近紫外光激发下KBaGd(MoO_(4))_(3)∶Er^(3+)的下转换发光及温度传感特性EI北大核心CSCD

近年来,Er^(3+)离子掺杂的无机发光材料被广泛应用于温度传感材料的研究。本文采用溶胶⁃凝胶法制备了Er^(3+)掺杂的KBaGd(MoO_(4))_(3)荧光粉,利用常温激发和发射光谱、荧光衰减曲线以及变温发射光谱对其光谱性能以及温度传感特性进行了分析。荧光光谱表明,KBaGd(MoO_(4))_(3)∶Er^(3+)在380 nm处有着较强的吸收峰,源自于Er^(3+)离子的4I_(15/2)→4G_(11/2)吸收跃迁。在近紫外光激发下,KBaGd(MoO_(4))_(3)∶Er^(3+)荧光粉在520~570 nm之间具有两个明亮的绿色发射。由于电偶极间相互作用,当Er^(3+)离子掺杂浓度超过8%时,样品发光开始出现浓度猝灭。基于荧光强度比(FIR)模型计算得到KBaGd(MoO_(4))_(3)∶Er^(3+)的相对灵敏度优于已报道的大部分同类温度传感材料,因此在光温传感领域有着更好的应用潜力。最后,对利用KBaGd(MoO_(4))_(3)∶Er^(3+)设计的LED进行了光电参数测试,并对其在照明领域的应用进行了客观评价。     

立方相KTa0.67Nb0.33O3晶体的系列相变研究

采用拉曼散射技术研究了立方相KTa0.67Nb0.33O3晶体的系列相变,从声子角度分析了各相变特点.降温过程中立方-四方和四方-正交相变分别发生在-29℃和-95℃左右,正交-三方相变可能发生在-150℃左右.最后简单讨论了晶体的相变机制和居里点与晶体组分的关系,并比较分析了居里点的实验值与理论值的差异.     

近紫外光激发KBaGd(MoO_4)_3:Dy~(3+)荧光粉的制备及发光性能

采用溶胶-凝胶法制备了KBa Gd(Mo O_4)_3∶Dy~(3+)荧光粉,并借助于扫描电镜(SEM)、X射线粉末衍射(XRD)、激发光谱、发射光谱及荧光衰减曲线等测试手段对其形貌、结构及光谱性能进行了分析。结果显示:与高温固相反应法相比,采用溶胶-凝胶法得到的样品粒径均匀,且形状更加规则。在近紫外光(390 nm)的激发下,KBa Gd(Mo O_4)_3∶Dy~(3+)荧光粉的两个主发射峰分别位于485 nm与577 nm处,样品蓝黄比约为0.7。在KBa Gd(Mo O_4)_3基质中,Dy~(3+)离子的最佳掺杂摩尔分数为10%,引起浓度猝灭的机理是激活离子间的电偶极间相互作用。随着Dy~(3+)离子浓度的升高,样品荧光寿命缩短,且荧光衰减曲线逐渐偏离单指数变化。     

Up-conversion Properties of Er~(3+)/Yb~(3+) Co-doped Li_3Ba_2Gd_3(MoO_4)_8 Phosphors

Er~(3+)/Yb~(3+)co-doped Li_3Ba_2Gd_3(Mo O_4)_8 phosphors were synthesized by conventional solid state reaction method,and their structure and spectral properties were investigated.The diffuse reflectance spectra showed that the ~4I_(15/2)→~4I_(11/2) transition of Er~(3+)and the ~2F_(7/2)→~2F_(5/2)transition of Yb~(3+)ions were highly overlapped.Under the excitation of 980 nm,three up-conversion(UC)luminescence bands around 530,555 and 660 nm were observed,corresponding to the~2H_(11/2)→~4I_(15/2),~4S_(3/2)→~4I_(15/2) and ~4F_(9/2)→~4I_(15/2) transitions of Er~(3+)ions,respectively.The effects of the concentration and pumping power on the UC intensities of Li_3Ba_2Gd_3(Mo O_4)_8:Er~(3+)/Yb~(3+)phosphors were investigated,and the possible UC mechanism was proposed based on the results.     

Growth and Spectroscopic Investigations of Disordered Nd3+:Li3Ba2La3(MoO4)8 Crystal

Nd3+: Li3Ba2La3(MoO4)8 crystal has been grown from a flux of Li2MoO4 by the top seeded solution growth method (TSSG) and its structure was confirmed by X-ray diffraction. The polarized absorption spectra, fluorescence spectra and fluorescence decay curve of the crystal were measured. The main spectral parameters were calculated by the Judd-Ofelt theory and compared with other Nd-doped crystals. The broad absorption bands and the large absorption cross sections around 805 nm indicate that the crystal is very suitable for diode-laser pumping. The broad emission bands around 1060 nm show that the crystal is a potential medium for tunable and short pulse lasers. The quantum efficiency of the crystal is up to 95%, which is higher than the value for Nd3+:YVO4 and Nd3+:YAG and comparable to that of other disordered molybdate crystals. The excellent spectroscopic properties show that Nd3+:Li3Ba2La3(MoO4)8 crystal may be regarded as a potential solid state laser host material for diode laser pumping.     

La:NdPO4晶体的生长和晶格振动特性

采用助熔剂自发成核法生长了La: NdPO4晶体,采用X射线衍射技术表征了晶体的物相结构,采用红外和拉曼散射技术研究了晶体的品格振动特性,主要结论为:生长的晶体为单斜晶系,P21/n空间群;对实验观测到的振动模进行了指认,其中高频模主要为PO4四面体的内振动模.由于晶体结构缺陷和某些内、外振动模的耦合等原因,观测到的振动模数量少于理论预测值.通过比较La: NdPO4和NdPO4晶体的声子谱得出其晶格振动特性基本一致,但由于Nd比La的原子半径小,Nd和PO4之间的作用力增强,从而使PO4四面体"收缩",因此实验观测到La:NdPO4晶体的内振动模的波数较NdPO4晶体的蓝移.