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Non-contact thermometry with dual-activator luminescence of Bi3+/Sm3+: YNbO4 phosphor Xiuna Tiana,∗, Hongjian Doua, Lingyuan Wub a b
Department of Public Sciences, Jinzhou Medical University, Jinzhou, Liaoning, 121001, China Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan, 621900, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Optical properties Sensors Niobates Spectroscopy
Based on the luminescence of Bi3+, novel temperature sensing materials YNbO4:Bi3+ and YNbO4:Bi3+/Sm3+ were successfully synthesized by solid state reaction. The XRD patterns show that the synthesized materials have a pure phase of YNbO4. With the excitation of 314 nm, the YNbO4:Bi3+ material shows intense temperaturedependent luminescence in the range of 303 K–463 K. Based on the temperature-dependent luminescence of Bi3+ in YNbO4, the maximum relative sensitivity can be obtained at 434 K (1.72% K−1). Under the excitation of 406 nm, the YNbO4:Sm3+ material shows the characteristic emission peaks of Sm3+. In YNbO4:Bi3+/Sm3+ phosphor, the large overlap between the emission spectra of Bi3+ and the excitation spectra of Sm3+ leads to a significant energy transfer from Bi3+ to Sm3+. With the excitation of 314 nm, the emission spectra of YNbO4:Bi3+/Sm3+ material shows the characteristic peaks of Bi3+ and Sm3+. The luminescence intensity ratio of Sm3+ and Bi3+ shows a strong temperature dependence. Based on the luminescence intensity ratio, a large relative sensitivity is obtained at 455 K (1.57% K−1).
1. Introduction Temperature is one of the basic physical parameters in various scientific fields. In recent years, non-contact optical thermometry has aroused researchers’ interests due to its fast response rate and high spatial resolution [1–3], such as quantum dot [4], rare earth doped upand down-conversion materials [5,6], rare earth and transition metal ions codoped materials [7]. However, it is still a challenge to obtain a thermometric material with high sensitivity and stability. Ions with s2 configuration are of great importance in the field of luminescence, and the influence of the host lattice on the luminescence is drastic. Over the last decade, the luminescence of ns2 ions has received considerable attention, such as Sb3+(5s2) [8], Bi3+ and Pb2+(6s2) [9,10]. In addition, Reisfeld et al. reported that the luminescence of Sn2+ and Sb3+ in oxide glasses strongly depended on the temperature in 1975 [11]. In 2019, Li et al. reported the ratiometric temperature sensing based on the luminescence of Bi3+/Eu3+ in Ca2Y8(SiO4)6O2 [12]; Ding et al. reported the temperature sensing based on the luminescence of Bi3+/Mn4+ in Ca14Al10Zn6O35 phosphor [13]. It can be seen ions with s2 configuration may have great potential application value in temperature sensing. So far, however, there are only a few researches on temperature sensing based on ions with s2 configuration [14,15]. In addition, it is well known that the optical ∗
thermometry based on the luminescence intensity ratio has the advantage of high accuracy. For trivalent rare earth ions (RE3+), the outer electronic configuration is 5s25p6, which shield the effect of the crystal field on the 4f shell electrons. So RE3+ in crystal field are less affected by the surrounding crystal field, and have atomic-like spectral properties. Among the RE3+, the trivalent samarium (Sm3+) ion is one of the essential activators to realize orange-red emission owing to its abundant energy levels. Recently, a series of Sm3+ activated phosphors were investigated, such as CaWO4:Sm3+ [16], Gd2MoO6:Sm3+ [17], YNbO4:Sm3+ [18], Y2(MoO4)3:Sm3+ [19], Sm3+ doped Li2O-MO-B2O3 glasses [20]. Therefore, the materials based on the different temperature-dependent luminescence of Bi3+ and Sm3+ may have great potential application value in temperature sensing. The fergusonite structure ABO4 compounds as host matrices are of great importance in the field of luminescent materials. The luminescence properties of rare earth doped YVO4 [21], YNbO4 [22], YPO4 and LaPO4 have been extensively investigated [23]. Jiang et al. studied the Bi3+/Eu3+ doped YNbO4 phosphor for UV pumped white light-emitting diodes [24]. Chen et al. reported the near-infrared downconversion quantum cutting phenomena of Tm3+ in Tm3+/Bi3+:YNbO4 phosphor [25]. Guo et al. reported the luminescence and energy transfer process of Bi3+/Sm3+ in YNbO4 phosphors [26]. In addition, lanthanide activated YNbO4 materials in temperature sensing have also been
Corresponding author. E-mail address:
[email protected] (X. Tian).
https://doi.org/10.1016/j.ceramint.2020.01.068 Received 1 December 2019; Received in revised form 22 December 2019; Accepted 8 January 2020 0272-8842/ © 2020 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Please cite this article as: Xiuna Tian, Hongjian Dou and Lingyuan Wu, Ceramics International, https://doi.org/10.1016/j.ceramint.2020.01.068
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investigated [27–29]. According to the report of Guo et al., Bi3+ yields bright blue emission as an activator and sensitizes Sm3+ to produce orange-red emission in YNbO4:Bi3+/Sm3+ system [26]. And the two emission bands of Bi3+ and Sm3+ are basically separated, which enables signal discrimination. However, there are few reports on Bi3+/ Sm3+ codoped YNbO4 phosphor for temperature sensing, which is based on the different thermal quenching properties between Bi3+ and Sm3+. Herein, the temperature-dependent fluorescence performance of Bi3+/Sm3+ codoped YNbO4 phosphor is studied in detail aiming to develop new application of this phosphor for temperature sensing. In the present paper, we synthesized YNbO4:xBi3+/ySm3+ materials via a high temperature solid state reaction method. By the excitation and emission spectra, we investigated the luminescence properties of the YNbO4:xBi3+/ySm3+ materials. In addition, we systematically studied the temperature-dependent luminescence properties of YNbO4:Bi3+ and YNbO4:Bi3+/Sm3+ materials. 2. Experimental procedure Fig. 2. Normalized PLE and PL spectra of (a)YNbO4 (λem = 406 and 443 nm, λex = 265 and 305 nm), (b) YNbO4:1%Bi3+ (λem = 475 nm, λex = 314 nm), (c) YNbO4:0.5%Sm3+ (λem = 650 nm, λex = 265 and 406 nm) and (d) YNbO4:1%Bi3+/0.5%Sm3+ (λem = 650 nm, λex = 314 nm) at room temperature.
All the materials are purchased from the Aladdin Chemical Reagent Company in Shanghai, China. The raw materials Y2O3 (99.99%), Nb2O5 (99.99%), Bi2O3 (99.0%) and Sm2O3 (99.9%) are used directly without any processing and purification. All samples were prepared by a high temperature solid state reaction method [30]. In a typical synthesis process of YNbO4:xBi3+/ySm3+ (x = 0, 1 mol%; y = 0, 0.5 mol%), the Stoichiometric raw materials (Y2O3, Nb2O5, Bi2O3, Sm2O3) are weighed and ground in an agate mortar for 1 h. The mixture is heated in a muffle furnace at 1473 K for 4 h. Then we obtained the final products after cooling to room temperature. The phase identification was performed by an X-ray diffractometer (Rigaku-TTR-III) with Cu Kα radiation (λ = 0.15418 nm) in the 2θ range from 20° to 70°. The optical measurements of the prepared samples at different temperatures were carried out using a Jobin-Yvon HRD-1 double monochromator equipped with a Hamamatsu R928 photomultiplier and a 150 W xenon lamp. The temperature of the samples ranging from 303 to 463 K was controlled by a homemade temperature control system.
23–1486 YNbO4, and no other impurity peak is detected, indicating that pure monoclinic phase of YNbO4 has been synthesized. In other words, the Bi3+ and Sm3+ ions have incorporated into the YNbO4 lattice to substitute for yttrium. In Fig. 2, it shows the excitation and emission spectra of YNbO4, YNbO4:Bi3+, YNbO4:Sm3+ and YNbO4:Bi3+/Sm3+. For YNbO4 phosphor, it is known as a self-activated phosphor, and the charge-transfer gap is reported to be 4.3 eV [31]. As shown in Fig. 2a, the emission spectra show blue luminescence with the excitation of 265 nm and 305 nm, which have peaks at 406 nm and 443 nm respectively. Under the excitation of 265 nm and 305 nm, the CIE coordinates of YNbO4 phosphor are (0.170, 0.106) and (0.185, 0.216). By monitoring the luminescence of 406 nm and 443 nm, the excitation spectra of YNbO4 phosphor show two excitation bands centered at 265 nm and 305 nm, which are attributed to the transition 1A1→1T2 and 1A1→1T1. The 265 nm band is well known by the host, whereas the 305 nm band has only been observed by Singh et al. and Shin et al. [22,32]. When Bi3+ ions were introduced into YNbO4 phosphor, the excitation spectrum shows a strong band at 314 nm, which is corresponding to the 1S0→3P1 transition of Bi3+ [22]. By the excitation of 314 nm, YNbO4:Bi3+ shows the characteristic luminescence of the host and Bi3+. The CIE coordinate of the emission spectrum in Fig. 2b is calculated to be (0.179, 0.225). As shown in Fig. 2b, the emission spectral shape of YNbO4:Bi3+ under the excitation of 314 nm is similar as that of YNbO4 host under the excitation of 305 nm, but the luminescence intensity of YNbO4:Bi3+ is strongly increased compared with that of the host, which can also be seen from the excitation spectrum. The possible reason for the similar spectral shape is that the spectral range of Bi3+ in YNbO4 phosphor overlap with that of the host. For YNbO4:Sm3+ phosphor, the excitation spectrum shows the characteristic excitation band and peaks of the host and Sm3+ by monitoring the luminescence of Sm3+ at 650 nm, which is shown in Fig. 2c. With the excitation of 265 nm, the YNbO4:Sm3+ shows the luminescence of the host and Sm3+. The luminescence peaks of Sm3+ at 566 nm, 613 nm, 650 nm and 710 nm correspond to the transitions 4G5/ 6 2→ HJ (J = 5/2, 7/2, 9/2, 11/2) [33,34]. In addition, by the direct excitation of Sm3+ at 406 nm, YNbO4:Sm3+ also shows the characteristic luminescence of Sm3+. With the excitation of 265 nm and 406 nm, the CIE coordinates of the emission spectra are (0.211, 0.129) and (0.513, 0.391), respectively.
3. Results and discussion The crystal structure of the as-prepared samples was identified by Xray diffraction measurements. As shown in Fig. 1, all diffraction peaks can be indexed by the standard powder diffraction file cards no.
Fig. 1. The XRD patterns of JCPDS No. 23–1486 YNbO4, and the synthesized YNbO4, YNbO4:1%Bi3+ YNbO4:1%Bi3+/0.5%Sm3+ and YNbO4: 0.5%Sm3+. 2
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Fig. 3. (a) The temperature-dependent emission spectra and (b) the relative sensitivity of YNbO4:Bi3+ in the temperature range of 303–463 K. The inset of (a) is the temperature-dependent integral intensity and fitting line of the emission spectra.
In Fig. 2d, it shows the excitation spectrum of YNbO4:Bi3+/Sm3+ by monitoring the luminescence of Sm3+ at 650 nm, which contains the excitation bands and peaks of the host, Bi3+ and Sm3+. It demonstrates that there is an obvious energy transfer from the host and Bi3+ to Sm3+. With the excitation of 314 nm, the YNbO4:Bi3+/Sm3+ shows the luminescence of the host, Bi3+ and Sm3+. And the CIE coordinate of the emission spectrum is (0.193, 0.206). In order to demonstrate the temperature sensing property of the phosphor, we measured the emission spectra of YNbO4:Bi3+ in the temperature range of 303–463 K with the temperature interval of 20 K. As shown in Fig. 3a, the luminescence intensity of the host and Bi3+ gradually decreases with the temperature increase. In the inset of Fig. 3a, we calculated the temperature-dependent integral intensity of
the YNbO4:Bi3+. The error bars in the inset of Fig. 3a represent the standard deviation of the measured intensity. When the temperature increases from 303 K to 463 K, the integral intensity drops to 12% of its original integral intensity at 303 K. The temperature-dependent intensity usually follows the Arrhenius-type equation [35,36]:
I (T ) ≈ I (Bi3 +) =
I0 1 + B exp(−ΔE / kB T )
(1)
where I0 and IT are the luminescence intensity at absolute temperature 0 K and T, respectively. B is a constant, and kB (kB = 8.629 × 10−5 eV K−1) is the Boltzmann constant. ΔE is the thermal quenching activation energy. By using the Arrhenius-type equation, we give the fitting line of the temperature-dependent 3
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[38–40]:
intensity in the inset of Fig. 3a. It can be seen the experimental result is well fitted with the Arrhenius-type equation. In the process of temperature-dependent intensity fitting, we ignore the luminescence intensity of the host, which is neglected compared with the luminescence intensity of Bi3+. It is known the relative sensitivity SR is a very important parameter for a thermometer, which is defined as:
SR =
1 dI I dT
R=
ISm IBi
=
I0Sm 1 + ABi exp(−ΔEBi / kB T ) ⋅ I0Bi 1 + ASm exp(−ΔESm / kB T )
≈ B + C exp(−ΔE / kB T )
(3)
The parameters in equation (3) are the same as these in equation (1). By using the fitting result we calculated the relative sensitivity SR and absolute sensitivity SA for YNbO4:Bi3+/Sm3+ material in Fig. 4c. The absolute sensitivity SA is another important parameter for a thermometer, which is defined as:
(2)
In Fig. 3b, we obtained SR of YNbO4:Bi by using the fitting result. The maximum relative sensitivity is 1.72% K−1 at 434 K. The possible reason for the strong temperature dependence of Bi3+ is the temperature quenching. As shown in the energy level diagram of Fig. 5, the different slopes of the ground state 1S0 and the excited state 3P0/3P1 may cause them to intersect somewhere. As the temperature rises, the electrons in the excited state may reach the intersection point of the excited state and the ground state. So the electrons on the excited states may reach the ground state without radiation by this way, and then reach the equilibrium position of the ground state through lattice relaxation. Therefore, the luminescence of Bi3+ shows a strong temperature dependence. Subsequently, we studied the temperature sensing property of YNbO4:Bi3+/Sm3+ phosphor. As shown in Fig. 4a, the luminescence intensity of Bi3+ decreases rapidly with the temperature increase while the luminescence intensity of Sm3+ decreases very slowly. In the inset of Fig. 4a, we calculated the temperature-dependent integral intensity of Bi3+ and Sm3+. The error bars in the inset of Fig. 4a represent the standard deviation of the measured intensity. For the integral intensity of Sm3+, we choose the transition 4G5/2 → 6H9/2 in the range of 628–685 nm. By using the Arrhenius-type equation (1), the temperature-dependent integral intensity of Bi3+ and Sm3+ can be well fitted, which are shown in the inset of Fig. 4 [1,37]. It is well known that the temperature sensing based on the luminescence intensity ratio has the advantages of high accuracy. So in Fig. 4b, we calculated the luminescence intensity ratio of Sm3+ and Bi3+. The error bars in Fig. 4b represent the standard deviation of the luminescence intensity ratio. It can be seen the luminescence intensity ratio of Sm3+ and Bi3+ gradually increases with the temperature increase in the range of 303–463 K. The temperature-dependent ratio can be well fitted with the equation 3+
SA =
dR dT
(4)
In the temperature range of 303–463 K, both SR and SA gradually increase with the temperature increase. And we can obtain the maximum value of SR and SA at 455 and 463 K, which are 1.57% K−1 and 0.27% K−1 respectively. To compare the temperature sensitivity with the published materials, we list the maximum relative sensitivities of different materials based on Bi3+ ions in Table 1 [12,14,15]. Besides the sensitivity, the repeatability is also very important for a temperature sensing material. So we repeated the measurement for the emission spectra of YNbO4:Bi3+ and YNbO4:Bi3+/Sm3+ materials four times in the temperature range of 303–463 K with the temperature interval of 20 K. As shown in Fig. 6, the luminescence intensity ratio of YNbO4:Bi3+/Sm3+ materials show good repeatability during the repeated heating and cooling processes. In addition, the error analysis of the standard deviations in aforementioned figures also shows that the integral intensity of Bi3+ and Sm3+ in YNbO4:Bi3+ and YNbO4:Bi3+/ Sm3+ materials has good repeatability. It indicates that this material has great potential application value in temperature sensing. 4. Conclusion In summary, Bi3+ and Sm3+ doped YNbO4 materials were successfully synthesized through a high temperature solid state reaction method. In the temperature range of 303–463 K, the luminescence intensity of Bi3+ in YNbO4:Bi3+ phosphor decreases rapidly with the temperature increase under the excitation of 314 nm. And the maximum relative sensitivity is 1.72% K−1 which can be obtained at 434 K. Fig. 4. (a) The temperature-dependent emission spectra of YNbO4:Bi3+/Sm3+ in the temperature range of 303–463 K with the temperature interval of 20 K. The inset is the temperature-dependent integral emission intensity and fitting line of Bi3+ (the blue) and Sm3+ (the pink). (b) The integral luminescence intensity ratio and fitting line of Sm3+ and Bi3+ in YNbO4:Bi3+/Sm3+ sample. (c) The relative sensitivity SR and absolute sensitivity SA of YNbO4:Bi3+/Sm3+ sample. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
4
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Fig. 5. The schematic diagram of energy levels of Bi3+, Sm3+ and [NbO4]3-, and the energy transfer processes in YNbO4:Bi3+/Sm3+ material. Table 1 The comparison of maximum SR among different materials. Materials
Temperature range(K)
SR (max) ( × 10−2K−1)
T (max) (K)
Ref.
Ca2Y8(SiO4)6O2:Bi3+, Eu3+ SrLu2O4:Bi3+,Eu3+ SrY 2O4:Bi3+,Eu3+ YNbO4:Bi3+ YNbO4:Bi3+/Sm3+
298–523 315–543 303–563 303–463 303–463
0.958 0.87 0.86 1.72 1.57
423 315 433 434 455
12 14 15 This work This work
Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgement This work was financially supported by Jinzhou medical university. References [1] P. Wang, et al., Double perovskite A2LaNbO6:Mn4+,Eu3+ (A = Ba, Ca) phosphors: potential applications in optical temperature sensing, Dalton Trans. 48 (2019) 10062–10069, https://doi.org/10.1039/c9dt01524h. [2] C. Matuszewska, K. Elzbieciak-Piecka, L. Marciniak, Transition metal ion-based nanocrystalline luminescent thermometry in SrTiO3:Ni2+,Er3+ nanocrystals operating in the second optical window of biological tissues, J. Phys. Chem. C 123 (2019) 18646–18653, https://doi.org/10.1021/acs.jpcc.9b04002. [3] K. Trejgis, L. Marciniak, The influence of manganese concentration on the sensitivity of bandshape and lifetime luminescent thermometers based on Y3Al5O12:Mn3+,Mn4+,Nd3+ nanocrystals, Phys. Chem. Chem. Phys. 20 (2018) 9574–9581, https://doi.org/10.1039/c8cp00558c. [4] J. Liu, H. Zhang, G.S. Selopal, S. Sun, H. Zhao, F. Rosei, Visible and near-infrared, multiparametric, ultrasensitive nanothermometer based on dual-emission colloidal quantum dots, ACS Photonics 6 (2019) 2479–2486, https://doi.org/10.1021/ acsphotonics.9b00763. [5] G. Xiang, et al., Dual-Mode optical thermometry based on the fluorescence intensity ratio excited by a 915 nm wavelength in LuVO4:Yb3+/Er3+@SiO2 nanoparticles, Inorg. Chem. 58 (2019) 8245–8252, https://doi.org/10.1021/acs.inorgchem. 9b01229. [6] Z. Liang, F. Qin, Y. Zheng, Z. Zhang, W. Cao, Noncontact thermometry based on downconversion luminescence from Eu3+ doped LiNbO3 single crystal, Sens. Actuators A Phys. 238 (2016) 215–219, https://doi.org/10.1016/j.sna.2015.12. 018. [7] D. Chen, S. Liu, Y. Zhou, Z. Wan, P. Huang, Z. Ji, Dual-activator luminescence of RE/TM:Y3Al5O12 (RE = Eu3+, Tb3+, Dy3+; TM = Mn4+, Cr3+) phosphors for selfreferencing optical thermometry, J. Mater. Chem. C 4 (2016) 9044–9051, https://
Fig. 6. The repeatability of the luminescence intensity ratio for YNbO4:Bi3+/ Sm3+ material with the temperature.
The luminescence intensity ratio of Sm3+ and Bi3+ in the YNbO4:Bi3+/ Sm3+ material gradually increases with the temperature increase upon the excitation of 314 nm. And the maximum relative sensitivity is 1.57% K−1 which can be obtained at 455 K. The repeatability test also shows that the YNbO4:Bi3+ and YNbO4:Bi3+/Sm3+ materials in temperature sensing have good stability and reproducibility. Considering all of these superiorities as well as the separated emission bands, the YNbO4:Bi3+/Sm3+ phosphor based on the temperature-dependent luminescence of Bi3+ is an excellent candidate for developing new optical temperature sensors. 5
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