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• The offset characteristics of HTS wireless power transfer (WPT) system was investigated systematically. • The transfer efficiency decreases monotonically with the increase of offset distance. A "flat top" exists in transfer efficiency at short-range radial offset, benefiting the practical applications. • The relationship between load receiving power (LRP) and offset distance is not monotonic. There is an optimal position to reach corresponding maximum LRP. • The HTS WPT system exhibits superior performance in both transfer efficiency and LRP than the copper WPT system. The usage of high-temperature superconducting (HTS) coils in magnetically-coupled resonant wireless power transfer (WPT) systems can considerably improve the transfer efficiency, and hence it attacked great attention. However, there are few studies on offset characteristics in HTS WPT systems. In order to further improve the performance of HTS WPT systems, we have studied experimentally the influences of relative displacement of the coils on the transfer efficiency and load receiving power (LRP) in a magnetically-coupled resonant WPT system. The WPT systems using copper coils and HTS coils were carefully compared. The results show that the transfer efficiency decreases monotonically with the increasing offset. However, there is an optimal position for the LRP to achieve the maximum value. Both the transfer efficiency and LRP of the HTS WPT system are higher than those of the copper WPT system under the same conditions. [ABSTRACT FROM AUTHOR]

Substrate engineering is very significant in the synthesis of the high-temperature superconductor (HTS) coated conductor. Here we design and synthesize several distinct and stable Cerium oxide (CeO 2 ) surface reconstructions which are used to grow epitaxial films of the HTS YBa 2 Cu 3 O 7-δ (YBCO). To identify the influence of annealing and post-annealing surroundings on the nature of nucleation centers, including Ar/5%H 2 , humid Ar/5%H 2 and O 2 in high temperature annealing process, we study the well-controlled structure, surface morphology, crystal constants and surface redox processes of the ceria buffers by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and field-emission scanning electronic microscopy (FE-SEM), respectively. The ceria film post-annealed under humid Ar/5%H 2 gas shows the best buffer layer properties. Furthermore, the film absorbs more oxygen ions, which appears to contribute to oxygenation of superconductor film. The film is well-suited for ceria model studies as well as a perfect substitute for CeO 2 bulk material. [ABSTRACT FROM AUTHOR]

Oxygenation is one of the most essential processes for practical applications of REBa 2 Cu 3 O 7−δ (RE123, RE = Y, Gd etc. rare earths) superconductors. Second generation high-T c superconducting coated conductors are based on biaxial textured RE123 thin films, on which, a cover layer of silver for protecting is normally applied. It results in a little more complicated oxygenation process compared to naked film without silver protective layer. In the present work, a series of absorbing oxygen post-annealing processes were carried out for YBa 2 Cu 3 O 7−δ coated conductors. The oxygen diffusion procedure and the kinetics in the annealing process were investigated. Analysis and calculations show that the activation energy was 1.01 eV, consistent with previous reports. Moreover, experiments show that the “over-doping” phenomena frequently occurs in coated conductors, and thus dropping the T c to as low as 86–88 K. To improve the temperature margin for practical applications (temperature difference between the superconducting transition temperature T c and application temperature), we investigated the potential of increase in T c by preventing from the “over-doped” happening, while keeping oxygen in order. Finally, by employing the new annealing process, we can produce long (several hundred meters) coated conductor with high T c,onset (92 K), narrow transition width and stable performance. [ABSTRACT FROM AUTHOR]

The influence of various gas flow conditions on the nucleation and growth rate of YBa 2 Cu 3 O 7-δ (YBCO) coated conductors in the high-temperature heat treatment stage of low fluorine chemical solution deposition (LF–MOD) process have been investigated, including the gas flow rate and gas flow direction. The results indicated that film-growth rate is faster while a -axis oriented phase coexisted with c -axis in the films at the higher gas flow rate. And YBCO ( 00 l) grains grew slowly while a -axis oriented phase also nucleated easily on the end of the long films along gas flow direction. It could be caused by large quantities of HF gas accumulating from the chemical reaction for converting YBCO phase. Hence, the crystal mechanism of various LF–MOD methods can be supposed as still “BaF 2 ” process as the TFA-MOD method, and orientation nucleation and growth rate of YBCO films can be artificial control by adjusting the gas flow conditions. [ABSTRACT FROM AUTHOR]

Y 1– x Gd x Ba 2 Cu 3 O 7–δ -Ag ( x = 0, 0.25, 0.5, 0.75, 1) thin films were prepared on oxide buffered Hastelloy substrates by low fluorine metalorganic depostion (MOD) process. The effects of co-doping of Ag and Gd on the microstructures and superconducting properties of YBCO thin films are investigated with respect to improvement on texture and superconducting performance in case of optimized doping content. It is found that optimum addition of Ag and Gd may lead to better c -axis orientation, superior surface microstructure and finally give rise to much improvement of superconducting performance. [ABSTRACT FROM AUTHOR]

Comparing with conventional physical vapor deposition methods, electrochemistry deposition technique shows a crack suppression effect by which the thickness of CeO 2 films on Ni–5 at.%W substrate can reach a high value up to 200 nm without any cracks, make it a potential single buffer layer for coated conductor. In the present work, the processes of CeO 2 film deposited by electrochemistry method are detailed investigated. A hydroxide reactive mechanism and an oxide reactive mechanism are distinguished for dimethyl sulfoxide and aqueous solution, respectively. Before heat treatment to achieve the required bi-axial texture performance of buffer layers, the precursor CeO 2 films are identified in nanometer scales. The crack suppression for electrochemistry deposited CeO 2 films is believed to be attributed to the nano-effects of the precursors. [ABSTRACT FROM AUTHOR]

Bilayer buffer architecture of Gd 2 Zr 2 O 7 (GZO)/Y 2 O 3 was prepared on the biaxially textured tape of Ni–5 at% W (NiW) by reactive sputtering deposition technique. The buffer layer of GZO films were deposited with different thicknesses on Y 2 O 3 seeding layer with a given thickness of 20 nm. According to the results of φ-scan, the in-plane FWHMs of GZO films decreased and then reversed with increasing thickness of GZO, which corresponded with the in-plane FWHMs and superconducting properties of YBa 2 Cu 3 O 7− δ (YBCO) films. Reflection High-Energy Electron Diffraction (RHEED) was carried out to examine the surface texture of GZO films and the deteriorated surface alignment was found for thicker films. The thickness effect of GZO on performance of YBCO is the coupling result of surface texture and blocking effect caused by thickness. With the balance of these two factors, the YBCO/GZO(120 nm)/Y 2 O 3 /NiW architecture exhibit relatively high performance with the transition temperature T c of 92 K, a transition width Δ T c below 1 K, and a critical current density J c of 0.65 MA/cm 2 . [ABSTRACT FROM AUTHOR]

• The frequency characteristics of the HTS wireless power transmission (WPT) system was investigated systematically. • The peak of the maximum output power of the HTS-Cu WPT system will appear at a low frequency. • The use of HTS coils instead of copper coils could significantly improve the transmission efficiency and load reception power of WPT systems in the low-frequency range. Wireless power transmission (WPT) based on magnetically coupled resonance technology, providing high power energy transmissions at longer distances, is promising for practical applications such as the charging of electric vehicles. The traditional WPT system needs to operate at high frequencies to keep efficient energy transmission, and as a result, it requires a high-frequency AC power supplement where pronounceable energy losses may arise from. In the present paper, a high-temperature superconducting (HTS) WPT system is proposed to enable efficient energy transfer at low operating frequencies. The maximum output power and transmission efficiency of HTS-Cu and Cu-Cu WPT systems were compared experimentally with operating frequencies from 33 kHz to 342 kHz. The results show that the usage of the HTS-Cu WPT system can significantly improve the maximum transmission efficiency as well as the output power, especially at low operating frequencies. This provides a method for high-power WPT applications in the low-frequency range. [ABSTRACT FROM AUTHOR]