NiW Substrates Research Articles

Zr:CeO2 Buffer by CSD on Ni-W Substrate for Low-Cost Fe(Se,Te) Coated Conductor

Zr:CeO₂ Buffer by CSD on Ni-W Substrate for Low-Cost Fe(Se,Te) Coated Conductor

Influence of fault current on electromagnetic-thermal characteristics of HTS coated conductors

In this paper, the electromagnetic-thermal coupling numerical model is used to study the loss and temperature distribution of two typical high temperature superconducting (HTS) coated conductors (CCs) under short-circuit fault, as well as the dynamic evolution law with time. The electromagnetic module adopts the widely used H-formulation, and the thermal module adopts the general form of heat conduction equation. The coupling between the two module is realized by using the loss calculated by the electromagnetic module as the heat source of the thermal module and combining the Jc0(B, T) relationship. A modified E-J relation suitable for any current density range is used to describe the resistivity of superconductors. Due to the difference of magnetic and thermal properties of the two kinds of structural tape substrate materials and geometric dimensions of copper stabilized layer, the losses of the two kinds of structural tape under different fault currents show obvious differences. At low fault transport current, the magnetic substrate of type B tape (NiW substrate) will obviously make the magnetic flux density perpendicular to the superconducting layer greater than that of type A tape (Hastelloy substrate), thus making the loss of type B tape greater. Under the condition of high fault transport current, the fault current will be shunted between different layers of the tape. Type B tape has a thicker copper stabilizer, which makes the current density of type B tape copper layer lower than that of type A tape, and the temperature rise and loss of type B tape are lower. Specifically, when Ip/Ic0 is less than about 0.65, the total loss of type A tape is less than that of type B tape. When Ip/Ic0 is greater than about 0.65, the total loss of type A tape is greater than that of type B tape.

Study on the Magnetic Properties of Metal Substrates at Low Temperature by Fabricated Compact SST

In recent years, a development of a high magnetic field magnet using a high temperature superconducting (HTS) wire has been advanced. On the other hand, we are planning to use the HTS wires for superconducting applications cooled by cryocooler. So, it is necessary to measure the temperature dependence of the magnetic properties of the metal substrates (Hastelloy, stainless steel and NiW) for HTS wire under conduction cooling conditions. We have been developing a single sheet tester (SST) that can evaluate the magnetic properties of electromagnetic steel sheets and other materials. However, since the size of an excitation coil in the conventional SST is large, it is difficult to install them in the conduction cooling system. In this study, we fabricated the compact SST and its measurement accuracy was compared with the conventional SST. The magnetic properties of metal substrates were measured at room temperature and liquid nitrogen temperature (77 K). As a result, although the measurement accuracy of the compact SST was slightly reduced by decreasing the coil size, we found that the error of the magnetic field homogeneity of the compact SST was within 2&#x0025; at the center region of the 5 mm length. The magnetic properties of Hastelloy and stainless steel were almost unchanged at both room temperature and liquid nitrogen temperature. However, the magnetic properties of the NiW substrate changed significantly at liquid nitrogen temperature. The <i>B</i>-<i>H</i> characteristics of the NiW substrate in the rolling and transverse directions were clearly different, and the iron loss increased significantly at liquid nitrogen temperature.

Fine patterned YBCO films grown on flexible nickel–tungsten substrates by photosensitive sol–gel method

In recent years, efforts devoted to the study of processing technologies for flexible devices have been increasing significantly. The fabrication of YBa2Cu3O7-x (YBCO) fine patterns on flexible nickel–tungsten (NiW) substrates is beneficial for the application of flexible superconducting electronic devices. The most challenging task is the simultaneous achievement of fine patterning and biaxial epitaxial growth of YBCO films on NiW substrates. This work reports the application of the photosensitive sol–gel lithography in combination with an all chemical deposition process to prepare fine patterned YBCO films on NiW substrates using gadolinium-doped lanthanum zirconate (LGZO) films as buffer layers. High-quality patterned YBCO films were epitaxially grown on LGZO–buffered NiW substrates, and the well-continuous YBCO patterns on flexible substrates could withstand bending deformations. The superconductivity remains good after the mechanical bending deformation process. These results are useful as guidance for the application of flexible superconducting devices.

Preparation of a Cube-Textured Ni-7at.%W Based Template Used for Coated Conductors

Although Ni-W substrate with high W content (>5at.%) substrates have been developed successfully, the quality of cube texture and grain boundary, as well as extensive applications in coated conductors should be further improved. In the present work, once intermediate annealing treatment (IAT) at 500°C for 2 h has been employed to optimize the deformation and recrystallization textures in Ni-7at.%W (Ni7W) substrates. As a result, competitive high cube texture content (2Zr2O7 (GZO) buffer layer with strong cube texture and high-quality surface deposited successfully on the Ni7W substrate using the chemical solution deposition method, demonstrating the advanced GZO/Ni7W template is promising for coated conductors.

Preparation of epitaxial La2-xGdxZr2O7 buffer layer for coated conductors using sol-gel method

La2-xGdxZr2O7 (LGZO) films were prepared on Ni-5at.%W rolling-assisted biaxially textured substrate (RABiTS-NiW) using sol-gel method. The lattice parameter of lanthanum zirconate was changed by gadolinium element doping, which reduced the lattice constant of lanthanum zirconate buffer layer to have a better match with the lattice of NiW substrate. In particular, the grain growth texture of the buffer layer film has been analyzed by X-ray diffraction, EBSD, SEM and TEM. The results show that the La1.25Gd0.75Zr2O7 film has the highest c-axis preferred orientation and dense microstructure. EBSD measurement reveals that the excellent grain-growth texture is formed within La1.25Gd0.75Zr2O7 film and the most misorientation angle is around 3°. Moreover, the epitaxial growth relationship of NiW(002)//La1.25Gd0.75Zr2O7(004) as well as NiW(200)//La1.25Gd0.75Zr2O7(440) is demonstrated by atomic resolution TEM observation. By means of suitable element substitution, the La1.25Gd0.75Zr2O7 is a quite promising candidate of single-phase buffer layer between YBa2Cu3O7-x and NiW substrate.

Improved Performance of CSD-Grown Y1- x Gd x Ba2Cu3O7-BaHfO3 Nanocomposite Films on Ni5W Substrates

Y1- x Gd x Ba2Cu3O7-BaHfO3 (YGBCO-BHO) nanocomposite films containing 12 mol% BHO nanoparticles and different amounts of Gd, x , were grown by Chemical Solution Deposition (CSD) on Ni5W substrates in order to investigate the impact of the rare-earth stoichiometry on the structure and superconducting properties of these films. For Gd contents x > 0.5, epitaxial YGBCO-BHO films with an approximate thickness of 270 nm self-field critical current density J c at 77 K ∼ 1,5 MA/cm² were obtained. The field dependence of the critical current density J c( B ) shows a much larger accommodation field and lower exponents α in J c ∼ B −α values compared to pristine YBCO films. This is both due to the high amount of individual nanoparticles in the matrix as observed in TEM images and the higher critical temperatures T c. The results show that the CSD is a potential candidate for the preparation of RE BCO films in long-length coated conductors.

Manifestation of granularity in the transport current of coated conductors

The effects of granularity on the angle and field dependence of the transport Jc in coated conductors (CCs) are discussed. The granularity is revealed by scanning Hall probe microscopy of the trapped field profiles in tapes with different architectures. It was found that pulsed laser deposited (PLD) YBCO film on a RABiTS NiW substrate has the most prominent granular morphology in its trapped field profiles. This is complemented by a peculiar behavior of the critical currents when the orientation of the applied field is within a certain angular range around the ab-planes: Jc(θ) becomes independent of the angle and Jc(B) exhibits a peak. These phenomena are explained by the physics of Abrikosov–Josephson vortices at grain boundaries (GB) that leads to a transition from a GB-limited to a grain-limited regime both in Jc(θ) and Jc(B). The effects of granularity are strongly suppressed by the chemical solution deposition route for growing YBCO films on NiW, and are almost absent in PLD-YBCO on ABAD-textured templates. These results identify the collective influence of the GB on the percolative current flow in CCs, which becomes most significant at low temperatures.

Influence of cube texture development on magnetic properties of Ni–5 at.%W alloy substrates

The metallic Ni–5 at.%W (Ni5W) substrate with sharp cube texture is found as one of the promising candidates used for fabrication of coated conductors. However, the alternating current (AC) loss, partly contributed by the ferromagnetic Ni5W substrate is unavoidable. In this work, we analyzed the evolution of magnetic properties of Ni5W substrates via the cube texture development. The results revealed that the cube texture has an important impact related to size advantage during recrystallization, leading towards the consumption of the deformation and other orientational grains, and hence giving rise to form a sharp cube texture. Increasing the annealing temperature, the grain size is found to be increased. In the fully developed cube-textured substrate, the grain boundary was replaced by small angle grain boundaries (SAGBs). Also the magnetic domain structure was transformed from 180°-structure to a branched one with the increasing annealing temperature. This transformation is dependent on the increase of grain size, particularly, the SAGBs plays an important role in the formation of perfect domain structure. Increased coercivity and hysteresis loss in the fully textured substrate can be attributed towards the ideal cube texture and perfect complex domain structure. Therefore, a potential solution has been proposed to resolve this limitation of the sharp cube texture and increased hysteresis loss in Ni5W substrates.

Comparative Characterization of Magnetic Properties of Textured Ni–5 at.%W Alloy Substrates

The hysteresis loss of Ni–5 at.%W (Ni5W) substrate contributes considerably to the alternating current (AC) loss of coated conductors (CCs) working at low transporting current or low-frequency field. In the present work, the evolution of texture and magnetic properties in Ni5W substrates is analyzed and also the relationship between magnetic properties and the extrinsic characteristics (evolved due to the processing techniques) is determined. By making the comparison, we discovered the magnetic domain structures of Ni5W substrates for the first time, achieving a strip/branched domain structures in the recrystallized substrates. The hysteresis loss has been decreased dramatically for the recrystallized substrates. Interestingly, we also observed that this loss is also related to the annealing temperature in the fully recrystallized substrates. The reduced loss can be mainly attributed toward the decrease of grain boundary, which proves the contribution of grain size toward the reduction of hysteresis loss. This result provides a new insight to tailor the hysteresis loss of Ni5W substrates used for coated conductors.

Preparation of biaxially textured Ce1-x(Y0.2Zr0.8)xOδ buffer layers on RABiTS NiW tapes by chemical solution deposition

Highly (100)-oriented Ce1-x(Y0.2Zr0.8)xOδ (CYZO) films were prepared on biaxially textured NiW substrates by a chemical solution deposition approach using metal inorganic salts as starting materials. It has been found that both the preferential orientation and surface roughness of CYZO films decrease gradually with increasing of the doping percentage of Y3+ and Zr4+ ions. The epitaxial growth relationship of (220)CYZO//(200)NiW and [00 l]CYZO//[001]NiW was demonstrated by XRD texture measurement as well as atomic resolution STEM observation. XRD, Raman and XPS spectra results indicate that Y3+ and Zr4+ ions were indeed introduced into CeO2 lattice to substitute Ce4+ ions and form cubic fluorite CYZO solid solution. Moreover, CeO2 buffer layer can be endowed a strong enough capability to prevent element diffusion through co-doping of yttrium and zirconium, provided that an optimal doping ratio of them is adopted. This will provide a new approach to fabricating strong-barrier single buffer layer for coated conductor.

Highly (001)-oriented zirconium-doped ceria films grown on biaxially textured nickel tungsten substrates through an inorganic-salts-based chemical solution deposition route

In this work, Zr-doped CeO2 (Ce1-xZrxO2, CZO) films with (001) preferential orientation were fabricated on biaxially textured NiW alloy substrates by using a novel sol-gel method. The precursor solutions were synthesized through a newly developed process using common inorganic metal salts of Zr and Ce as the starting materials instead of organic salts. The influence of annealing temperature and the Ce/Zr mole ratio in the precursor solutions on the growth texture of CZO films was investigated. The precursor solutions with the concentration of 0.3 mol/L were coated on the Ni5W substrates using a dip-coating method and then heat-treated at 1050 °C for an hour under a reducing atmosphere of high-purity Ar with 5 vol% H2. The CZO thin films show excellent c-axis preferential orientation when the content of Zr in CZO thin film is less than 40%. The full width of half maximum of the phi scan of (111) reflection and omega scan of (200) reflection of CZO films is as low as the value of about 5° and 6°, respectively. Moreover, it is found that the inside of CZO thin film exhibits quite dense and uniform without cracks and porosity with the aid of the scanning transmission electron microscopy analysis by which the epitaxial growth relationship of (220)CZO // (200)NiW between CZO and NiW is simultaneously confirmed. Finally, highly (00 l)-oriented YBCO film with good superconducting properties was deposited on CZO buffered NiW substrate. The above results indicate that the CZO film is a quite promising candidate of single buffer layer architecture for YBCO coated conductor.

Effect of post-annealing in low oxidizing atmosphere on the properties of CeO2 buffer layer for coated conductors

CeO2-x thin films have been fabricated by chemical solution deposition (CSD) technique on bi-axial textured Ni5W substrates. The effect of post-annealing in moderate oxidizing atmosphere on the structure and texture of the film has been studied by varying temperature and CO2 concentration during the post-annealing process. The results show that the structure and texture stability of the CeO2-x film is heavily dependent on the post-annealing temperature. A high post-annealing temperature could lead to the change of cerium valence and even oxidation of Ni5W substrate. In addition, an excess amount of CO2 could cause the degeneration of texture degree and surface flatness of CeO2-x film because of the increase of oxygen vacancy defects and the production of carbonates. Except effective removal of residual carbon in films, therefore, the production of both the oxygen vacancy concentration and carbonates should be greatly controlled to improve the texture degree and surface flatness of CeO2-x films by adjusting the concentration of oxidizing gas and the heat-treatment temperature during the post-annealing process or the YBCO deposition process. Moreover, the CeO2-x film post-annealed at 700 °C in the mixture atmosphere with 1% CO2 show sharper texture and smoother surface because of the existence of small amount of oxygen vacancy and carbonates compared with the as-prepared sample.

Simulated Hysteretic Loops for YBa2Cu3O7

This paper presents modification for a model to retrace magnetic hysteresis loop and calculate hysteresis energy loss (HEL) in YBa2Cu3O7 (YBCO). In comparison with reported experimental results, it is revealed that the modified model could retrace successfully magnetic hysteresis loop for YBCO. As an application of this model, the calculation formula of HEL has been included in this article. The results show also that HEL in YBCO increases by 14% with the addition of the magnetic NiW substrate. This leads to conclude that the type of substrate has an effect on HEL of YBCO. This modified model can help us to explain experimental results and expect the functioning of superconductor tapes.

Development and characterization of biaxially-textured lanthanum zirconate film grown on cold-rolled Ni-W substrate by chemical solution deposition

High temperature superconducting tapes based on cuprate compounds are nowadays available on long lengths by several companies. Because high superconducting properties are strongly influenced by the crystallographic orientation of the superconducting film, and because the appropriate crystallographic orientation is obtained through epitaxial film growth, the development of an oriented template is of crucial technological importance. In the rolling assisted biaxially textured substrate (RABiTS) technique, a strong cube texture is obtained by cold rolling fcc metal tape and high temperature annealing, followed by the deposition of one or more buffer layer by either physical vapor deposition (PVD) or chemical solution deposition (CSD). Using the latter approach, it has been recently shown that it is possible to combine substrate recrystallization and buffer layer growth in a single step if the onset of recrystallization occurs at a temperature lower than buffer layer nucleation. In the present contribution, a detailed investigation of biaxially-oriented La2Zr2O7 (LZO) buffer layer grown on cold-rolled Ni-W substrate by combined EBSD, AFM and TEM analyses is reported. It is shown that it is possible to obtain highly {001}〈110〉-textured LZO film directly on cold-rolled Ni-W substrate. Although some small polycrystalline regions appear, this approach leads to a strong suppression of grain boundary grooving typically occurring in RABiT-type substrates. Further, it is shown that, notwithstanding the microstructure of the metal substrate continues to evolve during the conversion heat treatment, the obtained LZO film is well adherent, without cracks or delamination.

Magnetic granularity in pulsed laser deposited YBCO films on technical templates at 5 K

The manifestation of granularity in the superconducting properties of pulsed laser deposited YBCO films on commercially available metallic templates was investigated by scanning Hall probe microscopy at 5 K and was related to local orientation mapping of the YBCO layer. The YBCO films on stainless steel templates with a textured buffer layer of yttrium stabilized ZrO2 grown by alternating beam assisted deposition have a mean grain size of less than with a sharp texture. This results in a homogeneous trapped field profile and spatial distribution of the current density. On the other hand, YBCO films on biaxially textured NiW substrates show magnetic granularity that persists down to a temperature of 5 K and up to an applied magnetic field of 4 T. The origin of the granular field profile is directly correlated to the microstructural properties of the YBCO layer adopted from the granular NiW substrate which leads to a spatially inhomogeneous current density. Grain-to-grain in-plane tilts lead to grain boundaries that obstruct the current while out-of-plane tilts mainly affect the grain properties, resulting in areas with low . Hence, not all grain boundaries cause detrimental effects on since the orientation of individual NiW grains also contributes to observed inhomogeneity and granularity.

Grain growth and surface modification of epitaxial (Ce0.8Gd0.2)1-xZrxO2-δ film on NiW substrate

CeO2 films with mixed doping of gadolinium and zirconium were deposited on NiW substrates by chemical solution deposition. The influences of mixed doping on the epitaxial growth and microstructure of films were systematically investigated. The morphological evolution of films with different dwell times was also discussed. The phase formation, texture and surface morphology of (Ce0.8Gd0.2)1-xZrxO2-δ (CGZO) films were characterized by X-ray diffraction and atomic force microscopy. It was noticed that Zr4+ doping had stronger effect on the crystal structure of CeO2 than Gd3+ doping. The increasing doping content of Zr4+ could be favorable for the self-limited grain growth of the CGZO films and promote the lattice match with substrate. Moreover, the sharp texture and smooth surface of CGZO film could be easily acquired by the mixed doping. The results indicated that the (Ce0.8Gd0.2)1-xZrxO2-δ film was beneficial for the subsequent film growth, which could be a candidate buffer layer for the coated conductors.

Tailoring Microstructure and Superconducting Properties in Thick BaHfO3 and Ba2 Y(Nb/Ta)O6 Doped YBCO Films on Technical Templates

The current transport capability of YBa 2 Cu 3 O 7-x (YBCO) based coated conductors (CCs) is mainly limited by two features: the grain boundaries of the used textured template, which are transferred into the superconducting film through the buffer layers, and the ability to pin magnetic flux lines by incorporation of defined defects in the crystal lattice. By adjusting the deposition conditions, it is possible to tailor the pinning landscape in doped YBCO in order to meet specific working conditions (T, B) for CC applications. To study these effects, we deposited YBCO layers with a thickness of about 1-2 μm using pulsed laser deposition on buffered rolling-assisted biaxially textured Ni-W substrates as well as on metal tapes having either an ion-beam-textured YSZ buffer or an MgO layer textured by inclined substrate deposition. BaHfO 3 and the mixed double-perovskite Ba 2 Y(Nb/Ta)O 6 were incorporated as artificial pinning centers in these YBCO layers. X-ray diffraction confirmed the epitaxial growth of the superconductor on these templates as well as the biaxially oriented incorporation of the secondary phase additions in the YBCO matrix. A critical current density J c of more than 2 MA/cm 2 was achieved at 77 K in self-field for 1-2 μm thick films. Detailed TEM (transmission electron microscopy) studies revealed that the structure of the secondary phase can be tuned, forming c-axis aligned nanocolumns, ab-oriented platelets, or a combination of both. Transport measurements show that the J c anisotropy in magnetic fields is reduced by doping and the peak in the J c (θ) curves can be correlated to the microstructural features.

Research on processes of texture formation in "NiW substrate and TiN coating" system and creation of the new type textured paramagnetic substrates for HTS based on YBa&lt;sub&gt;2&lt;/sub&gt;Cu&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt;

Research on processes of texture formation in "NiW substrate and TiN coating" system and creation of the new type textured paramagnetic substrates for HTS based on YBa&lt;sub&gt;2&lt;/sub&gt;Cu&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt;

YBa2Cu3O7-z superconducting coated conductors by chemical solution deposition approach

YBa2Cu3O7-δ (YBCO) superconducting coated conductors were prepared on SmBiO3 (SBO) buffered substrates by chemical solution deposition approach. In this work, SBO buffer layers with a rapid decomposition process were heat treated less than 2 h. The SBO buffer layers deposited on LaAlO3, yttria-stabilised zirconium and NiO-buffered NiW substrates possess pure SBO (l00) X-ray diffraction peaks and dense as well as smooth surface microstructures. And YBCO superconducting layers with c-axis texture and dense morphology were successfully fabricated on different SBO-buffered substrates, with superconducting transition temperature Tc of 90 K and critical current density (77 K, self-field) above 1 MA cm−2. This could offer a promising alternative to low cost and high-performance preparation of YBCO superconducting coated conductors.