ANISOTROPIC DIFFUSION OF OXYGEN IN ND2CUO4-DELTA SINGLE-CRYSTAL

Single crystal was grown by the TSFZ method, and the chemical diffusion coefficients of oxygen, D(ab) in the a-b-plane and D(c) in the direction of the c-axis were determined by means of a thermomicrobalance. The Arrhenius plot for D(ab) showed a break at 800-degrees-C, which was interpreted as the effect of surface reaction below 800-degrees-C. Above 800-degrees-C, D(poly) calculated from D(ab) and D(c) was almost the same as the measured one. The vacancy diffusion coefficients of oxygen, D(v)(c) and D(v)(ab), were calculated from the chemical diffusion coefficients, D(c) and D(ab). The anisotropy of vacancy diffusion was small. This might be due to the nearly equal jumping distance of the oxide ion vacancy in the a-b-plane and in the direction parallel to the c-axis.