Microstructure and superconducting properties of Ca substituted Y(Ba 1? x Ca x ) 2Cu 3O 7?δ ceramics prepared by thermal treatment method

摘要

The effect of Ca substitution in Ba site of Y(Ba 1? x Ca x ) 2 Cu 3 O 7?δ , ( x =0.00, 0.04, 0.08, 0.1 and 0.125), ceramics prepared by thermal treatment method was investigated. Surface morphology, structural and superconducting were studied using field emission electron microscope (FESEM), X-ray Diffraction (XRD) and four-probe method. FESEM analysis showed an increasing of samples’ grain size, homogeneity and compactness with increasing of Ca substitution. From XRD, the samples had orthorhombic crystal structure of space group Pmmm besides small amount of unknown peaks. The critical temperature ( T c R=zero ) decreased from 87K for the pure sample to 80K for sample with x =0.08, and it remained the same for samples with x ?0.08. Sample with x =0.04 showed the sharpest superconducting transition (Δ T c ), which could be due to good microstructure morphology and better crystallinity.