Ronald W. Barton

Microstructural interaction of Y 2 Ba 4 Cu 8 O 16 stacking faults within YBa 2 Cu 3 O 7−x

A transmission electron microscopy study of a post-annealed YBa 2 Cu 3 O 7−x thin film shows that extra Cu–O planes within the structure can aggregate as stacking faults to form a defect microstructure rather than forming the well-ordered Y 2 Ba 4 Cu 8 O 16 phase. Interaction of the stacking faults with the surrounding matrix results in strain effects and microstructural variations which may hinder ordering as well as influencing superconducting properties if occurring in higher concentration. When viewed normal to the plane of the film, the boundaries of the stacking faults can be imaged as dislocation-like defects, indicating the size and shape of the stacking faults and their relationship to other defects such as twins and second phase precipitates.

Two‐dimensional superstructure in the (001) plane of Bi2[Ca,Sr]3Cu2O8+δ thin films

Thin films of Bi‐Ca‐Sr‐Cu‐O showing superconductivity above 100 K have been made by electron beam evaporation with oxygen post‐annealing. The major superconducting phase, Bi2[Ca,Sr]3Cu2O8+δ (Tc ∼85 K), is oriented epitaxially with the (100)SrTiO3 substrate. In addition to the one‐dimensional incommensurate superstructure along the b axis, which is characteristic of this phase, we have observed by transmission electron microscopy a two‐dimensional incommensurate superstructure in the a‐b plane with a different periodicity and a different orientation relationship to the subcell.

Analogy between Y2Ba4Cu8O16−x and Bi4Ca2Sr4Cu4O16+x

Abstract The new superconducting phase Y 2 Ba 4 Cu 8 O 16− x in epitaxially grown thin films is compared to the newly discovered Bi 4 Ca 2 Sr 4 Cu 4 O 16+ x structure. Properties of Y 2 Ba 4 Cu 8 O 16− x are compared to those of Bi 4 Ca 2 Sr 4 Cu 4 O 16+ x . An analogy between the structure of those two materials is drawn and their properties are discussed.