Correlation Between Enhanced ${\rm T}_{\rm c}$, Orthorhombicity and the Volume of the Unit Cell in Argon Preheated $({\rm Y}_{1-{\rm x}}{\rm Sm}_{\rm x}){\rm SrBaCu}_{3}{\rm O}_{6+{\rm z}}$

Abstract

We report here on the preparation, X-ray diffraction with Rietveld refinement, AC susceptibility measurements and effect of heat treatments in (Y1-xSmx)SrBaCu3O6+z. Each sample was subject to two types of heat treatment: oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. For each x, the [AO] treatment increases the orthorhombicity epsiv = (b -a) / (b + a) (for 0 les x les 1), T c (for x ges 0.4) and the distance d [Cu(1) - (Sr / Ba)] (decrease T c ) for x 0.5 . When x increase from 0 to 1, epsiv decreases with T c[O]. However, T c[AO] decreases with epsiv until x = 0.2 and after it increases by 6 K to 85 K for x = 1 [AO]. A remarkable correlations were observed between Tc(x) and the volume of the unit cell V (x) ; and between deltaT c(x) = T c[AO] - T c[O] and deltaepsiv(x). A combination of several factors such as decrease in d [Cu(1) - (Sr / Ba)]; increase in cationic and chain oxygen ordering; the number p sh(x) of holes by Cu(2) - O2 superconducting plans and in-phase purity for the [AO] samples may account for the observed data.