THERMAL AND MECHANICAL INDUCED STRESSES IN SUPERCONDUCTING YBA2CU3OX COATINGS ON FIBERS

Thermal stresses induced during cooling from the fabrication temperature of a fiber with a noncubic superconducting ceramic coating are analyzed theoretically. The coating considered has a preferred crystallographic orientation such that the c axis of the coating material is perpendicular to the fiber surface which, in turn, results in different thermal expansion coefficients in the radial and the tangential directions in the coating. The thermal stresses are shown to result both from the mismatch between the fiber and the coating, and from the thermal expansion anisotropy of the coating. Stresses due to bending of the fiber/coating to form a superconducting component are also addressed. A critical radius of curvature of bending is obtained below which segmentation of the coating is predicted.