GdBCO Bulk Superconductors Research Articles

Comparison of the superconducting properties in GdBCO bulk superconductors fabricated with two different solid phases

In this paper, we investigated the two fabrication processes of single-domain GdBCO bulk superconductors with new solid phase sources (NSPs) and conventional solid phase sources (CSPs) by the modified top-seeded infiltration and growth (TSIG) technique. The CSPs is Gd2BaCuO5 powder, and the NSPs is made of a mixture of powders of Gd2O3 and BaCuO2. The reaction of the solid phase, morphology, microstructure and superconducting properties of the GdBCO samples were investigated. The properties of the sample with the NSPs have been improved compared with those of the sample fabricated by the CSPs. It is found that the improvement method cannot only increase the stability of the sample to complete the growth of the whole bulk during the TSIG process at a high temperature but also economize the raw material and experimental time. The results are helpful to us for the fabrication of large-grain single-domain GdBCO bulk superconductors using the improvement process method.

Effect of Ni2O3 doping on the properties of single domain GdBCO bulk superconductors fabricated by a new modified top-seeding infiltration and growth process

Single-domain GdBCO bulk superconductor (20 mm in diameter) has been fabricated by a top-seeding infiltration and growth (TSIG) mathod, it has a new solid phase of [(1-x)(Gd2O3+1.2BaCuO2) + x Ni2O3] (where x =0, 0.02, 0.06, 0.10, 0.14, 0.18, 0.30, 0.50 wt%). Effect of Ni2O3 additions on the growth morphology, microstructure, critical temperature Tc, magnetic levitation force, and trapped flux of single-domain GdBCO bulks have been investigated. Results show that the single-domain GdBCO bulk can be gained when x is in the range of 0-0.50 wt%; and the Gd211 particles are not affected by the Ni2O3 doping in the samples. The Tc of the samples decrease from 92.5 K (x=0 wt%) to 86.5 K (x=0.50 wt%) when x increases from 0 to 0.50 wt%, which is caused by the substitution of Ni3+ for Cu2 +. Both of the levitation force and trapped field of the samples increase first and then decrease with the increase of x; the largest levitation force of 34.2 N is obtained for the samples with x=0.14 wt%, and the largest trapped field of 0.354 T is obtained for the samples with x=0.10 wt%. The change of the levitation force and trapped field of the samples is closely related to the doping content x. As is known, the doping of Ni2O3 can result in substitution of Ni3+ for Cu2+ at its site in GdBCO crystals, which can reduce the critical temperature Tc of the samples; although Tc and the physical properties of the samples is reduced with the increase in the doping amount of Ni2O3, but at the same time, the substitutions of Ni3 + for Cu2 + in GdBCO crystals can produce local lattice distortions, which can act as magnetic flux pinning centers to improve the properties of the samples. The highest Tc is obtained in the samples without any Ni2O3 additions (x=0), but the magnetic flux pinning force of the samples is weak, so both of the levitation force and trapped field of the samples are relatively lower. When the doping content x ≤ 0.14 wt%, although the Tc is reduced slightly, it still has a value higher than 90 K; and the magnetic flux pinning force in the samples, due to the substitutions of Ni3+ for Cu2 +, would increase with the increase of doping content x, and result in an enhancement of levitation force and trapped field. When the doping content x is greater than 0.14 wt%, the magnetic flux pinning force of the samples is still increasing with the increase of x, but the Tc of the sample is significantly reduced and even less than 90 K, and finally result in an decrease of levitation force and trapped field. Only when the doping amount of Ni2O3 is appropriate, both of Tc and magnetic flux pinning force are of a relative optimal value, and lead to an enhancement of levitation force and trapped field.

采用顶部籽晶熔融辅助熔渗法制备高性能单畴GdBCO超导块材

In this paper, high performance and large single domain GdBCO bulk superconductors have been successfully fabricated by the top-seeded-melt-texture-infiltration-growth process (TSMT-IG). The effect of the growth morphology, growth interface, the magnetic levitation force and trapped flux of single domain GdBCO bulk superconductors has been investigated. The above result indicates that, the utilization of NdBCO seed crystal and the production efficiency of the single domain GdBCO bulk superconductor can be effectively improved by the new TSMT-IG process, which can inhibit the random nucleation phenomenon at some extent during the process of crystal growth. In addition, the application of new technology also helps to improve the growth performance of GdBCO samples.

Levitation Property of Parallel Magnetic Levitation System With Magnetic Shielding Effect of HTS Bulks

We studied a magnetic levitation system using the magnetic shielding effect of a GdBCO bulk superconductor. One set of permanent magnet, ferromagnetic rail, and HTS bulk is called the basic model. To increase the magnetic levitation force, we place two basic models side by side. There are two kinds of models. The first has the S poles of the permanent magnets in both modules on the upper side and is named the 2-set (SS) model. The second has the S pole on the upper side of the permanent magnet and the N pole on the upper side of the other permanent magnet, and is called the 2-set (SN) model. The levitation force of the 2-set (SS) and (SN) models was more than twice that of the basic model. To support the experimental approach, we numerically evaluate a magnetic flux distribution using finite element method software.

Modelling and comparison of trapped fields in (RE)BCO bulk superconductors for activation using pulsed field magnetization

The ability to generate a permanent, stable magnetic field unsupported by an electromotive force is fundamental to a variety of engineering applications. Bulk high temperature superconducting (HTS) materials can trap magnetic fields of magnitude over ten times higher than the maximum field produced by conventional magnets, which is limited practically to rather less than 2 T. In this paper, two large c-axis oriented, single-grain YBCO and GdBCO bulk superconductors are magnetized by the pulsed field magnetization (PFM) technique at temperatures of 40 and 65 K and the characteristics of the resulting trapped field profile are investigated with a view of magnetizing such samples as trapped field magnets (TFMs) in situ inside a trapped flux-type superconducting electric machine. A comparison is made between the temperatures at which the pulsed magnetic field is applied and the results have strong implications for the optimum operating temperature for TFMs in trapped flux-type superconducting electric machines. The effects of inhomogeneities, which occur during the growth process of single-grain bulk superconductors, on the trapped field and maximum temperature rise in the sample are modelled numerically using a 3D finite-element model based on the H-formulation and implemented in Comsol Multiphysics 4.3a. The results agree qualitatively with the observed experimental results, in that inhomogeneities act to distort the trapped field profile and reduce the magnitude of the trapped field due to localized heating within the sample and preferential movement and pinning of flux lines around the growth section regions (GSRs) and growth sector boundaries (GSBs), respectively. The modelling framework will allow further investigation of various inhomogeneities that arise during the processing of (RE)BCO bulk superconductors, including inhomogeneous Jc distributions and the presence of current-limiting grain boundaries and cracks, and it can be used to assist optimization of processing and PFM techniques for practical bulk superconductor applications.

The Effect of the Horizontal Distance between the Permanent Magnets on the Levitation Force in Hybrid Magnetic Levitation System

It has been investigated that the interaction force in hybrid magnetic levitation systems with a GdBCO bulk superconductor and a permanent magnet system and two permanent magnets (PM2) and two cubic permanent magnets (PM3) system in their coaxial configuration at liquid nitrogen temperature. A single-domain GdBCO sample is of 20mm and 10mm in thickness, the permanent magnet PM1 is of rectangular parallelepiped shape, the permanent magnets PM2 and PM3 are of cubic shape; the system placed on the middle of system and their coaxial configuration; It is found that the maximum levitation force decreases from 46.3N to 16.3N while the horizontal distance (Dpp) between the rectangle permanent magnet and two cubic permanent magnets (PM2) is increased from 0mm to 24mm and the horizontal distance (Dsp) between a GdBCO bulk superconductor and two cubic permanent magnets (PM3) is 0mm, The results indicate that the higher levitation force can be obtained by introducing PM-PM levitation system based on scientific and reasonable design of the hybrid magnetic levitation system, which is helpful for designing and constructing superconducting magnetic levitation systems.

Fabrication of single domain GdBCO bulk superconductors by a new modified TSIG technique

Single domain GdBCO bulk superconductors have been fabricated with new and traditional solid phases by a top seeded infiltration and growth (TSIG) process technique. In the conventional TSIG process, three types of powders, such as Gd2BaCuO5, GdBa2Cu3O7−x and Ba3Cu5O8, must be prepared, but in our new modified TSIG technique, only BaCuO2 powders are required during the fabrication of the single domain GdBCO bulk superconductors. The solid phase used in the conventional process is Gd2BaCuO5 instead of the solid phase (Gd2O3+BaCuO2) utilized in the new process. The liquid phase used in the conventional process is a mixture of (GdBa2Cu3O7−x+Ba3Cu5O8), and the liquid phase in the new process is a mixture of (Gd2O3+10BaCuO2+6CuO). Single domain GdBCO bulk superconductors have been fabricated with the new solid and liquid phases. The levitation force of the GdBCO bulk samples fabricated by the new solid phase is 28N, which is slightly higher than that of the samples fabricated using the conventional solid phases (26N). The microstructure and the levitation force of the samples indicate that this new method can greatly simplify the fabrication process, introduce nanometer-sized flux centers, improve the levitation force and working efficiency, and greatly reduce the cost of fabrication of single domain GdBCO bulk superconductors by the TSIG process.

The Effect of the Distance between the Permanent Magnets on the Levitation Force in Hybrid Magnetic Levitation System

t has been investigated that the interaction force in hybrid magnetic levitation systems with two GdBCO bulk superconductors and two permanent magnets system and a cubic permanent magnet (PM2) and a cubic permanent magnet (PM3) system in their coaxial configuration at liquid nitrogen temperature. The two single-domain GdBCO samples are of φ20mm and 10mm in thickness, the permanent magnet PM1 is of rectangular parallelepiped shape, the permanent magnets PM2 and PM3 are of cubic shape; the system placed on the middle of system and their coaxial configuration; It is found that the maximum levitation force decreases from 40.6N to 17.8N while the distance (Dpp) between the permanent magnets is increased from 0mm to 24mm and the distance (Dsp) between the two GdBCO bulk superconductors and a cubic permanent magnet PM3 is 0mm, The results indicate that the higher levitation force can be obtained by introducing PM-PM levitation system based on scientific and reasonable design of the hybrid magnetic levitation system, which is helpful for designing and constructing superconducting magnetic levitation systems.

Fabrication method of large size single domain GdBCO bulk superconductor using a new solid source

A new solid source was prepared and used to fabricate large size GdBCO single domain superconductor by top-seeded infiltration and growth (TSIG) process. The morphology, microstructure, and superconductivity properties of the GdBCO sample were investigated. It is found that the proposed solid source can be used to fabricate a well textured GdBCO single domain, and also reduce the fabrication cost and improve working efficiency. The results are helpful to fabricate high quality and large size single domain GdBCO bulk superconductors.

The effect of additional permanent magnet magnetizing methods on magnetic field distribution and the levitation force of single domain GdBCO bulk superconductor

It has been investigated that the interaction force between a cubic permanent magnet PM1 and a GdBCO bulk (HTSC) superconducting permanent magnet (SCPM) magnetized by a cubic permanent magnet PM2 under different configurations at 77 K. Two configurations were used for the magnetization of the GdBCO bulk, one is that the North pole of the PM2 is in upward direction, the other is in downward direction, so that the North pole of the SCPM is in two states SCPM↑ and SCPM↓; the vertical distance between the bottom surface of PM1 and the top surface of SCPM is kept as a constant value, but the PM2 can be fixed at any positions (x) along a diameter of the GdBCO bulk during the magnetization process. It is found that: for the PM1↓-SCPM↑ configuration, the maximum levitation force is increasing from 16.7 N to 23.1 N when x increases from –15 mm to 0, and then decreases to 16.6 N when x further increases to 15 mm; but for the PM1↓-SCPM↓ configuration, the maximum levitation force is decreasing from 17.7 N to 7 N when x increases from –15 mm to 0, and then increases to 17.6 N when x further increases to 15 mm. These results are not only much different in the two configurations, but also much different from the maximum levitation force 17.1 N of the sample under zero field cooled condition, which is closely related with the trapped field distribution of the SCPM at different x values. These results indicate that the levitation force of high temperature bulk superconductors can be effectively improved by introducing additional permanent magnet based on scientific and reasonable designing of the system configurations, which is very important during the practical design and applications of superconducting magnetic levitation systems.

The effects of magnetization methods with additional permanent magnet on the magnetic field distribution and levitation force of single domain GdBCO bulk superconductor

The effects of magnetization methods with additional permanent magnet on the magnetic field distribution and the levitation force of single domain GdBCO bulk superconductor are investigated with a cubic permanent magnet in their coaxial configuration in zero field cooled state at liquid nitrogen temperature in three different ways. It is found that when the N pole of the cubic permanent magnet, for the levitation force measurement, is placed above the GdBCO bulk superconductor and in the downward direction, the maximal levitation force can be improved to 31.8 N, and that when the N pole of the additional cubic permanent magnet points to upward and sticks to the bottom of the GdBCO bulk, the maximal levitation force is increased up to about 222% of the levitation force of 14.3 N for the system without additional permanent magnet. The maximal levitation force can be improved to 21.6 N (or reduced to 8.6 N), when the GdBCO bulk superconductor is closely placed below and magnetized by the additional cubic permanent magnet with N pole in the upward (or downward) direction, and the additional permanent magnet is removed away after the magnetization, the maximal levitation force is about 151% (or 60%) of 14.3 N for the system without the additional permanent magnet. The results indicate that the levitation force of high temperature bulk superconductors can be effectively improved by introducing additional permanent magnet based on the scientific and reasonable designing of the system configurations, which is very important for the practical design and application of superconducting magnetic levitation system.

Fabrication of single domain GdBCO bulks with different new kind of liquid sources by TSIG technique

Single domain GdBCO bulk superconductors have been fabricated with different new kinds of liquid sources by Top Seeded Infiltration and Growth process. A conventional liquid source is a mixture of REBa2Cu3O7−x and Ba3Cu5O8 in a ratio of 1:1; new liquid sources are made of a mixture of RE2BaCuO5+9BaCuO2+6CuO or RE2O3+10BaCuO2+6CuO. The microstructures and levitation forces of the GdBCO bulks have also been investigated. The properties of the samples fabricated are nearly the same as those of samples fabricated with conventional liquid sources, which indicates that the new liquid sources are very important to reduce the cost and improve the working efficient on the fabrication of single-domain GdBCO bulk superconductors.

Effects of additional permanent magnet on the levitation force of single domain GdBCO bulk superconductor

Effects of additional permanent magnet on the levitation force of a single domain GdBCO bulk superconductor have been investigated with a cylindrical permanent magnet in their coaxial configuration under zero field cooled state at liquid nitrogen temperature. The magnetic polarity N of cylindrical permanent magnet is pointed to the GdBCO bulk superconductor, and the two additional permanent magnet of rectangular parallelepiped shape are fixed on two sides of the GdBCO bulk superconductor in different arrangments. It was found that the levitation force can be improved to about 61.5 N, which is more than 2 times higher than that (29.8 N) of the system without the additional permanent magnet, when the magnetic polarity N of two additional permanent magnets points to the GdBCO bulk superconductor in horizontal direction. The levitation force is reduced to 19.6N, which is about 65.8% of the levitation force 29.8N of the system without the additional permanent magnets, when the magnetic polarity N of two additional permanent magnet are antiparallel to the magnetic polarity N of the cylindrical permanent magnet. The results indicate that the levitation force of high temperature bulk superconductors can be effectively improved by introducing additional permanent magnet based on reasonably designing the system configuration, which is very important during the practical design and applications of superconducting magnetic levitation systems.

The effect of Gd<sub>2</sub>Ba<sub>4</sub>CuNbO<sub>y</sub> doping on the properties of single domain GdBCO bulk superconductors

Single domain GdBCO bulk superconductors, with compositions of GdBa 2 Cu 3 O 7-δ (Gd123):Gd 2 BaCuO 5 (Gd211): Gd 2 Ba 4 CuNbO y (GdNb2411) =1:(0.4-x):x, (x=0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16), have been successfully fabricated by the top-seeding melt texture growth process (TSMTG). The effect of the different doping amounts of GdNb2411 on the growth morphology and the magnetic levitation force properties of single domain GdBCO bulk superconductors has been investigated. The results show that single domain GdBCO bulk samples can be fabricated within the scope of the doping, and the surface morphologies of the samples are closely related to the doping content x. It is of a smooth faced plane and four clear radius for the samples with x≤0.06 mol, but it is of a wrinkle surface for the samples with x≥0.08mol and the single domain area is observed to reduce with the increasing of x. The test results of the magnetic levitation force of the samples show that the levitation force of samples increases first and then decreases with the increasing of x, the largest levitation force of 25 N is obtained in the samples with x=0.06 mol. The results is very important for study in flux pinning of nanoparticles and further improvement in the properties of GdBCO bulk superconductors.

Effect of assembled bar magnet configuration on levitation force of single domain GdBCO bulk superconductor

By measuring the levitation forces between a single domain GdBCO bulk superconductor and assembled bar magnets(ABM) in different configurations at liquid nitrogen temperature, the effects of ABM configurations on the levitation force of single domain GdBCO bulk superconductor are investigated. The maximum levitation force is obtained at the same vertical gap distance Z=5 mm between the superconductor and the ABM for configurations with different lateral gap distance(D)between the magnets of the ABM. It is found that 1) for the ABM consisting of 3 bar magnet, the levitation force of the GdBCO bulk decreases from 22.8N to 9.7N with the D value increasing from 0 to 30 mm, when the magnetic pole N of the middle magnet is pointed upwards and the directions of magnetic pole N of two side magnets are pointed to the middle magnet in horizontal direction; the levitation force of the GdBCO bulk increases first from 9.2N to 13.9N and then decreases to10.4 N with D value increasing from 0 to 30mm, if the magnetic pole N of the middle magnet is pointed upwards and the directions of magnetic pole N of two side magnets are pointed downwards;2)for the ABM consisting of 2 bar magnets, the levitation force of the GdBCO bulk decreases from 11.2N to 1.2N with D value increasing from 0 to 30mm, when the directions of magnetic pole N of two side magnets are pointed upwards; the levitation force of the GdBCO bulk increases first from 6.0N to 6.8N and then decreases to 2.9N with D value increasing from 0 to 30mm, if the directions of magnetic pole N of two magnets are anti-parallel in horizontal direction; 3)for the ABM consisting of only 1 bar magnets, D≡0, and the levitation force of the GdBCO bulk is about 9.5N. The results indicate that the magnet configuration and its detailed parameters of ABM are very important for improving the levitation force of a superconductor and helpful for designing and application based on the superconducting magnetic levitation system.

Growth and superconductivity of REBCO bulk processed by a seed/buffer layer/precursorconstruction

The buffer layer has been used, for the first time, in the cold-seeding melt-growth (MG)process for REBCO superconductor bulks. In this modified method, a mini pelletwas inserted between the seed and the bulk precursor. Notably, the chemicalcontamination, from the seed material (either REBCO films or SmBCO/NdBCOcrystals), was mostly absorbed by the mini pellet. Thus a uniformly highTc REBCO bulk was readily gained. Secondly, the higher limits of the maximum processing temperature(Tmax) were evidently raised, which is promisingly beneficial for broadening the growth window andovercoming the self-nucleation in the growth of large-sized bulk. In short, the success of thiswork is that it protects the bulk from seed-induced contamination, and breaks the limit ofTmax caused by the intrinsic properties of the seed material. By means of this simple seed/bufferlayer/precursor construction, we successfully fabricated a large single grain of GdBCO bulksuperconductor with a diameter of 56 mm.

Fabrication of single-domain GdBCO bulk superconductors using new liquid sources by the top seeded infiltration and growth technique

Three new kinds of liquid source were prepared by mixing R2O3 (here R is Gd,Y or Yb respectively),BaCuO2 and CuO powders. Single-domain Gd-Ba-Cu-O bulk superconductors have been fabricated using these liquid sources by the top seeded infiltration and growth technique. The growth characteristic and microstructure of the samples have also been investigated in detail. The results indicate that, employment of the new liquid sources not only can help us reduce the experimental period and improve the fabrication efficiency, but also can be used to fabricate well-textured single domains. Additionally, using the liquid source mixed by Y2O3 or Yb2O3 can raise the utilization rate of the liquid source powders, as well as contribute to the refinement of Gd-211 particles in the molten liquid.

A modified TSIG technique for simplifying the fabrication process of single-domain GdBCO bulks with a new kind of liquid source

The top seeded infiltration and growth process (TSIG) is an effective way for the preparation of bulk REBa2Cu3O7−x (RE-123) with finely dispersed RE2BaCuO5 (RE-211) particles compared to the conventional melt growth (MG) method. However, it is more complicated and time-consuming because three kinds of precursor powders, involving RE-211, RE-123, and BaCuO2, have to be prepared before the conventional TSIG process. In this article, a new liquid source (NLS) composed of RE2O3 (RE-200), BaCuO2, and CuO powders, has been found for simplifying the TSIG process, which is different from the regular liquid source (RLS) composed of RE-123 and Ba3Cu5O8. In this modified TSIG technique, what we need is only to prepare RE-211 and BaCuO2 precursor powders for the whole TSIG flow. Single-domain GdBCO bulk superconductors have been fabricated using the RLS and NLS separately. The morphology, microstructure, and levitation force of the GdBCO bulks have also been investigated. The results indicate that the NLS can be used to simplify the process flow, reduce the cost and improve the efficiency on the fabrication of single-domain GdBCO superconductors.

Discussions About Measurement Results of Levitation Force and Its Time Relaxation Between GdBCO Bulk Superconductors and Superconducting Magnet With a High Magnetic Field Gradient

High temperature bulk superconductors have significant potential for various engineering applications such as a flywheel energy storage system. This system is expected to decrease the energy loss by using bulk superconductors for the bearing. Recently, the authors have developed a new superconducting magnet to realize the large levitation force. The magnet has two coils on the same axis and each coil's current flows to the opposite direction. In this system, the axial component of magnetic field is canceled each other but the radial component of magnetic field is expected to be enhanced. In this paper, the authors measured the levitation force and its time relaxation at different bulk positions in both cases of one and two bulks by using this new magnet. From the results, it was made clear that the levitation force of two bulks was twice as large as that of one bulk and its time relaxation was decreased. In addition, Hall sensors were attached on the sample surface to measure the surface magnetic field distribution. The behavior of the magnetic field was discussed.

Comparison of simulation and experiment on levitation force between GdBCO bulk superconductor and superconducting magnet

High temperature bulk superconductors have significant potential for various engineering applications such as a flywheel energy storage system. This system is expected to decrease the energy loss by using bulk superconductors for the bearing. Recently, the authors have developed a new superconducting magnet to realize large levitation force. In this system, the axial component of magnetic field is canceled each other but the radial component of magnetic field expects to be enhanced. Thus, it was expected that the large levitation force can be realized and its time relaxation will be decreased. And in the previous paper, the levitation force and its time relaxation were measured under the various conditions by using this new magnet. But it is difficult to consider what phenomenon has happened in the bulk from only experimental results. In addition the quantitative evaluation cannot be done only by the experimental results, for example, the influence of the magnetic field penetration and magnetic distribution around a bulk superconductor on the maximum force and so on. Thus, in this paper, the authors simulated the levitation force of bulk superconductor by using ELF/MAGIC, which is a three-dimensional electromagnetic analytical software. In the simulation the bulk was considered as a rigid body and the simulation was executed under the same conditions and model with the experiment. The distribution of magnetic field and the levitation force were obtained and discussed.