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 local formation of superconducting phase effected by a random neck synthesis in 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 allows evaluation of superconducting critical temperature, which turned out to be close to that of optimally doped YBCO. 
J.B. Willems, J. Albrecht, I.L. Landau and J. Hulliger