Two Crystal Phases in the Superconducting Ba-Y-Cu-O System and Their Reactivity to Water

Abstract

Crystals with a stoichiometry either Ba 2 YCu 3- x O 7- y or Ba 4 YCu 2 O 8- y are a high t c superconductor. The former is well known. With respect to the latter the crystal structure was determined to be tetragonal with lattice parameters a =5.78 Å and c =7.99 Å. It was found that both of them reacted with water. The former was slowly decomposed by warmed water at about 35°C, while the latter was destroyed at room temperature in an instant.