**5. Conclusions**

These studies indicate the optimization of the superconducting properties of the high-Tc superconductors (Y1−xSmx )SrBaCu<sup>3</sup> O6+z by a simple argon heat treatment. These results are a competition between oxygen disorder in basal plane and cationic disorder along c axis. In the samples [O], we are in the presence of a cationic disorder of Y/Sm on (Sr/Ba) sites that induced an anionic disorder of oxygen's chains in basal plane. Anionic order dominates in the samples [AO] in agreement with the previsions of [4, 5]. In the samples [AO], the remarkable improvement in the shielding effect (for x > 0.5) and the irreversibility line (for x ≥ 0.5) are explained, respectively, by the improvement of the quality of the grains and intergranular coupling, and to the improvement of the pinning properties and crystallographic quality of these samples. The structural, magnetic and superconducting properties are correlated with the effect of argon heat treatment.

These results were explained by the effect of the ionic size of the rare earth, the decrease in d[Cu(1)─(Sr/Ba)]; the increase in cationic and chain oxygen ordering; the number of holes psh(x) by Cu(2)─O2 superconducting plans and in phase purity for the [AO] samples.
