High-T_c Phase Promoted and Stabilized in the Bi, Pb-Sr-Ca-Cu-O System

Abstract

Partial substitution of Pb for Bi in the Bi-Sr-Ca-Cu-O system has been found to sharply increase the volume fraction of the high-T c phase when both the starting material (coprecipitated oxalate being used in the present study) and the heating process are appropriate. The sharp powder X-ray diffraction pattern obtained from well-grown particles, 5∼10 µm wide and 0.5 µm thick typically, was assigned to an orthorhombic cell with a=0.537 nm, b=2.682 nm, and c=3.726 nm. The electrical resistance dropped to zero at 107 K within the experimental limit of 10-6 Ω. A large diamagnetic response in the ac susceptibility due to the Meissner effect was seen below 120 K. The dominance of the high-T c phase over the low-T c phase was roughly estimated at 9/1 in volume.

Two-Phase Microstructures Generating Efficient Pinning Centers in the Heavily Pb-Substituted Bi2Sr2CaCu2O8+Single Crystals

“…Pb substitution of about 0.3 per formula unit is essential to the formation itself of Bi Sr Ca Cu O >B (Bi-2223) (9), while a range of solid solutions exist for Bi-2212 and Bi Sr CuO >B (Bi-2201) (10)(11)(12). In the case of Bi-2212, a series of single-phase polycrystalline materials were obtained for 04y40.8 in a formula Bi \W Pb W Sr CaCu O >B (10,13,14).…”

Modulated Structure of La2NiO4+δas a Mechanism of Oxygen Excess Accommodation

“…2b) is very similar in appearance to that found by Yanagisawa et al (14) in the (Bi 1Ϫx Pb x ) 2 Sr 2 Cu 2 O y (x ϭ 0.2) compound. The extra oxygen model has been most widely accepted in the bismuth-based superconductors as the origin of structural modulations (15)(16)(17). According to this model, this extra oxygen is located between two adjacent (BiO) planes.…”

Laser Induced Cylindrical Zone Melting of Bi2Sr2CaCu2O8+∂ Superconductors

“…Particularly, the discovery of Bi 2 Sr 2 CuO 6 (Bi-2201) [3] Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212) and Bi 2 Sr 2 Ca 2 Cu 3 O 10+δ (Bi-2223) [4,5] provided systems which could be melt-processed with relative ease. Although these materials exhibit incongruent melting, the influence of microstructural defects on the superconducting properties is less severe than in YBa 2 Cu 3 O 7 materials.…”