Samples of calcium titanate perovskite (CaTiO 3 ) 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 CaTiO 3 perovskite leads to the formation of complex (Ca 1-2x Ln 2x )(Ti 1-x Ca x )O 3 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.

Samples of calcium stannate perovskite (CaSnO 3 ) doped with a variable Nd content were synthesized by solid-state reaction in the system (1 − x )CaSnO 3 − x Nd 2 O 3 . The synthesized compounds were characterized by means of electron microprobe, powder X-ray diffraction, single-crystal X-ray diffraction and µ-Raman spectroscopy. The incorporation of Nd in the CaSnO 3 Pbnm structure leads to the formation of a complex (Ca 1 − 2 x Nd 2 x )(Sn 1 − x Ca x )O 3 perovskite. The A sublattice contains a random distribution of Ca and Nd in the whole range of composition of this system. For x < 0.28, the structure is Pbnm with Ca and Sn randomly distributed in the B sublattice. For x > 0.28 a symmetry change occurs; the structure turns into rock salt type P2 1 / n . In this latter case half of the octahedral sites are fully occupied by Sn and the other half is randomly occupied by Sn and Ca. For x = 0.28, both structures are present in the sample. The presence of a Raman two modes behavior of A 1g symmetry located near 700 cm − 1 coupled with the continuous linear evolution of the lattice parameters with Nd incorporation supports the proposed substitution mechanism.