TEM investigation of discommensurations in the bismuth-type high Tc superconductors

Abstract The existence of discommensurations in the superconducting bismuth-cuprates is established on the basis of several consistent features: translation-shift across a wall, characteristics of the nodes where several discommensurations merge, correspondence between the average distance of the lines in real space and the modulation wavelength deduced from microdiffraction. We have observed a variety of “latent” lock-in wavevectors between b ∗ /4 and b ∗ /10 depending either on the investigated phases or on the amount of substitution of lead to bismuth.