Effect of Cesium Substitution on the Superconducting Properties of Bi-2212 Samples Prepared Via Solid-State Reaction and Laser Floating Zone Technique

Abstract

In this work, the effect of cesium substitution on the structural and superconducting properties of Bi 2 Sr 2 Ca 1-x Cs x Cu 2 O y (where x = 0.0, 0.025, 0.050, 0.075, 0.10, 0.125, and 0.15) samples prepared by the solid-state reaction route and by directional growth using the laser floating zone (LFZ) technique has been studied. X-ray diffraction has shown that both kinds of samples present the 2212 phase as the major one, with pseudo tetragonal structure, accompanied by minor amounts of (Sr,Ca)CuO 2 and Bi 2 (Sr,Ca) 4 O 6+ secondary phases. SEM-EDX results indicate that Bi-2212 phase is the major one, with small amounts of secondary phases. Cs substitution diminishes the size and content of secondary phases. Magnetization measurements reflect different behavior for sintered and LFZ grown samples. Although the diamagnetic transition is very wide for the former samples, it is very sharp for the last ones. The critical onset temperatures, T C , are around 80 and 90 K, for sintered and LFZ grown samples, respectively. Moreover, M-H measurements indicate that LFZ grown samples exhibit larger areas than the sintered ones. The intragranular critical current, J C , calculated from the M-H loops and Bean's formula, is maximum for x = 0.025Cs sintered and x = 0.05Cs LFZ grown samples. The maximum pinning forces, F Pmax , determined in these samples are higher than those obtained in undoped ones, reaching 9 × 10 7 Oe*A/cm 2 and 10 × 10 8 Oe*A/cm 2 , at 10 K, for sintered and LFZ grown samples, respectively.

Effect of Rubidium Substitution on the Physical and Superconducting Properties of Textured High-Tc BSCCO Samples

“…A/cm 2 ) [30]. This effect may be associated with the different cation sizes affecting the oxygen quantity and the number of charge carrier.…”

Laser Floating Zone Growth: Overview, Singular Materials, Broad Applications, and Future Perspectives

“…Due to the higher stability of the Bi-2212 phase, an important amount of work reported was focused on this phase [132,135,164,168,[173][174][175][176][177][178][179][180][181][182][183]. During these works, the Nd:YAG radiation started to be used as an alternative to the CO 2 lasers [168,175], observing that, with similar focusing optics, 1.06-µm radiation is more adequate to process textured Bi-2212 superconductors because these oxides absorb the 10.6-µm radiation mostly in the surface, creating larger radial temperature gradients and larger radial inhomogeneities due to constitutional supercooling.…”

“…Also, the substitution of some cations has been explored. For instance, Ca substitution by Y ions [181] generates an increase in the critical temperature values but with a deterioration of the grain alignment, while substitution by Rb [182] or Cs [183] leads to an increase of the pinning force at 10 K by about 20%.…”