Neutron Scattering Study of Sr Substitution for Ba in YBa₂Cu₃O_7-y

Neutron diffraction and inelastic scattering were carried out on YBa_2-xSr_x Cu₃O_7-y(x=0.5, 1.0, 1.25). It was confirmed that the substitution of Sr for Ba in YBa₂Cu₃O_7-y increases the oxygen vacancies in the Cu O chain. Moreover, the substitution strengthens the coupling between the Ba O plane the Cu O chain, and reduces the crystal stability. These are possible causes of T_c depression for Sr substituted YBa₂Cu₃O_7-y.