Raman scattering characterization of bismuth based mixed oxides with Bi2O3 related structures

Orthorhombic Bi17Ln7O36 (=Bi0.708Ln0.292O1.5) and triclinic BiLnO3 (=Bi0.5Ln0.5O1.5) with Ln = Tm, Yb and Lu, as well as a cubic δ-type Bi0.7Yb0.3O1.5, have been characterized at room temperature by Raman scattering spectrometry. The Raman spectrum deconvolution of the δ-Bi2O3 type cubic form allowed us to establish a correlation between the different phases of these mixed metallic oxides for the lattice modes as well as for the internal species. Using the empirical relation from Hardcastle, the BiO bond lengths have been estimated from the stretching frequency value observed at 635, 597 or 639 cm−1 for cubic, orthorhombic or triclinic forms, respectively. A comparison with the X-ray results is discussed. The peritectoïdic transformation BiTmO3 → δ + Tm2O3 has also been characterized by Raman spectroscopy.