Excess Conductivity Analysis of an YBCO Foam Strut and Its Microstructure.

Struts of a superconducting YBaCuO (YBCO) foam prepared by the infiltration growth method on the base of commercial polyurethane foams were extracted from the bulk, and thoroughly characterized concerning the microstructure and the magnetoresistance, measured by the four-point technique. Optical microscopy, electron microscopy, electron backscatter diffraction and atomic force microscopy observations indicate a unique microstructure of the foam struts which shows a large amount of tiny YBaCuO (Y-211) particles (with diameters between 50 and 100 nm) being enclosed in channel-like grain boundaries between the YBCO grains and a one-of-a-kind surface of the struts covered with BaCuO-particles. The resistance data obtained at temperatures in the range 4.

Microstructural Parameters for Modelling of Superconducting Foams.

Superconducting YBa2Cu3Oy (YBCO) foams were prepared using commercial open-cell, polyurethane foams as starting material to form ceramic Y2BaCuO5 foams which are then converted into superconducting YBCO by using the infiltration growth process. For modelling the superconducting and mechanical properties of the foam samples, a Kelvin-type cell may be employed as a first approach as reported in the literature for pure polyurethane foams. The results of a first modelling attempt in this direction are presented concerning an estimation of the possible trapped fields (TFs) and are compared to experimental results at 77 K.

()BaCuO and the Roeser-Huber Formula.

We apply the Roeser-Huber formula to the ()Ba2Cu3O7-δ (BCO with = rare earths) high-Tc superconducting material class to calculate the superconducting transition temperature, Tc, using the electronic configuration and the crystallographic data. In a former publication (H. P.

Fabrication of Superconducting Nanowires Using the Template Method.

The fabrication and characterization of superconducting nanowires fabricated by the anodic aluminium oxide (AAO) template technique has been reviewed. This templating method was applied to conventional metallic superconductors, as well as to several high-temperature superconductors (HTSc). For filling the templates with superconducting material, several different techniques have been applied in the literature, including electrodeposition, sol-gel techniques, sputtering, and melting.

Excess Conductivity Analysis of Polycrystalline FeSe Samples with the Addition of Ag.

Bulk FeSe superconductors of the iron-based (IBS) "11" family containing various additions of silver were thoroughly investigated concerning the microstructure using optical microscopy and electron microscopy (TEM and SEM). The measurements of electrical resistivity were performed through the four-point technique in the temperature interval T= 2-150 K. The Aslamazov-Larkin model was employed to analyze the fluctuation-induced conductivity (FIC) in all acquired measurements.

Production of Sharp-Edged and Surface-Damaged YBaCuO by Ultrasound: Significant Improvement of Superconducting Performance of Infiltration Growth-Processed YBaCuO Bulk Superconductors.

Growth and physical properties of bulk REBaCuO (REBCO) superconductors fabricated by the infiltration growth (IG) method strongly depend on the initial size and morphology of the REBaCuO (211) particles. The present work details the novel method we developed for producing sharp-edged and surface-damaged 211 particles to be added to the REBCO bulks. We employed high-energy ultrasonic irradiation for pretreating the 211 particles and fabricated high-performance bulk single-grain YBaCuO (YBCO) superconductors via the top-seeded IG process.

Microstructure and Flux Pinning of Reacted-and-Pressed, Polycrystalline BaKFeAs Powders.

The flux pinning properties of reacted-and-pressed BaKFeAs powder were measured using magnetic hysteresis loops in the temperature range 20 K ≤ ≤ 35 K. The scaling analysis of the flux pinning forces ( F p = j c × B , with j c denoting the critical current density) following the Dew-Hughes model reveals a dominant flux pinning provided by normal-conducting point defects ( δ l -pinning) with only small irreversibility fields, H irr , ranging between 0.5 T (35 K) and 16 T (20 K).

Superconducting YBCO Foams as Trapped Field Magnets.

Superconducting foams of YBa₂Cu₃O (YBCO) are proposed as trapped field magnets or supermagnets. The foams with an open-porous structure are light-weight, mechanically strong and can be prepared in large sample sizes. The trapped field distributions were measured using a scanning Hall probe on various sides of an YBCO foam sample after field-cooling in a magnetic field of 0.

Giant Enhancement of Magnetostrictive Response in Directionally-Solidified FeGaEr Compounds.

We report, for the first time, correlations between crystal structure, microstructure and magnetofunctional response in directionally solidified [110]-textured FeGaEr (0 < < 1.2) alloys. The morphology of the doped samples consists of columnar grains, mainly composed of a matrix phase and precipitates of a secondary phase deposited along the grain boundary region.