Transport and magnetic properties of Bi(Pb)2212 superconducting ceramics doped by low rate of potassium

Samples of Bi1.5Pb0.5(Sr1.8−xKx)CaCu2O8+d and Bi1.5Pb0.5Sr1.8CaCu2O8+dKx have been prepared from powders of carbonates and primary oxides using the solid state reaction method and compared in this study. In the first case, potassium (K) is substituted in the strontium (Sr) site. In the second one, K is added. A part of the paper is devoted to discuss the results obtained by X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) observations of (Bi,Pb)2Sr1.8CaCu2O8+d samples doped by potassium to provide additional microstructural information related to the doping method. These analyses are supplemented by resistivity and magnetic measurements. Results show how the rate of doping by potassium affects transport and magnetic properties of Bi(Pb)2212 phase. The critical current density (Jc) is improved using the two methods and it reaches a double value by the addition of K as compared to the undoped sample.

EFFECT OF LIGHT ON THE RESISTANCE OF Bi/Pb SUPERCONDUCTORS SYNTHESIZED BY SOLAR ENERGY

The aim of the work is to expand the capabilities of solar technologies and areas of practical use of superconductors. The effect of white light on the interaction of superconducting ceramics with a magnet at room temperature was investigated. It has been established that the magnet is “ejected” by ceramic samples of nominal Bi1,7Pb0,3Sr2Ca(n-1)CunOy, (n = 5-20) under the influence of white light and there is no effect in the dark. The resistance of Bi/Pb superconducting ceramics is reduced by exposure to light compared to resistance in the dark. The resistance of ceramics containing higher superconducting higher superconducting phases Tc = 267-295 K is lower in comparison with “nitrogen” ceramics Tc = 110-120 K

LOW-RESISTANCE Bi/Pb CERAMICS CONTAINING Ts = 295К-315K PHASES SYNTHESIZED IN A SOLAR FURNACE (PARKENT)

The aim of this work is to obtain bulk textured superconducting ceramics based on glass-crystalline precursors of the Bi1.7Pb0.3Sr2Ca(n-1)CunOy (n=5-9) series. Technologies for obtaining superconducting materials are presented. The advantages of melt methods and “Super Fast Aloys Quenching–T” technology is shown. Compositions, methods of synthesis and study of properties of precursors and ceramics obtained by solar energy are presented. The interrelation of the morphology of glass-crystalline precursors and superconducting ceramics based on them is revealed. It is shown that nano-sized nuclei are the basis on which superconducting phases with Ts = 295-315K are formed as a result of the peritectic reaction. The mechanism of conduction in nanostructured layered ceramics containing higher superconducting phases is proposed. The contribution to the conductivity of low-resistance ceramics is assumed due to the mutual influence of Bi / Pb homologous phases, which represent a “quasi” heterogeneous system by analogy with the mechanism proposed by Rashba for heterophase semiconductors.

PROBLEMS OF COEXISTENCE OF SUPERCONDUCTIVITY AND MAGNETIC ORDERING OF COPPER SUBLATTICES IN YBa2Cu3-XFeXO7-X CERAMICS

The article studies the problems of coexistence of superconductivity and magnetic ordering of copper sublattices in YBa2Cu3-xFexO7-x ceramics. It is known that in superconducting ceramics YBa2Cu3O7-z with orthorhombic lattice as the oxygen content decreases, the transition temperature in superconducting state Tc decreases, and at z>0.6 superconductivity disappears, the lattice becomes tetragonal and at the same time, antiferromagnetic ordering of sublattices Cu (2) appears. The substitution in ceramics of YBa2Cu3O7 part of copper atoms by iron atoms (i.e., the formation of a solid solution of YBa2Cu3-xFexO7+y) is accompanied by similar effects: as x increases, Tc decreases, at x>0.05 the orthorhombic lattice becomes tetragonal, at x>0.45 the superconductivity disappears. The most significant moment is the fact of coexistence in ceramics YBa2Cu3-xFexO7+y in the region of compositions 0.03 < x < 0.45 of superconductivity and magnetic ordering of iron atoms in copper nodes (the latter is established by Mossbauer spectroscopy on isotope 57Fe in a large number of works. However, it remains unclear whether the magnetic ordering of iron atoms in the YBa2Cu3-xFexO7+y lattice is related to the magnetic ordering of copper atoms

Magnetic relaxation in (Bi, Pb)-2223 superconducting ceramics doped with α-Al2O3 nanoparticles

A preliminary study of the magnetic relaxation in (Bi, Pb)-2223 superconducting ceramics doped with α-Al2O3 nanoparticles is presented, taking as starting point the measurements of the M(t) dependence, both in samples in the form of powder as in pellet. The relaxation of the three types of vortices that can exist inside these materials is analyzed, emphasizing on the intragranular regionwhere the planar defects exist and, consequently, Abrikosov-Josephson vortices emerge. Finally, interesting results of the comparison between the behavior of the samples in the form of powder and in the form of pellet are shown from the estimation of the pinning energy of the vortices.