Isothermal growth of large YBaCuO single domains through an artificial array of holes

Abstract

For various applications, single domains (centimetric crystals with defects) of the YBa 2Cu 3O x superconductor oxide are grown using the top seeding melt growth (TSMG) method. During the oxygen annealing inducing superconductivity, cracks open at the surface layer and propagate into the bulk. Since the cracking can be reduced on thin samples, we proposed to grow single domains with thin wall geometry prior to oxygenation. Holes of 1 mm in diameter and distant of 2.4 mm are drilled parallel to the c-axis in YBa 2Cu 3O x sintered pellets to produce a geometry with walls having a thickness below 1.5 mm. The single domain is then grown from a SmBa 2Cu 3O x seed placed on the pellet prior to the process. Pictures of the sample surface are regularly taken to allow an in situ monitoring of the growth. The growth front is slightly distorted by the holes, but reaches the edges. Neutron quantitative texture analysis demonstrates a unique crystallographic orientation in the bulk. The growth of a single domain is confirmed by microscopic observation and by flux mapping of trapped field in the superconducting state. The porosity usually trapped within a plain single domain disappears thanks to reduced diffusion paths.