Temperature dependence investigation of dissipation processes in strongly anisotropic high-temperature superconductors of Bi-Pb-Sr-Ca-Cu-O system synthesized using solar energy

The investigation of temperature dependence of damping and period of vibrations of HTSC superconductive cylinder of Bi-Pb-Sr-Ca-Cu-O system suspended by a thin elastic thread and performing axial-torsional vibrations in a magnetic field at temperatures above the critical one for the main phase Tc=107 K were carried out. It was observed some "chaos" temperature region in the temperature interval 107-138 K, where it is seen separate ripples of dissipation and oscillation frequency. It is assumed that the "chaos" region could point to a possibility of existence of other magnetic and more high-temperature phases as single islands in a normal materials matrix.Comment: 10 pages, 0 figure

Superconductivity at Т≈200 K in Bismuth Cuprates Synthesized Using Solar Energy

When investigating low-frequency (0.1 Hz) oscillations of multiphase high-temperature cuprate superconductors (HTCS) Bi1,7Pb0,3Sr2Ca(n-1)CunOy (n=2-30), a wide attenuation peak (ΔT~100 К) with a maximum at Т≈200 К was detected. This peak was particularly pronounced in field cooling (FC) experiments, i.e. after abrupt cooling of the sample in the external magnetic field at the temperature Т\u3cТс with subsequent slow warming up to room temperature with invariance of the applied field. The attenuation peak height depended on the preliminaryorientation (before cooling) of the samples θ in the measured permanent magnetic field Н. On the one hand, it is well known that, after the FC procedure and subsequent slow warming up, at the temperatures close to the critical temperature Тс, the attenuation peak associated with “melting” of the Abrikosov frozen vortex structure and its disappearance at Т \u3eТс is detected in monophase samples. At the same time, in most multiphase bismuth HTCS samples, synthesized using solar energy and superfast quenching of the melt, the attenuation peak with the maximum at Т≈200 К was observed.Depending on the conditions of synthesis, the attenuation peak could be two-humped and could be located in the temperature range much wider than Тс of the major superconducting phase. We assume that this is due to the existence of frozen magnetic fluxes (after FC) in superconducting “dropping” regions, which gradually (with increasing temperature) transfer into the normal state and release pinned vortex threads. This fact could be a cause of observed dissipative processes, so as also the evidence of the existence of superconductivity at Т ≥240 К