Impact of the Starting Powder Composition on ${\rm GdSr}_{2}{\rm RuCu}_{2}{\rm O}_{8}$ Melt-Textured Processes

The superposition of strongly anisotropic magnetic and superconducting properties in GdSr₂RuCu₂O₈ (Gd1212) stimulates interest in the fabrication of oriented samples of macroscopic size by Melt-Texturing Growth (MTG). Up to now, the results obtained are unsatisfactory due to the small size and the random distribution of the oriented domains. In order to achieve MTG samples with higher oriented volume fractions, we prepared pellets adding either GdSr₂RuO₆ (Gd1210) or CuO to highly pure Gd1212 powders. X-ray Diffraction (XRD) analysis revealed a substantial difference between the two systems showing that only in Gd1212-Gd1210 samples it is possible to achieve a superconducting phase. The analysis of the two samples microstructures carried out by Scanning Electron Microscopy with implemented Energy Dispersive Spectroscopy (EDS) revealed that in the case of the Gd1212-Gd1210 samples a low concentration of Gd1210 and SrRuO₃ inclusions is observed in a Gd1212 predominant matrix. However, in the Gd1212-CuO samples, micro-sized precipitates of SrRuO₃, islands of Gd₂CuO₄ are homogeneously distributed throughout a CuO matrix. DTA measurements performed on all the samples confirm the presence of additional solidification reactions in the Gd1212-CuO samples. These features have a profound impact on the transport properties of the two samples. The addition of Gd1210 in highly pure Gd1212 powders has been proved to be a favorable condition to obtain superconducting Gd1212 MTG samples.