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
3Gd2O3-3Yb2O3-4Y2O3 （mole fraction, %） co-doped ZrO2 （GY-YSZ） thermal barrier coatings （TBCs） were produced by electron beam physical vapor deposition （EB-PVD）. The oxidation behavior of GY-YSZ at 1 050 ℃ was...3Gd2O3-3Yb2O3-4Y2O3 （mole fraction, %） co-doped ZrO2 （GY-YSZ） thermal barrier coatings （TBCs） were produced by electron beam physical vapor deposition （EB-PVD）. The oxidation behavior of GY-YSZ at 1 050 ℃ was investigated using impedance spectroscopy （IS） combined with scanning electron microscopy （SEM）, Raman spectroscopy and X-ray diffractometry （XRD）. Various electrical responses observed in the impedance spectra corresponding to GY-YSZ grains and grain boundaries were explained using circuit modeling. The change in the conduction mechanism of GY-YSZ was found to be related to the O^2- vacancy and lattice distortion due to the stabilizer diffusion during the oxidation. The results also suggested that the specific oxidation information about the GY-YSZ grains and grain boundaries should be acquired at a moderate measurement temperature, which was related to the resistance value in the impedance spectra. The resistance values of the GY-YSZ grains and grain boundaries should be measured at 200 ℃ and 300 ℃, respectively.展开更多
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.
基金Projects (50771009, 50731001 and 51071013) supported by the National Natural Science Foundations of China Project (2010CB631200) supported by the National Basic Research Program of China
文摘3Gd2O3-3Yb2O3-4Y2O3 （mole fraction, %） co-doped ZrO2 （GY-YSZ） thermal barrier coatings （TBCs） were produced by electron beam physical vapor deposition （EB-PVD）. The oxidation behavior of GY-YSZ at 1 050 ℃ was investigated using impedance spectroscopy （IS） combined with scanning electron microscopy （SEM）, Raman spectroscopy and X-ray diffractometry （XRD）. Various electrical responses observed in the impedance spectra corresponding to GY-YSZ grains and grain boundaries were explained using circuit modeling. The change in the conduction mechanism of GY-YSZ was found to be related to the O^2- vacancy and lattice distortion due to the stabilizer diffusion during the oxidation. The results also suggested that the specific oxidation information about the GY-YSZ grains and grain boundaries should be acquired at a moderate measurement temperature, which was related to the resistance value in the impedance spectra. The resistance values of the GY-YSZ grains and grain boundaries should be measured at 200 ℃ and 300 ℃, respectively.
