Synthesis and properties of LnBaFeCoO5 + δ (Ln = Nd, Sm, Gd)

LnBaFeCoO_{5 + δ} (Ln = Nd, Sm, Gd) layered oxides have been synthesized and their crystal structure, thermal stability, thermal expansion, electrical conductivity, thermoelectric power, and magnetic susceptibility have been studied. The oxides have a tetragonal structure (sp. gr. P4/mmm) with unit-cell parameters a = 0.3909(2) nm and c = 0.7695(6) nm for Ln = Nd (δ = 0.65), a = 0.3908(3) nm and c = 0.7662(6) nm for Ln = Sm (δ = 0.37), and a = 0.3908(2) nm and c = 0.7613(6) nm for Ln = Gd (δ = 0.37). The LnBaFeCoO_{5 + δ} compounds are antiferromagnetic p-type semiconductors. With decreasing Ln³⁺ ionic radius, their electrical conductivity and linear thermal expansion coefficient decrease and their thermoelectric power and antiferromagnetic ordering temperature increase. Near 518–653 K, the linear thermal expansion coefficient of the LnBaFeCoO_{5 + δ} oxides increases from (12.9–16.6) × 10^?6 to (19.3–26.5) × 10^?6 K^?1, which is due to the release of weakly bound oxygen from the oxides. We have determined parameters of charge transport in the [Fe(Co)O₂] layers in the crystal structure of the LnBaFeCoO_{5 + δ} phases.     

Preparation and thermophysical properties of nano-sized Ln2Zr2O7 (Ln?=?La, Nd, Sm, and Gd) ceramics with pyrochlore structure

Rare earth zirconates (Ln₂Zr₂O₇, Ln = La, Nd, Sm, and Gd) with pyrochlore structure were prepared by hydrothermal method with polyethylene glycol as surfactant. X-ray diffraction, thermogravimetric analysis/differential scanning calorimetry, Fourier transform infrared spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy were utilized to characterize the phase structure, thermal decomposition, and morphology of the products. Qualitative analysis indicates that the as-prepared zirconates are pyrochlore-type structures. The specific surface area, lattice parameter, and average crystallite size of the as-prepared products are closely related to the ionic radius. The activation energy of crystal growth shows an increasing trend with the decrease in ionic radii. The sintering behavior of compacted body was also investigated, revealing that the sintering-resistance properties of Ln₂Zr₂O₇ are descending as the order of La₂Zr₂O₇, Nd₂Zr₂O₇, Sm₂Zr₂O₇, and Gd₂Zr₂O₇.     

Transport Properties of TlInSe2〈Ln〉 (Ln = Eu, Sm, Yb)

The electrical conductivity and Hall coefficient of TlInSe₂Ln (Ln = Eu, Yb, Sm) were measured between 300 and 900 K. The results were used to determine the band gap, ionization energy of impurities, conductivity type, and Hall mobility of charge carriers in TlInSe₂Ln. The temperature at which the Hall coefficient changes sign is shown to increase with doping level.     

The influence of ionic radii on the grain growth and sintering-resistance of Ln2Ce2O7 (Ln = La, Nd, Sm, Gd)

Rare earth cerium oxides (Ln₂Ce₂O₇, Ln = La, Nd, Sm, and Gd) with cubic-fluorite structure were prepared by hydrothermal method using cetyltrimethyl ammonium bromide as surfactant. X-ray diffraction (XRD), thermogravimetric analysis/differential scanning calorimetry (TG/DSC), Raman spectroscopy, and field emission scanning electron microscopy (FESEM) were utilized to characterize the phase structure, thermal decomposition, and morphology of the products, respectively. Qualitative analyses indicate that the as-prepared products are fluorite-type structures. The lattice parameter and average crystallite size of the products are closely related to the ionic radii. The activation energy of crystal growth shows an increasing trend with the decrease in ionic radii. The sintering behavior of compacted body was also investigated, revealing that the sintering-resistance properties of Ln₂Ce₂O₇ are descending as the order of La₂Ce₂O₇, Nd₂Ce₂O₇, Sm₂Ce₂O₇, and Gd₂Ce₂O₇.     

Synthesis of Ln0.6Sr0.4Co0.8Fe0.2O3 – δ (Ln = La, Pr, Nd, Sm) Perovskite-like Phases

Ln_0.6Sr_0.4Co_0.8Fe_0.2O_{3 –} (Ln = La, Pr, Nd, Sm) solid solutions are prepared by a procedure which makes it possible to markedly reduce the synthesis temperature and duration. X-ray diffraction, microstructural analysis, and density measurements are used to optimize conditions for the fabrication of dense substituted-cobaltite ceramics.     

K_2Ln(NO_3)_5·2H_2O(Ln=La,Ce,Pr,Nd,Sm)的晶体生长和热重-差热分析研究

本文生长出了K2Ln（NO3）5.2H2O（Ln=La；Ce；Pr；Nd；Sm）的单晶，并对其进行了晶体结构及差热-热重分析研究．结果表明，K2Ln（NO3）5.2H2O（Ln=La；Ce；Pr；Nd）的晶体属正交晶系，Fdd2空间群．首次生长出KPrN单晶并用直接法解出其晶体结构．解得KPrN的晶胞参数为：a=11．2210（10）,b=21．411（3），c=12．208（2）,Z=6；R=0．0240．对KLnN加热，则依次出现脱水、熔化、不可逆相变和NO的分解过程（K2Ce（NO3）5·2H2O除外）K2Ln（NO3）5·2H2O（Ln＝La；Nd；Sm）的NO分三步分解，K2Ln（NO3）5·2H。O（Ln=Ce；Pr）的NO分两步分解·KNO3和Ln（NO3）3·nH2O的混合物在225℃左右生成K2Ln（NO3）5     

Synthesis and Study of Sr[HSiUO6]2·2H2O and Ba[HSiUO6]2·2H2O

Uranosilicates of the general formula M^{I I}[HSiUO₆]₂·2H₂O (M^{I I} = Sr, Ba) were prepared by hydrothermal synthesis. Previously unknown intermediate crystal hydrates were separated and studied by X-ray diffraction (XRD), IR spectroscopy, and thermal analysis. Polymorphic transitions -Sr[HSiUO₆]₂ -Sr[HSiUO₆]₂ and -Ba[HSiUO₆]₂ -Ba[HSiUO₆]₂ were revealed at 700 and 780°C, respectively.     

Ln2O3—SrO—V2O5（Ln=Y,Nd）系统的相关系

在修正各二元素的基础上研究了Ｙ２Ｏ３－ＳｒＯ－Ｖ２Ｏ５和Ｎｄ２Ｏ３－ＳｒＯ－Ｖ２Ｏ５三元系统的相关系，并提出了它们的亚固相图。在后一系统中发现了一个新相Ｎｄ８ＳｒＶ３Ｏ２０．５。在近Ｎｄ２Ｏ３－ＳｒＯ二元系处发现一个三元固溶区。     

Photocatalytic Properties of the MgHPO4·3H2O and MgKPO4·6H2O Phosphates

Inorganic Materials - Magnesium double phosphates, MgHPO4·3H2O and MgKPO4·6H2O, isostructural with the minerals newberyite and struvite-K have been synthesized in powder form via...     

Interdiffusion of rare-earth cations in Ln1−x ′Ln x ″ Ba2Cu3O7 − δ (Ln′, Ln″ = Y, Dy, Ho) High-T c superconductors

The Y³⁺/Ho³⁺, Y³⁺/Dy³⁺, and Dy³⁺/Ho³⁺ interdiffusion coefficients in the YBa₂Cu₃O_{7 ? δ}-HoBa₂Cu₃O_{7 ? δ}, YBa₂Cu₃O_{7 ? δ}-DyBa₂Cu₃O_{7 ? δ}, and DyBa₂Cu₃O_{7 ? δ}-HoBa₂Cu₃O_{7 ? δ} systems have been determined in air at a temperature of 1233 K by the Boltzmann-Matano method from the yttrium/holmium, yttrium/dysprosium, and dysprosium/holmium concentration profiles across the diffusion zone between two pellets of the high-T _c superconductors. The composition dependences of the interdiffusion coefficients in the solid-solution systems are presented.     

Synthesis, Physicochemical Properties, and Electrode Behavior of Ni2[Ni(OH)6W6O18 ] · 8H2O

Nickel(II) hexatungstonickelate(II) was synthesized and characterized by elemental analysis, x-ray diffraction, thermal analysis, IR spectroscopy, and ¹H nuclear magnetic resonance. The results demonstrate that constitutional water is present in the form of OH groups, which can be removed by heating to 230–370°C. The chemical formula of the compound is Ni₂[Ni(OH)₆W₆O₁₈] · 8H₂O. Nickel(II) hexatungstonickelate(II), a poorly soluble compound, was tested as an electrode for Ni(II) determination in solution. Its electrode properties and selectivity for other ions suggest that it is a promising material for such applications. At pH 5, the ion-selective electrode we fabricated has a Nernstian response to Ni(II) (10^–5 to 10^–1 mol/l) which is close to that predicted theoretically.     

络合溶胶-凝胶法制备纳米级Y2O3:Ln(Eu,Dy,Sm,Tb)发光体

以PEG(聚乙二醇)2000为络合剂,采用溶胶一凝胶法制备纳米级Y2O3：Ln(Eu、Dy、Sm、Tb)。用红外光谱(IR)、扫描电镜(SEM)、X射线衍射(XRD)、荧光光谱对其进行一系列表征。结果表明所制备的纳米发光粉体的粒径为50nm左右,分布比较均匀,同时XRD的宽化现象比较明显。由于添加不同的激活剂,因而其激发光谱表现出明显的差异。在紫外光的激发下,文中几种粉体具有很好的发光性能。     

Conductivity of (NH4)3[CrMo6O24H6]·7H2O Treated by Nd Chemistry-Heated Diffused Permeation

Rare earth co-permeation of (N H4)3 [CrMo6 O24 H6]·7H2O was reported and the conductivity of (N H4)3 [CrMo6O24 H6]was improved by 6.734× 109 times. X-ray fluorescence spectrometry (XRF), thermogravimetry-differential thermal sample. Experimental results showed that Nd could be permeated into the body of this sample and the XRD patterns showed great difference between (NH4)3[CrMo6O24H6]·7H2O and permeated sample. The structure of (NH4)3[CrMo6O24H6]·7H2O was destroyed and new compound MoN perhaps formed.     

X-ray powder diffraction and IR study of NaMg(H2O)2[BP2O8]·H2O and NH4Mg(H2O)2[BP2O8]·H2O

NaMg(H₂O)₂[BP₂O₈]·H₂O was prepared by hydrothermal synthesis and was characterized by X-ray powder difraction and IR method. The title compound was synthesized from MgCl₂·6H₂O, NaBO₃·4H₂O, and (NH₄)₂HPO₄ with variable molar ratios using hydrothermal method by heating at 165 °C for 3 days. The X-ray powder diffraction data was indexed in hexagonal system, the unit cell parameters were found to be as a = 9.428, c = 15.82 Å, Z = 4 and the space group is P6₁22. It is isostructural with M^lM^ll(H₂O)[BP₂O₈] type compounds where M^l = Na, K; M^ll = Mg, Mn, Fe, Co, Ni and Zn. In addition NH₄Mg(H₂O)₂[BP₂O₈]·H₂O was also synthesized the first time in this research. Its unit cell parameters and hkl values were in good agreement with the sodium magnesium compound. The unit cell parameters are a = 9.529, c = 15.736 Å. The indexed X-ray powder diffraction data of both compounds which were not reported in the literature is presented in this work. The IR data of NaMg(H₂O)₂[BP₂O₈]·H₂O is also reported.     

Order–Disorder Transformations in Ln2Ti2O7(Ln = Lu, Yb, Tm, Gd)

The ordering processes in the rare-earth titanates Ln₂Ti₂O₇ with Ln = Lu, Yb, Tm, and Gd are studied by x-ray diffraction, thermal analysis, IR spectroscopy, electron microscopy, and electrical conductivity measurements. The compounds are prepared via hydroxide coprecipitation, followed by freeze-drying and heat treatment in the temperature range 350–1700°C. The compounds Ln₂Ti₂O₇ with Ln = Lu, Yb, and Tm are found to have the fluorite structure between 600 and 800°C. Above 800°C, they undergo a fluorite-to-pyrochlore transformation, with cation disordering and the formation of Ln_Ti + Ti_Ln antistructure pairs. Gd₂Ti₂O₇ has the pyrochlore structure over the entire temperature range studied and contains no antistructure defects. In contrast to Gd₂Ti₂O₇, the compounds Ln₂Ti₂O₇ with Ln = Lu, Yb, and Tm undergo a high-temperature pyrochlore-to-fluorite phase transition around 1700°C. The 750°C conductivity of Ln₂Ti₂O₇ (Ln = Lu, Yb, Tm) samples sintered at 1700°C is 5 × 10^–3 to 10^–2 S/cm, which is two orders of magnitude higher than that of ceramics of the same composition prepared at lower temperatures (950 or 1400°C). The conductivity of the Gd₂Ti₂O₇ ceramic prepared at 1500°C is two orders of magnitude lower than that of Ln₂Ti₂O₇ with Ln = Lu, Yb, and Tm.     

Framework materials containing polyoxovanadates as building units: synthesis and characterization of (N2H5)2[M3(H2O)12V18O42(EO4)]·24H2O (M = Mg,Ca) and Li6[Mn3(H2O)12V18O42(EO4)]·24H2O (E = V,S)

The reaction of an aqueous solution of lithium vanadate with hydrazinium sulfate results in a dark-colored solution that reacts with magnesium sulfate heptahydrate, calcium sulfate dihydrate, and manganese(II) chloride tetrahydrate to yield single crystals of (N₂H₅)₂[M₃(H₂O)₁₂V₁₈O₄₂(EO₄)]·24H₂O (M = Mg, Ca) and Li₆[Mn₃(H₂O)₁₂V₁₈O₄₂(EO₄)]·24H₂O (E = V, S), respectively. The crystal structures of the new solids consist of interpenetrating three-dimensional networks of {V₁₈O₄₂(EO₄)} clusters interlinked via bridging {M(H₂O)₄} (M = Mg, Ca, Mn) groups. The voids in these structures are occupied by lattice water and ion exchangeable cations.     

Hydrothermal synthesis of mixed phosphates of neodymium and alkaline metals (Me2O·Nd2O3·4P2O5)

The phase formation in the system Me₂O-Nd₂O₃-P₂O₅-H₂O (where Me = Li, Na, K, Rb and Cs) has been studied under hydrothermal conditions in the temperature and pressure range 300 to 700 C and 0.5 to 600 atm, respectively, using vitreous carbon glass liners. A composition diagram showing the possible fields of crystallization of different phases under equilibrium conditions is given. AB-diagrams of fields of crystallization of different phases in the system investigated are given. These diagrams are in correspondence with the theoretical composition diagram. The advantages and disadvantages of different methods employed in the growth of MeNd-phosphates are discussed. The crystals obtained were characterized by various methods.     

Complexes with substituted 2,5-dihydroxy-p-benzoquinones: The inclusion compounds [Y(H2O)3]2 (C6Cl2O4)3·6.6H2O and [Y(H2O)3]2 (C6Br2O4)3·6H2O

Single crystal of [Y(H₂O)₃]₂ (C₆Br₂O₄)₃·6H₂O and [Y(H₂O)₃]₂ (C₆Cl₂O₄)₃·6.6H₂O were grown in aqueous silicagel. The compounds are in principle isostructural. In Y chloranilate one additional water site is occupied as verified by X-ray single crystal structure analysis. Y³⁺ is nine-coordinated by three water molecules and six oxygen atoms of the bischelating (C₆X₂O₄)²⁻ ions (XCl, Br). The coordination polyhedron is an only slightly distorted tri-capped trigonal prism. The connection of Y³⁺ with the dianions leads to infinite, corrugated layers. The layer stacking yields cage-like cavities in which water molecules are accomodated. Hydrogen bonds interlink adjacent layers. Further hydrogen bonds involve the entrapped water molecules. DSC measurements indicated a complicated dehydration process which caused right at the start destruction of the single crystals.     

复合氧化物Ln0.67Sr0.33MnO3（Ln=La,Pr,Nd,Sm）的制备,结构与电性

本语文通过共沉淀工艺合成了复合氧化物Ｌｎ０．６７Ｓｒ０．３３ＭｎＯ３（Ｌｎ＝Ｌａ、Ｐｒ、Ｎｄ、Ｓｍ）与传统陶瓷制备方法相比，成相温度降低约４５０℃，经Ｘ射线衍射分析表明，所得复合氧化物为立方钙钛矿结构，晶胞参数随稀土离子半径变化而呈规律性变化，样品的四极法电阻率测试结果表明；样品中的稀土离子Ｌｎ的离子半径对其本身的地电性起决定性的作用，应用双交换理论，样品中的稀土离子Ｌｎ的离子半径对其本身的导电性