Article pubs.acs.org/jced
Phase Equilibrium System of CsCl−TbCl3−HCl(∼7.6 mass %)−H2O at 298.2 ± 0.1 K and Fluorescent and Thermal Properties of Its SolidPhase Compounds in the System Hui Wang,*,† Qi-Chao Yang,‡ and Li Li† †
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry (Ministry of Education), College of Chemistry & Materials Science, Northwest University, Xi’an 710069, P. R. China ‡ College of Chemistry and Pharmacy Engineering, Nanyang Normal University, Nanyang 473061, P. R. China ABSTRACT: The solubility data of the quaternary system CsCl−TbCl3−HCl(∼7.6 mass %)−H2O at 298.2 K were determined, and the corresponding phase diagram according to central projection data on the trigonal basal face CsCl−TbCl3−H2O was plotted. The diagram includes three invariant points and four crystallization fields corresponding to CsCl, Cs5TbCl8·6H2O, Cs2TbCl5·6H2O, and TbCl3·6H2O. Two new solid-phase compounds of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O, which are congruently soluble in the system, were isolated and characterized by the methods of powder X-ray diffraction, thermogravimetric, and differential thermal analysis. The standard molar enthalpies of solution for the two compounds of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O were measured to be (60.64 ± 0.28) and (14.08 ± 0.45) kJ·mol−1 by heat conduction microcalorimetry under the conditions of infinite dilution, and their standard molar enthalpies of formation were calculated to be −(5087.1 ± 1.7) kJ·mol−1 and −(3764.2 ± 1.0) kJ·mol−1. The fluorescence excitation and emission spectra of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O were measured. The results show that upconversion spectra exhibit for Cs5TbCl8·6H2O at 500 nm and 545 nm and for Cs2TbCl5·6H2O at 495 nm and 545 nm excited at 750 nm, and the upconversion intensity increases with the increase of TbCl3 contents in CsCl.
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INTRODUCTION
EXPERIMENTAL SECTION Reagents. Cesium chloride (99.5+ mass % pure) purchased from Sinopharm Chemical Reagent Co., Ltd., Shanghai, China, was analytical reagent grade and without further purification. Terbium chloride (99.99 mass % pure) was extra pure grade, purchased from National Engineering Research Centre of Rare Earth Metallurgy and Function Materials, Baotou, China. Hydrochloric acid (guaranteed reagent) was purchased from Luoyang Haohua Chemical Reagent Company, Luoyang, China. Potassium chloride (99.99 mass % pure) was spectrum pure grade, purchased from Sinopharm Chemical Reagent Co., Ltd., Shanghai, China. Deionized water was used (resistivity = 5.7 MΩ·cm) in the present work. Investigations on the System at 298.2 ± 0.1 K and Analysis Methods. For he method of investigation of the solubility of the CsCl−TbCl3−HCl(∼7.6 mass %)−H2O system, see refs 9 and 12. The phase equilibrium of the solubility of the CsCl−TbCl3−HCl(∼7.6 mass %)-H2O quaternary system can be reached in about 5 days. For analysis methods of saturated solutions and the corresponding wet solid phases of the samples, see ref 13. The accuracy of weighing was ± 0.0001 g.
In previous papers we reported a series of the results concerning on the equilibrium phase diagrams of quaternary system of CsCl−RECl3−HCl−H2O (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tm, Lu, and Y).1−10 Relevant results had been evaluated.11 Twenty new solid-phase compounds in the systems, Cs5EuCl8·14H2O (5:1 type), Cs4RECl7·nH2O (RE = Gd, Lu, Y, n = 1, 5, 10) (4:1 type), Cs3RECl6·nH2O (RE = La, Ce, Pr, n = 3, 7) (3:1 type), Cs2RECl5·nH2O (RE = La, Nd, Sm, Eu, Gd, Lu, n = 2, 4, 7, 9) (2:1 type), CsRECl4·nH2O (RE = La, Ce, Pr, Nd, n = 4, 6, 9) (1:1 type), Cs3RE2Cl9·14H2O (RE = Tm, Y) (3:2 type), and Cs9Lu5Cl24·29H2O (9:5 type), were synthesized by using the phase equilibrium method. Among these compounds, some of them show the phenomenon of upconversion fluorescence excited in the near-infrared region such as Cs3CeCl6·3H2O, CsCeCl4·4H2O, Cs5EuCl8·14H2O, and Cs2EuCl5·4H2O. This demonstrates that there is a potential application for these compounds. As a part of the systematic investigation on the quaternary system of CsCl−REX3−HX− H2O, this paper is concerned with phase relationships of the CsCl−TbCl3−HCl(∼7.6 mass %)−H2O system at 298.2 K. Based on the phase relation, two new solid-phase compounds of formation in the 5:1 type (Cs5TbCl8·6H2O) and 2:1 type (Cs2TbCl5·6H2O) were derived from the system at 298 K and were characterized by X-ray, TG-DTG, and fluorescence spectra. The standard molar enthalpies of solution of new solid-phase compounds in water were measured. © 2013 American Chemical Society
Received: January 11, 2013 Accepted: March 18, 2013 Published: March 29, 2013 1034
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Table 1. Solubility Data (in Mass Fraction) of the Saturated Solution of the Quaternary System CsCl−TbCl3−HCl(∼7.6 mass %)−H2O at (298.2 ± 0.1) K and Central Projection Data on the Trigonal Basal Face CsCl−TbCl3−H2Oa composition of solution/mass %
composition of residue/mass %
composition in the tetrahedral
composition in the trigonal basal faceb
no.
HCl
CsCl
TbCl3
CsCl
TbCl3
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 170 18 19
7.32 8.02 7.16 7.63 7.58 7.36 7.51 7.39 7.85 7.96 7.28 7.66 7.33 7.83 7.25 7.82 8.05 7.74 7.58
53.13 51.46 50.36 46.72 47.36 47.10 44.33 42.32 39.00 37.94 34.45 31.35 27.53 22.23 20.11 19.68 13.71 7.73 0.00
0.00 1.70 4.59 8.84 8.74 9.25 10.99 12.68 14.64 15.15 18.19 19.53 23.42 25.43 27.45 26.97 28.95 32.37 36.08
57.33 55.94 54.25 50.57 51.24 50.85 47.93 45.69 42.33 41.22 37.15 33.95 29.70 24.12 21.68 21.35 14.92 8.38 0.00
w(HCl) 0.00 1.84 4.94 9.57 9.46 9.98 11.88 13.69 15.89 16.47 19.62 21.15 25.27 27.59 29.60 29.26 31.48 35.08 39.04
composition in the tetrahedral HCl
CsCl
composition in the trigonal basal face
TbCl3
CsCl
TbCl3
solid phasec
0.83 0.44 8.62 16.74 19.24 19.75 19.96 25.11 34.44 31.06 34.75 33.56 35.02 36.49 43.91 62.52 59.32 70.10
87.33 96.63 76.96 65.39 67.17 66.04 65.50 52.63 46.49 45.56 45.83 41.51 44.23 37.40 21.21 3.23 2.56 0.00
0.85 0.44 8.85 17.26 19.66 20.20 20.43 25.82 34.86 31.78 35.17 34.30 35.50 37.24 45.06.C+D 65.53 60.76 70.10
A A A A+B A+B B B B B+C C C C C C C+D C+D D D D
= ∼7.6 mass % 2.50 0.52 2.59 2.99 2.13 2.27 2.27 2.76 1.18 2.27 1.19 2.14 1.35 2.04 2.56 1.60 2.38 0.00
85.15 96.12 74.97 63.44 65.74 64.54 64.01 51.17 45.94 44.53 45.29 40.62 43.63 36.64 20.66 3.18 2.50 0.00
The estimated accuracy (in the mass fraction) for HCl, TbCl3, and CsCl is ±0.25%, ± 0.15%, and ±0.30%, respectively. bDouble saturation point (average): E1: TbCl3 9.51%, CsCl 50.90%; E2: TbCl3 15.89%, CsCl 42.33%; E3: TbCl3 29.43%, CsCl 21.51%. cCompounds: A: CsCl; B: Cs5TbCl8·6H2O; C: Cs2TbCl5·6H2O; D: TbCl3·6H2O. a
0.01) K, which was controlled by water put in the 15 cm3 stainless steel sample cell and reference cell of the calorimeter. After thermal equilibration for at least 1.5 h, the solid sample was dissolved in deionized water. The thermal effect was then recorded automatically on a computer. The total time required for the complete dissolution was about 20 min. There were no solid residues observed after the dissolution in each calorimetric experiment.
Equipment and Conditions. Thermal characterization of the compounds was undertaken with a NETZSCH STA449C thermal analysis apparatus (TG-DTG) that worked with a heating rate of 10 K·min−1 under a N2 atmosphere with a flow rate of 100 cm3·min−1; X-ray diffraction (XRD) measurements were performed by a D/Max-3C diffractometer using Cu Kα radiation, 50 kV and 80 mA, at room temperature, in air. The excitation and emission spectra of the compounds were recorded on the Hitachi model F-4500 fluorescence spectrophotometer. The excitation illuminant of the Hitachi model F-4500 fluorescence spectrophotometer is equipped with the Xe lamp. Excitation and emission illuminants are continuously in the range of 250 nm to 900 nm and 250 nm to 700 nm, respectively; the scanning rate is 12 000 nm·min−1, and excitation and emission slits are 5.0 nm and 5.0 nm, respectively. The enthalpies of solution were measured by using an RD496-III-2000 heat conduction microcalorimeter (Southwest Institute of Electron Engineering, China), which was described in detail previously.14 To test the performance of the RD496III-2000 heat conduction microcalorimeter, the calorimetric constant at 298.15 K was first determined by the Joule effect. The calorimetric constant obtained in this way was (57.29 ± 0.041) μV·mW−1. The reliability of the calorimeter was confirmed by measuring the enthalpy of solution of KCl(s) in deionized water. The average value of ΔsolHm(KCl) obtained by the experiment was (17.36 ± 0.07) kJ·mol−1 (n = 6), which is in excellent agreement with that of 17.234 kJ·mol−1 reported in the lierature.15 It shows that the device used for measuring the enthalpy of solution in this work is reliable. Each calorimetric experiment was carried out five times. The temperature of the calorimetric experiment was (298.15 ±
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RESULTS AND DISCUSSION CsCl−TbCl3−HCl (∼7.6 mass %)−H2O Quaternary System at 298.2 ± 0.1 K and Characterization of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O. The solubility data of the CsCl−TbCl3−HCl (∼7.6 mass %)−H2O quaternary system and central projection data of CsCl−TbCl3−H2O triangle basal face are listed in Table 1. The corresponding phase diagram is shown in Figure 1. In the phase diagram, there are three discontinuity points and four crystallization fields which correspond to the four equilibrium solid phases CsCl, Cs5TbCl8·6H2O (5:1 type), Cs2TbCl5·6H2O (2:1 type), and TbCl3·6H2O, respectively. The formation of the solid phase compounds Cs5TbCl8·6H2O and Cs2TbCl5·6H2O was determined with the wet residue method of Schreinemarkers.16 Their results of chemical analysis are TbCl3 22.71 mass % (theor. 21.83 mass %), CsCl 69.43 mass % (theor. 69.28 mass %) and TbCl3 37.26 mass % (theor. 37.36 mass %), CsCl 47.69 mass % (theor. 47.42 mass %), respectively. Furthermore, the two compounds 5:1 type and 2:1 type are congruently soluble in the hydrochloric acid medium of 7.59 mass % at 298 K, and both can be obtained from the system easily. To the best of our knowledge, the compounds both Cs 5 TbCl8 ·6H 2 O and Cs2TbCl5·6H2O have not been reported, thus far. 1035
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were different, which proved that Cs5TbCl8·6H2O and Cs2TbCl5·6H2O obtained from the region of solid phase were new compounds. T h e T G - D T G g r a p h s o f Cs 5 T bC l 8 · 6 H 2 O a n d Cs2TbCl5·6H2O were displayed in Figures 4 and 5. According
Figure 1. Solubility diagram of the quaternary system CsCl−TbCl3− HCl(∼7.6 mass %)−H2O projected on CsCl−TbCl3−H2O at (298.2 ± 0.1) K. The E1, E2, and E3 stand for double saturation points.
Figure 4. Thermogravimetry and differential thermogravimetry (TG, DTG) curves of Cs5TbCl8·6H2O.
The X-ray powder diffraction patterns of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O depicted in Figures 2 and 3, respectively.
Figure 5. Thermogravimetry and differential thermogravimetry (TG, DTG) curves of Cs2TbCl5·6H2O. Figure 2. X-ray powder diffraction spectrum of Cs5TbCl8·6H2O.
to Figure 4, the dehydration temperature of Cs5TbCl8·6H2O was between 328 K and 398 K, and the percent of the mass loss is 9.32 mass % (theoretical, 8.89 mass %); according to the figure 5, the dehydration of Cs2TbCl5·6H2O occurred between 321 K and 496 K, and the percent of the mass loss is 14.94 mass % (theoretical, 15.22 mass %). The mass-loss value of the both compounds agreed with the data of water determined by the Schreinemaker method16 and analyzed by a titration method.12 Enthalpies of Solution and Standard Molar Enthalpy of Formation. Table 2 give the results of the calorimetric measurements under the condition of infinite dilution. The molar enthalpies of solution Δ sol H m and Δ sol H m of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O are (60.64 ± 0.28) kJ·mol−1 and (14.08 ± 0.45) kJ·mol−1 in water at 298.15 K, respectively. The uncertainty is estimated as twice the standard deviation of the mean. The molar enthalpies of formation of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O can be calculated according to the following equations:
Figure 3. X-ray powder diffraction spectrum of Cs2TbCl5·6H2O.
Comparing the X-ray graphs of Cs 5 TbCl 8 ·6H 2 O and Cs2TbCl5·6H2O with that of CsCl and TbCl3·6H2O, they 1036
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Table 2. Molar Enthalpies of Solution of ΔsolHΘm (Cs5TbCl8·6H2O) and ΔsolHΘm (Cs2TbCl5·6H2O) in Deionized Water at (298.15 ± 0.01) Ka ΔsolHΘm (Cs5TbCl8·6H2O)
a
no.
m/mg
Qs/mJ
1 2 3 4 5 meanb
10.00 8.77 8.90 8.89 8.82
500.6 435.1 447.4 443.3 438.5
−1
kJ·mol
60.83 60.29 61.08 60.60 60.41 60.64 ± 0.28
ΔsolHΘm (Cs2TbCl5·6H2O) m/mg
Qs/mJ
kJ·mol−1
11.30 7.00 8.12 8.52 8.83
228.8 138.9 166.5 158.9 174.5
14.38 14.09 14.56 13.24 14.13 14.08 ± 0.45
In each experiment, 4.0 cm3 water was used. bUncertainty is twice the standard deviation of the mean.
Δf Hm Θ(Cs5TbCl8· 6H 2O)(s) = 5Δf Hm Θ(Cs+)(aq) + Δf Hm Θ(Tb3 +)(aq) + 8Δf Hm Θ(Cl−)(aq) + 6Δf Hm Θ(H 2O)(l) − Δsol Hm Θ(Cs5TbCl 8·6H 2O)(s)
Δf Hm Θ(Cs2TbCl5· 6H 2O)(s) = 2Δf Hm Θ(Cs+)(aq) + Δf Hm Θ(Tb3 +)(aq) + 5Δf Hm Θ(Cl−)(aq) + 6Δf Hm Θ(H 2O)(l) − Δsol Hm Θ(Cs 2TbCl5·6H 2O)(s)
The standard molar enthalpies of formation of Cs+, Tb3+, Cl−, and H2O were taken from the NBS tables,17 namely, −(258.28 ± 0.5) kJ·mol−1, −(682 ± 0.5) kJ·mol−1, −(167.159 ± 0.1) kJ·mol−1, and −(285.83 ± 0.042) kJ·mol−1 for Cs+, Tb3+, Cl−, and H2O, respectively. The standard molar enthalpies of formation of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O were −(5087.1 ± 1.7) kJ·mol−1 and −(3764.2 ± 1.0) kJ·mol−1 calculated by using these schemes and data. Upconversion Fluorescence of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O. A series of excitation spectra were observed in the range of 650 nm to 900 nm when Cs5TbCl8·6H2O was monitored in the range of 450 nm to 600 nm. Among these excitation spectra, their intensity monitored at 545 nm is the strongest. Figure 6 shows corresponding excitation spectra
Figure 7. Upconversion luminescence spectra of Cs5TbCl8·6H2O (λex = 750 nm).
nm or 850 nm which are attributed to the f → f (5D4 → 7F6) energy-transfer of Tb3+ ion in CsCl. The corresponding luminous energy of emission fluorescence are about ΔE = 19999 cm−1, λEM = 500 nm (λEX = 750 nm) and ΔE = 18348 cm−1, λEM = 545 nm (λEX = 700, 750, 810 and 850 nm). The same spectroscopic examination was also implemented for the compound Cs2TbCl5·6H2O. Similarly, the illuminant intensity of those excitation spectra monitored at 545 nm is the strongest (Figure 8). The peaks were observed at 700 nm, 750
Figure 6. Excitation spectra of Cs5TbCl8·6H2O (λem = 545 nm). Figure 8. Excitation spectra of Cs2TbCl5·6H2O (λem = 545 nm).
emitted at 545 nm, and the intensity of the excitation spectrum at 750 nm is the strongest. When excited by the illuminant of 850 nm, the emission spectra of the compound exhibited at 545 nm. When excited at 750 nm (see corresponding Figure 7), emission spectra exhibited at 500 nm and 545 nm, respectively, and the intensity of the emission spectra at 545 nm is stronger than that at 500 nm. This indicates that the compound Cs5TbCl8·6H2O has upconversion luminescence excited at 750
nm, 810 nm, and 850 nm, respectively, and at 700 nm and 750 nm are the strongest. Figure 9 shows that the emission spectra of the compound at 495 nm and 545 nm when it was excited by the illuminant of 750 nm or 700 nm. It demonstrates that Cs2TbCl5·6H2O compound also has upconversion luminescence phenomenon when excited at 700 nm or 750 nm, and 1037
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(2) Wang, H.; Duan, J. X.; Ran, X. Q.; Gao, S. Y. Study on the Phase Diagram of CsCl−CeCl3−HCl(11%)−H2O System at 298.15 K and the Fluorescence Properties of its Compounds. Chin. J. Chem. 2002, 20 (9), 904−908. (3) Li, Y. H.; Ran, X. Q.; Chen, P. H. Studies on Quaternary Systems CsCl−PrCl3−13% HCl−H2O (298 K) and CsCl−PrCl3−42% HAc− H2O (303 K). Chem. J. Chin. Univ. 1997, 18 (3), 353−356 (in Chinese). (4) Jiao, H.; Wang, H.; Ran, X. Q.; Chen, P. H. Study on the Quaternary System of CsCl−NdCl3−13%HCl−(42%HOAc)−H2O. Acta Chim. Sin. 1998, 56, 854−858 (in Chinese). (5) Li, Y. H.; Ran, X. Q.; Chen, P. H. Phase Behavior of Hydrochloric Aqueous Solution Containing Cesium and Samarium Chloride and Two Sub-Group Effect of The Light Rare Earth Element. Zh. Neorg. Khim. 1999, 44, 1207−1209. (6) Wang, H.; Duan, J. X.; Ran, X. Q. Study on Phase Diagram of (Cesium Chloride + Europium Trichloride + Hydrogen Chloride + Water) Quaternary System at T = 298.15 K and the Fluorescence Spectra of its Compounds. J. Chem. Thermodyn. 2002, 34, 1495−1506. (7) Wang, H.; Ran, X. Q.; Chen, P. H. A Study on Quaternary Systems MCl−GdCl3−HCl−H2O (M = K, Rb, Cs; 20 °C). Acta Chim. Sin. 1994, 52, 789−796 (in Chinese). (8) Qiao, Z. P.; Zhuo, L. H.; Zhang, S. S.; Wang, H. CsCl−TmCl3− HCl−H2O at 25 °C: Phase Equilibrium and New Solid Phase Compound. Chin. Inorg. Chem. 2006, 22, 1545−1549 (in Chinese). (9) Qiao, Z. P.; Xie, H. Q.; Zhuo, L. H.; Xin, C. Study on Phase Equilibrium in the Quaternary System CsCl−LuCl3−HCl (10.06%)− H2O at 298.15 ± 0.1 K and New Solid-Phase Compounds. J. Chem. Eng. Data 2007, 52, 1681−1685. (10) Wang, H.; Duan, J. X.; Ran, X. Q.; Gao, S. Y. Phase Equilibrium System of CsCl−YCl3−(9.5%) HCl−H2O at T = 298.15 K and Its Compounds. Chin. J. Chem. 2004, 22, 1129−1132. (11) Mioduski, T.; Gumiński, C.; Zeng, D. W. IUPAC-NIST Solubility Data Series. 87. Rare Earth Metal Chlorides in Water and Aqueous Systems. J. Phys. Chem. Ref. Data 2008, 37, 1765. (12) Wang, H.; Li, L.; Ran, X. Q.; Wang, X. F. Studies on Phase Equilibria in the Systems CdCl2−PrCl3−HCl (8.3%)−H2O and CdCl2−PrCl3−H2O at 298 ± 1 K. J. Chem. Eng. Data 2006, 51, 1541−1545. (13) Qiao, Z. P.; Ge, G.; Chen, X. Phase Equilibrium System of RbCl-SmCl3-HCl(12.84, 22.66% by Mass)-H2O at 298.15 K and Standard Molar Enthalpy of Formation of RbSmCl4·4H2O. J. Chem. Eng. Data 2009, 54, 1807−1810. (14) Ji, M.; Liu, M. Y.; Gao, S. L. A New Microcalorimeter for Measuring Thermal Effects. J. Instrum. Sci. Technol. 2001, 29, 53−57. (15) Weast, R. C. CRC Handbook of Chemistry and Physics, 70th ed.; CRC Press: Boca Raton, FL, 1989. (16) Chen, Y. S. Analysis of Physical Chemistry; Higher Education Press: Beijing, 1988; pp 505−506. (17) Wagman, D. D.; Evans, W. H.; Parker, V. B.; Schumm, R. H.; Halow, I.; Bailey, S. M.; Chumey, K. L.; Nuttal, R. L. The NBS Tables of Chemical Thermodynamic Properties; American Chemical Society: Washington, DC, 1982.
Figure 9. Upconversion luminescence spectra of Cs2TbCl5·6H2O (λex = 750 nm).
the upconversion fluorescence spectrum of Cs2TbCl5·6H2O at 495 nm and 545 nm is attributed to the f → f (5D4 → 7F6) energy level transition of Tb3+ ion in Cs2TbCl5·6H2O. The luminous energy of emission fluorescence are aboutΔE = 20202 cm−1, λEM = 495 nm (λEX = 700 nm and 750 nm) and ΔE = 18348 cm−1, λEM = 545 nm (λEX = 700 nm, 750 nm, 810 nm, and 850 nm). Comparing Cs5TbCl8·6H2O with Cs2TbCl5·6H2O, the result in Figures 7 and 9 shows that the upconversion luminescence intensity of Cs 2 TbCl 5 ·6H 2 O is stronger than that of Cs5TbCl8·6H2O. This indicates that upconversion luminescence intensity of the compounds made up of CsCl and TbCl3 will increase with the increasing of Tb3+ in CsCl.
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CONCLUSION The quaternary system CsCl−TbCl3−HCl (∼7.6 mass %)− H2O was investigated, and the corresponding phase diagram was constructed, in which two new solid-phase compounds Cs5TbCl8·6H2O and Cs2TbCl5·6H2O were found, and they are congruently soluble in an average medium of ∼7.6 mass % HCl. The standard molar enthalpies of solution for the two compounds of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O were measured under the condition of infinite dilution and their standard molar enthalpies of formation were calculated to be −(5087.1 ± 1.7) kJ·mol−1 and −(3764.2 ± 1.0) kJ·mol−1, respectively. Furthermore, the fluorescence excitation and emission spectra of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O were also measured. The results show that the two new compounds have upconversion fluorescence properties. The upconversion spectra for Cs5TbCl8·6H2O exhibit at 500 nm and 545 nm excited at 750 nm and for Cs2TbCl5·6H2O at 495 nm and 545 nm excited by 750 nm or 700 nm, and the upconversion intensity increase with the increasing of Tb3+ contents in CsCl.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Li, Y. H.; Ran, X. Q.; Chen, P. H. Studies on Solvent System of Cesium Chloride and Lanthanum Chloride and Synthesization of Four Types of New Compounds. J. Rare Earth 1997, 15 (2), 113−116. 1038
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