Nanocrystalline monoclinic and cubic Gd 2O 3∶Eu with different Eu 3+ concentration were prepared using glycine-nitrate combustion synthesis. By changing the ratio of glycine to nitrate and proper heat treatment, p...Nanocrystalline monoclinic and cubic Gd 2O 3∶Eu with different Eu 3+ concentration were prepared using glycine-nitrate combustion synthesis. By changing the ratio of glycine to nitrate and proper heat treatment, pure monoclinic and cubic Gd 2O 3∶Eu with particle size less than 40 nm can be easily formed. Under ultraviolet excitation, main emission of Eu 3+ ( 5D 0→ 7F 2) locates at 624 nm in monoclinic Gd 2O 3∶Eu and 611 nm in cubic sample. In excitation spectrum two broad bands corresponding to the host absorption and charge transfer state (CTS) and f-f transitions of Gd 3+ and Eu 3+ were observed and discussed. The quenching concentration of monoclinic and cubic Gd 2O 3∶Eu is 10% and 15%, respectively, both of which are much higher than that of bulk Gd 2O 3∶Eu.展开更多
Alumina (Al2O3) has been synthesized through combustion synthesis (CS) technique. The calcined products were characterized using X-ray diffractional analysis (XRD), scanning electron microscopy (SEM), transmission ele...Alumina (Al2O3) has been synthesized through combustion synthesis (CS) technique. The calcined products were characterized using X-ray diffractional analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermo-gravimetric analysis (TGA). TG-DTA results reveal the various stages involved in transition from γ-phase to α-Al2O3 phase. The first phase γ-Al2O3 was presented in the temperature range from 600°C-875°C as deduced from the XRD patterns with cubic crystal structure. The second stage occurs in the temperature range from 900°C-1000°C. In the final step, above 1000°C, the aluminium oxide appears completely as α-Al2O3, showing high crystallinity. The particle sizes are closely related to γ- to α-Al2O3 phase transition.展开更多
Lutetium oxide nanocrystals codoped with Tm3＋ and Yb3＋ were synthesized by the reverse-like co-precipitation method, using ammonium hydrogen carbonate as precipitant. Effects of the Tm3＋, Yb3＋ molar fractions and ...Lutetium oxide nanocrystals codoped with Tm3＋ and Yb3＋ were synthesized by the reverse-like co-precipitation method, using ammonium hydrogen carbonate as precipitant. Effects of the Tm3＋, Yb3＋ molar fractions and calcination temperature on the structural and upconversion luminescent properties of the Lu2O3 nanocrystals were investigated. The XRD results show that all the prepared nanocrystals can be readily indexed to pure cubic phase of Lu2O3 and indicate good crystallinity. The experimental results show that concentration quenching occurs when the mole fraction of Tm3＋ is above 0.2%. The optimal Tm3＋ and Yb3＋ doped molar fractions are 0.2% and 2%, respectively. The strong blue （490 nm） and the weak red （653 nm） emissions from the prepared nanocrystals were observed under 980 nm laser excitation, and attributed to the 1G4→3H6 and IG4→3F4 transitions of Tm3＋, respectively. Power-dependent study reveals that the 1G4 levels of Tm3＋ can be populated by three-step energy transfer process. The upconversion emission intensities of 490 nm and 653 nm increase gradually with the increase of calcination temperature. The enhancement of the upconversion luminescence is suggested to be the consequence of reducing number of OH- groups and the enlarged nanoerystal size.展开更多
A structure transition of Fe2O3 nanocrystal was studied by using DTA and TG thermal analysis and X-ray diffraction method. We found that size increase of the nanocrystals is larger after the structure transition than ...A structure transition of Fe2O3 nanocrystal was studied by using DTA and TG thermal analysis and X-ray diffraction method. We found that size increase of the nanocrystals is larger after the structure transition than that before the transition. It means that the structure transition is beneficial on growth of nanocrystals展开更多
New phosphors Sr2ZnSi2O7： M （M=Mn2＋, Tb3＋） were synthesized through solid-state reaction, and their photoluminescent properties under UV and VUV region were investigated. The results showed that Sr2ZnSi2O7：Mn2＋...New phosphors Sr2ZnSi2O7： M （M=Mn2＋, Tb3＋） were synthesized through solid-state reaction, and their photoluminescent properties under UV and VUV region were investigated. The results showed that Sr2ZnSi2O7：Mn2＋ emitted green light with the strongest emission peak centered at 525 nm, and its quenching concentration under 254 and 147 nm excitation occurred at x = 0.08 and 0.06, respectively. Sr2ZnSi2O7： Th3＋ emitted green light with the strongest emission peak centered at 541 nm, and its quenching concentration under 254 and 147 nm excitation also appeared at y = 0.25. At 147 nm excitation, the emission intensities of Sr2Zn0.54Si2O7： 0.06Mn2＋ and Sr1.75ZnSi2O7： 0.25Tb3＋ phosphors were 54% and 36% of that of Zn1.96SiO4：0.04Mn2＋, respectively. And their decay times （τ1/e） were about 3.18 ms and 3.9 ms, respectively.展开更多
文摘Nanocrystalline monoclinic and cubic Gd 2O 3∶Eu with different Eu 3+ concentration were prepared using glycine-nitrate combustion synthesis. By changing the ratio of glycine to nitrate and proper heat treatment, pure monoclinic and cubic Gd 2O 3∶Eu with particle size less than 40 nm can be easily formed. Under ultraviolet excitation, main emission of Eu 3+ ( 5D 0→ 7F 2) locates at 624 nm in monoclinic Gd 2O 3∶Eu and 611 nm in cubic sample. In excitation spectrum two broad bands corresponding to the host absorption and charge transfer state (CTS) and f-f transitions of Gd 3+ and Eu 3+ were observed and discussed. The quenching concentration of monoclinic and cubic Gd 2O 3∶Eu is 10% and 15%, respectively, both of which are much higher than that of bulk Gd 2O 3∶Eu.
文摘Alumina (Al2O3) has been synthesized through combustion synthesis (CS) technique. The calcined products were characterized using X-ray diffractional analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermo-gravimetric analysis (TGA). TG-DTA results reveal the various stages involved in transition from γ-phase to α-Al2O3 phase. The first phase γ-Al2O3 was presented in the temperature range from 600°C-875°C as deduced from the XRD patterns with cubic crystal structure. The second stage occurs in the temperature range from 900°C-1000°C. In the final step, above 1000°C, the aluminium oxide appears completely as α-Al2O3, showing high crystallinity. The particle sizes are closely related to γ- to α-Al2O3 phase transition.
基金Foundation item: Projects (10704090,10774140,11047147)supported by the National Natural Science Foundation of ChinaProjects (KJ090514,KJTD201016)supported by the Natural Science Foundation of Chongqing Municipal Education Commission,China
文摘Lutetium oxide nanocrystals codoped with Tm3＋ and Yb3＋ were synthesized by the reverse-like co-precipitation method, using ammonium hydrogen carbonate as precipitant. Effects of the Tm3＋, Yb3＋ molar fractions and calcination temperature on the structural and upconversion luminescent properties of the Lu2O3 nanocrystals were investigated. The XRD results show that all the prepared nanocrystals can be readily indexed to pure cubic phase of Lu2O3 and indicate good crystallinity. The experimental results show that concentration quenching occurs when the mole fraction of Tm3＋ is above 0.2%. The optimal Tm3＋ and Yb3＋ doped molar fractions are 0.2% and 2%, respectively. The strong blue （490 nm） and the weak red （653 nm） emissions from the prepared nanocrystals were observed under 980 nm laser excitation, and attributed to the 1G4→3H6 and IG4→3F4 transitions of Tm3＋, respectively. Power-dependent study reveals that the 1G4 levels of Tm3＋ can be populated by three-step energy transfer process. The upconversion emission intensities of 490 nm and 653 nm increase gradually with the increase of calcination temperature. The enhancement of the upconversion luminescence is suggested to be the consequence of reducing number of OH- groups and the enlarged nanoerystal size.
文摘A structure transition of Fe2O3 nanocrystal was studied by using DTA and TG thermal analysis and X-ray diffraction method. We found that size increase of the nanocrystals is larger after the structure transition than that before the transition. It means that the structure transition is beneficial on growth of nanocrystals
基金Funded by Key Project of Natural Science for Education Department of Sichuan Province(No.14ZA0102)State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials,Southwest University of Science and Technology,Mianyang
文摘New phosphors Sr2ZnSi2O7： M （M=Mn2＋, Tb3＋） were synthesized through solid-state reaction, and their photoluminescent properties under UV and VUV region were investigated. The results showed that Sr2ZnSi2O7：Mn2＋ emitted green light with the strongest emission peak centered at 525 nm, and its quenching concentration under 254 and 147 nm excitation occurred at x = 0.08 and 0.06, respectively. Sr2ZnSi2O7： Th3＋ emitted green light with the strongest emission peak centered at 541 nm, and its quenching concentration under 254 and 147 nm excitation also appeared at y = 0.25. At 147 nm excitation, the emission intensities of Sr2Zn0.54Si2O7： 0.06Mn2＋ and Sr1.75ZnSi2O7： 0.25Tb3＋ phosphors were 54% and 36% of that of Zn1.96SiO4：0.04Mn2＋, respectively. And their decay times （τ1/e） were about 3.18 ms and 3.9 ms, respectively.
