Correlation Between Local Anisotropy and Microstructure in Y_1Ba_2Cu_3O_(7-δ)

摘要

In the present investigation, we report the results of transmission electron microscopy (TEM) for YBa_(2-y)Sr_yCu_3O_(7-δ) bulk samples with y = 0.0, 0.50 and 1.0. The partial substitution of Ba~(2+) by Sr~(2+) site in YBa_2Cu_3O_(7-δ) system leads to decrease in superconducting transition temperature (T_c) of the doped system. The microstructural variants being studied by TEM technique in imaging and selected area diffraction (SAD) modes revealed an increase in the density of twins with increase in Sr concentration despite of the fact that there is slight decrease in the orthorhombicity. This is against the general conviction of decrease in twin density with decreasing orthorhombicity. An increase in twin density is accompanied by sharpening of twin boundaries with increasing Sr concentration. These observations are similar to that as reported by us for Y_(1-x)Ca_xBa_2Cu_3O_(7-δ) system. A possible correlation between microstructural features and superconducting properties has been put forward and discussed in the present investigation.