High temperature superconducting (HTS) tape can be cut and stacked to generate large magnetic fields at cryogenic temperatures after inducing persistent currents in the superconducting layers. A field of 17.7 T was trapped between two stacks of HTS tape at 8 K with no external mechanical reinforcement. 17.6 T could be sustained when warming the stack up to 14 K. A new type of hybrid stack was used consisting of a 12mm square insert stack embedded inside a larger 34.4mm diameter stack made from different tape. The magnetic field generated is marginally higher than the previous trapped field record achieved by a bulk HTS magnet and 30% greater than previously achieved in a stack of HTS tapes. Such stacks are being considered for superconducting motors as rotor field poles where the cryogenic penalty is justified by the increased power to weight ratio. The sample reported can be considered the strongest permanent magnet ever created.

The future of the international accord on mitigating the impact of climate change is linked to the successful implementation of nano-technology. The latter is strongly dependent on finding commercially viable methods for nano-functionalization of the energy related materials. Drop-on-demand inkjet printing methods combining scalability and low equipment cost with high-resolution ink delivery have been proven a feasible solution in various areas: 2D functionalization — (i) fabrication of multifilamentary superconducting YBCO structures by inkjet printing of a low-fluorine YBCO precursor solution on SS/ABAD-YSZ/CZO substrates creating a multifilamentary structure by an inverse technique (Jc of up to 3 MA cm-2 at 77 K) [1]; (ii) in situ fabrication of conductive silver coatings without additional heat treatment from micron-sized elongated silver flakes [2]. 3D functionalization — Composite solid oxide fuel cells LSCF/CGO cathodes were nano-engineered via "dual" inkjet printing infiltration. The structure was found to extend the active three-phase boundary and to promote adsorption/dissociation/surface exchange reactions. Electrochemical impedance tests showed a reduction in the polarisation resistance of between 1.5 and 7.0 times.

If coated conductors are to be used in large-scale ac applications such as motors and generators, energy losses must be minimised. Hysteretic ac losses can be reduced by dividing the coated conductor into filaments. In this study, a new method for producing filamentary coated conductors is presented. An electrical spark discharge was used to selectively degrade regions of superconducting tape. The robust, noncontact and scalable method was used to striate tapes into four filaments. The filamentary samples had lower ac losses than nonstriated tapes with less than a 7% reduction in current carrying capacity.

The effect of solid oxide fuel cell cathode microstructure modification on its electrochemical activity is investigated. Inkjet printing infiltration was used to develop a nano-decoration pattern on the composite cathode scaffolds. Two types of composite La0.6Sr0.4Co0.2Fe0.8O3−δ:Ce0.9Gd0.1O1.9 cathodes with different volume ratios (60:40 and 40:60 vol%) were fabricated using inkjet printing of suspension inks. The electrodes were altered by single-step inkjet printing infiltration of ethanol-based Ce0.9Gd0.1O1.9 ink. After heat treatments in air at 550 °C the cathodes’ surfaces were shown to be nano-decorated with Ce0.9Gd0.1O1.9 particles (~20–120 nm in size) dispersed uniformly onto the electrode scaffold. The nano-engineered microstructure enhanced the active triple phase boundary of the electrode and promoted the surface exchange reaction of oxygen. Electrochemical impedance tests conducted on symmetrical cells showed a reduction in the polarization resistance of between 1.3 and 2.9 times. The effect was found to be more pronounced in the 60:40 vol% composite cathodes. Ageing of infiltrated electrodes up to 60 h in air revealed enhanced stability of gadolinium doped ceria nanoparticles decorated electrodes ascribed to the suppression of SrO surface segregation. This work demonstrated that single-step inkjet printing infiltration can produce reproducible performance enhancements and thus offers a cost-effective route for commercial solid oxide fuel cell infiltration processing.

Commercially available anode supported solid oxide fuel cells (NiO-8YSZ/8YSZ/LSCF- 20 mm in diameter) were anode infiltrated with gadolinium doped ceria (CGO) using a scalable drop-on-demand inkjet printing process. Cells were infiltrated with two different precursor solutions—water based or propionic acid based. The saturation limit of the 0.5 μm thick anode supports sintered at 1400 °C was found to be approximately 1wt%. No significant enhancement in power output was recorded at practical voltage levels. Microstructural characterisation was carried out after electrochemical performance testing using high resolution scanning electron microscopy. This work demonstrates that despite the feasibility of achieving CGO nanoparticle infiltration into thick, commercial SOFC anodes with a simple, low-cost and industrially scalable procedure other loss mechanisms were dominant. Infiltration of model symmetric anode cells with the propionic acid based ink demonstrated that significant reductions in polarisation resistance were possible.

The effect of inkjet printing infiltration of Gd0.1Ce0.9O2−x in NiO-Gd0.1Ce0.9O2−x anodes on the performance of symmetrical and button cells was investigated. The anodes were fabricated by inkjet printing of suspension and sol inks. Symmetrical cells were produced from composite suspension inks on Gd0.1Ce0.9O2−x electrolyte. As-prepared scaffolds were infiltrated with Gd0.1Ce0.9O2 ink. Increasing the number of infiltration steps led to formation of “nano-decoration” on pre-sintered anodes. High resolution SEM analysis was employed for micro-structural characterization revealing formation of fine anode sub-structure with nanoparticle size varying in the range of 50–200 nm. EIS tests were conducted on symmetrical cells in 4% hydrogen/argon gas flow. The measurements showed substantial reduction of the activation polarization as a function of the number of infiltrations. The effect was assigned to the extension of the triple phase boundary. The i–V testing of a reference (NiO-8 mol% Y2O3 stabilized ZrO2/NiO-Gd0.1Ce0.9O2−x /Gd0.1Ce0.9O2−x /Gd0.1Ce0.9O2−x -La0.6Sr0.4Co0.2Fe0.8O3−δ ) cell and an identical cell with infiltrated anode revealed ~2.5 times improvement in the maximum output power at 600 °C which corresponded with the reduction of the polarization resistance of the symmetrical cells at the same temperature (2.8 times). This study demonstrated the potential of inkjet printing technology as an infiltration tool for cost effective commercial SOFC processing.

Impressive performance has been achieved in (RE)Ba 2 Cu 3 O 7-δ (REBCO) coated conductors, but for many applications, the high cost and ac losses remain prohibitive. Inkjet printing methods combine scalability and low equipment cost with high-resolution patterning, potentially addressing both issues by enabling the production of multifilamentary coated conductors without subtractive processing. The successful production of multifilamentary superconducting YBa 2 Cu 3 O 7-δ (YBCO) structures by inkjet printing of a low-fluorine YBCO precursor solution on SS/ABAD-YSZ/CZO substrates is reported. Two approaches have been developed. In the first method, YBCO filaments were directly deposited on the buffered substrate by piezoelectric printing; and in the second approach, CeO 2 tracks were first printed to pattern a subsequently overprinted YBCO film, creating a multifilamentary structure by an inverse technique. Scanning Hall probe measurements have been used to compare the filamentary structures and critical currents achieved by both methods, and a J c of up to 3 MA cm -2 has been obtained at 77 K. For the inverse printing approach, the ac hysteresis losses have been also measured and compared with theoretical models.

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 NiW/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.

Data supporting the publication including: Hall probe magnetometry, scanning electron microscopy, critical current measurements and AC loss measurement raw data.