The microstructure of Ca doped Y1-xCaxSr2Cu2GaO7 and Ca substituted YSr2-xCaxCu2GaO7 have been investigated by electron microscopy. A common feature found in the Y1-xCaxSr2Cu2GaO7 superconductors is the existence of line defects, which are not observed in non-superconducting YSr2-xCaxCu2GaO7. At the higher doping level, x ≈ 0.35, the line defects develop into modulated structures. The transition temperature and Meissner fraction increases with the doping level as does the defect concentration, indicating that the defects and superconductivity in these materials are interrelated. The line defects are associated with an asymmetrical distortion (ap ≠ bp) of the gallium-oxygen plane which plays a similar role to the copper-oxygen chains in YBa2Cu3O7-°.
ASJC Scopus subject areas
- Condensed Matter Physics