7082
|
wileyonlinelibrary.com/journal/jace J Am Ceram Soc. 2020;103:7082–7094. © 2020 American Ceramic Society (ACERS)
1
|
INTRODUCTION
Temperature, as one of the fundamental parameters of ther-
modynamics, is a key parameter to describe the physical and
chemical properties for functional materials.
1
Therefore, it
is necessary to accurately and fleetly detect temperature for
practical applications. The conventional contact thermome-
ters based on bimetal and glass liquid would frequently suf-
fer from environmental disturbance and long response time
which result in a difficulty of measuring temperature distri-
bution in some areas.
2−4
Fortunately, the optical thermome-
ters based on the fluorescence intensity ratio (FIR) technique
in luminescent materials have been widely investigated and
promised for next-generation noncontact thermometers as a
potential application in electrical power stations, biological
environments, oil refineries, coal mines, and intracellular
temperature measurements due to lots of obvious advantages
of high detection spatial resolution, high precision, and excel-
lent sensing sensitivity in comparison with the conventional
contact thermometers as we mentioned above.
5−8
The FIR
technique could estimate the sensing sensitivity of lumines-
cent materials via comparing the temperature-dependent
emission intensity between in a pair of thermal-couple levels
at varying temperatures.
9
Currently, rare-earth (RE) ions-activated phosphors have
been lucubrated and could be potentially used in optical ther-
mometers, flexible-display films, white lighting-emitting
didoes, security inks, field emission displays, and some nu-
merous optical applications.
10−16
Especially, the non-contact
optical thermometers based on RE ions-activated lumines-
cent materials have drawn much research attention owing
to their unique functions of simple operation, applicability,
and intuition. Various members such as Tm
3+
(
3
F
2/3
,
3
H
4
),
Ho
3+
(
5
F
2/3
,
3
K
8
), Dy
3+
(
4
F
9/2
,
4
I
15/2
), Nd
3+
(
4
F
7/2
,
4
F
3/2
), and
Received: 5 June 2020
|
Revised: 3 July 2020
|
Accepted: 8 July 2020
DOI: 10.1111/jace.17386
ORIGINAL ARTICLE
Thermal-couple levels of
4
S
3/2
and
2
H
11/2
in Na(Ca, Sr)
La(VO
4
)
2
:Er
3+
phosphors for potential optical thermometers
Yongbin Hua
|
Jae Su Yu
Department of Electronic Engineering,
Institute for Wearable Convergence
Electronics, Kyung Hee University,
Gyeonggi-do, Republic of Korea
Correspondence
Jae Su Yu, Department of Electronic
Engineering, Institute for Wearable
Convergence Electronics, Kyung Hee
University, Yongin-si, Gyeonggi-do 17104,
Republic of Korea.
Email: jsyu@khu.ac.kr
Funding information
National Research Foundation
of Korea, Grant/Award Number:
2018R1A6A1A03025708 and
2020R1A2B5B01002318
Abstract
Novel green-emitting erbium(III) (Er
3+
)-activated Na(Ca, Sr)La(VO
4
)
2
phosphors
with an interesting and stable trigonal structure were prepared. The crystal structure,
elemental composition, morphology, photoluminescence, and sensing properties were
investigated in detail. The color purity values of optimal NaSrLa(VO
4
)
2
:0.05Er
3+
and NaCaLa(VO
4
)
2
:0.05Er
3+
phosphors were calculated to be about 92.91% and
90.73% with the Commission Internationale de I’Eclairage color coordinates of
(0.283, 0.684) and (0.295, 0.676), respectively. Meanwhile, the sensing property
and cycling performance of those samples were also studied based on the thermal-
couple levels of
4
S
3/2
and
2
H
11/2
. The maximum absolute sensing sensitivity values
of the NaCaLa(VO
4
)
2
:Er
3+
and NaSrLa(VO
4
)
2
:Er
3+
phosphors were found to be
9.23 × 10
−3
and 7.69 × 10
−3
K
−1
while the relative sensing sensitivity values were
found to be 1.15% and 1.20% K
−1
, respectively. Furthermore, several repeated tests
confirmed that the cycling performance was stable, demonstrating that the result-
ant samples with high and stable sensing sensitivity are great potential for optical
thermometers.
KEYWORDS
cycling performance, FIR technique, optical thermometers, sensitivity