First-principles study of He point-defects in HCP rare-earth metals

He defect properties in Sc, Y, Gd, Tb, Dy, Ho, Er and Lu were studied using first-principles calculations based on density functional theory. The results indicate that the formation energy of an interstitial He atom is smaller than that of a substitutional He atom in all hcp rare-earth metals considered. Furthermore, the tetrahedral interstitial position is more favorable than an octahedral position for He defects. The results are compared with those from bcc and fcc metals.     

内蒙古中部渣尔泰山群微量元素地球化学特征

通过对内蒙古中部渣尔泰山群各层位岩石采样,对该山群中共43个微量元素（含稀土元素）与地壳丰度进行了对比分析,总结了该山群微量元素的地球化学特征。研究表明,该山群富集W、Re、Cu、Pb、Co等元素,而In、V、Cr、Ni等元素亏损较严重;微量元素在板岩和云母石英片岩中相对含量较高,在灰岩中相对贫化;此外,该山群稀土元素地球化学特征表现为轻稀土富集,重稀土亏损;具有明显的Eu的负异常,Ce的弱正异常。     

五个无心四元硫化物AlxLn3（SiyAl1-y）S7（Ln=Y,Gd,Dy）和In0.33Sm3SiS7的合成、结构及性质

使用一种新的高温固相反应方法合成得到了五个新的异质同构的四元稀土硫化物.它们结晶于六方晶系的手性空间群P63,属于ALn3EQ7（A：碱金属或货币金属 Ln：稀土元素 E：第IVA族元素 E：硫属元素）结构类型,晶胞参数为a=9.621（1）～10.038（2）A,c=5.672（2）～5.939（1）A,V=476.1（1）～494.9（2）A^3,Z=2.它们的晶体结构可以描述为：LnS8双帽三棱柱之间相互连接成三维框架结构,而A位和E位原子分别占据所形成的八面体和四面体空隙.化合物4的光学和磁性质的研究表明：它是光学带隙为2.34eV的半导体,并表现出类似于反铁磁相互作用的磁行为.     

连铸结晶器喂稀土处理的碳锰钢夹杂物研究

为研究钢中添加稀土带来的夹杂物问题,采用金相夹杂物评级、电解夹杂分析以及电子探针和扫描电镜观察分析,对经稀土处理的微合金化碳锰钢夹杂物进行了研究.结果表明,采用铝脱氧和RH真空充分脱气的微合金化碳锰钢,经连铸结晶器喂稀土处理后,钢中的A,B,C,D类夹杂物分别不大于1.0级、1.5级、0.5级、1.5级,氧化物夹杂总量约为0.0030%.试验钢中主要形成球状稀土硫化物,同时还形成有链状"稀土硫化物包围氧化铝"的复合夹杂物,而稀土氧化物难以生成.     

铈铽共惨杂氟化镧纳米晶体的快速合成和荧光特性

用一种简单的方法快速合成了水溶性铈铽共惨杂氟化镧纳米晶体。这种荧光纳米晶体直径只有14 nm,具有很好的生物相容性,并且在活体干细胞中显示出很强的荧光。结果表明这种铈铽共惨杂氟化镧纳米晶体可作为一种有效的生物荧光标记材料。     

YFe2B2电子结构的第一性原理计算

基于密度泛函理论,从头计算了具有ThCr₂Si₂型四方晶系的稀土金属化合物Yfe₂B₂体相的物理特性.能量计算结果表明Yfe₂B₂体相处于顺磁金属态;而能带结构、态密度、布居数以及差分电荷　分布的计算结果表明Y原子的5s,5p电子具有很强的局域性;Fe原子的3d电子和B的1s,2s和2p电子强烈耦合,使得最近邻Fe原子与B原子形成了Fe—B共价键;最近邻的两个Fe原子之间由于 关键词： 稀土金属化合物 第一性原理计算 能带结构 态密度     

Synthesis,structures and magnetic properties of Pr-lean Pr2Fe14B/Fe3B nanocomposite alloys

The lean rare-earth Pr_4.5Fe_77−xTi_xB_18.5 (x=0, 1, 4, 5) nanocomposite alloys were prepared by melt spinning method and subsequent thermal annealing. The effect of Ti content and annealing temperature on the magnetic properties and the microstructure of these magnets were investigated. The enhancing coercivity H_c from 211.4 to 338.2 kA/m has been observed at the optimal annealing temperature of 700 °C by the addition of 5 at% Ti in Pr₂Fe₁₄B/Fe₃B alloys. It was also found that increasing Ti content leads to marked grain refinement in the annealed alloys, resulting in strong exchange-coupling interaction between the hard and the soft phases in these ribbons. In addition, the magnetization reversal behaviors of Pr₂Fe₁₄B/Fe₃B nanocomposites were discussed in detail.     

稀土铝磷酸盐玻璃中镨离子的可见光致发光

研究了稀土铝磷酸盐5.8Li2O-3CaO-5BaO-6Al2O3-4.2La2O3-66P2O5(LCBALP)玻璃中镨离子的可见光致发光特性,采用积分球测试系统对其绝对荧光光谱进行表征。1D2→3H4的自发辐射跃迁几率和最大受激发射截面分别为926.5 s-1和3.5×10-21cm2。在蓝色LED激发下,镨离子可见特征发射峰的辐射通量和光通量分别为112.6μW和29.7 mlm,其可见特征发射的总荧光量子产率为4.1%。光学玻璃中镨离子的光谱评估为其在光电子器件和紧凑型照明光源领域的发展提供了重要的参考依据。     

Effect of Cation Nonstoichiometry on the Properties of Solid Electrolyte Ba x Ce0.97Nd0.03O3 - δ (0.90 ≤ x ≤ 1.10)

The effect of the cation nonstoichiometry on the electroconduction, electrotransfer, and stability in humid air of solid proton-conducting electrolyte Ba _x Ce_0.97Nd_0.03O_{3 -} (0.90 x 1.10) is studied. The electroconduction is found to decrease with decreasing content of BaO (x 1.0) and weakly depend on the BaO excess (x> 1.0). Ceramics of a stoichiometric composition (x = 1) and with lack of barium is stable when stored in humid air at room temperature, as opposed to the ceramics with barium excess, which rapidly decomposes in these conditions. The conduction of materials under study in oxidizing environment is ion-hole and in reducing media, ionic (proton + oxygen). The cation nonstoichiometry barely affects the nature of the ion transfer. An analysis of possible models for the formation of defects shows oxygen vacancies to be always present in Ba _x Ce_0.97Nd_0.03O_{3 -} , even at the CeO₂ excess exceeding the content of neodymium.