DIFFUSION OF SR IN BI2SR2CAN-1CUNO2N+4

Tracer diffusion of Sr-85 in polycrystalline Bi2Sr2Can-1CunO2n+4 has been investigated for n = 1, 2, and 3 in an oxygen atmosphere between 775 and 850-degrees-C. A radiotracer serial-sectioning technique was used to measure the concentration profiles, which were fit to a solution of the diffusion equation to calculate the diffusivities. The activation energies were 403, 553, and 519 kJ/mole, for n = 1, 2, and 3, respectively. However, the absolute values of D for the various layered superconductors did not differ by more than an order of magnitude over the measured temperature range. The diffusivity of Sr at 800-degrees-C for n = 1 or 2 over an oxygen partial pressure range of 10(3) to 10(5) Pa increased as the pressure decreased.