The crystal structures and physical properties of the solid solution compound Ba₅Y_8-xMn₄O_21-1.5x（x = 0,1）

New oxometallides with the formula Ba5Y8 xMn4O21 1.5x(x = 0,1) are prepared through an atmospherecontrolled solid-state reaction.Two single-phase samples with Ba/Y/Mn atomic ratios 5/8/4(Y8) and 5/7/4(Y7) are obtained.The crystal structures and the physical properties of the compounds are investigated by X-ray powder diffraction,magnetization,conductivity,and dielectricity measurements.The Ba5Y8 xMn4O21 1.5x compound is demonstrated to be a Y-deficient solid solution.The solid solution compound Ba5Y8 xMn4O21 1.5x crystallizes into tetragonal symmetry with the space group I4/m.Detailed structure analysis by Rietveld refinement of the X-ray powder diffraction data reveals that the Y vacancies occur preferentially at the Y(2) site.Thermal magnetization measurements indicate the presence of antiferromagnetic interaction between Mn ions in the compounds,and temperature-dependent resistivity measurements show that insulator-semiconductor transitions occur around 175 K and 170 K for the Y8 and Y7 samples,respectively.Strong frequency dependences of the dielectric constant are observed above ～175 K for the two compounds.     

The crystal structures and physical properties of the solid solution compound Ba5Y8-xMn4O21-1.5x (x=0, 1)

New oxometallides with the formula Ba5Y8 xMn4O21 1.5x(x = 0,1) are prepared through an atmospherecontrolled solid-state reaction.Two single-phase samples with Ba/Y/Mn atomic ratios 5/8/4(Y8) and 5/7/4(Y7) are obtained.The crystal structures and the physical properties of the compounds are investigated by X-ray powder diffraction,magnetization,conductivity,and dielectricity measurements.The Ba5Y8 xMn4O21 1.5x compound is demonstrated to be a Y-deficient solid solution.The solid solution compound Ba5Y8 xMn4O21 1.5x crystallizes into tetragonal symmetry with the space group I4/m.Detailed structure analysis by Rietveld refinement of the X-ray powder diffraction data reveals that the Y vacancies occur preferentially at the Y(2) site.Thermal magnetization measurements indicate the presence of antiferromagnetic interaction between Mn ions in the compounds,and temperature-dependent resistivity measurements show that insulator-semiconductor transitions occur around 175 K and 170 K for the Y8 and Y7 samples,respectively.Strong frequency dependences of the dielectric constant are observed above ～175 K for the two compounds.     

Giant magnetocaloric effect in Tb5Ge2-xSi2-xMn2x compounds

The crystal structure,magnetic and magnetocaloric characteristics of the pseduo ternary compounds of Tb5Ge2 xSi2 xMn2x(0 ≤ 2x ≤ 0.1) were investigated by x-ray powder diffraction and magnetization measurements.The x-ray powder diffraction results show that all compounds preserve the monoclinic phase as the majority phase and all the synthesized compounds were observed to be ferromagnetic from magnetization measurements.Magnetic phase transitions were interpreted in terms of Landau theory.Maximum isothermal magnetic entropy change value(20.84 J.kg-1.K-1) was found for Tb5Ge1.95Si1.95Mn0.1 at around 123 K in the magnetic field change of 5 T.     

Magnetic Properties and Magnetoresistance Effect of YMn6 Sn6—x Crx （x=0—0.8） Compounds

The magnetic properties and magnetoresistance effect of YMn6Sn6-x Crx(x=0-0.8) compounds have been experimentally studied by magnetic properties and resistivity measurements in the applied field range 0-5T.The compound (x=0.8) displays a ferromagnetic behaviour,while the compounds (x=0-0.4) display an antiferromagnetic behaviour in the whole ordering temperature range.The compounds(x=0.5,0.6) experienced a transition from an antiferromagnetic state to a ferromagnetic state with increasing temperature.The compound with x=0.8 is rapidly saturated in the lower magnetic field with saturation magnetization of 35.92emu/g.The compounds(x=0-0.6) display a field-induced metamagnetic transition,and the threshold fields decrease with increasing Cr content.The cell-volume V of compounds(x=0-0.8) increases,and the ordering temperature decreases with the increasing Cr content.A large magnetoresistance effect was observed for the compounds (x=0.4,0.5),and the maximum absolute value at 5K are 32% and 24% under 5T for x=0.4 and x=0.5,respectively.     

Magnetocaloric effects in Mn1.35Feo.65P1-xSix compounds

The structural and magnetocaloric properties of Mn1.35Fe0.65P1-xSix compounds are investigated.The Sisubstituted compounds,Mn1.35Fe0.65P1-xSix with x = 0.52,0.54,0.55,0.56,and 0.57,are prepared by high-energy ball milling and the solid-state reaction.The X-ray diffraction shows that the compounds crystallize into the Fe 2 P-type hexagonal structure with space group P■2m.The magnetic measurements show that the Curie temperature of the compound increases from 253 K for x = 0.52 to 296 K for x = 0.56.The isothermal magnetic-entropy change of the Mn1.35Fe0.65P1-xSix compound decreases with the Si content increasing.The maximal value of the magnetic-entropy change is about 7.0 J/kg·K in the Mn1.35Fe0.65P0.48Si0.52 compound with a field change of 1.5 T.The compound quenched in water possesses a larger magnetic entropy change and a smaller thermal hysteresis than the non-quenched samples.The thermal hysteresis of the compound is less than 3.5 K.The maximum adiabatic temperature change is about 1.4 K in the Mn1.35Fe0.65P0.45Si0.55 compound with a field change of 1.48 T.     

R-site cation randomness effect in the A-site ordered Y0.5La0.5BaMn2O6 compound

The R/Ba-ordered and R-site mixed compound Y0.5La0.5BaMn2O6 is synthesized, in which (Y, La) and Ba are regularly arranged, while Y and La randomly occupy the R-site. Y0.5La0.5BaMn2O6 has a tetragonal unit cell with a space group of P4/mmm. A structural transition between tetragonal and orthorhombic is observed at about 325 K by X-ray powder diffraction (XRD). Thermal magnetic measurement shows the occurrence of an antiferromagnetic transition at the temperature TN～190 K. Anomalies in magnetization, resistivity and lattice parameters observed around 340 K indicate a charge/orbital order transition accompanying the structural phase transition. The R-site randomness effect is discussed to interpret the different properties of Y0.5La0.5BaMn2O6 between NdBaMn2O6 and SmBaMn2O6.     

Preparation and the physical properties of antiperovskite-type compounds Cd1_xInxNNi3（n〈x〈0.2）and Cd1-yCuyNNi3（0〈y〈0.2）

Two series of Cdl-xInxNNi3 （0 〈 x 〈 0.2） and Cd1_yCuyNNi3 （0 〈 y 〈 0.2） samples were prepared from CdO, In203, CuO, and nickel powders under NH3 atmosphere at 773 K. The structural and physical properties were investigated by means of X-ray powder diffraction temperature-dependent resistivity and magnetic measurements. X-ray powder diffraction results showed that the Cd1-xInxNNi3 and Cd1_yCuyNNi3 compounds have a typical antiperovskite structure, and the CdNNi3, Cd0.9In0.1NNi3, and Cd0.9Cu0.1NNia compounds show metallic temperature-dependent resistivity and exhibit a Fermi liquid behavior at low temperature. In contrast to the paramagnetism previously reported, the CdNNi3 sample exhibits very soft and weak ferromagnetism, and no superconductivity was found in the Cd1-xInxNNi3 and Cdl-yCuyNNi3 samples down to 2 K. Each sample exhibited very soft and weak ferromagnetism, and the temperature dependence of the magnetization of the Cd1-xInxNNi3 and Cd1_yCuyNNi3 samples can be well fitted to the combination of a Bloch term and a Curie-Weiss term.     

Single crystal growth and characterizations of iron arsenide superconductor BaFe2-xNixAs2（0.0≤x≤0.12）

A series of big single crystals of BaFe2 xNixAs2 have been prepared by the FeAs self-flux method, with nominal nickel doping x=0-0.12. The dimensions of the cleaved crystals are over 10 mm along ab plane and～2 mm in maximum along the c direction. The measurements of x-ray diffraction, electrical resistance and magnetic property are carried out on the crystals. For the undoped parent compound BaFe2As2, both resistance and magnetization data display an anomaly associated with spin density wave and/or structural phase transition, with the transition temperatures at～138 K. For Ni-doped BaFe2 xNixAs2 crystals, the superconducting critical temperature Tc ranges from 4.3 K for x = 0.06 sample to 20 K for the optimally doped x = 0.10 crystal.     

Phase relations in the ZnO-V2O5-K2O system

The subsolidus phase relations of a ZnO-V 2 O 5-K 2 O system are investigated by X-ray powder diffraction.There is 1 ternary compound,11 binary compounds and 14 three-phase regions in this system.The phase diagrams of V 2 O 5 K 2 O with the K 2 O content ranging from 0 to 71 mol% and pseudo-binary system of ZnO-K 2 ZnV 2 O 7 are also studied by X-ray powder diffraction and differential thermal analysis methods.     

Structural,M?ssbauer spectroscopy,magnetic properties,and thermal measurements of Y(3-x)Dy_x Fe_5O_(12)

Yttrium iron garnet powder samples((3-x)Dy_x Fe_5O_(12)), where part of yttrium ions are substituted by dysprosium ions with different concentrations are prepared by the solid state reaction method. The properties of the prepared samples are examined by different methods such as x-ray diffraction(XRD), Mssbauer spectroscopy, macroscopic magnetization measurements, and thermal measurements. The XRD measurements show that all the samples reveal the presence of a single garnet phase with a BCC structure. Room temperature Mssbauer spectra indicate that iron ions occupy three magnetic sites, i.e., two octahedral sites and one tetrahedral site. The saturation magnetization and the initial magnetic susceptibility decrease with the increase of Dy~(3+) substitution. The Curie temperature obtained from the thermal measurements seems to be independent of Dy~(3+) substitution.     

稀土离子Eu3+掺杂Y2SiO5晶体的光谱和结构研究

用５１４．５ｎｍ、４８８．０ｎｍ的Ａｒ＾＋激光和４４１．６ｎｍ的Ｈｅ－Ｃｄ激光激发Ｅｕ＾２＋：Ｙ２ＳｉＯ５晶体的获得了一系列窄带荧光谱线,其中双重谱线结构源于Ｅｕ３＾＋离子发光中在该材料中占据两种不等价的非对称光学格位,测得了Ｅｕ＾３＋：Ｙ２ＳｉＯ５的Ｘ射线多晶衍射谱的面间距数据;计算了晶格常数和晶在角度,通过和非掺杂Ｙ２ＳｉＯ５晶体数据的比较,探讨了Ｅｕ＾２＋和Ｙ２ＳｉＯ５格位的相互影响。     

CaCu_xMn_(3-x)Mn_4O_(12)(x=0.2,0.4,0.6,0.8,1.0,1.2,1.4)的结构及磁电阻效应的研究

利用湿化学反应法制备了CaCuxMn3-xMn4O12(x=0.2,0.4,0.6,0.8,1.0,1.2,1.4)系列材料的前驱体,然后加入10wt%的KCL后,在850℃的纯氧中烧结制成样品。X射线衍射表明,CaCuxMn3-xMn4O12样品呈单相立方结构,空间群Im 3-。研究表明:随掺杂浓度x的增加,晶格常数减小,晶体结构发生畸变,从而直接影响材料的电输运性质。实验表明,样品在5T的外磁场下,随x的增大,样品的磁电阻MR呈现先增大后减小的趋势,在x=1.0时磁电阻达到最大,这可能是晶粒边界处粒子的自旋极化散射和双交换作用共同作用的结果。     

多孔配位聚合物[Nd2(C6H8O4)3(H2O)2]n·n(4,4'-bpy)的合成及晶体结构

合成了标题配位聚合物, 借助于元素分析、 红外光谱和X射线单晶衍射等分析方法确定了其晶体结构, 并测定了其TDA-DTA. 该配位聚合物属正交晶系, Pbcn空间群, 晶胞参数为a=2.201 2 nm(6), b=0.777 8 nm(2), c=1.972 4 nm(5), α=β=γ=90°, V=337.70 nm(15)3, Z=4, Dc=1.796 g·cm-3, μ=3.108 mm-1, F(000)=1 800, R1=0.043 0, wR2=0.056 0. 波谱分析结构显示, 通过己二酸配体羧基氧原子桥联Nd3+离子形成三维多孔结构, 4,4'-bpy通过氢键连接存在于孔道中.     

水杨酸镧的流变相合成、表征及掺杂Tb3+的水杨酸镧的发光性质

用流变相反应法合成了水杨酸镧和掺杂Tb3 的水杨酸镧 ,通过元素分析 ,TG ,DTA ,X射线粉末衍射及红外光谱分析确定了水杨酸镧的组成、晶体结构和羧酸根与金属离子的配位方式 ,测定了掺杂Tb3 的水杨酸镧的激发和发射光谱 ,并对其发光特性进行了讨论。X射线粉末衍射表明该化合物为具有层状结构的单斜晶系 ,晶胞参数为 :a =2 1 6 0 1 0 ,b =1 3 80 1 5 ,c =3 81 0 3 ,β=97 1 1° ,V =1 1 2 7 2 3 ,Z =2 ,ρcal =1 6 2 1g·cm-3 ,ρexp =1 6 5 3g·cm-3 。掺杂Tb3 的水杨酸镧固体样品在紫外光激发下可观测到很强的三价铽离子的绿色发光 ,其中5D4→ 7F5的跃迁发射最强。     

非晶纳米发光材料(Y,Eu)2O3-SiO2发射光谱的分析研究

EXAFS测定表明sol-gel方法制备的纳米非晶(Y,Eu)₂O₃-SiO₂发光材料中,发光中心Eu³⁺的局域环境和晶态X₂型Y₂SiO₅Eu中Eu³⁺离子的局域环境相似。以此结构为依据,用M. F. Reid的方案计算了晶场迭加模型中的能级参数及光谱强度参数,并得到了与实验结果基本一致的理论光谱图.     

Phase separation in Sr doped BiMnO3

Phase separation in Sr doped BiMnO3 （Bil_xSrxMnO3, x = 0.4-0.6） was studied by means of temperature-dependent high-resolution neutron powder diffraction （NPD）, high resolution X-ray powder diffraction （XRD）, and physical property measurements. All the experiments indicate that a phase separation occurs at the temperature coinciding with the reported charge ordering temperature （Tco） in the literature. Below the reported TCO, both the phases resulting from the phase separation crystallize in the orthorhombically distorted perovskite structure with space group Imma. At lower temperature, these two phases order in the CE-type antiferromagnetic structure and the A-type antiferromagnetic structure, respectively. However, a scrutiny of the high-resolution NPD and XRD data at different temperatures and the electron diffraction exper- iment at 300 K did not manifest any evidence of a long-range charge ordering （CO） in our investigated samples, suggesting that the anomalies of physical properties such as magnetization, electric transport, and lattice parameters at the TCO might be caused by the phase separation rather than by a CO transition.     

In-situ high pressure X-ray diffraction studies of orthoferrite SmFeO_3

The high-pressure behaviors of SmFeO3 are investigated by angle-dispersive synchrotron X-ray powder diffraction under a pressure of up to 40.3 GPa at room temperature. The crystal structure of SmFeO3 remains stable at up to the highest pressure. The different pressure coefficients of the normalized axial compressibility are obtained to be βa = 0.60 × 10-3 GPa-1,βb = 0.79 × 10-3 GPa-1, βc = 1.28 × 10-3 GPa- 1, and the bulk modulus （B0） is determined to be 293（3） GPa by fitting the pressure-volume data using the Birch-Murnaghan equation of state. Furthermore, the larger compressibility of the FeO6 octahedra suggests the evolution of the orthorhombic structure towards higher symmetry configuration at high pressures.