Experimental study of trivalent rare-earth element incorporation in CaTiO3 perovskite: evidence for a new substitution mechanism.

Samples of calcium titanate perovskite (CaTiO₃) substituted with variable amounts of trivalent La, Pr, Nd or Sm were synthesized by solid-state reaction. The synthesized compounds were characterized by means of electron microprobe (EMPA), powder X-ray diffraction and µ-Raman spectroscopy. The incorporation of the studied lanthanides in the CaTiO₃ perovskite leads to the formation of complex (Ca_1-2xLn_2x)(Ti_1-xCa_x)O₃ perovskites with a Pbnm disordered structure. This mechanism was revealed by the Ca/Ti ratio analyses of the samples, the study of the lattice parameter evolution and the Raman A_1g octahedral breathing mode frequency comparison for all systems. [ABSTRACT FROM AUTHOR]