Michael Bäcker

Chemical solution deposition using ink-jet printing for YBCO coated conductors

This paper reports the successful application of ink-jet printing to the deposition of both continuous coatings and multi-filamentary structures of YBCO. Stable inks have been prepared using both the established TFA-MOD route and novel fluorine-free precursors with appropriate rheological properties for ink-jet printing. Continuous and well textured coatings with lengths exceeding 100?m and a thickness of 0.5??m have been deposited by electromagnetic ink-jet printing from TFA precursors on LZO-buffered Ni?W substrates and samples have achieved a Jc around 1.5?MA?cm?2 (self-field, 77?K). On single crystal substrates, continuous coatings and multi-filamentary structures have been deposited using piezoelectric ink-jet printing both from TFA-?and water-based precursors, achieving Jc values up to 3?MA?cm?2.

Elucidation of the Mechanism in Fluorine-Free Prepared YBa2Cu3O7−δ Coatings

In this work, the reaction mechanism used in the preparation of fluorine-free superconducting YBa(2)Cu(3)O(7-delta) (YBCO) was investigated. To determine which precursor interactions are dominant, a comprehensive thermal analysis (thermogravimetric analysis-differential thermal analysis) study was performed. The results suggest that a three step reaction mechanism, with a predominant role for BaCO(3), is responsible for the conversion of the initial state to the superconducting phase. In the presence of CuO, the decarboxylation of BaCO(3) is kinetically favored with the formation of BaCuO(2) as a result. BaCuO(2) reacts with the remaining CuO to form a liquid which ultimately reacts with Y(2)O(3) in a last step to form YBCO. High temperature X-ray diffraction experiments confirm that these results are applicable for thin film synthesis prepared from an aqueous fluorine-free sol-gel precursor.

Sol-Gel Ink-Jet Printing Technique for Synthesis of Buffer Layers of Coated Conductors

In this present work, two buffer layers (La2Zr2O7 and CeO2) were deposited by a non-contact computer-controlled ink-jet coating technique with sol-gel precursors on highly textured Ni-5%W Rolling Assisted Biaxially Textured substrates (RABiTS). Lanthanum acetate and cerium acetylacetonate were used as precursors for the LZO and CeO2 sol respectively. After a high temperature heat treatment (heating at 900°C for LZO and at 1100°C for CeO2) under reducing atmosphere, epitaxial textured buffer layers were obtained. XRD and pole figures were used to analyse the texture of the films, the microstructure was analysed by SEM.

Inkjet printing of multifilamentary YBCO for low AC loss coated conductors

Considerable progress has been made with the development of REBCO coated conductors in recent years, and high performance conductors are available commercially. For many applications, however, the cost remains prohibitive, and AC losses discourage their selection for higher frequency applications. Chemical solution deposition (CSD) methods are attractive for low-cost, scalable preparation of buffer and superconductor layers, and in many respects inkjet printing is the method of choice, permitting non-contact deposition with minimal materials wastage and excellent control of coating thickness. Highly textured coatings of YBCO and Gd-doped CeO2 have previously been reported on buffered metal substrates. Inkjet printing also introduces the possibility of patterning - directly depositing two and three dimensional structures without subtractive processing - offering a low-cost route to coated conductors with reduced AC losses. In this contribution, the inkjet deposition of superconducting YBCO tracks is reported on industrially relevant buffered metal substrates both by direct printing and an inverse patterning approach. In the latter approach, ceria tracks were printed reported, which are a candidate both for resistive filament spacers and buffer layers. TFA-based precursor solutions have been printed on SS/ABAD-YSZ/CeO2 and Ni-W/LZO/CeO2 RABiTS substrates, and the resulting multifilamentary samples characterised by microscopy and scanning Hall probe measurements. The prospects for future inkjet-printed low AC loss coated conductors are discussed, including control of interfilamentary resistivity and bridging, transposed filamentary structures and stabilisation material.