J. Mater. Sci. Technol. ›› 2019, Vol. 35 ›› Issue (4): 483-490.DOI: 10.1016/j.jmst.2018.10.018
• Orginal Article • Previous Articles Next Articles
Kaishun Zouab, Guangzong Donga, Juncheng Liua*(), Boxu Xua, Danping Wanga
Received:
2017-12-12
Revised:
2018-07-03
Accepted:
2018-07-19
Online:
2019-04-05
Published:
2019-01-28
Contact:
Liu Juncheng
Kaishun Zou, Guangzong Dong, Juncheng Liu, Boxu Xu, Danping Wang. Effects of calcination temperature and Li+ ions doping on structure and upconversion luminescence properties of TiO2:Ho3+-Yb3+ nanocrystals[J]. J. Mater. Sci. Technol., 2019, 35(4): 483-490.
Fig. 1. XRD patterns of (a) pure TiO2, (b) Ho3+-Yb3+ co-doped TiO2, (c) Ho3+-Yb3+-Li+ tri-doped TiO2 nanocrystals at various calcination temperatures, (d) Ho3+-Yb3+ co-doped TiO2 (2θ from 20 to 30°), (e) Ho3+-Yb3+-Li+ tri-doped TiO2 calcined at 700 °C. Standard data for anatase (JCPDS No. 21-1272) and rutile (JCPDS No. 21-1276) are shown as reference. (Py: Pyrochlore, L: Li2Ti4O9).
Anatase | Rutile | |
---|---|---|
Crystal structure | Tetragonal system | Tetragonal system |
Lattice constant (?) | a = 3.78 | a = 4.59 |
b = 3.78 | b = 4.59 | |
c = 9.52 | c = 2.96 | |
Space group | I41 / amd | P42 / mnm |
Molecule/unit | 2 | 2 |
Volume/molecule (?3) | 136.3 | 62.4 |
Density (g/cm2) | 3.89 | 4.23 |
Bond length of Ti-O (?) | 1.94 (4) | 1.95 (4) |
1.97 (2) | 1.98 (2) | |
Bond angle of O-Ti-O | 77.7° | 81.0° |
92.6° | 90.0° |
Table 1 Two crystal lattice structures of TiO2.
Anatase | Rutile | |
---|---|---|
Crystal structure | Tetragonal system | Tetragonal system |
Lattice constant (?) | a = 3.78 | a = 4.59 |
b = 3.78 | b = 4.59 | |
c = 9.52 | c = 2.96 | |
Space group | I41 / amd | P42 / mnm |
Molecule/unit | 2 | 2 |
Volume/molecule (?3) | 136.3 | 62.4 |
Density (g/cm2) | 3.89 | 4.23 |
Bond length of Ti-O (?) | 1.94 (4) | 1.95 (4) |
1.97 (2) | 1.98 (2) | |
Bond angle of O-Ti-O | 77.7° | 81.0° |
92.6° | 90.0° |
Fig. 4. Upconversion spectra of Ho3+-Yb3+ co-doped TiO2 (a) and Ho3+-Yb3+-Li+ tri-doped TiO2 (c) nanocrystals calcined at different temperatures for 2 h with 980 nm laser excitation. Integral intensity of green and red emission of TiO2:Ho3+-Yb3+ (b) and TiO2:Ho3+-Yb3+-Li+ (d) as a function of calcination temperature.
Sample | Calcination temperature (°C) | Intensity of green emission (a.u.) | IGLi+/IG | Intensity of red emission (a.u.) | IRLi+/IR |
---|---|---|---|---|---|
TiO2:Ho3+,Yb,3+ | 600 | 175.1 | 45.4 | ||
700 | 404.4 | 89.9 | |||
800 | 546.2 | 95.3 | |||
900 | 177.0 | 19.0 | |||
1000 | 124.4 | 16.6 | |||
TiO2:Ho3+,Yb,3+,Li+ | 600 | 1425.0 | 8.1 | 293.1 | 6.5 |
700 | 9543.0 | 23.6 | 875.9 | 9.8 | |
800 | 1346.0 | 2.5 | 217.1 | 2.3 | |
900 | 1058.0 | 5.9 | 196.6 | 10.3 | |
1000 | 744.1 | 6.0 | 182.7 | 11.4 |
Table 2 Intensity of the green and red emission from the photoluminescence spectrum.
Sample | Calcination temperature (°C) | Intensity of green emission (a.u.) | IGLi+/IG | Intensity of red emission (a.u.) | IRLi+/IR |
---|---|---|---|---|---|
TiO2:Ho3+,Yb,3+ | 600 | 175.1 | 45.4 | ||
700 | 404.4 | 89.9 | |||
800 | 546.2 | 95.3 | |||
900 | 177.0 | 19.0 | |||
1000 | 124.4 | 16.6 | |||
TiO2:Ho3+,Yb,3+,Li+ | 600 | 1425.0 | 8.1 | 293.1 | 6.5 |
700 | 9543.0 | 23.6 | 875.9 | 9.8 | |
800 | 1346.0 | 2.5 | 217.1 | 2.3 | |
900 | 1058.0 | 5.9 | 196.6 | 10.3 | |
1000 | 744.1 | 6.0 | 182.7 | 11.4 |
Fig. 5. (a) Upconversion intensity of Ho3+-Yb3+-Li+ tri-doped TiO2 calcined at 700 °C as a function of excitation power at 980 nm, (b) Energy level diagrams of Yb3+ and Ho3+ ions.
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