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

We report here on the preparation, X-ray diffraction with Rietveld refinement, AC susceptibility measurements and effect of heat treatments in (Y sub(1-x)Sm sub(x))SrBaCu sub(3)O sub(6+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 sub(c) (for x ges 0.4) and the distance d [Cu(1) - (Sr / Ba)] (decrease T sub(c) ) for x 0.5 . When x increase from 0 to 1, epsiv decreases with T sub(c)[O]. However, T sub(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 sub(c)(x) = T sub(c)[AO] - T sub(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 sub(sh)(x) of holes by Cu(2) - O sub(2) superconducting plans and in-phase purity for the [AO] samples may account for the observed data.