Structural ordering and charge variation induced by cation substitution in (Sr,Ca)AlSiN3:Eu phosphor
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Nitride phosphors which are suitable for white light-emitting diode applications. In this study, the structure of phosphor has been modified through cation substitution to induce charge variation and a rearrangement of neighboring nitride clusters, and consequently enhance its luminescent behavior. Substitution of Ca2+ by Sr2+ cations expanded the lattice volume and the b-c plane, but shortened the distance between the layers along the a axis. Lattice distortion of the framework introduced high-coordination sites in the Sr/Eu centers and adequate space, thereby facilitating charge variation of activators under reduced atmosphere, as detected through X-ray absorption near-edge structure spectroscopy. As such, the photoluminescent intensity of the phosphors increased by more than 10% and a blue shift occurred. The microstructures of the samples were also analyzed using high-resolution transmission electron microscopy. Cation substitution induced a special change in the anion environment, as indicated in the solid-state Raman spectra. Moreover, a typical ordering variations in the SiN4 and AlN4 clusters are generated in the lattice. Meanwhile, neighbor sequence of (Si/Al)N4 around the divalent centers were observed through solid-state nuclear magnetic resonance spectroscopy. The modified ordering distribution resulted in a rigid structure and improved the thermal quenching behavior. Thermal stability has been enhanced by 10% at 473 K when x = 0.9 in SrxCa0.993-xAlSiN3:Eu2+0.007 compared with that at x = 0. This study promotes the research of neighbor sequence for selective tetrahedral sites such as Li, Mg, Al, Si coordinated by N atoms contact with cation sites.
Tsai , Y-T , Chiang , C-Y , Zhou , W , Lee , J-F , Sheu , H-S & Liu , R-S 2015 , ' Structural ordering and charge variation induced by cation substitution in (Sr,Ca)AlSiN 3 :Eu phosphor ' Journal of the American Chemical Society , vol 137 , no. 28 , pp. 8936-8939 . DOI: 10.1021/jacs.5b06080
Journal of the American Chemical Society
Copyright © 2015 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/full/10.1021/jacs.5b06080
This work was supported by the Ministry of Science and Tech-nology of Taiwan (Contract No. MOST 101-2113-M-002-014-MY3) and Mitsubishi Chemical Group, Science and Technology Research Center Inc., Japan. We also appreciate to the discussion by Dr. Kyota Ueda and Mr. Fumitaka Yoshimura.