Superconducting single crystals of pure FeTe 1-x Se x and FeTe 0.65 Se 0.35 doped with Co, Ni, Cu,

Metamaterials offer new unusual electromagnetic properties, which have already been demonstrated, and many postulated new functionalities are yet to be realized. Currently, however, metamaterials are mostly limited by narrow band behavior, high losses, and limitation in making genuinely 3D materials. In order to overcome these problems an overlap between metamaterial concepts and materials science is necessary. Engineered self‐organization is presented as a future approach to metamaterial manufacturing. Using directional solidification of eutectics, the first experimental realization of self‐organized particles with a split‐ring resonator‐like cross section is demonstrated. This unusual morphology/microstructure of the eutectic composite has a fractal character. With the use of TEM and XRD the clear influence of the atomic crystal arrangement on the microstructure geometry is presented. The materials obtained present very high anisotropy and can be obtained in large pieces. Metallodielectric structures can be created by etching and filling the space with metal. The next steps in the development of self‐organized materials exhibiting unusual properties are discussed.

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The self-organized rodlike microstructure of terbium-scandium-aluminum garnet-terbium-scandium perovskite, Tb 3 Sc 2 Al 3 O 12 -TbScO 3 , eutectic crystals has been studied. The growth of the eutectic by the micro-pulling down method is presented. The obtained self-organized dielectric microstructure is made of perovskite fibers embedded in a garnet phase matrix. The crystal quality of both phases is confirmed by the structural analysis. Both phases can be etched away, depending on the composition, leaving a pseudo-hexagonally packed dielectric array of pillars or an array of pseudo-hexagonally packed holes in dielectric material. Both structures can be filled with metal or another material and, hence, have possible metamaterials or photonic crystals applications.

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The reactivities of several oxide materials (OM) in direct contact with BSCCO powder has been tested at a temperature of approximately 845 • C in air. The OM such as BaZrO 3 , SrCO 3 , MgO and ZrO 2 showing little or no reactivity with BSCCO were mixed (10 wt%) with a BSCCO precursor powder and used for monocore tapes made by a standard powder-in-tube technique. The microstructure of the BSCCO+OM cores was analysed by SEM and XRD and the transport current properties-critical current, pinning force and resistance up to 16 T-were measured as a function of the magnetic field for various orientations with respect to the ab plane. The OM used influenced the electrical properties of the Bi-2223 phase in different ways. This is because the oxides react with BSCCO during the heat treatment and simultaneously affect the 2212 → 2223 phase transformation as well as the Bi-2223 grain growth and grain connectivity. Submicrometre commercial SrCO 3 powder was evaluated as the best material from all those tested, for resistive barriers in Bi-2223/Ag tapes.

In situ nano-SiC doped MgB 2 wires were fabricated from MgH 2 and B powders. Hydrostatic extrusion, followed by rotary swaging and two-axial rolling, were applied as the forming processes. The critical current J c of MgB 2 wires, made from MgH 2 and B powders, was significantly improved by nano-SiC doping. Nano-SiC doping substantially increased the upper critical (irreversibility) field B c2 above 20 T. The maximum J c values were measured for samples having 6 at.% SiC in low field and for those having 12 at.% SiC in high field, above 10 T. During the final sintering at 670 • C, the SiC decomposed and formed an Si-rich layer at the inner circumference of the Fe sheath. The composition of the core of SiC doped wires is more inhomogeneous in comparison to undoped ones, with MgO, Mg 2 Si and probably Mg 2 SiO 4 as the major segregated phases. Strong segregation of Si within the MgB 2 core was also observed. The highest T c−mid = 39.3 K was measured for undoped wire. For the optimal SiC doping amount ∼6 at.%, at high field, there was no difference in J c between hydrostatically extruded and hydrostatically extruded plus two-axially rolled wire. This can be attributed to the beneficial effect of hydrostatic extrusion, which causes higher density of the core in comparison to traditional deformation processes.