Isovalent Substitution and Heat Treatments Control of T c, Chain Oxygen Disorder and Structural Phase Transition in High T c Superconductors (Y1−x Nd x )SrBaCu3O6+z

• Published in: Journal of low temperature physics Vol. 171; no. 5-6; pp. 818 - 827
• Main Authors: Morghi, R., Nafidi, A., Aboulkassim, A., Chaib, H., Charafi, H., Ait Taleb, T., Marí Soucase, B., Mollar García, M., Hartiti, B., Chander Singh, K., Khallouq, K.
• Format: Journal Article
• Language: English
• Published: 01.06.2013
• Subjects: Annealing; Chains; Heat treatment; Low temperature physics; Neodymium; Order disorder; Superconductors; Unit cell
• ISSN: 0022-2291; 1573-7357
• DOI: 10.1007/s10909-012-0834-x

We report here on the preparation, X-ray diffraction with Rietveld refinement, AC magnetic susceptibility measurements and effect of heat treatments in (Y1?x Nd x )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] heat treatment increases the orthorhombicity ?=(b?a)/(b+a) (for 0?x<1), T c (for x>0.2) and the distance d[Cu(1)a(Sr/Ba)] (decrease T c) for x<0.25 and decrease it (increase T c) for x>0.25. When x increase from 0 to 1, ? decreases to 0 with transition from orthorhombic to tetragonal structure. ?[O] decreases with T c[O]. However, T c[AO] decreases with ?[AO] until x=0.2, increases for x=0.4 and after it decreases by 9.8 K to 77.2 K for x=1 [AO]. Remarkable correlations were observed between T c(x) and the volume of the unit cell V(x); and between ?T c(x)=T c[AO]?T c[O] and ??(x). A combination of several factors such as decrease in d[Cu(1)a(Sr/Ba)]; increase in cationic and chain oxygen ordering; the number p sh(x) of holes by Cu(2)aO2 superconducting plans and in-phase purity for the [AO] samples may account for the observed data.