The up-conversion luminescence composite NaYF4：Er3＋/TiO2 is prepared using the sol-gel method. The specimen has good crystallinity and two shapes, i.e., viereck and round, while the sizes of viereck and round partic...The up-conversion luminescence composite NaYF4：Er3＋/TiO2 is prepared using the sol-gel method. The specimen has good crystallinity and two shapes, i.e., viereck and round, while the sizes of viereck and round particles are both micron-sized. The TiO2 has an anatase structure, while the NaYF4 has a hexagonal phase, which can be hardly obtained through the common sol-gel method. Due to the big particle size and the high crystallinity of pure NaYF4： Er3＋, the composite has a small specific surface area that is less than Degussa P25 TiO2. The NaYF4：Er3＋/TiO2 composite shows several emission peaks at 211, 237, and 251 nm under the excitation of 388 nm, at 395 nm and 411 nm under the excitation of 500 nm, and at 467, 481,492, and 508 nm under the excitation of 570 nm.展开更多
The experimental monoclinic CF parameter （CFP） sets obtained by Duan et al. （Phys. Rev. B 75 （2007） 195130） for Er3＋ and Nd3＋ ions in YAIO3 were reanalyzed. These CFPs fitted using R-approach, i.e. with the mo...The experimental monoclinic CF parameter （CFP） sets obtained by Duan et al. （Phys. Rev. B 75 （2007） 195130） for Er3＋ and Nd3＋ ions in YAIO3 were reanalyzed. These CFPs fitted using R-approach, i.e. with the monoclinic second-rank CFP set to zero, and additionally with one six-rank CFP fixed to zero, turned out to be non-standard. In order to understand better the low symmetry aspects involved in the fitted CFPs and extract useful structtral information inherent in monoclinic CFPs, an approach comprising four methods was utilized. First, superposition model （SPM） was applied to calculate CFPs in the crystallographic axis system. Second, the principal values for the SPM determined CFPs and the orientation of the principal axis system w.r.t, the crystallographic axis system were obtained using the procedure 3DD for diagonalization of the 2rid-rank CFPs. Third, analysis of higher symmetry approximations, i.e. orthorhombic and tea＇agonal, was carried out using the pseudosymmetry axes method. Fourth, the closeness factors and norm ratios were employed for quantitative comparisons of various CFP sets. Partial results for Er3＋ ions in YAlO3 were presented here, whereas detailed results would be given in a follow-up paper.展开更多
The influence of Er_2 O_3 addition on the phase evolution and mechanical properties of sintered(1600 ℃,4 h) ZTA(yttria stabilized zirconia toughened alumina)-TiO_2 composites was investigated. The SEM and XRD results...The influence of Er_2 O_3 addition on the phase evolution and mechanical properties of sintered(1600 ℃,4 h) ZTA(yttria stabilized zirconia toughened alumina)-TiO_2 composites was investigated. The SEM and XRD results reveal the formation of a new erbium zirconium oxide,Zr_3 Er_4 O_(12),with a granulate morphology when Er_2 O_3 content is higher than 1 wt%. The grain sizes of both Al_2 O_3 and yttria-stabilized zirconia phases decrease with an increase in the Er_2 O_3 content. The relative density, Vickers hardness and fracture toughness of the composites are found to be strongly dependent on their grain sizes, relative densities and the formation of the Zr_3 Er_4 O_(12) secondary phases. The composite with 5 wt% Er_2 O_3 shows the highest relative density(99.93%), Vickers hardness(1752 HV) and fracture toughness(7.92 MPa·m^(1/2)).展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 20876125)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20096101110013)the Northwest University Graduate Cross-Discipline Funds (Grant Nos. 09YJC27,09YJC24,and 201031)
文摘The up-conversion luminescence composite NaYF4：Er3＋/TiO2 is prepared using the sol-gel method. The specimen has good crystallinity and two shapes, i.e., viereck and round, while the sizes of viereck and round particles are both micron-sized. The TiO2 has an anatase structure, while the NaYF4 has a hexagonal phase, which can be hardly obtained through the common sol-gel method. Due to the big particle size and the high crystallinity of pure NaYF4： Er3＋, the composite has a small specific surface area that is less than Degussa P25 TiO2. The NaYF4：Er3＋/TiO2 composite shows several emission peaks at 211, 237, and 251 nm under the excitation of 388 nm, at 395 nm and 411 nm under the excitation of 500 nm, and at 467, 481,492, and 508 nm under the excitation of 570 nm.
基金supported by the research grant from the Polish Ministry of Science and Tertiary Education in the years 2006-2009
文摘The experimental monoclinic CF parameter （CFP） sets obtained by Duan et al. （Phys. Rev. B 75 （2007） 195130） for Er3＋ and Nd3＋ ions in YAIO3 were reanalyzed. These CFPs fitted using R-approach, i.e. with the monoclinic second-rank CFP set to zero, and additionally with one six-rank CFP fixed to zero, turned out to be non-standard. In order to understand better the low symmetry aspects involved in the fitted CFPs and extract useful structtral information inherent in monoclinic CFPs, an approach comprising four methods was utilized. First, superposition model （SPM） was applied to calculate CFPs in the crystallographic axis system. Second, the principal values for the SPM determined CFPs and the orientation of the principal axis system w.r.t, the crystallographic axis system were obtained using the procedure 3DD for diagonalization of the 2rid-rank CFPs. Third, analysis of higher symmetry approximations, i.e. orthorhombic and tea＇agonal, was carried out using the pseudosymmetry axes method. Fourth, the closeness factors and norm ratios were employed for quantitative comparisons of various CFP sets. Partial results for Er3＋ ions in YAlO3 were presented here, whereas detailed results would be given in a follow-up paper.
基金Project supported by National Natural Science Foundation of China(51571103,51501079)China Postdoctoral Science Foundation(2017M623319XB,2018T110999)Yunnan Provincial Department of Education Science Research Fund Project(2018JS033)
文摘The influence of Er_2 O_3 addition on the phase evolution and mechanical properties of sintered(1600 ℃,4 h) ZTA(yttria stabilized zirconia toughened alumina)-TiO_2 composites was investigated. The SEM and XRD results reveal the formation of a new erbium zirconium oxide,Zr_3 Er_4 O_(12),with a granulate morphology when Er_2 O_3 content is higher than 1 wt%. The grain sizes of both Al_2 O_3 and yttria-stabilized zirconia phases decrease with an increase in the Er_2 O_3 content. The relative density, Vickers hardness and fracture toughness of the composites are found to be strongly dependent on their grain sizes, relative densities and the formation of the Zr_3 Er_4 O_(12) secondary phases. The composite with 5 wt% Er_2 O_3 shows the highest relative density(99.93%), Vickers hardness(1752 HV) and fracture toughness(7.92 MPa·m^(1/2)).
