PREPARATION AND STRUCTURAL STUDY OF HIGH T-c SUPERCONDUTING PHASE LaBa2Cu3O7-delta

A stable orthorhombic supereonduting phase LaBa2Cu3O7-delta, with T-c 82K and Meissner effect 13.6%, has been prepared by citric acid complerstion with nitrates. It is determined to be an orderly three layer Ba-La-Ba, oxygen deficient perovskite structure by X ray powder diffraction and atomic valence calculation. Through high temperature XRD and DTA-TG study,the phase transition of orthor hombic into tetragonal structure is found to be reversible, and occurs at 450 degrees C, not the value 350 degrees C proposed by A.Maeda et al. The superconduting properties are improved as the responsible orthorhombic structure deviates more from tetragonality.Chemistry, PhysicalSCI(E)0ARTICLE3239-243