Progress in field ion microscopy imaging of high-Tc superconducting oxides

Field ion microscopy (FIM) of many of the new high-transition-temperature superconducting oxides has become routine. The older La-Sr-Cu-O type and the newer R-Ba-Cu-O (''1, 2, 3'') type, with R=Y, Yb, Sm, Gd, Dy, Ho, Er, Pr, Eu or La, consistently image well at low temperature in hydrogen FIM and argon FIM at higher temperatures, and less consistently in neon FIM. The newest Bi-Sr-Ca-Cu-O type and Tl-Ba-Ca-Cu-0 type) can be imaged by hydrogen FIM, but the Bi-based specimens thus far have been mechanically weak and phase identification in both types poses a significant problem. Some details of FIM image interpretation for the ''1, 2, 3'' superconductors are addressed, in particular, the various degrees of order apparent in the images and the question of identity of the imaging species