Sc^3＋-doped lithium manganese oxides were synthesized by solid-state reaction. The influences of doping element on structure, mean valence of manganese, and electrochemical performances were studied by X-ray diffract...Sc^3＋-doped lithium manganese oxides were synthesized by solid-state reaction. The influences of doping element on structure, mean valence of manganese, and electrochemical performances were studied by X-ray diffraction （XRD）, galvanostatic charge-discharge and cyclic voltammetric tests, and also electrochemical impedance spectroscopy （EIS）. XRD tests showed that doped lithium manganese oxides were pure spinel structure without other phases. Redox titration and visible spectrophotometry tests indicated that the mean valence of manganese in doped lithium manganese oxides was higher than that of pure one. LiSc0.02Mn1.9804 remained 92.9% of the initial specific discharge capacity after 50th cycle at a constant current of 50 m/g, and the reversibility of LiSc0.02Mn1.98O4 was improved in comparison with pure LiMn2O4 at 50 ℃. EIS indicated that film deposition on spinel particles was suppressed because of Sc^3＋ doping, and the charge transfer between the surface film and spinel particles with increasing temperature for Sc^3＋-doped materials became easier as compared with undoped one.展开更多
Y0.75-xGdxAl0.10BO3：Eu0.10^3＋,0.05R^3＋（R=Sc,Bi）（0.00≤x≤0.45）powder samples are prepared by solid-state reaction and their luminescence properties are investigated. With the replacement of Y^3＋ ions by Sc^3＋...Y0.75-xGdxAl0.10BO3：Eu0.10^3＋,0.05R^3＋（R=Sc,Bi）（0.00≤x≤0.45）powder samples are prepared by solid-state reaction and their luminescence properties are investigated. With the replacement of Y^3＋ ions by Sc^3＋ （or Bi^3＋）and Gd^3＋ ions in （Y,Al）BO3：Eu,the intensities of emission at 254 and 147 nm are remarkably improved, because Sc^3＋ inos can absorb UV light and transfer the energy to Eu^3＋ ions efficiently. Moreover, Gd^3＋ and Bi^3＋ ions act as an intermediate ＂bridge＂ between the sensitizer and the activator （Eu^3＋） in energy transfer to produce light in the （Y, Gd）BO3：Bi^3＋, Eu^3＋ system more effectively. After doping an appropriate concentration of Gd^3＋ into Y0.50Gd0.25Al0.10BO3：Eu0.01^3＋,Bi0.05^3＋,the emission intensity reaches its maximum, which is nearly 110% compared with the red commercial phosphor （Y,Gd）BO3：Eu and better chromaticity coordinates （0.650, 0.350） are obtained.展开更多
文摘Sc^3＋-doped lithium manganese oxides were synthesized by solid-state reaction. The influences of doping element on structure, mean valence of manganese, and electrochemical performances were studied by X-ray diffraction （XRD）, galvanostatic charge-discharge and cyclic voltammetric tests, and also electrochemical impedance spectroscopy （EIS）. XRD tests showed that doped lithium manganese oxides were pure spinel structure without other phases. Redox titration and visible spectrophotometry tests indicated that the mean valence of manganese in doped lithium manganese oxides was higher than that of pure one. LiSc0.02Mn1.9804 remained 92.9% of the initial specific discharge capacity after 50th cycle at a constant current of 50 m/g, and the reversibility of LiSc0.02Mn1.98O4 was improved in comparison with pure LiMn2O4 at 50 ℃. EIS indicated that film deposition on spinel particles was suppressed because of Sc^3＋ doping, and the charge transfer between the surface film and spinel particles with increasing temperature for Sc^3＋-doped materials became easier as compared with undoped one.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10874061)the Doctoral Program Foundation of Institutions of Higher Education of China (Grant No. 20040730019)the Project of the Combination of Industry and Research by the Ministry of Education and Guangdong Province of China (Grant No. 0712226100023)
文摘Y0.75-xGdxAl0.10BO3：Eu0.10^3＋,0.05R^3＋（R=Sc,Bi）（0.00≤x≤0.45）powder samples are prepared by solid-state reaction and their luminescence properties are investigated. With the replacement of Y^3＋ ions by Sc^3＋ （or Bi^3＋）and Gd^3＋ ions in （Y,Al）BO3：Eu,the intensities of emission at 254 and 147 nm are remarkably improved, because Sc^3＋ inos can absorb UV light and transfer the energy to Eu^3＋ ions efficiently. Moreover, Gd^3＋ and Bi^3＋ ions act as an intermediate ＂bridge＂ between the sensitizer and the activator （Eu^3＋） in energy transfer to produce light in the （Y, Gd）BO3：Bi^3＋, Eu^3＋ system more effectively. After doping an appropriate concentration of Gd^3＋ into Y0.50Gd0.25Al0.10BO3：Eu0.01^3＋,Bi0.05^3＋,the emission intensity reaches its maximum, which is nearly 110% compared with the red commercial phosphor （Y,Gd）BO3：Eu and better chromaticity coordinates （0.650, 0.350） are obtained.
