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https://doi.org/10.3938/NPSM.69.1220
The Effects of Crystal Lattices on Luminous Properties in Eu$ ^{3+}$ Doped Sr$ _{9-x}$La$ _{1+x}$(PO$ _{4}$)$ _{7-x}$(SiO$ _{4}$)$ _{x}$ System
New Phys.: Sae Mulli 2019; 69: 1220~1225
Published online December 31, 2019;  https://doi.org/10.3938/NPSM.69.1220
© 2019 New Physics: Sae Mulli.

Dorim KIM, Eunhye YANG, Jung Hyun, JEONG*

Department of Physics, Pukyong National University, Busan 48513, korea
Correspondence to: jhjeong@pknu.ac.kr
Received September 2, 2019; Revised October 11, 2019; Accepted October 21, 2019.
cc This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
The red-emitting phosphors of Eu$^{3+}$-doped Sr$ _{9-x}$La$ _{1+x}$(PO$ _{4}$)$ _{7-x}$(SiO$ _{4}$)$ _{x}$ ($x$ = 0, 1, 3, 5, 7) were prepared via a solid-state reaction method. The structural and the optical properties were investigated by using X-ray powder diffraction (XRD) and photoluminescence (PL) measurements, respectively. An analysis of the XRD patterns revealed that the crystal structure changed from a whitlockite to an apatite structure with increasing $x$. A Rietveld refinement of Sr$ _{9}$La(PO$ _{4}$)$ _{7}$ ($x$ = 0) and Sr$ _{2}$La$ _{8}$(SiO$ _{4}$)$ _{7}$ ($x$ = 7) was performed to obtain more detailed information on the crystal structure. In the PL excitation spectra, with increasing $x$, the charge-transfer-band (CTB) shifted towards longer wavelengths with enhanced excitation intensity. However, the excitation intensity from the $f$-$f$ transition of Eu$ ^{3+}$ centered at 393 nm decreased. The PL spectra showed a strong red emission ($ ^{5}$D$ _{0}$ $\rightarrow$ $ ^{7}$F$ _{2}$) and a considerable orange emission ($ ^{5}$D$ _{0}$ $\rightarrow$ $ ^{7}$F$ _{1}$). To obtain insight into the possible structural changes, the Judd-Ofelt theory are used to calculate the experimental intensity parameters $\Omega_{2}$ and $\Omega_{4}$. The red-emitting Sr$ _{9-x}$La$ _{1+x}$(PO$ _{4}$)$ _{7-x}$(SiO$ _{4}$)$ _{x}$ ($x$ = 0, 1, 3, 5, 7) phosphors can play key roles for phosphor-converted white-light-emitting diodes (pc-LEDs).
PACS numbers: 78.55.-m, 78.55.Hx
Keywords: Luminescencen, Phosphor, Judd-Ofelt theory


December 2019, 69 (12)
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