Abstract
The temperature of superconductive transitions T c was measured for a variety of compositions ( x, c) of the 1:2:3 tetragonal superconductors (Ca x La 1− x )(Ba c− x La 2−c+ x )Cu 3O y (so called CLBLCO or CLBCO or Ca–La–Ba–Cu–O) both in oxygen underdoped and overdoped region. The maximal values of T c ( T c,max) were calculated directly from these T c vs y graphs. We found that instead of the 1:2:3 superconductors without calcium where substitution of Ba for La effectively decreases T c,max, Ca rich compositions of CLBLCO do not change T c,max over the wide range of this substitution. This fact and also the previously found increasing of T c,max with the Ca-content ( x) are explained by the cluster component method; we found that the compositions with unit cells containing La on both the Y and Ba-sites, are nonsuperconductive, while all compositions containing unit cells with Ca on the Y-site have the highest T c,max =81 K. All the experimentally found T c,max( x, c) may be described by the varying of the ratios of these unit cells in the sample. The role of Ca in stabilizing of T c,max at substitution of Ba for La, and also in the increasing of T c,max with increasing the Ca-content is because of the much higher ability of Ca to bind La (from the Ba site) than the ability of La on the Y site for the same binding. This prevents the formation of La(LaBa)Cu 3O y unit cells, the presence of which in CLBLCO decreases T c,max.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call