采用溶胶-凝胶法制备出Y_(2-2 x)MgTiO_(6)∶2 x Eu^(3+)(YMT∶2 x Eu^(3+),0≤x≤0.11)新型红色荧光粉。通过X射线衍射仪(XRD)检测样品的纯度,结果显示YMT∶Eu^(3+)样品属于单斜晶系,空间群为P21/n,无其他杂相。扫描电子显微镜(SEM)照...采用溶胶-凝胶法制备出Y_(2-2 x)MgTiO_(6)∶2 x Eu^(3+)(YMT∶2 x Eu^(3+),0≤x≤0.11)新型红色荧光粉。通过X射线衍射仪(XRD)检测样品的纯度,结果显示YMT∶Eu^(3+)样品属于单斜晶系,空间群为P21/n,无其他杂相。扫描电子显微镜(SEM)照片显示荧光粉为2μm的不规则颗粒。当激发波长为264 nm时,发射光谱出现四个尖锐的发射峰,分别位于591(^(5)D_(0)→^(7)F_(1))、619(^(5)D_(0)→^(7)F_(2))、657(^(5)D_(0)→^(7)F_(3))和693 nm(^(5)D_(0)→^(7)F_(4))。Eu^(3+)离子之间能量传递为电偶极子-电偶极子(d-d)相互作用。YMT∶0.14Eu^(3+)荧光粉的CIE色度坐标为(0.645,0.332),与红光标准色坐标(0.67,0.33)非常接近。变温PL光谱及热激活能计算结果显示荧光粉具有一定的热稳定性,因此YMT∶Eu^(3+)是一种具有潜在应用价值的LED红色荧光粉。展开更多
In this work,a group of Bi^(3+)/Eu^(3+)-doped SiO2-Al_(2)O_(3)-MCO_(3)(M=Ca,Sr,Ba) glasses were fabricated through melt-quenching method.Their structure and photoluminescence characters were studied via Xray diffracti...In this work,a group of Bi^(3+)/Eu^(3+)-doped SiO2-Al_(2)O_(3)-MCO_(3)(M=Ca,Sr,Ba) glasses were fabricated through melt-quenching method.Their structure and photoluminescence characters were studied via Xray diffraction(XRD),UV-Vis transmission spectra(TRS),excitation spectra,emission spectra and decay lifetimes.The XRD results show that no nano-crystal phase forms in glass matrix with different doping concentrations of Bi^(3+)and Eu^(3+)ions.Through regulating optical alkalinity value,the intensity of Bi^(3+)ions increases and the peak position shifts to red wavelength.The Bi^(3+)/Eu^(3+) co-doped glasses show a blue-white-yellow-red luminescence by changing concentration of Eu^(3+) ions.Energy transfer efficiency from Bi^(3+) to Eu^(3+) can reach as high as 10.54%.At 423 K, the emission intensity of 55SiO_(2)-10Al_(2)O_(3)-35BaO-0.25Bi_(2)O_(3)(GBE0.5) is 31.1% of that at 308 K.Meanwhile,the activation energy of the glass matrix is 0.251 eV.All results suggest that these Bi^(3+)/Eu^(3+) co-doped glass samples possess potential application in LED field.展开更多
We investigated the emission properties of Eu^(3+)-doped GdNbO_(4)-based oxide phosphors,aiming at improving the Eu^(3+)emission by codoping of Bi^(3+)and Li^(+).Eu^(3+)singly doped,Eu^(3+)and Bi^(3+)doubly doped,and ...We investigated the emission properties of Eu^(3+)-doped GdNbO_(4)-based oxide phosphors,aiming at improving the Eu^(3+)emission by codoping of Bi^(3+)and Li^(+).Eu^(3+)singly doped,Eu^(3+)and Bi^(3+)doubly doped,and Eu^(3+),Bi^(3+),and Li^(+)triply doped GdNbO_(4)were prepared using a high-temperature solid-state reaction method.The red-orange emissions from Eu^(3+)in the singly doped samples are significantly improved by the codoping of Bi^(3+),mainly due to the energy transfer from Bi^(3+)to Eu^(3+).The additional codoping of Li^(+)is found to increase the Eu^(3+)emission significantly.This improvement might be attributed to the increase in the photoluminescent quantum yield originating from larger grain sizes and better crystallinity.A detailed analysis of the X-ray diffraction pattern and the asymmetric ratio estimated from the photoluminescence spectra show that the local lattice environment around Eu^(3+)in GdNbO_(4)does not change significantly with the codoping of Bi^(3+)and Li^(+).Our results indicate that Li^(+)doping is a promising way to improve the emission properties of rare-earth ion-doped GdNbO_(4)phosphors.展开更多
LiYGeO_(4):Eu^(3+)is a red persistent luminescent material with a duration of more than 21 h.Although its persistent luminescence phenomenon has been fully studied,its detailed mechanism is still the subject of debate...LiYGeO_(4):Eu^(3+)is a red persistent luminescent material with a duration of more than 21 h.Although its persistent luminescence phenomenon has been fully studied,its detailed mechanism is still the subject of debates.Herein,we performed first-principles study on the intrinsic point defects and the charge transfer processes in LiYGeO_(4):Eu^(3+)to reveal the mechanism of persistent luminescence.The results show that,under charge transfer excitation,the electron is promoted from the valence band(oxygen ion ligand)to the central Eu^(3+)ion to form Eu^(2+)ion in LiYGeO_(4):Eu^(3+),leaving a hole behind.The charge transfer excitation can relax quickly to the excited state of the Eu^(3+)ion,which produces the characteristic^(5)D_(0)→^(7)F_(J)(J=0-6)emission.The Li vacancies(V_(Li))and the antisite defects of Li replacing Y site(Li_(Y))and Y replacing Li site(YLi)are main defects,while O vacancies(V_(O))are less important in concentration due to high formation energy.VLi and Liy can serve as hole-type traps,with the trap depths suitable for trapping the holes produced by illumination.The delayed release holes can combine with the Eu^(2+)left behind by the illumination,leading to persistent luminescence.The VLi trap is shallower than Li_(Y),and the latter is responsible for the long duration of persistent luminescence.A schematic based on the calculation results is constructed to illustrate the mechanism of persistent luminescence.展开更多
文摘采用溶胶-凝胶法制备出Y_(2-2 x)MgTiO_(6)∶2 x Eu^(3+)(YMT∶2 x Eu^(3+),0≤x≤0.11)新型红色荧光粉。通过X射线衍射仪(XRD)检测样品的纯度,结果显示YMT∶Eu^(3+)样品属于单斜晶系,空间群为P21/n,无其他杂相。扫描电子显微镜(SEM)照片显示荧光粉为2μm的不规则颗粒。当激发波长为264 nm时,发射光谱出现四个尖锐的发射峰,分别位于591(^(5)D_(0)→^(7)F_(1))、619(^(5)D_(0)→^(7)F_(2))、657(^(5)D_(0)→^(7)F_(3))和693 nm(^(5)D_(0)→^(7)F_(4))。Eu^(3+)离子之间能量传递为电偶极子-电偶极子(d-d)相互作用。YMT∶0.14Eu^(3+)荧光粉的CIE色度坐标为(0.645,0.332),与红光标准色坐标(0.67,0.33)非常接近。变温PL光谱及热激活能计算结果显示荧光粉具有一定的热稳定性,因此YMT∶Eu^(3+)是一种具有潜在应用价值的LED红色荧光粉。
基金Project supported by the Natural Science Foundation of Zhejiang Province (LY21A040005)the National Natural Science Foundation of China (11804303,11974315,51802285)。
文摘In this work,a group of Bi^(3+)/Eu^(3+)-doped SiO2-Al_(2)O_(3)-MCO_(3)(M=Ca,Sr,Ba) glasses were fabricated through melt-quenching method.Their structure and photoluminescence characters were studied via Xray diffraction(XRD),UV-Vis transmission spectra(TRS),excitation spectra,emission spectra and decay lifetimes.The XRD results show that no nano-crystal phase forms in glass matrix with different doping concentrations of Bi^(3+)and Eu^(3+)ions.Through regulating optical alkalinity value,the intensity of Bi^(3+)ions increases and the peak position shifts to red wavelength.The Bi^(3+)/Eu^(3+) co-doped glasses show a blue-white-yellow-red luminescence by changing concentration of Eu^(3+) ions.Energy transfer efficiency from Bi^(3+) to Eu^(3+) can reach as high as 10.54%.At 423 K, the emission intensity of 55SiO_(2)-10Al_(2)O_(3)-35BaO-0.25Bi_(2)O_(3)(GBE0.5) is 31.1% of that at 308 K.Meanwhile,the activation energy of the glass matrix is 0.251 eV.All results suggest that these Bi^(3+)/Eu^(3+) co-doped glass samples possess potential application in LED field.
基金Project supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(NRF-2021R1A6A1A10044154)。
文摘We investigated the emission properties of Eu^(3+)-doped GdNbO_(4)-based oxide phosphors,aiming at improving the Eu^(3+)emission by codoping of Bi^(3+)and Li^(+).Eu^(3+)singly doped,Eu^(3+)and Bi^(3+)doubly doped,and Eu^(3+),Bi^(3+),and Li^(+)triply doped GdNbO_(4)were prepared using a high-temperature solid-state reaction method.The red-orange emissions from Eu^(3+)in the singly doped samples are significantly improved by the codoping of Bi^(3+),mainly due to the energy transfer from Bi^(3+)to Eu^(3+).The additional codoping of Li^(+)is found to increase the Eu^(3+)emission significantly.This improvement might be attributed to the increase in the photoluminescent quantum yield originating from larger grain sizes and better crystallinity.A detailed analysis of the X-ray diffraction pattern and the asymmetric ratio estimated from the photoluminescence spectra show that the local lattice environment around Eu^(3+)in GdNbO_(4)does not change significantly with the codoping of Bi^(3+)and Li^(+).Our results indicate that Li^(+)doping is a promising way to improve the emission properties of rare-earth ion-doped GdNbO_(4)phosphors.
基金the Natural Science Foundation of Xinjiang Uygur Autonomous Region(2022DO1A98)the National Natural Science Foundation of China(11974338,11974022,21805082)China-Poland Intergovernmental Science and Technology Cooperation Program(202015/10)。
文摘LiYGeO_(4):Eu^(3+)is a red persistent luminescent material with a duration of more than 21 h.Although its persistent luminescence phenomenon has been fully studied,its detailed mechanism is still the subject of debates.Herein,we performed first-principles study on the intrinsic point defects and the charge transfer processes in LiYGeO_(4):Eu^(3+)to reveal the mechanism of persistent luminescence.The results show that,under charge transfer excitation,the electron is promoted from the valence band(oxygen ion ligand)to the central Eu^(3+)ion to form Eu^(2+)ion in LiYGeO_(4):Eu^(3+),leaving a hole behind.The charge transfer excitation can relax quickly to the excited state of the Eu^(3+)ion,which produces the characteristic^(5)D_(0)→^(7)F_(J)(J=0-6)emission.The Li vacancies(V_(Li))and the antisite defects of Li replacing Y site(Li_(Y))and Y replacing Li site(YLi)are main defects,while O vacancies(V_(O))are less important in concentration due to high formation energy.VLi and Liy can serve as hole-type traps,with the trap depths suitable for trapping the holes produced by illumination.The delayed release holes can combine with the Eu^(2+)left behind by the illumination,leading to persistent luminescence.The VLi trap is shallower than Li_(Y),and the latter is responsible for the long duration of persistent luminescence.A schematic based on the calculation results is constructed to illustrate the mechanism of persistent luminescence.
