Structure,superconductivity and magnetism of new rare earth-rhodium silicides RE2Rh3Si5 of U2Co3Si5-type

New ternary silicides RE₂Rh₃Si₅ (RE = Y, La, Nd, Sm, Gd, Tb, Dy, Ho, Er) have been prepared. They crystalize in the U₂Co₃Si₅-type structure. Only the silicides containing the diamagnetic rare earths Y and La show a superconducting transition at T_Cr = 4.4 ± 0.2K and T_Cr = 2.7 ± 0.1K respectively, those with magnetic rare earths order antiferromagnetically at low temperature.     

New ternary silicides in rare earth-rhodium-silicon systems. Crystal structure and magnetic properties

New ternary silicides have been prepared in rare earth-rhodium-silicon systems. They have the hexagonal CeCo₃B₂- type structure (space group $\text{P}\text{6/}\text{mmm-D}\text{1}\text{6}\text{h}$) with the general formulae RERh₃Si₂ (RE = Y, La, Nd, Sm, Gd, Dy, Ho, Er). Except the Y and La compounds which are diamagnetic, they are ferromagnetically ordered at low temperature. No superconductivity has been found for YRh₃Si₂ and LaRh₃Si₂ at temperatures as low as 50 mK.     

Crystal structure and magnetic properties of new rare earth ternary equiatomic silicides RERhSi

New ternary silicides RERhSi (RE=Y, Gd, Tb, Dy, Ho, Er) have been prepared by arc melting from the elements and annealed for for several days at 800°C. Single crystal studies show these materials to be of orthorhombic symmetry and isostructural with TiNiSi (anti-PbCl₂ structure). Gd, Tb and Dy compounds show a spontaneous magnetization and their ordering consists probably of a non-colinear arrangement of the moments. HoRhSi and ErRhSi order antiferromagnetically at 8K and 7.5K respectively. At 4.2K HoRhSi undergoes a metamagnetic transition above 6kOe. A field transition appears also at 4.2K for ErRhSi above 12kOe.     

Vingt nouveaux germaniures ternaires TR5T4Ge10 de metaux tr des terres rares et T = Co,Rh, Ir. Supraconductivite de Lu5Rh4Ge10 et Lu5Ir4Ge10

Twenty ternary germanides, which crystallize in the Sc₅Co₄Si₁₀ type, have been prepared in the RE-T-Ge systems where RE is a rare earth and T = Co, Rh, Ir: with Co, RE = Tm-Lu; with Rh, RE = Y, Gd-Lu; with Ir, RE = Gd-Lu. Lu₅Rh₄Ge₁₀ and Lu₅Ir₄Ge₁₀ show superconducting transitions at 2.2?1.6 K and 2.01?1.94 K respectively.     

New ternary superconductors with silicon

A new superconducting ternary system with the formula MRu₃Si_2+x, where x ～ +.2 is reported. M is Y, La and Th. The superconducting transition temperatures range from 7.6 K for La to 3.5 K for Y.     

New superconducting equiatomic ternary silicides MIrSi (M = Y,Zr, Hf) with TiNiSi-type structure (anti-PbCl2)

New equiatomic ternary silicides MIrSi (M = Y, Ti, Zr, Hf) crystallizing with the TiNiSi-type structure (anti-PbCl₂) have been prepared. Those with Y(T_cr = 2.70 K), Zr(T_cr = 2.04 K) and Hf(T_cr = 3.50 K) are the first superconducting ternary silicides having such a structure. The titanium compound has not been found to be superconducting above 1.7 K.     

Superconductivity of new ternary borides with the LuRuB2-type structure

A new group of superconducting ternary borides has been found with the general formula MTB₂, where M is Sc, Y or Lu and T is Ru or Os. The superconducting transition temperatures range from 1.3K for ScOsB₂ to 10.0K for LuRuB₂. Additionally, ismorphous compounds with M=Tb, Dy, Ho, Er or Tm order magnetically with critical temperatures in the range 2K to 46K. The occurrence of superconductivity and magnetism in this new ternary boride structure is discussed with respect to analogous data in MT₄B₄ systems.     

De nouveaux stannures ternaires de rhodium et d'elements des terres rares : TR2Rh3Sn5 OU TR = Y,Gd, Tb,Dy, Ho. structure cristalline et proprietes electriques et magnetiques de Y2Rh3Sn5

New ternary stannides are reported : RE₂Rh₃Sn₅ (RE = Y, Gd, Tb, Dy, Ho). Y₂Rh₃Sn₅ has been studied by single - crystal X-ray diffraction analysis. Its structure is of a new type with space group Cmc2₁ and Z = 4 : a = 4,387(2), b = 26,212(4), $\text{c}\text{= 7,1550(8)}\text{A}\text{?}$, D_x = 8,71 Mgm^?3, μ(AgK_α) = 17 mm^?1, F(000) = 1851, R = 0,045 for 478 independant reflexions (R_w = 0,046). This structure is characterized by a tridimensionnal lattice of RhSn covalent bonds with two very different sites for yttrium. Y₂Rh₃Sn₅ is diamagnetic and semimetallic according to its electrical properties.     

Sol-Gel Synthesis and Photoluminescence of RE<Subscript>x</Subscript>Lu<Subscript>2-<Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>3</Subscript>:Eu<Superscript>3+</Superscript> (RE = Y,Gd) Nanophosphors

RE_xLu_2-x O₃:Eu³⁺ (RE = Y, Gd) nanophosphors with x = 0.4, 1.0, and 1.6 were synthesized using rare-earth salicylate coordination polymers as precursors for the luminescent species RE_xLu_2-x O₃:Eu³⁺ (RE = Y, Gd) composed of polyethylene glycol both as a dispersing medium and fuel. Their particle sizes were around 100 nm as determined by scanning electron microscopy and x-ray diffraction.__________From Neorganicheskie Materialy, Vol. 41, No. 6, 2005, pp. 706–710.Original English Text Copyright © 2005 by Zhou, Yan.This article was submitted by the authors in English.     

Synthesis of New Pb-based 1222 Layered Cuprates in the (Pb,S)Sr2(RE,Ce)2Cu2O z (RE=Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, and Y) System

A new family of the Pb-based layered cuprate with the 1222 structure has been synthesized in the (Pb,S)Sr₂(RE,Ce)₂Cu₂O _z (RE=Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, and Y) system. The almost-single phase samples are obtained for x=0.25 and y=1.0 in the composition of (Pb_1?x S _x )Sr₂(RE_2?y Ce _y )Cu₂O _z . Each of the samples has the crystal structure with a tetragonal symmetry. Both of the lattice parameters a and c are decreasing with the decrease of the ionic radius of RE element. Among these samples, the sample with RE=Er has the smallest resistivity in the whole temperature range and the slope of the resistivity versus temperature is the most gentle. Despite annealing under O₂ atmosphere at high-pressure of 121 atm, this sample is a semiconductor with the transport process characteristics of three-dimensional variable range hopping conduction. Then the samples of RE=Er with smaller y are investigated for the composition of (Pb_0.75S_0.25)Sr₂(RE_2?y Ce _y )Cu₂O _z , the sample with y=0.4 is found to show an onset of resistivity drop phenomenon at about 11 K with the decrease of temperature. Moreover, we also discover that the samples of RE=Ho with y=0.4 show an onset of the resistivity dropping at over 20 K and zero resistivity at 13 K. From these results, the present (Pb_0.75S_0.25)Sr₂(RE_2?y Ce _y )Cu₂O _z system is considered to be a new family of the Pb-based superconducting cuprates with the 1222 structure.     

Structural and electrical properties of new silicides: ThCoxSi2−x (0 ⩽ x ⩽ 1) and ThTSi (T = Ni,Pt)

New silicides have been prepared in ternary systems: thorium-transition element (T = Co, Ni, Pt)-silicon. With cobalt compounds ThCo_xSi_2?x (0 ? x ? 1) a structural change occurs with the sequence α 1bThSi₂(tetr.) → β 1bThSi₂(hex) →α 1b ThSi₂(tetr.) as x increases. It has been clearly shown that ThPtSi is isostructural with LaPtSi (i.e. of ordered α 1bThSi₂ type). However structure refinement from X-ray powder measurements is not conclusive to decide whether Si and T atoms are ordered or disordered in ThTSi (T = Co, Rh, Ir, Ni) compounds of α 1bThSi₂ type. ThNiSi, ThPtSi and the cobalt poor and rich compounds have clearly been found to be superconducting above 2K.     

Crystal structure of new superconducting materials LaIrSi3 and LaRhSi3. Structural relation between LaRh2Si2, La2Rh3Si5 and LaRhSi3

New superconducting ternary silicides LaRhSi₃ and LaIrSi₃ have been prepared by arc melting from the elements and annealing for ten days at 900°C. A single crystal study shows these materials to be of tetragonal symmetry and isostructural with BaPtSn₃. Their superconducting transition temperature which depends strongly on stoichiometry and thermal treatment occurs between 1.9 K and 2.7 K. The structures have been compared to those of the superconducting compounds LaRh₂Si₂ and La₂Rh₃Si₅. The occurence of superconductivity in these materials seems to be related to the presence of similar coordination polyhedra for Rh or Ir and Si atoms.     

Electrical and Structural Properties of RE<Subscript>3</Subscript>Ba<Subscript>5</Subscript>Cu<Subscript>8</Subscript>O<Subscript>18</Subscript> (RE=Y,Sm and Nd) Superconductors

This paper presents the synthesis and characterization of the new superconducting compounds with nominal composition, RE₃Ba₅Cu₈O₁₈, RE=Y, Sm and Nd. The onset critical temperatures of the present samples are 97.5, 97 and 95 K for the RE=Y, Sm and Nd, respectively. The first two values are the highest for the RE–Ba–Cu–O superconductors recorded to date. The RE₃Ba₅Cu₈O₁₈ samples crystallize in the orthorhombic system, with increased unit cell volume as Sm and Nd replace the element Y.     

Susceptibility of rare earth bromates between 1 and 4.2 K

AC magneitic susceptibilities measured between 1 and 4.2 K are reported for a series of rare earth bromate hydrates, RE(BrO₃)₃ · 9H₂O, for the rare earths Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Yb. Results for Pr, Tb, Dy, and Er are in good agreement with a previous determination. New results are reported for Nd, Sm, Gd, Ho, and Yb, some of which show interesting differences from the structurally similar rare earth ethylsulfates and anhydrous trichlorides.     

The Effect of Linker-to-Metal Energy Transfer on the Photooxidation Performance of an Isostructural Series of Pyrene-Based Rare-Earth Metal–Organic Frameworks

The tetratopic linker, 1,3,6,8-tetrakis(p-benzoic acid)pyrene (H₄TBAPy) along with rare-earth (RE) ions is used for the synthesis of 9 isostructures of a metal–organic framework (MOF) with shp topology, named RE-CU-10 (RE = Y(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III), and Lu(III)). The synthesis of each RE-CU-10 analogue requires different reaction conditions to achieve phase pure products. Single crystal X-ray diffraction indicates the presence of a RE₉-cluster in Y- to Tm-CU-10, while a RE₁₁-cluster is observed for Yb- and Lu-CU-10. The photooxidation performance of RE-CU-10 analogues is evaluated, observing competition between linker-to-metal energy transfer versus the generation of singlet oxygen. The singlet oxygen produced is used to detoxify a mustard gas simulant 2-chloroethylethyl sulfide, with half-lives ranging from 4.0 to 5.8 min, some of the fastest reported to date using UV-irradiation and < 1 mol% catalyst, in methanol under O₂ saturation.     

The crystal structure of a new ternary silicide in the system rare-earth-ruthenium-silicon

The structural properties of a new group of ternary silicides in the system M-Ru-Si (M = Y, La, Th and RE) have been investigated. The structure is presented as determined from X-ray powder diffraction.     

Synthesis,order-disorder transition and magnetic properties of LiLnS2, LiLnSe2, NaLnS2 and NaLnSe2 (Ln=Lanthanides)

Ternary chalcogenides LiLnS₂, LiLnSe₂, NaLnS₂, and NaLnSe₂ (Ln-La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Er, or Y) were prepared by heating the mixtures of elements. DTA(differential thermal analysis) measurements showed the first order transitions at high temperatures above 600 °C in LiLnS₂ (Ln=Dy, Ho, Er, Y), LiLnSe₂ (Ln=Gd to Er), NaNdS₂, and NaCeSe₂, which are considered order-disorder transitions between a NaCl and an α-NaFeO₂ structure. This is consistent with X-ray diffraction measurements. Magnetic susceptibility measurements revealed that all the lanthanides ions are in trivalent state.     

Etude cristallochimique d'une nouvelle serie d'oxydes doubles de rhenium et de terres rares

The preparation of a new series of heptavalent rhenium compounds of Ln₃ReO₈ type (Ln = rare earths) is described. The crystals are orthorombic for Ln = La (space groups Ccmm, Ccm2₁ or Cc2m) and Ln = Pr, …, Gd (space group B22₁2), face centered cubic of fluorite type for Ln = Tb, …, Lu and Y.     

High temperature phase equilibrium of SiC-based ceramic systems: SiC–Si<Subscript>3</Subscript>N<Subscript>4</Subscript>–R<Subscript>2</Subscript>O<Subscript>3</Subscript> (R = Gd,Y) systems

The phase relations of the ternary systems SiC–Si₃N₄–R₂O₃ (R = Gd and Y) have been investigated by XRD phase analyses of the hot-pressed samples from SiC, Si₃N₄, and R₂O₃ powders. Their subsolidus phase diagrams were presented. In situ SiO₂ impurity in the powders always led to form some oxygen-richer rare-earth siliconoxynitrides and extend the ternary systems to the quaternary systems of SiC–Si₃N₄–SiO₂–R₂O₃ (R = Gd, Y). Within these systems all rare-earth siliconoxynitrides coexist with SiC. The phase diagrams of the quaternary systems of SiC–Si₃N₄–SiO₂–R₂O₃ (R = Gd, Y) were established, in which the subsolidus diagram of Si₃N₄–SiO₂–Gd₂O₃ system was first reported.     

不同稀土元素掺杂对钛酸钡陶瓷导电性的影响

采用溶胶－凝胶法制备了１４种稀土掺杂的ＢａＴｉＯ３超细粉体（ＲＥ＝Ｙ，Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｓｍ，Ｅｕ，Ｇｄ，Ｔｂ，Ｄｙ，Ｈｏ，Ｅｒ，Ｙｂ，Ｌｕ），用一般陶瓷工艺将这些超细粉体分别烧成了１４种稀土掺杂的ＢａＴｉＯ３陶瓷，测得了这些陶瓷体的电阻率并对Ｅｕ和Ｙｂ掺杂的ＢａＴｉＯ３陶瓷成绝缘体的原因进行了初步讨论。