Approaches to the synthesis of High-TCsuperconducting oxides in La–Ba–Cu–O and Y–Ba–Cu–O systems

High-TC superconducting oxides of nominal La1.85Ba0.15 CuO4 and YBa2 Cu3 O7 have been prepared by using nitrate, carbonate, oxalate/malonate and citrate precursors. While the samples in the Y-system are generally monophasic YBa2Cu3O7−δ with TC around 90K, the preparations in the La-system are biphasic containing K2NiF4-like La1.85Ba0.15 CuO4 (TC = 30K) and a perovskite-like phase with' a much higher TC (200–300K). Effect of Ca, Zr, Ce as well as S substitution in YBa2Cu3O7−δ has also been investigated