Morphological effects of grinding on bismuth-based cuprate superconductors

Morphological changes of bismuth-based cuprate superconductors, such as the 2223 phase, via a small mechanical force were studied mainly by means of high-resolution transmission electron microscopy and atomic force microscopy. Even light mechanical grinding of the sintered 2223 samples led to the formation of superfine particles that had a width of ∼5 nm. Moreover, we found first that the superfine particles had a discrete thickness of odd numbers of a half unit length c/2 of the 2223 phase, e.g. 1.9 nm, 5.6 nm, and so on. The formation of the superfine particles was due to cleavage at Bi-O double layers that were bound weakly to each other in a unit cell.