Vibrational spectroscopy of Ca (2)LnTaO(6) (Ln = lanthanides, Y, and In) and Ca2InNbO6 double perovskites

Abstract

Ca(2)LnTaO(6) (Ln = lanthanides, Y, and In) and Ca2InNbO6 ceramics were prepared by the solid-state route, and their vibrational properties were investigated using Raman scattering and infrared spectroscopy. The correct crystal structure and phonon mode features for this lanthanide series in Ca-based double perovskites were determined using experimental data besides group-theoretical models. It was observed that the ceramics with Y, Er, and In exhibit orthorhombic, Pbnm (D-2h(16)) structures, similarly to those previously observed in Ca(2)LnNbO(6) ceramics, whereas the materials with La, Nd, Sm, Eu, Gd, Tb, and Ho show a monoclinic P2(1)/n (C-2h(5)) structure, like Sr(2)LnTaO(6) ceramics. Together with another two previous publications (Dias, A.; Khalam, L. A.; Sebastian, M. T.; Paschoal, C. W. A.; Moreira, R. L. Chem. Mater. 2006, 18, 214-220 and Dias, A.; Khalam, L. A.; Sebastian, M. T.; Lage, M. M.; Matinaga, F. M.; Moreira, R. L. Chem. Mater. 2008, 20, 5253-5259), the present results conclude the study for the A(2)LnTaO(6) materials with alkaline-earth metals in the A-site, showing the changing in the crystalline structure as a function of the chemical environment.