Synthesis and Crystal Structure of Ho_4S_3Si_2O_7

1 INTRODUCTION Halide fluxes are excellent media for growing single crystals of chalcogenides[1~5]. On our research in the Ln-Cu-Zn-Se system to find new phases and to search for potential infrared ceramic materials, two new compounds, KHo2CuSe4 and KEr2CuSe4, were synthesized from the reaction of the precursor with KCl flux[6]. In an attempt to synthesize the homologous sulfide by the same method using KBr as flux in a sealed evacuated quartz tube, single crystals of Ho4S3Si2O7 w…     

焦硅酸镥(Lu2Si2O7:Ce)闪烁晶体的生长与发光性能研究

铈掺杂的焦硅酸镥晶体(简写为LPS:Ce)是新近发现的一种具有潜在应用价值的无机闪烁晶体.本文用提拉法成功地生长出尺寸为φ15mm×40mm的LPS:Ce晶体.XRD结构测试表明,该晶体属于单斜晶系,C2/m空间群,晶体中分布有少量的LPS和石英颗粒包裹体.对从毛坯中切割出的无色透明晶体样品在室温下分别进行了透射光谱、紫外激发、X射线激发发射光谱和衰减时间测试.结果表明,铈(Ce3+)离子掺杂使LPS晶体的紫外吸收边从175nm红移到350nm,紫外和X射线激发的荧光光谱中都可以分解出384nm和412nm两个发射峰,它们分别对应于电子从铈(Ce3+)离子的5d轨道向4f轨道的两个能级(2F5/2和2F7/2)的辐射跃迁,从衰减曲线中可以拟合出一个38.75ns的时间常数.这些发光特征与该晶体独特的晶体结构密切相关.     

Ce:Lu2Si2O7闪烁晶体的结构和光谱特性

采用中频感应提拉法生长出Ce:Lu₂Si₂O₇（Ce:LPS） 晶体. 通过x射线粉 末衍射分析，晶体结构属单斜晶系的C2/m空间群. 光学显微镜下可观测到晶体的（110 ）解理. 在室温下测试了Ce:LPS晶体的吸收光谱、激发光谱和发射光谱. 结果表明，Ce:LPS 晶体的吸收峰只有两个，分别位于302和349 nm，且与激发峰的位置一致，归因于Ce³⁺ 的4f¹→5d¹跃迁的特征吸收所致. 发射光谱具有Ce^{3+< /sup>典型的双峰特征 ，经Gaussian多峰值拟合，带状谱是由384和407 nm两个发射峰叠加而成，且后者的强度明 显高于前者. 关键词： 2Si₂O₇')" href="#">Ce:Lu₂Si₂O₇ 提拉法 晶体结构 光学 特性}     

Photoluminescence and structural characteristics of Lu2O3:Eu nanocrystallites in silica matrix

Two silica ceramics were obtained by mixing nanocrystalline Lu₂O₃:Eu³⁺ with silica sol using the sol-gel technique. The synthesis procedure for both samples differed in the pH of the sol and time of the sol condensation before substrates were mixed together, which implied their different optical properties. The first one has the same spectroscopic properties as Lu₂O₃:Eu³⁺ nanocrystallites with an exception of small lowering of the charge transfer (CT) band intensity. This feature is preserved up to about 950 °C. Above this temperature, nanocrystallites of Lu₂O₃:Eu³⁺ react with the silica matrix synthesis pyrosilicate (Lu₂Si₂O₇). The Eu³⁺ ions occupy only one crystallographic site in the crystal lattice for low concentration of the activator (1%) and two sites for higher concentration (10%). The second sample exhibits different Eu³⁺ emission than Lu₂O₃:Eu³⁺ nanocrystallites and, additionally, a broad band of the matrix originating at the green region of the spectrum. Sintering the sample at higher temperatures leads to disappearance of this broad emission and continuous changes of the Eu³⁺ emission because of the progressive conversion of the Lu₂O₃:Eu³⁺ to pyrosilicate. At 1300 °C for both samples, the reaction of synthesis lutetium pyrosilicate is completed. Structural characteristic of the samples is presented and correlate with the decay profile of the Eu³⁺ emission.     

Synthesis and Structure of a New Polymorph Ba_2CuSi_2O_7

1INTRODUCTIONTheuniqueelectronicpropertiesofcopperoxidesandoxyhalideshaveattractedmuchattentionduetotheirpotentialapplicationsassupercon-ductors,catalysts,luminescentmaterialsandp-typetransparentconductors[1].Inanefforttoexplorenewframeworkstructuresofmixed-metaloxyha-lidessuchasCuAgOCl,wehaveobtainedanewpolymorphofthebariumdicopperdisilicate,b-Ba2CuSi2O7.Inthispaper,wewillreportthesolid-statesynthesisandcrystalstructureofthisnewphaseanddiscussthedifferencesbetweenthestructuresofb-Ba2C…