119Sn and151Eu Mössbauer study of EuBa2(Cu1-xSnx)3O7-y perovskites

Eu and Sn Mossbauer spectroscopy was used to study EuBa2(Cu1-xSnx)3O7-y metallic oxides. The spectra are characteristic for EuIII and SnIV states in all cases. The existence of at least two different Sn states was determined by decomposition of the Sn Mossbauer spectra. These Sn sites can be associated with nonequivalent Cu sites replaced by Sn atoms in the perovskite type lattice. Anomalous changes were observed in the isomer shifts and area fractions in the spectra measured at room temperature and at 77 K. It can be interpreted assuming low temperature phase transformation and phonon softening. Time dependent changes were found in the Sn spectra recorded at 77 K in the case of highest Sn concentration. The observed changes are consistent with a transitional stage of the low temperature phase transformation.