Bismuth strontium calcium copper oxide high-T_c superconducting films from nitrate precursors

Superconducting films of bismuth strontium calcium cuprate were prepared by spray pyrolysis of mixed nitrate solutions onto heated (100) orientated MgO substrates, as well as yttria-stabilized zirconia and SrTiO3. Various compositions and annealing temperatures were explored. Best results -Tc = 82 K, TR=0=77 K, Jc (60 K) = 800 A/cm2-were obtained on MgO for a Bi2.15Sr1.68Ca1.17Cu2Ox composition after brief annealing in air just below its melting point. A mixture of phases with c-axis normal to the substrate is obtained; the "Bi2Sr2CaCu2O8+x" phase predominates in the best samples, while a phase with c0=24.4 A ̊ (or 48.8 Å) is always present. The superconductivity of the films is not significantly degraded by a 3 day immersion in water. © 1988.