Superconducting phase formation in random neck syntheses: a study of the Y–Ba–Cu–O system by magneto-optics and magnetometry

Magneto-optical imaging and magnetization measurements were applied to investigate the local formation of a superconducting phase effected by a random neck synthesis in the Y–Ba–Cu–O system. Polished pellets of strongly inhomogeneous ceramic samples show clearly the appearance of superconducting material in the intergrain zones of binary primary particles reacted under different conditions. Susceptibility measurements allowed evaluation of the superconducting critical temperature, which turned out to be close to that of optimally doped YBa2Cu3O7−x.