High temperature c-axis resistivity of Bi2Sr2CaCu2O8+x single crystals anddependence on oxygen stoichiometry

The c-axis resistivity of Bi2Sr2CaCu2O8+x crystals has been measured as a f unction of thermal cycling in the range between 70 and 856 K in flowing oxy gen and nitrogen. Hysteresis in the temperature-dependent c-axis resistivit y provides evidence of thermally activated oxygen diffusion in and out of t he crystal varying as D(T) = 6 x 10(7) exp(-Delta(1)/kT) and D(T) = 55 exp( -Delta(2)/kT), where Delta(1) = 2.2 eV and Delta(2) = 1.2 eV, respectively. Oxygen diffusion into the crystals becomes significant above T-0 similar t o 595 K and out of the crystal above T-1 similar to 750 K. The implications for the stoichiometric control, superconductivity, and intrinsic high temp erature dependence of the resistivity of Bi2Sr2CaCu2O8+x crystals are consi dered. (C) 1999 American Institute of Physics. [S0003-6951(99)04739-7].