Abstract
Sol-gel films of YBa 2Cu 3O x (YBCO) were deposited by spray pyrolysis on 10 cm diameter by 0.05 cm thick polycrystalline MgO wafers. The films were deposited in 1 microm increments up to 5 microm and characterized by electrical measurements, optical and electron microscopy, and X-ray diffraction. In plane residual stresses of the films were obtained by a shadow moire interferometry technique. The YBCOMgO interface was characterized by bevel polishing and fluorescence analysis. The films contain substantial in-plane residual stresses as a result of chemical reaction of the YBCO and MgO. Cu diffuses into the MgO so that a substantial amount of Y 2BaCuO 5 phase forms near the interface. The largest tensile stress was 0.96 GPa in a 4 microm thick film. The stresses were highest at the center of the wafer and decreased toward the edge, and the in-plane stresses caused cracks to form. Formation of the 211 phase influenced T c (onset) and T c (zero resistance). The T c onset was 78 to 92 K, and T c (zero resistance) was 15–65 K depending on film thickness.
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