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The influence of the in-plane lattice constant on the superconducting transition temperature of FeSe0.7Te0.3 thin films
2017, Yuan, Feifei, Iida, Kazumasa, Grinenko, Vadim, Chekhonin, Paul, Pukenas, Aurimas, Skrotzki, Werner, Sakoda, Masahito, Naito, Michio, Sala, Alberto, Putti, Marina, Yamashita, Aichi, Takano, Yoshihiko, Shi, Zhixiang, Nielsch, Kornelius, Hühne, Ruben
Epitaxial Fe(Se,Te) thin films were prepared by pulsed laser deposition on (La0.18Sr0.82)(Al0.59Ta0.41)O3 (LSAT), CaF2-buffered LSAT and bare CaF2 substrates, which exhibit an almost identical in-plane lattice parameter. The composition of all Fe(Se,Te) films were determined to be FeSe0.7Te0.3 by energy dispersive X-ray spectroscopy, irrespective of the substrate. Albeit the lattice parameters of all templates have comparable values, the in-plane lattice parameter of the FeSe0.7Te0.3 films varies significantly. We found that the superconducting transition temperature (Tc) of FeSe0.7Te0.3 thin films is strongly correlated with their a-axis lattice parameter. The highest Tc of over 19 K was observed for the film on bare CaF2 substrate, which is related to unexpectedly large in-plane compressive strain originating mostly from the thermal expansion mismatch between the FeSe0.7Te0.3 film and the substrate.
Towards a reliable bridge joint between REBCO coated conductors
2020, Kirchner, A., Nielsch, K., Hühne, R.
REBa2Cu3O7-x (REBCO; RE = Y, Gd) coated conductor wires are commercially available up to a length of about 1 km. However, for large-scale devices like superconducting coils for high-field magnets several kilometres of a coated conductors are required. Therefore, it is desirable to use joints, which exhibit similar superconducting properties as the coated conductor itself. In this study, we jointed commercial REBCO coated conductors by a two-step procedure. At first, a superconducting soldering solution was developed and deposited on unstabilized coated conductors via chemical solution deposition. The soldering precursor is based on a Cu-rich solution with a metal cation ratio Y:Ba:Cu of 1:2:4. Secondly, a piece of the coated conductor was delaminated between the superconducting and the buffer layer and used as bridge between two other conductors covered with the soldering layer. Annealing the resulting bridge joint under pressure results in a mechanical stable configuration. © Published under licence by IOP Publishing Ltd.
The Bain library: A Cu-Au buffer template for a continuous variation of lattice parameters in epitaxial films
2014, Kauffmann-Weiss, S., Hamann, S., Reichel, L., Siegel, A., Alexandrakis, V., Heller, R., Schultz, L., Ludwig, A., Fähler, S.
Smallest variations of the lattice parameter result in significant changes in material properties. Whereas in bulk, lattice parameters can only be changed by composition or temperature, coherent epitaxial growth of thin films on single crystals allows adjusting the lattice parameters independently. Up to now only discrete values were accessible by using different buffer or substrate materials. We realize a lateral variation of in-plane lattice parameters using combinatorial film deposition of epitaxial Cu-Au on a 4-in. Si wafer. This template gives the possibility to adjust the in-plane lattice parameter over a wide range from 0.365 nm up to 0.382 nm.