaI2:Eu2+ in a chemically stable, translucent
crystalline SiO2 matrix. Using this approach, we successfully
prepared a nanocomposite phosphor by means of self-organization through
a simple solid-state reaction. Single nanocrystals of 6H polytype (thr notation) CaI2:Eu2+ with diameters of about 50 nm could be generated not only
in a SiO2 amorphous powder but also in a SiO2 glass plate. The nanocomposite phosphor formed upon solidification
of molten CaI2 left behind in the crystalline SiO2 that formed from the amorphous SiO2 under the influence
of a CaI2 flux effect. The resulting nanocomposite phosphor
emitted brilliant blue luminescence with an internal quantum efficiency
up to 98% upon 407 nm violet excitation. We used cathodoluminescence
microscopy, scanning transmission electron microscopy, and Rietveld
refinement of the X-ray diffraction patterns to confirm that the blue
luminescence was generated only by the CaI2:Eu2+ single nanocrystals. The phosphor was chemically durable because
the luminescence sites were embedded in the crystalline SiO2 matrix. The phosphor is suitable for use in near-ultraviolet light-emitting
diodes. The concept for this nanocomposite phosphor can be expected
to be effective for improvements in the practicality of poorly durable
materials such as halides and chalcogenides.
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Daicho, Hisayoshi; Iwasaki, Takeshi; Shinomiya, Yu; Nakano, Akitoshi; Sawa, Hiroshi; Yamada, Wataru; et al. (2017). Nanocomposite
Phosphor Consisting of CaI2:Eu2+ Single Nanocrystals
Embedded in Crystalline SiO2. ACS Publications. Collection. https://doi.org/10.1021/acsami.7b14132