GdBa 2 Cu 3 O 7 x -BaHfO 3 (GdBCO-BHO) nanocomposite (NC) films containing 12 mol% BHO nanoparticles were prepared by chemical solution deposition (CSD) following the TFA route on SrTiO 3 (STO) single crystals and buffered metallic tapes supplied by two different companies: Deutsche Nanoschicht GmbH and SuperOx. We optimized the preparation of our GdBCO-BHO solutions with acetylacetone making the film synthesis very robust and reproducible, and obtained 220 nm films with excellent superconducting properties. We show the structural, morphological and superconducting properties of the films after a careful optimization of the processing parameters (growth temperature, oxygen partial pressure and heating ramp). The films reach critical temperatures (T c ) of ∼94 K, self-field critical current densities (J c ) of >7 MA cm 2 and maximum pinning force densities (F p ) of ∼16 GN m 3 at 77 K on STO and T c of ∼94.5 K and J c > 1.5 MA cm 2 on buffered metallic tapes. The transport properties under applied magnetic fields are significantly improved with respect to the pristine GdBCO films. The GdBCO-BHO NC films on STO present epitaxial c-axis orientation with excellent out-of-plane and in-plane texture. The films are, in general, very dense with a low amount of pores and only superficial indentations. On the other hand, we present, for the first time, a systematic study of CSD-grown GdBCO-BHO NC films on buffered metallic tapes. We have used the optimized growth conditions for STO as a reference and identified some limitations on the film synthesis that should be overcome for further improvement of the films' superconducting properties.

High temperature superconductors (HTSs), like for instance REBCO (RE=rare earth) coated conductors, are of high potential for building large superconducting magnets. Some magnets, such as accelerator magnets, require the use of superconducting cables to allow fast ramping, and low magnetization loss to mitigate field quality issues. One of the methods to lower ac loss is to divide the superconducting layer in the tape into filaments. In this paper, conductors with copper stabilization for practical applications are laser scribed into narrow filaments. Striated tapes are then wound into conductor on round core (CORC ® ) cables. The critical current and magnetization ac loss of single tapes were measured. We found that the stabilizing copper layer causes difficulties for laser scribing. The degradation of the critical current is more pronounced than in the case of non-stabilized tapes. The selection of the number of filaments is therefore a compromise between critical current degradation and reduction of ac loss. Based on the results obtained from single tape experiments, the optimum number of filaments in 4 mm wide tapes was chosen, and CORC ® cables with 2, 3 and 4 layers of tapes with and without filaments were manufactured. Magnetization ac loss measurements at 77 K showed a reduction of ac loss in the cables with filaments. This reduction corresponds almost to the number of filaments. Measurement at different frequencies also showed that the coupling loss in CORC ® cables with a short twist-pitch is relatively small in comparison to hysteretic loss.

In this work we demonstrate that the use of striated tapes from coated conductors (CCs) significantly reduces the dissipation of a cable made of tapes wound helically on a round core when it is exposed to AC magnetic field. The coupling loss can vanish provided that the striations ensure electrical insulation between filaments and the cable length corresponds to an entire number of lay pitches. In our study we compare the magnetization loss in two cable models exposed to magnetic field perpendicular to their longitudinal axis. The overall geometry of the models was identical: each consisted of three tapes 4 mm wide that were placed with a pitch of 50 mm in a single layer on the 8 mm diameter round core. The cable length was designed to reach two complete tape pitches. In the first cable (the reference cable) tapes without striation were used; the second cable was prepared using similar tapes but striated to five filaments by laser processing. The AC loss was measured for cables without terminations as well as with low resistance terminations; this latter configuration simulates the conditions in a magnet winding. Our experiments have clearly shown the loss behavior expected in the regime of uncoupled filaments. In particular, at AC fields of 0.1 T amplitude the loss in the cable from striated tapes is five times lower than in the reference cable. Numerical models have explained the experimentally observed cable behavior in the whole range of AC fields.

The assembly of meander shaped coated conductor tapes by the Roebel technique is a promising way to manufacture high current cables with low ac losses. The application of longitudinal striations to the single strands can be an option to create a filament structure for further possible reduction of the ac losses. Due to the complex Roebel strand geometry, it was important to identify a reliable technique to produce such structures using a picosecond-infrared (IR) laser for the groove etching process. We analyzed the effects of the filament structure on the magnetization ac loss behavior by comparing the losses of a cable with striated strands with those of a reference one with non-striated strands. The ac loss reduction in the Roebel cable with striated strands was confirmed. The measured magnetization loss of the 125 mm striated single strand is five times lower than that of the non-striated one. In the case of the cable sample the loss reduced by a factor of three, but not in the whole interval of amplitudes of the applied magnetic field. We also compared the results with those for a cable with insulated striated strands: they seem to indicate that the coupling currents occur mostly between the filaments, not between the strands.

The synthesis of linear symmetric ethynyl‐ and acetylide‐amidinates of the coinage metals is presented. Starting with the desilylation of the complexes [{Me3SiC≡CC(NDipp)2}2M2] (Dipp=2,6‐diisopropylphenyl) (M=Cu, Au) it is demonstrated that this compound class is suitable to serve as a versatile metalloligand. Deprotonation with n‐butyllithium and subsequent salt metathesis reactions yield symmetric tetranuclear gold(I) acetylide complexes of the form [{(PPh3)AuC≡CC(NDipp)2}2M2] (M=Cu, Au). The corresponding Ag complex [{(PPh3)AuC≡CC(NDipp)2}2Ag2] was obtained by a different route via metal rearrangement. All compounds show bright blue or blue‐green microsecond long phosphorescence in the solid state, hence their photophysical properties were thoroughly investigated in a temperature range of 20–295 K. Emission quantum yields of up to 41 % at room temperature were determined. Furthermore, similar emissions with quantum yields of 15 % were observed for the two most brightly luminescent complexes in thf solution.