Higher order elastic constants of rare earth metals: gadolinium,dysprosium and erbium

The expressions for the second and third order elastic constants of the rare earth metals, gadolinium dysprosium and erbium have been worked out and their values have been determined. The present theoretical values are compared with the experimentally observed results. It is also suggested that the third order elastic constants of these metals may be measured using ultrasonic technique under high pressures.     

微波消解-紫外分光光度法测定茶叶中的稀土含量

本文采用了微波消解技术处理茶叶样品,紫外分光光度法测定汉中绿茶稀土含量。通过样品比较,加标回收试验表明取得了较好结果。     

The luminescent properties, thermal stability of phthalic acid and energy transfer from phthalic acid to Tb in sol—gel derived silica xerogels

In recent years, the energy transfer between different rare earth ions and the luminescent properties of rare earth ions have been studied extensively. However, the research of luminescent properties, thermal stability and structural variations of organic compounds, as well as their energy transfer to rare earth ions in silica xerogel, have not been reported. Organic—inorganic composites have even more efficient luminescence than pure rare earth ions. We describe the fabrication of silica xerogels doped with phthalic acid and Tb³⁺, their luminescent properties and thermal stability. The results show that, in silica xerogels, phthalic acid can exist steadily at 300 °C, and it can transfer the energy that it has absorbed to Tb³⁺.     

Doping Fe-based diamond tool matrix composites with a rare-earth element

The paper presents the experiments on adding rare-earth element cerium to diamond matrix composites. Based on the doping of rare earth in metal powders including tungsten carbide, a small amount of nickel, iron entirely replacing cobalt in diamond matrix and the process route of rare earth doping is indicated. The performance of matrix composites with and without rare-earth elements has been assessed. The results obtained show that the flexural strength, the hardness, and the impact ductility of matrix composites with rare-earth elements have been improved. The flexural strength and the impact ductility increased correspondently by 10–62% and about 5, as compared to composites free of rare-earth elements. Rare-earth diamond tool matrix composites where Co was r’eplaced with Fe, which provides a good practical service performance and a low price, have been successfully studied, corresponding diamond bits and saw blades have been manufactured.     

Magnetic properties of rare earth orthoferrites grown by a floating zone technique

Large useful areas of single crystal rare earth orthoferrites have been grown using a floating zone apparatus. The growth of mixed rare earth orthoferrites without any great segregation is also reported. Several types of defects, such as laminar twins and regions of optical non-uniformity were observed. The coercivity of these defects was investigated and a new method of measuring the domain wall mobility is described. The results obtained using this method for crystals grown by the floating zone technique are presented.     

Characterization of a rare earth oxide obtained from xenotime mineral

This paper reports on the characterization of a rare earth oxide obtained by hydrometallurgy of the mineral xenotime, an yttrium phosphate containing other rare earths, and comparison with mixtures of rare earth oxides prepared in different ways. The results indicated that hydrometallurgy from xenotime yielded a solid solution of the rare earth oxides. However, when the pure rare earth oxides were simply mixed physically then heat-treated at 1000 °C, a similar solid solution was not obtained. On the other hand, when the mixtures were prepared using a co-precipitation process, subsequent heat treatment did produce oxide solid solutions similar to that produced by hydrometallurgy of xenotime.     

Tailoring the microwave dielectric properties of BaRE2Ti4O12 and BaRE2Ti5O14 ceramics by compositional variations

Ceramic dielectric resonators in the BaO-RE₂O₃-TiO₂ (RE=rare earth) system have been prepared by the conventional solid state ceramic route. The dielectric properties have been tailored by substitution of different rare earth oxides and by bismuth oxide addition. The dielectric constants increased with Bi addition whereas the Q decreased. The temperature coefficient of the resonant frequency improved with bismuth addition.     

Hydrothermal synthesis and characterization of LaPO<Subscript>4</Subscript> for bio-imaging phosphors

Rare earth orthophosphates, RPO₄ (LaPO₄ and Nd: LaPO₄) have been synthesized under hydrothermal conditions with an experimental temperature of 120 °C and duration of 16–30 h. Crystals were typically in the size range of 50–120 nm. The nanoparticles obtained were characterized using powder X-ray diffraction, infrared spectroscopy, photoelectron spectroscopy, SEM, and optical absorption spectroscopy. The typical morphology of the rare earth phosphate particles obtained was either rod-shaped or spherical depending upon the experimental conditions.     

Preparation and magnetic property of new rare earth compounds R2GeBe2O7 (R = La,Pr, Sm,Gd, Dy,Er) and Y2GeBe2O7

New rare earth compounds which are isostructural with silicate minerals of the melilite family have been prepared. The cell dimensions vary linearly with the radii of rare earth ions, showing a typical Lanthanoid contraction. Magnetic susceptibilities of the rare earth compounds were measured in the temperature range from 77 K to 1000 K. A trend toward weak ferromagnetism with decreasing temperature was observed in the heavy rare earth compounds.     

稀土对Al-Zn-M g-Cu/Al2O3陶瓷界面润湿性的影响

采用真空座滴法和熔铸法研究了在Al-Zn-Mg-Cu 合金中加入稀土(Ce、Y) 对Al2Zn2M g2Cu/Al₂O₃陶瓷界面润湿性的影响。结果表明,Al-Zn-Mg-Cu 合金中加入稀土可有效降低铝合金/Al₂O₃界面的接触角, 改善界面结合状态; 稀土改善界面润湿性存在一最佳含量范围, 添加Ce 的最佳含量约为0. 5w t% , Y 约为0. 7w t%。稀土改善润湿性的作用主要是稀土与Al₂O₃膜、Al₂O₃陶瓷发生反应。Mg、Zn、Cu 等合金元素在界面富集并参与界面反应对润湿性有利; 稀土与Mg、Zn、Cu 等合金元素适当组合改善润湿性的效果比单一稀土明显。      

稀土元素对中碳钢组织、力学性能和渗氮的影响

在一种中碳钢中通过添加微量稀土元素,研究稀土微合金化对钢的微观组织、力学性能以及在渗氮热处理条件下对渗层的影响.结果表明,添加稀土后,长条状的MnS夹杂和粗大块状的A12O3转变成小球状的稀土硫氧化物夹杂;铁素体的含量降低,并促进细小片层结构的珠光体形成;冲击性能提升126％以及塑性提高10％;渗氮处理后,添加稀土能显...     

Magnetodielectric properties of rare earth metal-doped BiFeO3 nanoparticles

Pure and rare earth metal ions (Gd³⁺, Tb³⁺, Dy³⁺)-doped BiFeO₃ nanoparticles have been synthesized by the sol–gel method. The effect of doping of rare earth metal ions on structural, magnetic, dielectric and magnetodielectric properties of synthesized nanoparticles have been investigated. Synthesized nanoparticles have been found to be possessing spherical morphology, with average particle size, 25–46 nm. Structural study confirms that 15 % mole fraction doping of the rare earth metal ions results in structural transformation from rhombohedral to orthorhombic phase. Magnetic study reveals that the synthesized nanoparticles exhibit well saturated ferromagnetic magnetic loops. Dielectric measurements show that doping of rare earth metal ions results in high dielectric constant as compared to that of pure BiFeO₃. Magnetoelectric coupling in the synthesized nanoparticles, established by performing magnetodielectric measurements, reveals that the doped nanoparticles exhibit high magnetodielectric coefficient as compared to its pure form. The high value of saturation magnetization, 5.22 emu/g, dielectric constant, 900 and magnetodielectric coefficient, 5.82 %, have been observed in Dy-doped BiFeO₃ nanoparticles. The observed trend in the properties of the synthesized nanoparticles has been explained on the basis of doping as well as size of the synthesized nanoparticles.     

Oxygen content determination in perovskite-type cobaltates

Three oxygen content determination methods (iodometric titration, gas volumetric analysis and thermogravimetric hydrogen reduction) have been evaluated for the case of rare earth cobaltates LnBCo₂O_5+δ (were Ln-rare earth, B-alkali earth elements). All the methods are based on oxidation properties of both Co⁴⁺ and Co³⁺ cations but different instrumentation was used for each of the method. We have obtained good agreement within ±0.02 in δ for both the iodometric titration and the gas volumetric analysis, whereas the thermogravimetric hydrogen reduction was found to be less credible.     

Effects of trace amount addition of rare earth on properties and microstructure of Sn–Ag–Cu alloys

Ternary lead free solder alloys Sn–Ag–Cu were considered as the promising alternatives to conventional SnPb alloys comparing with other solders. In the present work, effects of trace amounts of rare earth Ce on the wettability, mechanical properties and microstructure of Sn–Ag–Cu solder have been investigated by means of scanning electron microscopy and energy dispersive X-ray analysis systematically. The results indicate that adding trace amount of rare earth Ce can remarkably improve the wettability, mechanical strength of Sn–Ag–Cu solder joint at different temperature, especially when the content of rare earth Ce is at about 0.03%, the tensile strength will be 110% times or more than that of the lead free solder joint without rare earth Ce addition. Moreover, it was observed that the trace amount of rare earth Ce in Sn–Ag–Cu solder may refine the joint matrix microstructure, modify the Cu₆Sn₅ intermetallic phase at the copper substrate/solder interface, and the intermetallic compound layer thickness was reduced significantly. In addition, since rare earth Ce possesses a higher affinity to Sn in the alloy, adding of rare earth Ce can also lead to the delayed formation and growth of the intermetallic compounds of Ag₃Sn and Cu₆Sn₅ in the alloy.     

High resolution electron microscopic studies of HoAl3, Er0·5Gd0·5Al3 and Y0·91Er0·09Al3 in thin film form

Rare earth trialuminides (RAl₃) exhibit an interesting series of structures changing from 2H to 3C in the bulk form. Many of the rare earth trialuminides have been recently found to exhibit curious structural characteristics such as the occurrence of the modulated phases. A detailed investigation of the formation synthesis and characterization of some binary and ternary alloys of the rare earth-aluminium system has been carried out. High resolution microscopic technique has been employed to study the modulated phases for some alloyse.g. HoAl₃, Er_0·5Gd_0·5Al₃ and Y_0·91Er_0·09Al₃. With the help of lattice imaging technique, several new modulated phases have been investigated. A possible mechanism for the formation of these phases has been suggested. The details of the results obtained by lattice imaging technique are discussed.     

Preparation and characterization of bismuth rare earth tungstate (BiREWO6) dielectric ceramics

BiREWO₆[RE=La, Nd, Pr, Sm, Gd, Dy, Tb, Yb, Y] ceramics have been prepared by the conventional solid-state ceramic route. The sintered samples are characterized by X-ray diffraction and SEM methods. The ceramics have high dielectric constants in the range 25–55 depending on the rare earth element. The dielectric losses of these ceramics increase with increase in the frequency and with increase in the rare earth crystal radii.     

Phase transition of nanostructure zirconias doped with rare earth elements

Nanostructure zirconias doped with rare earth elements were obtained by coprecipitation. The morphology, structure, and phase transition of the as-prepared samples were studied. According to transmission electron microscopy, the particles appear in near spherical shape and have a mean particle sizes of about 150 nm without change with the rare earth elements. From laser Raman and X-ray diffraction results, it is known that the tetragonal phase of zirconia is stabilized by a certain concentration of the rare earth dopants, and the cubic phase is obtained if enough dopants are added. The crystal lattice increases with the increase of dopant concentration. Moreover, the heavy rare earths are better than the light ones in stabilizing effect. According to our study, laser Raman is more sensitive than X-ray diffraction in monitoring the phase transition.     

Proprietes magnetiques de quelques ferrites mixtes d'alcalinoterreux et de terre rare

Magnetic properties of some members of the series Sr(Ba)Ln₂Fe₂O₇ (Ln = rare earth) have been investigated by measurements of their magnetic susceptibility in the temperature range 4.2 to 1300 K. The iron sublattice orders antiferromagnetically at temperatures close to 550 K. Below this temperature the rare earth ion remains paramagnetic.     

Preparation and luminescence properties of the mesoporous MCM-41s intercalated with rare earth complex

Rare earth complex Eu(DBM)₃phen (DBM: dibenzoylmethane, phen: 1,10-phenanthroline) has been incorporated into unmodified MCM-41 and modified MCM-41s by aminopropyltriethoxysilane (APTES) or N-[(3-triethoxysilyl)propyl]ethylenediamine (TEPED). Thus, the assemblies of unmodified or modified MCM-41s with rare earth (RE) complex have been obtained. XRD spectra, NMR spectra, diffuse reflectance spectra, and the luminescence spectra were used to characterize the pure RE complex and the corresponding assemblies. The assemblies have better luminescence properties under UV irradiation, and their fluorescence lifetimes on the excited state are longer than that of the corresponding pure complex. The possible mechanisms are also discussed in the context.     

稀土(Ce/La)对碳素钢耐海洋性大气腐蚀影响的电化学研究

稀土元素提高钢铁材料耐大气腐蚀性能的机理已有多种解释,但它本身所具有的缓蚀特性对提高钢铁材料耐候性的机理没有深入研究报道.为此,使用极化曲线、交流阻抗测试、锈层微观分析等方法研究了Ce/La混合稀土对碳素结构钢耐海洋性大气腐蚀性能的影响.结果表明:在中性氯化钠溶液中,钢中加入稀土后自腐蚀电位负移,阴极反应受到阻碍;随着稀土含量的增加,试验钢的锈层变得较为致密,厚度减薄,裂纹和空洞也明显减少,锈层中的电荷传递电阻呈上升趋势,而锈层电阻成下降趋势.对稀土提高钢铁材料耐候性的缓蚀机理进行了讨论.