2019年4月稀土市场分析

<正>1稀土市场运行概况进入3月,受缅甸矿进口消息影响,中重稀土产品镝铽价格继续上行,厂商看好后市,氧化镝铽市场询单积极活跃,热度只增不减,持货商家看涨情绪浓厚、报价上涨明显。但氧化镝成交陷入窘境,金属厂及贸易商买货犹豫,成交量少而价格居高,投机及炒作成分浓重。部分镝铁价格与氧化镝持平、甚至低于氧化镝,以至出现氧化镝成交以贸易囤货为目的     

Effect of MgF2-H3BO3 flux on the properties of (Ce,Tb)MgAl11O19 phosphor

The green-emitting(Ce,Tb)MgAl11O19(CTMA) phosphor was prepared by the conventional high temperature solid-state reaction method.The effect of fluxes on the crystal structure,particle morphology,size distribution and photoluminescence properties of CTMA phosphor was investigated by means of the X-ray powder diffraction,scanning electron microscopy and photoluminescence spectrum.The results showed that the addition of appropriate amount of MgF2-H3BO3 flux improved the phase purity of CTMA phosphor,and influen...     

Benzene ring impact on energy transfer system of Eu（TTA）3DPBT

Eu(TTA)3DPBT was found most likely to lead a special singlet photosensitization pathway by means of time-resolved luminescence spectroscopic studies.For further understanding of its intra-molecular energy transfer mechanism,another lanthanide complex Eu(TTA)3BDDT was synthesized,using a related ligand BDDT,changing the D-π-A structure of DPBT to the D-A structure of BDDT.The luminescence characteristics of both complexes were investigated and compared.Results show that π bridge plays an important role in the energy transfer process.π bridge can change the charge separation strength by affecting the electron-density distribution over the diethylaniline and the dipyrazoletriazine moieties.Without the π bridge connection,the benzene ring,BDDT gets a smaller conjugated system,and the absorption peak in the UV-Vis spectrum of BDDT has a blue shift of 114 nm relative to that of DPBT.So the energy level of ligand BDDT and the central ion Eu(Ⅲ) does not match well,and the energy transfer efficiency drop 33%.     

Effect of Li+ ions doping on structure and luminescence of (Y,Gd)BO3:Tb3+

The (Y,Gd)BO3:Tb3+ and Li+-doped (Y,Gd)BO3:Tb3+ phosphors were prepared by high temperature solid-state method. The inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD), scanning electron microscopy (SEM), and the excitation and emission spectra were used to characterize the samples. The results of ICP-AES and XRD indicated that Li+ ions could enter the (Y,Gd)BO3:Tb3+ lattice and induce the lattice expansion. It could be seen from SEM that the particles were spherical a...     

Effect of SiN substituting for AI-O bonds on luminescence properties of Sr3AIO4F：Ce3＋ phosphor

Cerium-doped Sr3（A11-x,Six）O4-xNxF oxynitride phosphors with different x values were synthesized by solid-state reaction. The structure and optical properties of these phosphors were investigated by X-ray diffraction （XRD）, energy dispersive spectroscopy （EDS） and photoluminescence （PL） spectra. The XRD results showed that SiN substitution for Al-O） did not change the structure of Sr3A104F host and there was no impurity for x〈0.6. With the increasing ofx values, the absorption of phosphors at the blue region was enhanced and the emitting band varied from 519 to 529 nm under the 460 nm blue light excitation. The red shift of the emission band was associated with an increase in the crystal-field splitting and the covalence, which arose from the incorporation of N. More- over, the incorporation of N also improved the thermal quenching properties and the external quantum efficiency with a maximum value up to 43.3%, indicating that this phosphor is a promising candidate for white LEDs application.     

不同结晶相的三(8-羟基喹啉)铝的研究进展

综述了三(8-羟基喹啉)铝(Alq3)的5种结晶相(α,β,γ,δ和ε)的制备方法以及这五相之间的相互转变。阐述了Alq3的两种异构体(fac-Alq3和mer-Alq3)的相互转变和存在条件,研究表明:由于室温下fac-Alq3在溶液中很不稳定,所以很难被检测到,其只能在低温下存在,并随着温度的升高逐渐向mer-Alq3转变。归纳了Alq3的5种结晶相的不同结晶形式和晶体结构。并对比了这5种结晶相在固态和溶液中的光致发光光谱,发现不同结晶相的荧光峰值波长不同,并分布在466～515 nm之间。最后简述了Alq3合成过程中的化学老化机制:在水和氧气存在的情况下,Alq3易水解进而发生氧化缩合,因此在制备Alq3的过程中需要在无水无氧的条件下进行。