The effect of Nd 2 O 3 addition on superconducting and structural properties and activation energy calculation of Bi-2212 superconducting system

The effect of Nd ₂ O ₃ addition on the micro-structural and the superconducting properties of Bi-2212 superconductor ceramics, prepared by solid state reaction method, was analyzed by performing X-ray diffraction (XRD), scanning electronic microscope (SEM), energy dispersive spectroscopy (EDS) and dc Resistivity (ρ-T) measurements. The magnetoresistivity of the samples was measured for different values of the applied magnetic field strengths (0–7 T). Also, the activation energies were calculated using the Arrhenius equation. According to these results, the T _c ^offset value of the undoped sample was decreased from 79 to 42 K with the growth of magnetic field. In the same way, the activation energy (U _o ) values were significantly diminished by the increasing of magnetic field. A similar situation was observed in other doped samples. Activation energy for 0.05 % Nd ₂ O ₃ doped sample under 7 T magnetic field was 550 J/mol the least. In addition, lattice parameter c, calculated by analysis of XRD data, was decreased with doping while lattice parameter a was increased. SEM analysis shows that particles were shrinking with the addition. When compared with other elements for EDS analyses, it was analyzed an important decrease in the percentage of Sr with the increasing of Nd contribution.     

Effect of K substitution on Structural,Electrical and Magnetic Properties of Bi-2212 system

In this work, the effect of K in the Bi₂Sr₂Ca_1?xK_xCu₂O_8+y superconductor with x = 0.0, 0.05, 0.075, and 0.1, has been investigated. The samples were prepared by a polymer solution technique using polyethyleneimine, PEI. The effects of K substitution have been investigated by electrical resistivity (ρ?T), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy, and magnetic characterizations. SEM and XRD results have shown that the Bi-(2212) phase is the major one independently of the K concentration. Moreover, the microstructure of samples is improved with K-concentration up to x = 0.075. From electrical resistivity measurements we have found that Tc is slightly higher than 91 K for K-concentrations up to 0.075, and then it decreases for higher doping for about 0.5 K. Moreover, this trend is maintained in the magnetic measurements in which the hysteresis loops are increased until 0.075 K-concentrations. The maximum calculated Jc, using Bean’s model, has been found at around 4.5 10⁶ A/cm² at 10 K and ~1,000 Oe for the 0.05 K doped samples.     

The effect of Pr addition on superconducting and mechanical properties of Bi-2212 superconductors

In this work, the effects of Pr doping on the superconducting, structural and mechanical properties of the samples are analyzed. Pr doped Bi-2212 superconductors are obtained using solid state reaction method. Dc resistivity measurements are made to investigate the superconducting properties, microhardness measurements are made to analyze the mechanical properties, XRD and SEM measurements are done for crystal structure determination and calculation of the lattice parameters. Using EDS measurements, the change in the elemental composition with doping is analyzed. The Vickers microhardness is calculated for undoped and doped samples. The experimental results of the microhardness measurements are analyzed using Kick’s Law, PSR (proportional specimen resistance), modified PRS (MPSR) and Hays–Kendall (HK) approach. The microhardness values of the samples decrease with Pr addition. The results can be successfully explained by HK approach.     

Mechanical tests on the surface-coated Bi-2212 superconducting tapes

The strain dependence of the critical current of surface-coated Bi-2212 tapes is reported. Two methods are used in the measurements. The effect of bend strain on the critical current is obtained by a stepped cone apparatus. Peak stress or strain dependence of the critical current and the effect of the number of strain cycles on the critical current is also studied on multiple samples by employing a new in situ stress/strain device. The results show that the number of strain cycles does not significantly affect the critical current. Rather, the critical current of the tape depends only on the level of peak strain.     

Effect of metallic Ag on the properties of Bi-2212 ceramic superconductors

Samples of Bi₂Sr₂CaCu₂Ag_xO_y with small Ag additions (x = 0.05, 0.1 and 0.2) have been prepared by the classical solid state reaction method. The effect of Ag has been investigated using electrical resistivity, scanning electron microscopy, XRD, mechanical and dc-magnetization techniques. It has been found that very small amounts of Ag are enough to improve the physical and magnetic properties of the samples. The best J_c values obtained from dc magnetization measurement (M-H), employing the well known Bean’s critical model, have been obtained for the Bi₂Sr₂CaCu₂O_y samples with 0.05 Ag addition, reaching about 3000 A/cm² at 15 K, which is a very high value for bulk materials with randomly oriented grains.     

Change of formation velocity of Bi-2212 superconducting phase with annealing ambient

This exhaustive study enables the researchers to recognize the role of the annealing conditions (temperature and time) on the microstructural, mechanical, electrical and superconducting properties of the Bi-2212 superconducting material with the aid of ρ-T, X-ray diffraction, scanning electron microscopy and Vickers microhardness (H_v) measurements. For this aim, the superconducting samples are elaborated by standard solid-state reaction route at different annealing temperature and different annealing duration. The results show that the annealing temperature of 840 °C and the annealing duration of 72 h are the best for the formation velocity of Bi-2212 superconducting phase. In this study we have focused on microhardness measurements to investigate the mechanical properties. Vickers microhardness, Young’s modulus, fracture toughness and yield strength values are calculated separately for all samples. Experimental results of hardness measurements are analyzed using the some models. Finally, the Hays–Kendall model is determined as the most successful model describing the mechanical properties of our samples.     

Bi系2223高温超导带材力学性质

对4种Bi系2223高温超导带材77 K下的力学性质进行了实验研究.通过选择合适的合金包套替代传统的银包套,带材的机械性能能有所提高,但电学性质有所降低,尤其是内包套采用合金、外包套采用银,其机械性能反而低于纯银包套带材.通过X射线衍射图谱发现,当包套采用合金材料,尤其是内包套采用合金、外包套仍采用纯银,会大大降低样品中2223相的体积含量.相比较临界电流密度,n值对材料的破坏更为敏感.利用X光同步辐射技术初步探讨了银包套带材在室温和77 K下的损伤破坏过程.     

Effect of Ce Addition on the Magnetoresistivity, Irreversibility Field, Upper Critical Field and Activation Energies of Bi-2212 Superconducting Ceramics

This study aims to analyze the effect of Ce addition on the microstructural, superconducting and physical properties of Bi_1.8Sr_2.0Ce _x Ca_1.1Cu_2.1O _y ceramics with x=0, 0.001, 0.003, 0.005, 0.01, 0.03, 0.05 and 0.1 via X-Ray analysis (XRD), scanning electron microscopy (SEM), electron dispersive X-Ray (EDX) and magnetoresistivity measurements. The ceramics produced in this work are prepared using the standard solid-state reaction method. The zero resistivity transition temperatures (T _c), activation energies (U ₀), irreversibility fields (?? ₀ H _irr) and upper critical fields (?? ₀ H _c2) are determined from the resistivity versus temperature (R?CT) curves under dc magnetic fields up to 7?T. The results show that T _c and U ₀ values of the samples are found to decrease dramatically with the increase in the Ce-content and applied magnetic field. Moreover, XRD results indicate that all the samples contain the Bi-2212 phase only and exhibit the polycrystalline superconducting phase with less intensity of diffraction lines with the increase of the Ce addition. As for the results of SEM images, the texturing, crystallinity, grain size distribution, layered grain growth and grain connectivity are observed to degrade with the increase of the Ce doping. Besides, the irreversibility fields and upper critical fields are found to degrade as Ce doping increases. Penetration depths (??) and coherence lengths (??) are also discussed.     

Influence of preparation conditions on superconducting properties of Bi-2223 thin films

We report electrical transport properties of Bi₂Sr₂Ca₂Cu₃O_10+x (Bi-2223) superconducting thin films fabricated by pulsed-laser deposition on SrTiO₃ substrate. The aim of the study was to investigate the influence of preparation conditions such as deposition temperature (T _S), annealing time (t _A) and deposition rate (r). A critical temperature (T _c) as high as 110 K and critical current density (J _c) of 6·2 × 10⁶ A/cm² at 20 K were obtained for T _S = 760°C, t _A = 4 h and r = 1·5 Å/s. We also investigated the effect of Li doping on Bi-2223 thin films. Li intercalation results in high resistive onset transition temperature and the resistivity shows broadening in magnetic field that increases with field. The large broadening of resistivity curve in magnetic field suggests that this phenomenon is directly related to the intrinsic superconducting properties of the copper oxide superconductors. The sudden drop in J _c at relatively low magnetic field (H < 0·5 tesla) is due to the effect of Josephson weak-links at the grain boundaries.     

Effect of Sr substitution on structural properties of LaCrO3 perovskite

Journal of Materials Science: Materials in Electronics - We present the structural studies of perovskite-type La1?xSrxCrO3 (0?≤?x?≤?0.30) compounds...     

Effect of Pressure on the Out-of-Plane Critical Current and T c of Bi-2201 and Bi-2212 Single Crystals

We used the hydrostatic pressure P <1 GPa as a tool to change the c-axis critical current (interlayer coupling) of Bi-2201 and Bi-2212 single crystals. The c-axis critical current drastically increases with pressure (up to 270 % GPa ^–1 ). The superconducting critical temperature, on the contrary, only slightly increases with a rate of 2-6 % GPa ^–1 . This implies that the CuO-interlayer coupling has little effect on T _c in Bi-compounds.     

Environmental Degradation Effect on the Properties of Bi-2212 Highly Textured Rods

It is well know that H₂O and CO₂ (both present in the atmosphere) can react chemically with BSCCO superconductors, especially with the alkaline–earth cations, producing chemical degradation and reducing their performances. In this work, Bi-2212 highly textured rods were grown from the melt through a laser floating zone melting technique. In order to determine the influence of H₂O and CO₂ on these bulk textured samples, they were immersed in distilled water and in CO₂ saturated water. The evolution of the electrical and mechanical properties of these rods was determined as a function of the immersion time in both media and compared with their initial properties. It has been found that performance degradation was higher in distilled water than in CO₂ saturated one. Nevertheless, in any case, the degradation has been found to be not very important.     

The Effect of PbSe Addition on the Mechanical Properties of Bi-2212 Superconductors

The effects of PbSe addition and heat treatment on the structure and mechanical properties of Bi-2212 superconductors are analyzed. Glass ceramic method is used to produce PbSe added samples. The mechanical properties are derived using Vickers microhardness measurement results. Well known analysis methods like Meyer??s law, PSR (Proportional Sample Resistance) Model, EDP (Elastic/Plastic Deformation Model), Hays-Kendall approach and IIC (Indentation-Induced Cracking Model) are used to calculate load independent microhardness values of the samples. HK approach produces successful results for the samples A, E, F, G and H indicating ISE (Indentation Size Effect) behavior. The IIC model successfully explains RISE (Reverse Indentation Size Effect) behavior for the samples B, C and D. RISE behavior is observed only for the samples where the plastic deformation is dominant. ISE behavior is observed for the samples where both elastic and plastic deformation are produced. The results of XRD and SEM analysis show improvement with PbSe addition in the crystal structures and surface morphologies of superconducting samples.     

Effect of Mn substitution on structural and magnetic properties of ferromagnetic shape memory alloys

The structure and the magnetic transitions have been investigated as a function of Mn in stoichiometric Ni₂MnGa heusler alloys. Particular attention is paid to examine the linear increase of martensite transformation temperature on substituting Mn for Ga. It is observed that the martensite temperature increases and Curie temperature decreases with the effect of Mn content. Room-temperature magnetic measurements show the composition-dependent characteristics with decreasing magnetic saturation values and increasing coercivity values due to decrease in the magnetic exchange interaction strength with increasing Mn in place of Ga. The scanning electron microscopy image confirms that the Mn-rich alloys have the martensitic plates.