RAMAN-SCATTERING STUDY OF ACCEPTOR-DOPED BACEO3

Raman scattering studies of perovskite-structured BaCeO3 acceptor-doped with the rare earth ions Yb3+, Gd3+ and Nd3+ are presented. Room temperature spectra of BaCeO3 doped with 5% Yb3+ and 5% Gd3+ are similar to that observed for undoped BaCeO3, having an orthorhombic perovskite structure. However, 5% doping with Nd3+ results in a strikingly different Raman spectrum with fewer bands, indicating a tetragonal structure. Moreover, the distortion of the structure towards the higher symmetry phase is an increasing function of Nd dopant concentration, 10% doping giving a nearly cubic structure. A broad band appearing at 624 cm-1 which increases in intensity with increasing Nd dopant concentration probably arises from dopant-oxygen ion vibrational modes. The Raman scattering results are interpreted in terms of the ionic radii of the dopants and, further, are compared to existing conductivity results.