Study of oxygen diffusion in NdBa 2Cu 3O 7−δ single crystal by in-situ observation of twin formation

Abstract

Chemical oxygen diffusion coefficients in NdBa 2Cu 3O 7− δ (Nd123) single crystals grown by a top-seeded solution-growth (TSSG) method were estimated over a temperature range from 300° to 600°C by an accurate and easy technique of in situ observations of twinned/untwinned boundaries during annealing in a pure oxygen gas flow. The chemical oxygen diffusion coefficients of the orthorhombic phase and the tetragonal phase in the single crystals were estimated, respectively. These oxygen diffusion coefficients were almost equal. Furthermore, the oxygen diffusion coefficients in the Nd123 single crystals were compared with those in YBa 2Cu 3O 7− δ (Y123) single crystals, which were also grown by the TSSG method. The chemical oxygen diffusion coefficients in the Nd123 single crystals were also quite close to those in the Y123 single crystals. The results in the present study suggest that the oxygen diffusion in the Nd123 single crystals was affected by nonstoichiometry of the Nd123 single crystals, of which composition was Nd:Ba:Cu=1.07:0.95:3.00.