Modulated structural characteristics and microwave properties of spray pyrolyzed superconducting BCSCO films

Low-cost-based high-T-c superconducting thin film of Bismuth Strontium Calc ium Cuprate on yittriya stabilized zirconia (YSZ) using spray pyrolysis dep osition technique from nitrate precursors followed by rapid annealing at te mperatures between 830 and 840 degreesC in air and in O-2 is described. The films are highly oriented with the c-axis parallel to the plane of the sub strate. Some satellite reflections that occur due to the modulation along t he crystal lattice (parallel to c-axis) are observed. The prominent X-ray d iffraction lines can be fitted to a tetragonal structure. A number of satel lite X-ray reflections lines are observed which suggest the existence of mo dulation. These lines have been fitted in a superspace group (N I I I) with a = 3.832 Angstrom and c = 48.826 Angstrom indicating the existence of sup erposed modulated structure. Substrates (Al2O3, LiNbO3, Si3N4, Si) other th an YSZ could not produce superconducting films due to the diffusion of meta l ions in the film causing poisoning effect in superconducting properties. Resistivity measurements indicate superconducting onset at 92 K and zero re sistance at 77 K. Microwave induced dc voltage (muV) measurements as a func tion of microwave power (mW) were carried out at different temperatures dow n to 65 K for different annealing temperatures. It is noted that the slope of the line (muV vs. mW) are dependent on ramping of the processing tempera tures. The decrease of slope suggested that weak-links between the supercon ducting grains are decreased as the ramping of the processing temperature i s decreased keeping the ramping time constant. The interactions between fil m and the-substrate are qualitatively discussed.