High-efficiency energy transfer in the strong
orange-red-emitting phosphor CeO
2
:Sm
3+
, Eu
3+
Nguyen Van Hai,
a
Nguyen Thi Khanh Linh,
a
Dinh Thi Hien,
a
Bui Thi Hoan,
b
Nguyen Minh Tu,
c
Vuong-Hung Pham,
d
Duy-Hung Nguyen,
d
Vu Tuan Anh
e
and Hoang Nhu Van
*
e
High-efficiency energy transfer (ET) from Sm
3+
to Eu
3+
leads to dominant red emission in Sm
3+
, Eu
3+
co-
doped single-phase cubic CeO
2
phosphors. In this work, a series of Sm
3+
singly and Sm
3+
/Eu
3+
co-doped
CeO
2
cubic phosphors was successfully synthesized by solution combustion followed by heat treatment at
800 °C in air. The crystal structure, morphology, chemical element composition, and luminescence
properties of the obtained phosphors were investigated using X-ray diffraction, scanning electron
microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence analysis. Under 360 nm
excitation, the Sm
3+
singly doped CeO
2
phosphor emitted strong yellow-red light at 573 nm (
4
G
5/2
–
6
H
5/
2
) and 615 nm (
4
G
5/2
–
6
H
7/2
). Meanwhile, the CeO
2
:Sm
3+
, Eu
3+
phosphors showed the emission
characteristic of both Sm
3+
and Eu
3+
, with the highest emission intensity at 631 nm. The emission
intensity of Sm
3+
decreased with increasing Eu
3+
content, suggesting the ET from Sm
3+
to Eu
3+
in the
CeO
2
:Sm
3+
, Eu
3+
phosphors. The decay kinetics of the
4
G
5/2
–
6
H
5/2
transition of Sm
3+
in the CeO
2
:Sm
3+
,
Eu
3+
phosphors were investigated, confirming the high-efficiency ET from Sm
3+
to Eu
3+
(reached 84%).
The critical distance of energy transfer (R
C
= 13.7 Å) and the Dexter theory analysis confirmed the ET
mechanism corresponding to the quadrupole–quadrupole interaction. These results indicate that the
high-efficiency ET from Sm
3+
to Eu
3+
in CeO
2
:Sm
3+
, Eu
3+
phosphors is an excellent strategy to improve
the emission efficiency of Eu
3+
.
1. Introduction
White-light emitting diodes (WLEDs) have been extensively
used in many elds of application, such as in solid lighting,
display devices, and optoelectronic devices, because of their
high luminous efficiency, long lifetime, energy saving, and
environment friendliness.
1–3
A popular method for
manufacturing WLEDs is combining tricolor phosphor powder
(blue, green, and red phosphors) with an ultraviolet (UV) InGaN
chip.
4,5
However, these WLEDs present a high correlated color
temperature and low color rendering index due to the lack of
a red component.
6,7
To overcome these drawbacks, scholars
should explore new red phosphors for WLED applications.
The europium trivalent ion (Eu
3+
) is an important rare-earth
(RE) ion that has been widely used as an activator in red-
emitting phosphors for WLEDs.
8–10
The red emission of Eu
3+
is originally from electric dipole transitions. Notably, Eu
3+
-
doped phosphors typically exhibit relatively narrow absorption
in UV and near-UV regions because of the spin-forbidden
transition of Eu
3+
, resulting in low emission efficiency.
11,12
This defect can be compensated by introducing sensitizing
ions, such as Tb
3+
, Bi
3+
, Gd
3+
, and Sm
3+
,
13–15
which can absorb
excitation energy efficiently and transfer it to Eu
3+
. Sm
3+
is
a popular sensitizer for improving the efficiency emission of
Eu
3+
ion due to the small energy difference between the
4
G
5/2
level of Sm
3+
and the
5
D
0
level of Eu
3+
(about 600 cm
-1
), leading
to easy phonon-assisted energy transfer (ET).
13
Hence, the
energy transfer between Sm
3+
and Eu
3+
ions was widely inves-
tigated in a variety of host lattices.
12,16,17
J. Wu et al.
16
found that
the ET efficiency from Sm
3+
to Eu
3+
up to 65% in YPO
4
:Sm
3+
,
Eu
3+
phosphor corresponds to the electric dipole–electric dipole
interaction mechanism. Y. Li et al.
17
reported that ET efficiency
from Sm
3+
to Eu
3+
was 13.7% in La
2
CaB
10
O
19
:Sm
3+
, Eu
3+
phos-
phor, further conrmed by Judd–Ofelt theory. Meanwhile, X.
Zhang et al.
12
developed Ca
2
GdNbO
6
:Sm
3+
, Eu
3+
phosphor with
high quantum yield (82.7%), excellent thermal stability, and up
to 28.6% ET efficiency. In addition, the LED device fabricated
a
Faculty of Chemistry, Hanoi National University of Education, 136 Xuan Thuy Road,
Cau Giay District, Hanoi, Viet Nam
b
Faculty of Electrical–Electronics Engineering, Thuyloi University, No. 175 Tay Son
Road, Hanoi, Viet Nam
c
Faculty of Pharmacy, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 12116,
Viet Nam
d
International Training Institute for Materials Science (ITIMS), Hanoi University of
Science and Technology, No. 01, Dai Co Viet Road, Ha Noi, Viet Nam
e
Faculty of Materials Science and Engineering, Phenikaa University, Yen Nghia, Ha-
Dong District, Hanoi 12116, Viet Nam. E-mail: van.hoangnhu@phenikaa-uni.edu.vn
Cite this: RSC Adv. , 2023, 13, 34510
Received 6th November 2023
Accepted 17th November 2023
DOI: 10.1039/d3ra07567b
rsc.li/rsc-advances
34510 | RSC Adv., 2023, 13, 34510–34519 © 2023 The Author(s). Published by the Royal Society of Chemistry
RSC Advances
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