Critical temperature of the superconducting transition of individual phases of multiphase bismuth cuprates after cooling in a magnetic field to a temperature of 77 K

Abstract

Using a highly sensitive torsional vibration technique, the authors have determined the critical temperatures of the superconducting transition (Tc) of individual phases of multiphase cuprates [Bi1.7Pb0.3Sr2Ca(n-1)CunOy (n = 2–30)] in a constant external magnetic field (H) in the temperature range of 77 to 270 K. It has been found that oscillation damping peaks are more pronounced when a sample is rapidly cooled in an external magnetic field (FC) to a temperature of 77 K and then is slowly warmed to room temperature. An increase in the time of sample exposure to a magnetic field at 77 K leads to a rise in the temperature Tc of different phases, and to an increase in the intensity of a signal corresponding to high-temperature phases with Tc > 240 K. Structural studies have shown that with increasing sample exposure time at 77 K, as a result of sample compression an increase in stress concentration at grain boundaries appears to increase defect density and to enhance the pinning of Abrikosov vortices, i.e. creates new (additional) conditions for their “freezing” during the field cooling (FC) procedure. It has been established that in samples of the Bi1.7Pb0.3Sr2Ca(n-1)CunOy (n = 2–30) series, the critical temperature Tc increases from 107 K to ≥ 240 K with an increase in n.

Vibrating Reed Study of Superconducting Cuprates Fabricated by Superfast Melt Quenching in a Solar Furnace

“…The location of the coils in the immediate vicinity of the sample allows the creation of a sufficiently strong alternating field on it by using a standard low-frequency generator. The alternating field h created by the Helmholtz coils can also be directed at different angles that were combined with application of solar energy and superfast quenching melt technology [1][2][3][4][5]. Amorphous precursors and their use make possible the manufacturing of high-density low porous texturized ceramics with given dimensions of grains.…”

“…From this point of view, particular interest attracts the Bi-Pb-Sr-Ca-Cu-O system, because it is characterized by high Т с =107К and the record high second critical magnetic field Н с2 ~150T. Our group has undertaken research on the possibility to increase the Т с of this system [1][2][3][4][5]. In [1][2][3]5] the melt technology for obtaining Bi-Pb-Sr-Cu-O HTSC ceramics using solar energy for melting and subsequent superfast melt quenching for increasing of internal inhomogeneities was developed, allowing the receiving of homogeneous, highquality, textured ceramic samples with controllable microstructure and pinning centers.…”

“…Our group has undertaken research on the possibility to increase the Т с of this system [1][2][3][4][5]. In [1][2][3]5] the melt technology for obtaining Bi-Pb-Sr-Cu-O HTSC ceramics using solar energy for melting and subsequent superfast melt quenching for increasing of internal inhomogeneities was developed, allowing the receiving of homogeneous, highquality, textured ceramic samples with controllable microstructure and pinning centers. In [4], Hot Shock Wave Consolidation Technology was used to produce Bi-Pb-Sr-Ca-Cu-O compositions with increased internal inhomogeneity and for studying their superconducting precursor phases by torsional magnetometry method.…”

Superconducting Precursors in Bi/Pb Multiphase Cuprates Fabricated by the Solar Technology and their Comparative Study by Torque Magnetometry Methods

“…The Bi/Pb phase with high T c = 197 K was obtained at a pressure of 10 3 Torr, but it decomposed at atmospheric pressure [13]. The progressive results achieved in the synthesis of superconductors with increasing critical temperatures of the superconducting transition from 97 to 260 K [14][15][16][17][18][19] provided an optimistic basis for continuing the research for an unconventional way for the synthesis of Bi/Pb. This study aimed to compare the high-temperature precursors in Bi 1.7 Pb 0.3 Sr 2 Ca (n-1) Cu n O y using two different methods of torque magnetometry to further substantiate their existence and assess the potential possibilities of the precision VR method for the evaluation of Т с of the high-temperature precursors in this multiphase system.…”