出生缺陷发生率与环境特征异常的相关性研究

我国新生儿高出生缺陷发牛率影响着人口素质,选择了出生缺陷率高的山西省和顺县作为研究地点,从轻重病区分别采集了土壤、水、粮食、头发等作为指标,在实验室中用ICP-电感耦合等离子体发射光谱仪测定了指标中23种元素含量,比较后得出可能与出生缺陷有关的环境元素。结果表明,致病因子可能是以Se为主的复合元素,在和顺县除了低Se外,As,Mg,S,Mo,Ca等元素的小协调叮能起着与低Se复合致病的作用。     

Photoluminescence properties of Ce3＋ and Mn2＋-activated Ba9Sc2Si6O24 phosphor for white light emitting diodes

A single-phased silicate compound (Ba1-xCex)9(Sc1-yMny)2Si6O24 was prepared by solid-state reaction at high temperature. From powder X-ray diffraction (XRD) analysis, the formation of Ba9Sc2Si6O24 with an R3 space group was confirmed. In the photoluminescence spectra under ultraviolet (UV) ray excitation, the Ba9Sc2Si6O24:Ce3+,Mn2+ phosphor emits two distinctive color light bands: a blue one originating from Ce3+and a red one caused by Mn2+. The energy transfer process from Ce3+ to Mn2+ was confirmed, the critical radius as well as the transfer efficiency was calculated, and the energy transfer mechanism was discussed. In addition, the decay-time testing indicates that the energy transfer efficiencies from Ce(1) to Mn2+ and Ce(2) to Mn2+ are different. The emission chromaticity of Ba9Sc2Si6O24:Ce3+,Mn2+ phosphor could be tuned from blue to red by altering the Ce3+/Mn2+ concentration ratio.     

A red oxide phosphor,SreScAlO5：Eu^2＋ with perovskite-type structure,for white light-emitting diodes

Sr2ScAlO5：Eu^2＋, a red oxide phosphor with a perovskite-type structure, has been synthesized through a solid-state reaction and its luminescence properties have been investigated. An absorption band centering at 450 nm is observed from the diffuse reflection spectra and the excitation spectra, indicating that the phosphor can match perfectly with the blue light of InGaN light-emitting diodes. A broad red emission band at 620 nm is found from the emission spectra, originating from the 4f^65d-4f^7 transition of the Eu^2＋ ions. The best doping content of Eu in this material is about 5%. S Sr2ScAlO5：Eu^2＋ is a highly promising red phosphor for use in white light-emitting diodes.     

A red oxide phosphor, Sr2ScAlO5:Eu2+ with perovskite-type structure, for white light-emitting diodes

Sr2ScAlO5:Eu2+,a red oxide phosphor with a perovskite-type structure,has been synthesized through a solid-state reaction and its luminescence properties have been investigated.An absorption band centering at 450 nm is observed from the diffuse reflection spectra and the excitation spectra,indicating that the phosphor can match perfectly with the blue light of InGaN light-emitting diodes.A broad red emission band at 620 nm is found from the emission spectra,originating from the 4f 6 5d-4f 7 transition of the Eu 2+ ions.The best doping content of Eu in this material is about 5%.Sr2ScAlO5:Eu2+is a highly promising red phosphor for use in white light-emitting diodes.     

Solid solubility and photoluminescence of Y_3Al_5O_(12):Ce~(3+)prepared by using(Y_(1-x)Ce_x)_2O_3 as precursor

Trivalent cerium-doped yttrium aluminum garnet(YAG:Ce3+) phosphors are synthesized by solid-state reaction method through using(Y1-xCex)2O3 solid solutions as precursors. Solid solubility limits of Ce3+replacing Y3+in Y2O3and YAG are determined to be 40% and 7.5%, respectively, based on the relationship between the lattice parameter and chemical composition. Using(Y1-xCex)2O3 as precursors we synthesize YAG:Ce3+single phase at 1450°C and N2atmosphere. However, under the same conditions using CeO2there exists a second phase YAlO3as impurity. The photoluminescence intensity of YAG:Ce3+increases monotonically with the increase of Ce concentration until it reaches a maximum at solid solubility limits of Ce3+in YAG.     

Y3AlsO12.t：e prepared Solid solubility and photoluminescence of YeAl5O12：Ce3＋ preparedby using （Y1-xCex）203 as precursor

Trivalent cerium-doped yttrium aluminum garnet （YAG：Ce3＋） phosphors are synthesized by solid-state reaction method through using （Yl-xCex）203 solid solutions as precursors. Solid solubility limits of Ce3＋ replacing y3＋ in Y203 and YAG are determined to be 40% and 7.5%, respectively, based on the relationship between the lattice param- eter and chemical composition. Using （Y1-xCex）203 as precursors we synthesize YAG：Ce3＋single phase at 1450 ~C and N2 atmosphere. However, under the same conditions using CeO2 there exists a second phase YA103 as impurity. The photoluminescence intensity of YAG：Ce3＋ increases monotonically with the increase of Ce concentration until it reaches a maximum at solid solubility limits of Ce3＋ in YAG.