Structure and Superconductivity of the Y4Ba8Cu12O27 Nanosuperconductor

A nanosuperconductor was prepared and characterized in the present work. The nanosuperconductor consisted of nanocrystals with superconducting transition temperature, T _c, of 88 K. Dimension of the nanocrystals is dozens nm in diameter and hundreds nm in length. The compound of the nanocrystals has a formula of Y₄Ba₈Cu₁₂O₂₇. The structure of the nanocrystals was found to be an orthorhombic perovskite, and the lattice constants were determined as a = 7.634 Å, b = 7.758 Å, and c = 11.654 Å, respectively.     

Scandium and gallium substitution effects in the (Y1−xScx)Ba2Cu4O8 and (Y1−xGax)Ba2Cu4O8 superconducting oxides

In this study scandium and gallium substitution effects in the YBa₂Cu₄O₈ (Y-124) superconducting cuprate have been investigated. The superconducting (Y_1?xSc_x)Ba₂Cu₄O₈ and (Y_1?xGa_x)Ba₂Cu₄O₈ (x = 0.0, 0.05, 0.1 and 0.2) compounds have been synthesized using a simple sol–gel synthesis technique. The obtained oxides were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG) and resistivity measurements. The X-ray diffraction patterns of the samples with x = 0.0, 0.05, and 0.1 showed that the single phase (Y_1?xSc_x)Ba₂Cu₄O₈ and (Y_1?xGa_x)Ba₂Cu₄O₈ compounds have formed. Moreover, the XRD results are completely supported by TG measurements. The results of resistivity measurements for the (Y_1?xSc_x)Ba₂Cu₄O₈ samples showed that the onset critical temperature of superconductivity for these samples slightly increased. Contrarily, T_C for the (Y_1?xGa_x)Ba₂Cu₄O₈ samples decreased monotonically with the increasing amount of gallium.     

Superconducting Fluctuations in Polycrystalline Y3Ba5Cu8O18

The Y₃Ba₅Cu₈O₁₈ superconductors are synthesised using the solid state reaction method under different annealing conditions. Structure characterisation using X-ray diffraction shows that the lattice parameters are different from those of the standard YBCO system. The resistivity measurements are performed using the four-probe method in the temperature range from 77 to 300 K. The electrical resistivity indicates the transition temperature T _c (O₂)=100.2 K and T _c (air)=92.3?K. Thermal fluctuations were experimentally studied. The correlations of the critical exponents with the dimensionality of the fluctuation system for each Gaussian regime were performed using the Aslamazov-Larkin theory. Near T _c , a critical regime with a critical exponent of λ _CR=0.35 is effectively described by the E-model.     

High Temperature Superconductivity on the New Superconductor System Yb1.8Sm1.2Ba5Cu8O18

The synthesis of the new high temperature superconductor system Yb_1.8Sm_1.2Ba₅Cu₈O₁₈ is reported. The new material was produced using the standard solid-state reaction method. The structural characterization of the compound was performed by X-ray diffraction and Rietveld refinement using a polycrystalline sample of the material. Structural ordering corresponds to an orthorhombic structure, from the space group Pmm2. The lattice parameters of the material are reported here. The superconducting nature of the material was determined by measuring the magnetization, as a function of its temperature, in the regime of low and mean field. A critical temperature value of T _c ～88 K was determined for Yb_1.8Sm_1.2Ba₅Cu₈O₁₈. The experimental results have shown that the production of a novel group RE₃Ba₅Cu₈O₁₈ of high-T _c superconductivity is possible, by substitution of RE instead of Y in the recently reported new superconductor material Y₃Ba₅Cu₈O₁₈.     

Superconducting gap in Pr x Y1−x Ba2Cu4O8 and YBa2−y Sr y Cu4O8 probed by infrared phonon self-energies

We report a reflectivity study of thez-polarized TO-phonons of Pr _x Y_1?x Ba₂Cu₄O₈ and YBa_2?y Sr _y Cu₄O₈ alloys in the temperature range 10–300 K. Anomalies of the frequency and linewidth of the plane-oxygen vibration atω～300 cm^?1 due to the opening of the superconducting gap are found to occur upon crossing the superconducting transition temperatureT _c . Phonon self-energy effects are strongly dependent onT _c , providing evidence for a relative shift of the gap with respect to the energy of phonon.     

Distributions of Y2Ba1Cu1O5 particles in fluorine-doped Y1Ba2Cu3O x superconductors

An experimental study has been carried out on the relationship between Y₂Ba₁Cu₁O₅ particles in Y₁Ba₂Cu₃O _x superconductors and electric furnace cooling rates. As the electric furnace cooling rates decrease, the Y₂Ba₁Cu₁O₅ particles become uniformly disperse in fluorine-doped Y₁Ba₂Cu₃O _x superconductors. However, the Y₂Ba₁Cu₁O₅ particles do not appear in the undoped Y₁Ba₂Cu₃O_x superconductors.     

Structure and polytypic faults in Ba4NdMn3O12 compound

We have studied the structure and polytypic defect formation in the 12R perovskite-type Ba₄NdMn₃O₁₂ compound. Its structure was characterized using transmission electron microscopy (TEM). Like in the 12R ordered oxides of Ba₄CeMn₃O₁₂ and Ba₄PrMn₃O₁₂ (Fuentes et al., J. Solid State Chem. 177 (2004) 714), a cationic ordering between Nd and Mn is also expected to be established in Ba₄NdMn₃O₁₂ with the Nd ions located in the corner-sharing octahedra and the Mn ions located in the face-sharing octahedra. We also observed in the Ba₄NdMn₃O₁₂ phase two types of polytypic faults, i.e., the extrinsic hexagonal-type fault with the stacking sequence …cch h hcc… and the extrinsic cubic-type fault with the stacking sequence …hhc c chh….     

PZT/Y0.9Ca0.1Ba2Cu4O8及Ag2O掺杂的复合氧化物陶瓷的NTC效应

报道了压电材料ＰＺＴ中掺杂超发Ｙ０．９Ｃａ０．１Ｂａ２Ｃｕ４Ｏ８,而超导粉中又能Ａｇ２Ｏ的掺杂,这种复合氧化物陶瓷的制备方法及电导率的测试结果,表明材料具有很强的ＮＴＣ效应。     

Investigation of Y1Ba2Cu3O6.9 and Er1Ba2Cu3O6.8 during cyclic temperature variations

Gravimetric investigations of the superconductive ceramics Y₁Ba₂Cu₃O_6.9, Y₁Ba₂Cu_2.7Al_0.3O_7.1 and Er₁ Ba₂Cu₃O_6.8 during cycling heating cooling in the interval 293–1323 K at partial pressure of the oxygen 0.02 and 0.2 × 10⁵ Nm^–2 are presented. Intervals of intense weight changes during heating and cooling are determined. Oxygen loss was shown to be the main reason for the weight changes. Structural characteristics and resistivity of the yttrium ceramics in the above-mentioned temperature interval are investigated. Experimental data are discussed within the framework of the models of the quasi-equilibrium and essentially nonequilibrium processes. Binding energy and diffusional parameters of the evolving gas are estimated.     

Y3Ba5Cu8Ox Superconductor Under Hydrostatic Pressure

Journal of Low Temperature Physics - Superconducting Y3Ba5Cu8O18 samples were prepared by standard solid-state reaction method in comparison with Y1Ba2Cu3O7 sample. Resistance vs. temperature of...     

Superconductivity in single crystals of the nonperovskite-like cuprate Ba2Cu3O6−x

Spontaneous crystallization from a solution in a melt at a pressure of (0.8–1)×10⁻³ Pa was used to obtain single crystals of a new nonperovskite-like superconducting phase Ba₂Cu₃O_6−x space group P _ccm, a=13.065, b=20.654, and c=11.431 Å). The superconducting properties of the crystals were investigated by modulated microwave absorption. The superconducting transition temperatures were 5 K (sample No. 1), 7 K and 13 K (sample No. 2). The superconductivity in the Ba₂Cu₃O_6−x crystals is attributed to the presence of CuO₂ chains of edge-sharing copper-oxygen squares. Nonperovskite-like Ba₂Cu₃O_6−x crystals are a new class of one-dimensional (1D) superconductors. Pis’ma Zh. Tekh. Fiz. 23, 27–34 (December 26, 1997)     

Role of Ba2Cu3O5 for the formation of YBa2Cu4O8 in the presence of nitric acid

The formation mechanism of YBa₂Cu₄O₈ in the presence of nitric acid was carefully studied by utilizing X-ray powder diffraction to monitor the reaction route. Contrary to the formation of YBa₂Cu₃O_7- in which BaCuO₂ was the dominant intermediate, an intermediate Ba₂Cu₃O₅ was identified and its yield was proportional to the amount of the nitric acid present in the formation of YBa₂Cu₄O₈. This seems to play an important role in determining the formation of the YBa₂Cu₄O₈ phase. To confirm the existence of this intermediate, Ba₂Cu₃O₅ was prepared from the same condition directly. Also, the structure similarity between Ba₂Cu₃O₅ and BaCuO₂ was discussed and emphasized.     

Doping of Nb to the Ba and Cu Sites in the Y0.6Gd0.4Ba2Cu3O7−δ

Polycrystalline samples of Y_0.6Gd_0.4Ba_2?x Nb _x Cu₃O_7?δ and Y_0.6Gd_0.4Ba₂Cu_3?x Nb _x O_7?δ with different Nb contents (x=0.025, 0.075, 0.125, 0.175 and 0.225) were prepared using the solid state reaction method. Structural and electrical properties of new compounds were investigated with optical microscope, scanning electron microscopy (SEM), X-ray diffraction (XRD), Four Point Probe (FPP). The results indicated that Nb constituted YBa₂NbO₆ structure instead of substituting to the Y_0.6Gd_0.4Ba₂Cu₃O_7?δ structure. YBa₂NbO₆ structures gathered between grains. Transition temperature did not change significantly, but critical current (J _c) values decreased with increase of Nb concentration. The underlying reason is that the oxygen concentration of compounds remained unchanged due to Gd; thus, T _c values did not change significantly.     

Superconductivity in compound Y1-2x Ce x Ba2+x Cu3O6·5+δ system

Partial substitution of Ce in place of Y has been achieved by taking care of charge compensation and compounds with the general formula Y_1-2 xCe_xBa₂₊ xCu₃O_6·5+δ have been successfully prepared. X-ray powder diffraction analysis reveals that this substitution gives orthorhombic single phase for 0⩽x⩽0·3. TheT _c remains nearly unchanged between 94-90 K.     

Superconductivity in (Y1−x Sr x ) (Ba1.5Sr0.5)Cu3O7−d compounds

Careful characterization of (Y_0.95Sr_0.05)(Ba_1.5Sr_0.5)Cu₃O_7−δ and Y(Ba_1.5Sr_0.5)Cu₃O_7−δ ceramic samples has confirmed the simultaneous substitution of Sr for both Y and Ba in the YBa₂Cu₃O₇ structure. The substitution at the Y site has a distinct effect on the superconducting properties of the material. The inter-grain transport properties of both samples in an external d.c. field are enhanced with respect to undoped YBa₂Cu₃O₇ ceramics.     

Thermogravimetric studies of Y1Ba2Cu3O7−x superconductors

The synthesis conditions and oxygen stoichiometry were determined using a thermogravimetric analyser. The kinetics of oxygenation at different temperatures and at different atmospheres were studied. The oxygenation kinetics were found to be sensitive to porosity of the material. The appropriate oxygenation temperature was found to be 400 °C. For oxygenation temperatures below 400 °C, the oxygenation occurs by a nucleation and growth process, whereas for higher temperatures it is diffusion limited.     

Ba2TiGe2O8 and Ba2TiSi2O8 pyroelectric glass-ceramics

Pyroelectric glass-ceramics of composition Ba₂TiGe₂O₈ and Ba₂TiSi₂O₈ were prepred by crystallizing the glasses in a temperature gradient. High pyroelectric responses up to 50% of the single-crystal values were observed because of the high degree of orientation of the crystallites in the glass-ceramic samples. The piezoelectric and dielectric properties of the glasses and the glass-ceramics are also consistent with the properties of the single crystals.