Oxygen stoichiometry and structural parameters of Sm1+xBa2-xCu3Oy solid solutions versus composition and temperature

The effects of temperature and samarium content on oxygen stoichiometry and crystal lattice parameters of the Sm1+xBa2-xCu3Oy solid solutions (Sm123ss) prepared by the citrate sol-gel method were studied. It was found that there are three compositional ranges of variation of the structural-chemical characteristics of the Sm123ss corresponding to the regions of existence of the following three phases: orthorhombic phase I (0≤x<0.15-0.20), tetragonal phase (0.20≤x<0.60) and orthorhombic phase II (x≥0.65). The above phases behave differently with temperature: (a) the orthorhombic phase I behaves with temperature like the Y123 phase; (b) the lattice parameters a and c of the tetragonal phase vary, i.e., its lattice is relatively rigid as oxygen is removed; (c) the orthorhombic phase II has a very rigid crystal lattice