In Situ Microscopic Observation of the Formation Process of Pinning Centers in Nd-Ba-Cu-O Superconductor

Novel method of investigation the development of nanolevel microstructure to introduce effective pinning centers in Nd-123 superconductor was attempted. Compositional deviation in nanometer scale of Ba and Nd developed during post heat treatment of Nd-123 crystal grain was observed by means of in situ high temperature microscopic observation, suggested as the origin of improved pinning force. Crystal growth condition of Y-123 superconductor in polycrystalline bodies under applied stress was studied for the microstructure control to improve transport current properties. Behavior of crystal growth front of superconducting grains through the solid state diffusion or the existence of small amount of liquid phase was examined in various conditions of temperature and applied stress. Interfacial reaction of introduced pinning centers and growing surface of superconducting matrix grains was investigated to promote the uniform dispersion of nanoparticles in matrix for increasing Jc.