The effect of heat-treatment environment on the superconducting properties of plasma-sprayed YBa2Cu3Oy deposits

Abstract
Plasma‐sprayed YBa2CU3Oy coatings consist of a nonsuperconducting tetragonal phase with an a/c ratio of 1/3 (c=11.61) in the as‐sprayed condition. This phase is tentatively assigned to the solid solution Y1(Ba2−xYx) Cu3O7+δ. Heat treatment of this phase at 930 °C/24 h in oxygen results in orthorhombic symmetry, an expansion of the c axis (11.66 Å), and the appearance of superconductivity. In this study it is shown that heat treatment in argon at 850 °C prior to the oxygen heat‐treatment leads to a crystal structure which closely matches the desired YBa2Cu3Oy (c=11.68), raises Tc, and narrows the transition width.