2658 IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 13, NO. 2, JUNE 2003 Solution Processing of Lanthanum Zirconate Films as Single Buffer Layers for High YBCO Coated Conductors Srivatsan Sathyamurthy, M. Parans Paranthaman, Hong-Ying Zhai, Sukill Kang, Hans. M. Christen, Claudia Cantoni, Amit Goyal, and Patrick. M. Martin. Abstract—Sol-gel processing of lanthanum zirconate (La Zr O – referred to as LZO) buffer layers on biaxially textured nickel and Ni-3 at.% W alloy substrates using spin coating and a continuous reel-to-reel dip-coating unit has been studied. The epitaxial LZO films obtained have a strong cube texture and uniform microstructure. This coating and annealing process was repeated to get the desired buffer layer thickness. On these all-solution single buffer layer substrates, YBCO films were grown using pulsed laser deposition process. Critical current density about 2 MA cm at 77 K and self-field has been obtained on these samples. Continuous processing of these substrates and processing of high YBCO films on them will be discussed. Index Terms—All-solution buffer layers, coated conductors, lan- thanum zirconate, single buffer layer. I. INTRODUCTION A focus of research in the area of high-temperature supercon- ductivity (HTS) in recent years has been the development of second-generation wires also known as coated-conductors [1]–[3]. One of the leading processing approaches for the fab- rication of coated-conductors is the rolling assisted biaxially textured substrates (RABiTS) approach [2]. In this approach, cube textured nickel substrates, obtained by cold rolling and recrystallization, act as a template for the epitaxial deposition of buffer layers and the YBCO superconductor. The buffer layers, apart from providing a structural template, also act as a chemical barrier between the metal substrate and the HTS coating. Using such architecture, sufficient biaxial texturing of the HTS layer has been obtained to avoid problems associated with weak-linked, high-angle grain boundaries [4]. To date, in the processing of high current coated con- ductors using RABiTS, the best results have been obtained reproducibly using two or three layer buffer architectures like Manuscript received August 6, 2002. The U.S. DOE, Division of Materials Sciences, Office of Science and Office of Power Technologies-Superconduc- tivity Program, and Office of Energy Efficiency and Renewable Energy spon- sored this research. This research was performed at the Oak Ridge National Laboratory, managed by UT-Battelle, LLC for the U.S. DOE under Contract DE-AC05-00OR22725. S. Sathyamurthy and M. P. Paranthaman are with the Chemical Sciences Di- vision, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA (e-mail: sathyamurths@ornl.gov). H-Y. Zhai, H. M. Christen, and C. Cantoni are with Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA. S. Kang, A. Goyal, and P. M. Martin are with Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA. Digital Object Identifier 10.1109/TASC.2003.811940 Fig. 1. XRD patterns of multiple coats of LZO on textured Ni substrates. CeO /YSZ/CeO /Ni [5], [6]. The fabrication of this multi-lay- ered buffer architecture, however, may present significant roadblocks to the scale-up of the process to long-lengths. Typically, deposition of the buffer layer stack would involve a combination of vacuum and nonvacuum deposition techniques coupled with the exposure of the samples to thermal cycling and ambient environment. These requirements could lead to the degradation of the individual buffer layers and add to the complexity, and cost of the over-all process. However, if a single buffer layer deposited using a scaleable technique is developed, it would significantly decrease the processing time and make the process simpler and more conducive to scale-up to long lengths. II. EXPERIMENTAL OUTLINE Stoichiometric quantities of lanthanum isopropoxide and zir- conium-n-propoxide were dissolved in 2-methoxyethanol and refluxed in a Schlenk-type apparatus to obtain the precursor so- lution with 0.25 M cation concentration. All-solution buffered substrates were prepared by spin coating the precursor solution on textured Ni and Ni-3at. % W (NiW) substrates, and heat treating the films at 1100 C for 1 h in Ar/4%H atmosphere. The process was repeated to get thicker coating of the buffer layer. The YBa Cu O (YBCO) was deposited using pulsed laser deposition (PLD) at 790 C in 120 mTorr oxygen with av- erage laser energy of 400-410 mJ. Resistivity and transport critical current density, , were measured using a standard four-point probe technique. The U.S. Government work not protected by U.S. copyright.