Recent Advances in Superconductivity-Materials Synthesis, Multiscale Characterization, and Functionally Layered Composite Conductors

Not Available 9:00 AM C6.2 Thickness Effects of SrTi0 3 Buffer Layers on Superconducting Properties of YBa2Cu307_6 Coated Conductors. Haiyan Wang ' , Stephen R. FOltyn ' , Paul N. Arendt ' , Quanxi Jia l , Judith L. MacManus-Drisco1l3 . 1 and Xinghang Zhang2 ; lLos Alan10s National Lab, Los Alan10s, New Mexico; 2Materials Science Division, Los Alan10s National Lab, Los Alan10s, New Mexico; 3Dept. of Materials Science and Metallurgy, Univ. of Cambridge, Can1bridge, United Kingdon1. A thin layer of SrTi03 has been successfully used as a buffer layer to grow high quality superconducting YBa2Cu307-8 (YBCO) thick films on polycrystalline metal substrates with a biaxially oriented MgO template produced by ion-beam-assisted deposition (IBAD). Using this architecture, 1.5 "m-thick-YBCO films with an in-plane mosaic spread in the range of 2.5°$'"'-' 4° in full width at half n1axin1un1 and critical current density over 2 x lOG A/cm2 in self-field at 75 K have been achieved routinely. We have demonstrated that the pulsed laser deposition growth conditions of SrTi03 buffer layers, such as growth ten1perature and oxygen pressure, have strong effects on the superconducting properties of YBCO.[l] In this talk, the interesting thickness effects of SrTi03 buffer layers on the properties of YBCO are discussed in detail. The critical current density of YBCO films increases dran1atically when the thickness of the SrTi03 buffer layer reaches optin1un1. Microstructure studies including transn1ission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to explore the n1icrostructure and growth n1echanisn1s of SrTi03 thin films deposited at different thickness and to further understand their effects on the growth and properties of YBCO films. Cross-sectional TEM studies reveal that SrTi03 has a good lattice n1atch with YBCO and clean and sharp interfaces with both MgO and 83 YBCO, which further proves that SrTi03 is a pron1ising candidate as the buffer layer for high perforn1ance superconductor coatings. [1] H. Wang, S. R. Foltyn, P. N. Arendt, Q. X. Jia, J. L. MacManus-Driscoll, X. :6hang and P. C. Dowden, J.Mater.H.es., 19, 1869 (2004). 9:15 AM C6.3 Pulsed Laser Deposition of Bi-axially Textured YSZ/Ce02 Films on Electrodeposited Ir/Ni-W Tapes for YBCO Superconductors. Tapas Chaudhuri, Priscila Spagnol, Raghu Bhattacharya and Sovannary Phok; Basic Science Center, National Renewable Energy Laboratory, Golden, Colorado. Ir filn1 is a potential candidate for conducting buffer layer on Ni-W tapes used for YBCO superconductor. We have developed in our laboratory electrodeposited Ir coating as buffer layer on Ni-W substrates. To complete the buffer structure it was imperative that bi-axially textured YSZ/Ce02 layers be grown on these substrates. This paper reports the deposition of YSZ/Ce02 layers by PLD on Ni-W tapes electroplated with Ir. The PLD system consisted of a standard chamber (Neocera) and an excimer KrF laser (Lambda Physik, ?=248 nm) operated at 260 mJ with a f1uence of 2-3 MJ /cm2 at the target kept at 8 cm from the substrate holder. Layers of YSZ and Ce02 were deposited sequentially on Ir/NiW substrates. Two different approaches were investigated: in one the substrate ten1perature and in another the environn1ent for '"'-' 50 nn1 seed layer of YSZ was varied. The layers were characterized by XRD and AFM. When YSZ and Ce02 layers were deposited on Ir/Ni-W at 775 to 850 oC in 10-4 Torr of oxygen, the layers had both (111) and (200) oriented growth. The (111) orientation was more pronounced at amI above 8250C while (200) orientation dominated below it. There was marked change when a seed layer of YSZ was deposited prior to optimum YSZ/Ce02 layers. In this case deposition temperature was fixed at 800 oC and different seed layers were first deposited in H2/Ar (0.2 Torr), 02 ( 10-4 Torr) and vacuum (~ 10-6 Torr). The H2/Ar produced YSZ films with (111) with a small (200), 02 gave films with mixed (111) and (200) while YSZ films grown in vacuum was (200) oriented. The XRD studies revealed that the YC layers are bi-axially textured with phi = 6.50 and on1ega = 80. The surface roughness measured by AFM is about 5 nm. 9:30 AM C6.4 Development of Ho-123 Coated Condnctors. Munetsugu Ueyan1a, Shuji Hahakura, Katsuya Hasegawa and Kazuya Ohmatsu; Electronics & Materials R&D Laboratories, Sumitomo Electric Industries, Ltd., Osaka, Japan. We have been developing Ho-123 thin films by using pulsed laser deposition (PLD) method. Ho-123 shows high Jc up to 5MA/cm2 in the case deposited on single crystal substrates such as sapphire and LAO. In this work, based on our PLD technique, Ho-123 coated conductors have been developed on flexible n1etal tape substrates. Oxide buffer layers such as YSZ and (;e02 have been deposited on textured Ni-alloy tapes. A basic technique of the formation of buffer layer was investigated, and hetero-epitaxial buffer layer of Ce02 / YSZ/ Ce02 showed excellent in-plane alignment with the delta phi value in the range of 5 to 7 degrees. Surface roughness (Ra) was several nm and the surface was almost flat with few particles. Ho-12:l film deposition was conducted on the buffer layers by PLD method. Sample less than 0.2 "m in thickness showed Jc (77.3 K, OT) over 2 MA/cm 2 Sample with 1.4 "m in thickness showed Jc (77.3 K, self field) over 1MA/cm2. In another sample, Ie was 190A/cm-w. X-ray (103) pole figure of Ho-123 shows in-plane texture of approximately 6 degree. This demonstrated fine epitaxial Ho-123 growth on Ce02 /YSZ / Ce02 textured Ni-alloy tape. SEM photograph of Ho-123 layer revealed relatively sn100th fihn Inorphology with son1e particles. Furthennore, Jc-B characteristics at 4.2 K under the high n1agnetic field up to 30 Tesla were evaluated. Ic (4.2 K, 30 T) was 1,310A/cm-w when the external n1agnetic field was applied parallel to the tape surface. Concerning the results of the long length conductors, high Ic of 110 175 A/cm-w was achieved for 35 m conductor by using n1ulti-Iayer forn1ation of superconducting layer. High production speed was also achieved by using industrial large scale excin1er laser. A part of this work was supported by NEDO as Collaborative Research and Development of Fundamental Technology for Superconductivity Applications. The authors would like to thank Dr. T. Takeuchi and Dr. N. Banno of NIMS for Ic n1easuren1ent under low ten1perature and high n1agnetic field. 10:15 AM *C6.5 Chemical Solution Deposition of Functional Buffers for YBCO Coated Conductors. Mariappan Parans Paranthan1an l , Srivatsan Sathyamurthy', Md. Shafiq Bhuiyan ' , Amit Goyal ' , Thon1as Kodenkandath2 , Xiaoping Li2 , Wei Zhang2 , Cees Thien1e2, Urs Schoop2, Darren Verebelyi2 and Martin Rupich 2; IOak Ridge National Laboratory, Oak Ridge, Tennessee; 2An1erican Superconductor Corporation, Westborough, Massachusetts. Buffer layers playa key role in second generation YBa2Cu307_6 (YBCO) coated conductors. The purpose of the buffer layers is to provide a continuous, sl1100th and chenlically inert surface for the growth of the YBCO film, while transferring the biaxial texture from the substrate to the superconductor layer. Important buffer layer characteristics are to prevent 111etal diffusion frolll the substrate into the superconductor, as well as, to act as oxygen diffusion barriers. The 1110St C01111110nly used RABiTS architectures consisting of a starting template of biaxially textured Ni-W substrate with a seed layer of Y 203, a barrier layer of YSZ, and a Ce02 cap. In t.his t.hree layer architecture, all the buffers were deposited using physical vapor deposit.ion (PVD) t.echniques. We have developed a low-cost., non-VaCUU111, chenlical solution deposition process to grow highly aligned oxide buffers on textured Ni-W substrates. Using an all solution buffer architecture comprising of La2Zr207 and Ce02, we demonstrated the growth of high performance YBCO films with an Ie (crit.ical current) of 140 A/cm-widt.h. This process could potent.ially decrease the overall cost of the conductors. We will report in detail about results achieved on all solution buffers. Supported by the U.S. DOE, Division of Materials Sciences, Office of Science, and Office of Electric TranS111ission and Distribution. The research was perfornled at the Oak Ridge National Laboratory, managed by UT-Battelle, LLC for the USDOE under contract D EACO.'i-OOOR2272.'i 10:45 AM *C6.6 Interface Control in All MOD Coated Conductors: Influence on the Critical Currents. Alberto Pomar, M. Coli, A. Cavallaro, J. Gazquez, F. Sandiumenge, J. C. Gonzalez, N. Mestres, T. Puig and X. Obradors; Institut de Ciencia de Materials de Barcelona, J:lellaterra-08193, Spain. Ex-situ growth techniques are the subject of an intense research in order to get low-cost high-critical-current YBa2CU307-ce (YBCO) coated conductors (CC). In particular, the nlain goal is to obtain an all chemical CC where superconducting YBCO is grown by the so-called triflnoroacetates ronte (TFA) and the buffer layers are grown by metalorganic deposition (MOD). To that end, several oxides have been successfully grown by MOD that can be potentially used as internlediate (as for exanlple, La2Zr207, BaZr03, ... ) or cap (Ce02, SrTi03) buffer layers. On the other hand, progresses made on the optimization of TFA-YBCO growth have been impressive in the last years and the critical currents reported on single crystals or on vacuum buffer layers largely exceed the target value of 1 MA/cm2 at. 77K in self-field. Most of the studies have been focused on improving the in-plane texture of both the YBCO and the buffer layers. However, there is still a lack of studies on the role of the interface quality between the different MOD layers and the final superconducting properties of the CC. For exanlple, it is known that several buffer properties can dranlatically affect the critical current as for example, surface roughness or lattice matching with YBCO. These properties can be tuned by nlodifyi