Sr substitution for Ba in Y(Ba1-xSrx)(2)Cu3O7-d at varying d

In order to understand the difference between the effects induced by chemic al substitutions and those induced by applying mechanical pressure, we synt hesised and characterised samples of Y(Ba1-xSrx)(2)Cu3O7-d. The structural refinements based on powder neutron diffraction data were carried out as a function of x and, for x = 0.5, as a function of d. The electric and magnet ic properties have also been measured and correlated with the structural pa rameters and oxygen content. It seems that the Ba cations play an important role in the high T-c of YBCO. Its substitution with a smaller cation corre sponds to the application of a chemical pressure, but the release of the as sociated strain seems to play a negative role on T-c.